ALBERT

Notes: Two antigenically distinct populations of b-negative light chains have been identified in the serum of two b locus homozygous rabbits undergoing total b locus suppression. Whilst one population of molecules is readily detected in all rabbit sera and represents the previously described lambda chain, a second and minor population of b-negative molecules is detected which is readily detected in normal rabbit serum only rarely. Thus, it appears that it is not specificities of the c7-, c-21 system that are being detected but rather a previously unrecognized allotypic system or the products of a different light chain locus.

Notes: Two genetically inbred strains of rats with new histocompatibility alleles—the KGH and WKA strains—were characterized. Neither the KGH nor WKA strain cells reacted with known Ag-B * specific antisera; specific antisera against these strains did not react with cells from any known Ag-B group; and there was no cross-reactivity between the histocompatibility antigens of the two strains. On the basis of these data, the KGH strain was assigned the Ag-B7 allele and the WKA strain, the Ag-B8 allele. Both strains were low responders to the test antigen poly(Glu52Lys33Tyr15). In various crosses, the antibody response segregated as expected, i.e. low response was associated with the Ag-B7 or Ag-B8 alleles in the F2 and backcross generations.

Notes: The relationship between the mixed leukocyte reaction (MLR) and the serologically defined antigens of the major histocompatibility complex was examined in twenty-three strains of genetically inbred rats. Interstrain cell combinations involving representative members of the different major Ag-B groups were associated with significant MLR responses. Strain combinations within a single Ag-B group were never associated with significant MLR responses, suggesting that non-Ag-B loci probably do not play an important role in MLR reactivity among inbred strains of rats. The WKA and KGH strains, representing newly defined histocompatibility groups, were also examined. The WKA strain (Ag-B8) showed positive MLR responses against representative members of all the different Ag-B groups, including the KGH strain. The KGH strain (Ag-B7) had positive MLR responses against all Ag-B groups except Ag-B1: no reactions occurred with three strains in this group, and inconsistent and weak reactivity was observed with a fourth strain (F344).

Notes: The amino acid sequence near the N-terminus of a human immunoglobulin (Ig) light (L) chain has been determined. This sequence is more homologous to avian Ig L chains than to human Ig L chains, and defines an additional variable (V-) region subgroup designated as VλVI. These data also suggest that all vertebrates share large numbers of Ig V-region genes and that 'species-specific’residues reflect the expression in different species of different sets of V-region genes. Control at a level equivalent to ‘regulatory genes’* determines which genes are expressed. Our findings raise a question concerning the possible role of redundant DNA, in that at least some of the ‘nonsense’ DNA in one species may actually be 'sense’DNA in another. We hypothesize that in evolution‘gene expansion’is a regular mechanism for the generation of new genes and that different members of a given group of repetitious genes are expressed in different species. Such a phenomenon is basically similar to the‘mechanism’controlling the differential expression of genes during embryonic differentiation. Our hypothesis differs from the previous version of the germ-line hypothesis proposed for genetic control of antibody variability which involves ‘sudden excessive gene expansion and contraction’. Evidence suggesting that the‘gene expansion’mechanism may also be applicable to a lesser degree to other gene systems is briefly reviewed and discussed.

Notes: Stepwise incubation with specific H-2 antibody and rabbit-anti-mouse Ig was used to modulate the expression of selected H-2 specificities on the surface of lymph node cells or EL 4 leukaemia cells. Modulation was reflected in a loss of sensitivity to complement-dependent lysis and a polar pattern of immunofluorescence (‘capping’). Specificity H-2.5 on H-2a cells was co-modulated with H-2.11 and so was H-2.11 with H-2.5 on H-2k cells. However, when H-2.11 on H-2k cells was modulated, the cells did not loose cytotoxic sensitivity for H-2.5. This asymmetry in co-modulation of H-2.5 and H-2.11 may be accommodated by the duplication model of the H-2 complex which postulates a double determination of H-2.5 in the H-2k (unlike H-2a) chromosome, with one determinant being in the K region (where also the H-2.11 determinant is located) and the other in H-2D. The modulation results with H-2.5 and H-2.11 are compatible with the view that various H-2K specificities may represent distinct antigenic sites on the same glycoprotein molecule whereas H-2D specificities are on separate molecule(s). The independent modulation of H-2D.4 and H-2K.11 specificities further indicates that molecules of the two classes are also secondarily not linked in the membrane structure. Modulation-induced cytotoxicity resistance was further shown to persist even when the specific H-2 antibody is newly added; this suggests that it is a change in the distribution of the H-2 antigen to be held responsible (rather than the loss of the sensitizing antibody).A modulated expression of a certain H-2 specificity might then be expected to affect its blocking relationship to another H-2 specificity; the blocking index expresses the degree of interference by antibody attached to one of them with the attachment of antibody to the other. The blocking relationship between H-2.4 and H-2.11 was shown to be completely abolished by the independent modulation of H-2.11. In contrast to this, the blocking index for H-2.5 and H-2.11 remained practically constant following the modulation of either specificity; this indicates that the intramolecular configuration of such two H-2 sites may not be altered by the gross redistribution of the whole molecule in the plane of the membrane. The rigidity of this configuration seems to be maintained by neuraminidase-sensitive groups as suggested by the reduced blocking index in neuraminidase pretreated cell.

Notes: The effects of varying degrees of multiparity on placental and foetal weights were examined in BALB/c female mice pregnant by either BALB/c or C3H males. Continual decreases in placental weights are observed through third pregnancies followed by progressive increases in both syngeneic and allogeneic placentas. In syngeneic pregnancies, foetal weights are generally proportional to placental weights, but those of allogeneic pregnancies tend to oppose placental weights. Evidence is presented that placental weights are also influenced by foetus-specific antigens and the genotype of previous litters. In this strain combination, placental weights reflect changes in maternal reactivity different from those previously reported with tumour allografts.

Notes: The Ag system, inherited antigenic determinants on serum low density lipoprotein and Australia antigen (Au), an antigen associated with an infectious agent which can cause hepatitis in man were discovered by reacting in immunodiffusion tests sera from multiply transfused patients and sera from geographically human populations. The approach has been pursued in the experiments described herein and has resulted in the identification of seventeen precipitating systems. They are different from the previously described anti-Au and anti-Ag precipitins. In some cases they may be confused with Australia antigen precipitins, and care should be taken in the evaluation of Au test systems where comparisons with antigen controls are not routinely performed.

Notes: Book Review in this Article. Einfiihrung in die Immungenetik, Grundlagen der Modernen Genetik 9, KLAUSDIETER BAUER

Notes: A new type of Gm genetic marker combination in an IgG1 immunoglobulin, Gm(z) together with a non-a marker, is here described. This indicates the presence of a new gene, Gmz,non-a, which most likely originated on the basis of an intragenic recombination at the IgG1 cistron. Immunochemical and immunogenetic studies showed that no other IgG1 Gm markers were expressed by the unusual gene, and there was no evidence for deletions or duplications at the IgG1 cistron.

Notes: The cell mediated lympholysis (CML) test is normally carried out in 2 steps–first, the lymphoid cells are allowed to interact in mixed allo-culture (MLC) and secondly, they are reacted against chromium labelled phytohaemagglutinin transformed lymphoblast cells, carrying the appropriate target allo-determinants. The genetic control of target structures has already been localized to the H-2D and H-2K regions of the H-2 gene complex, but the genetic basis of the generation of effector capacity is not understood and is the subject of this report; the suggestion that there is a separate genetic basis came from the observation that H-2D and/or H-2K region incompatibility alone was insufficient for CML to occur and that incompatibility at the Ir-Ss-Slp regions of the H-2 complex was also required. In the Ir region also reside the genetic control for the strong lymphocyte activating determinants (LAD) of the H-2 gene complex and it was thought possible that they might also be responsible for activating the effector cells for CML.The genetic experiments were done with congenic resistant and recombinant mouse strains, so it was possible to study in relative isolation, and in selected combinations which of the various defined regions of the H-2 gene complex control the initiation of effector capacity in CML.Five day,‘one-way’(parent-F1) mixed lymphocyte cultures–incompatible only for defined regions of the H-2 gene complex were reacted with 51Cr-labelled PHA blast cells and the specific chromium release was calculated.The results give evidence for a separate but closely linked genetic control for the effector cell stimulating (ECS) and LAD functions. The ECS genes map between the LAD and Ss-Slp genes of the H-2 complex.

Notes: Gonad development was studied in young carp of the European and Chinese (big-belly) races. The effects of age and body weight on gonad and egg size were partitioned and the following findings were made: (i) Gonad weight was correlated, in both males and females, with body weight, but proportional gonad weight, i.e. the ratio gonad weight divided by body weight, was independent of body weight, (ii) Proportional gonad weight had reached its maximum value in one year old males, but it more than doubled in two year old females, (iii) Egg size of two year old females was more than twice the size of eggs of one year old females, (iv) The European and Chinese races of carp differed in several aspects of gonad development. In particular, the Chinese matured earlier and their relative gonad sizes were considerably larger, (v) Genetic variation in gonad development was also found within the European race, where faster rate of development is dominant over slower rate. The evolutionary implications of the above differences were discussed.

Notes: Changes in haematocrit values under lowered oxygen tension and aerobically treated blood samples of rainbow trout Salmo gairdneri (Richardson), landlocked Baltic salmon S. salar (L.), brown trout S. trutta lacustris (L.) and lake trout Salvelinus namaycush (Walbaum) have been studied in vitro. The mean haematocrit value increased during 2 h incubation under lowered oxygen tension by 32.7 ± 3.1% in rainbow trout, 28.2 ± 2.8% in landlocked Baltic salmon, 29.2 ± 5.6% in brown trout and 25.2 ± 2.8% in lake trout. During corresponding incubation with oxygen the mean haematocrit value decreased below the starting level by 18.1 ± 1.9% in rainbow trout, 18.3 ± 4.8% in landlocked Baltic salmon, 22.4 ± 0.7% in brown trout and 11.8 ± 1.7% in lake trout. Consequently, the changes in the haematocrit values were greater in the species belonging to the genus Salmo than in that of the genus Salvelinus. The increase in the haematocrit values seems to have resulted from swelling of the erythrocytes and their decrease is similarly attributable to shrinking of the cells. The reasons for this swelling, which may be complicated, and its apparent significance for haematocrit determinations are discussed.

Notes: Wild plaice and flounders with lymphocystis were sampled and their lesion distribution noted. Regression of the lymphocystis cells was seen by histology and a host response including macrophages and immune cells occurred. Antibodies were detectable by a double diffusion precipitin test. The epidemiology is discussed with reference to these findings and to the life histories of the two species.

Notes: The stomachs of 148 elasmobranch and teleost fishes representing 35 families and 62 species were examined by viscometry for cellulase activity. Sixteen species of Georgia estuarine fish and the freshwater fish, Ictalurus punctatus (Rafinesque) showed some cellulase activity. Elasmobranchs and teleosts captured in Florida Bay, Florida, and over the continental shelf off Georgia lacked cellulase activity. Cellulase activity in fishes is probably produced by microflora of the alimentary tract.

Notes: Rates of acclimation and the response to fluctuating low temperatures of juvenile striped mullet Mugil cephalus (L.) have been described in terms of changes in heat resistance over a period of time. Fish changed from 25.5 to 27 or 29° C were acclimated within seven days. Acclimation to 23 or 15° C required a maximum of 11 days. Thermal responses to fluctuating low temperatures were lower than responses to constant temperature levels. Cyclic variations in heat resistance were present in all experimental and control tests.

Notes: Juvenile Rhabdosargus holubi (Steindachner), one of the commonest teleosts in south east African estuaries, are strong osmoregulators, showing little change in their internal osmotic concentration over an extremely wide salinity range. In 35‰ seawater the internal osmotic concentration is held at 370 mosmol/1. At a salinity of 1‰ the internal osmotic concentration falls to 216 mosmol/1 and at a salinity of 65‰ rises to 381 mosmol/1. When exposed to a new salinity the internal osmotic concentration does not change until after 10 h; this may be of considerable importance to fish living in areas subject to short term changes of salinity.

Notes: Sardinella gibbosa and Sardinella albella of Dar es Salaam coast were studied from January 1969 to March 1970. Measurements on the standard length, weight, body depth, length and width of the gonads were taken and qualitative assessments of fat coverage on the alimentary canal and maturation stages were made. New size-groups of both the species appeared in the lamp-fishery at c. 6 cm SL between October 1969 and February 1970 and the largest specimens caught were 14.1 and 12.9 cm SL for the first and second species respectively. Length-weight equations of the two species show higher values of the regression coefficients for the females compared to the males. Fat content of fishes 〉 10 cm SL was high during March to May and low during August to December 1969. First maturation and spawning are probably attained at c. 10.5 and 10 cm SL in the first and second species respectively. Mature S. gibbosa occurred between August and November 1969 and probably the species has a single, annual spawning season of 3.4 months duration. Mature S. albella, 10.1–12.5 cm SL occurred between August 1969 and February 1970; mature females, 12.6–12.9 cm SL were encountered throughout the sampling period.

Notes: In the horse mackerel the gametes develop asynchronously and are released in batches. The maturity cycle is characterized by a rapid post-spawning recovery period and a relatively long period of oocyte maturation. Mean gonad weight reached a peak in June and intraovarian hyaline oocytes occurred from May to August. Determination of fecundity was complicated by resorption of oocytes both before and after spawning, and by the fact that resting and developing oocytes were not clearly separated by size. An estimate of‘potential fecundity‘was obtained by a combination of histology and oocyte measurement. Plankton surveys showed that a major spawning area exists in the Southern Bight of the North Sea, with eggs occurring from May to late August. An estimate of annual egg production was combined with the fecundity data to give an estimate of stock size of about 500 000 tons.

Notes: The results of the application of Schnabel (Chapman modification), Schumacher & Eschmeyer, Fisher & Ford, and Jolly capture-recapture techniques on the Barbus barbus (L.) population in four areas of the middle Severn are compared. The survival of tagged fish varied in different areas and fish released in some time periods were less vulnerable to recapture than fish released from other samples. It is suggested that the shoaling behaviour of Barbus barbus resulted in non-random mixing of marked fish. The average population size of Barbus barbus greater than 18 cm in length in each of the four sections for the total period of investigation gave population densities ranging from 0.024/m2 to 0.202/m2.

Notes: Scales of 497 dace from the river Stour and 573 from the river Frome were used for age determinations. Annuli were laid down in late May to early June at the start of the growth period. Minimal growth occurred from November to April. Male dace grew minimally faster than females; Frome dace faster than those from the Stour. Growth rates in the two rivers were similar to those published for most other European waters. Variation in growth rates in different years was not great, but there were marked differences in recruitment success. Spawning occurred in the second half of March and elaboration of the gonads between September and March. Immature dace have an annual cycle in condition with a maximum in June and a minimum during the winter months. The condition of the mature females is affected by the gonad cycle. The fecundity of Stour dace is represented by the formula: 〈displayedItem type="mathematics" xml:id="mu1" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00221112:JFB237:JFB_237_mu1"/〉 and for Frome dace by: 〈displayedItem type="mathematics" xml:id="mu2" numbered="no"〉〈mediaResource alt="image" href="urn:x-wiley:00221112:JFB237:JFB_237_mu2"/〉 Most dace were mature by age IV, but there were more mature II and III group fish in the Frome population. Molluscs and Trichoptera larvae comprised the bulk of the winter diet of Stour dace, and Ephemeroptera nymphs, Simulium and chironomid larvae were the principal constituents during the summer.

Notes: Synthetic detergents are reported to be acutely toxic to fish in concentrations between 0.4 and 40 mg/1. Factors affecting toxicity include the molecular structure of the detergent, water hardness, temperature and dissolved oxygen concentration; the age and species of the test fish, and acclimation to low concentrations of detergent. Some of these factors appear to be of only limited importance. Gill damage is the most obvious acute toxic effect; the immediate cause of death may be asphyxiation, but detergents may also be toxic internally. Lethal effects not related to gill damage have not been investigated. Sublethal effects include retardation of growth, alteration of feeding behaviour and inhibition of chemoreceptor organs. Low levels of detergents may also increase the uptake of other pollutants. Invertebrates, especially in their juvenile stages, are extremely sensitive to detergents: concentrations below 0.1 mg/1 interfere with growth and development in some species. The interactions between detergents and proteins, and their influence on membrane permeability may be the basis of the biological action of detergents. Detergents in natural waters are usually partially degraded, and a maximum permissible concentration of 0.5 mg/1 would probably be harmless under most conditions.

Notes: Argentine pejerreys were collected in Lake Peñuelas during January 1973. Calculated growth rate was maximum during the 3rd year of life. The length–weight relationship was: log W=-5.69395+3.25248 log L where W=weight (g), and L=total length (mm). Agegroup I was sexually mature. The sex ratio was 85 males (54%) to 73 females (46%). Young-of-the-year pejerreys fed primarily on copepods, but cladocerans [Bosmina sp. (Baird), Diaphanosoma brachyurum (Liéven), Simocephalus serrulatus (Koch)], ostracods, and dipterans were also represented. Feeding occurred during daylight.

Notes: Scanning microscopic observations were made of the surface structures of isolated scales of Tilapia mossambica (Peters). The circuli were found to form numerous minute processes called scalar denticles, which may act to secure the position of the scale with reference to surrounding dermal tissues. The skin covering the lunula of the scale includes a number of pores which are thought to represent the terminal openings of dermal mucous cells. This part of the skin also shows peculiar epidermal surface patterns. These surface patterns may be indicative of areas subject to increased mechanical stress.

Notes: The electrophoretic patterns of the general proteins, esterases, creatine kinase and phosphoglucomutase of white muscle from Lough Neagh pollan, Lough Erne pollan, Lake Bala gwyniad, Loch Lomond powan, Haweswater schelly and Bassenthwaite vendace are consistently of three types. It is therefore suggested that the coregonids examined are three distinct species: the pollans; gwyniad, powan and schelly; vendace. Vendace is genetically closer to the gwyniad group than to the pollans.

Notes: Carp Cyprinus carpio L. populations of known composition as to size and descent were fished in drainable ponds in various ways to judge the validity of the mark-recapture method for estimation of population size. Six combinations of gear for capture and recapture were employed, including fyke-traps, seines and angling-rods. Satisfactory estimates could be obtained only when the selectivity of the gear for recapture differed from that used for marking. Some differences and changes in behaviour of the carp underlying observed biased estimates are examined.

Notes: A description is given of Pseudochromis porphyreus, a new species of serranoid reef fish from the Pacific which is overall bright magenta in coloration; it was recorded from the Ryukyu Is., Philippine Is., Palau Is., Gilbert Is., New Hebrides, Fiji and American Samoa.

Notes: Clarias gariepinus (Burchell) can be stimulated to spawn in aquaria by hormonal treatment and the breeding habits could be observed. After pre-spawning activities such as the raising of dorsal fins and chasing of the female, the male folds around the head of the female and small batches of eggs are laid, followed by some gas bubbles. Eggs are distributed by the female over a wide area. This behaviour agrees with field observations. The final stimulant to spawning under natural conditions is thought to be a substance called petrichor dissolved in flood waters that have run over dry ground.

Notes: The development of chromatophores and the formation of colour patterns in Tilapia mossambica are described. A number of colour patterns are associated with certain aspects of behaviour. Four different melanophore systems are involved in the colour pattern formation. There appear to be 14 patterns which, in various combinations, produce a series of colour patterns. Each of these may convey a different message to different species of Tilapia.

Notes: A new species of Dermocystidium is reported to be the causative agent of three outbreaks of gill disease in carp observed in recent years in Czechoslovakia. No other parasites or influences could be held responsible for the disease. It is suggested that at least some of gill disease of unknown aetiology in carp is due to dermocystidia, and the disease might be distributed in many regions of Europe. A description of a greater part of the developmental cycle of the species D. cyprini n.sp. Červinka et Lom, is presented, supplemented by a discussion of other species of the genus. A summary of known facts on the host-parasite relation in these parasites is also given.

Notes: The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at 5, 10 and 15° C, using a photographic method of recording activity. The activity patterns at 10 and 15° C were very similar, there being a high level of swimming activity during the light period, which fell to a low level at 5° C. It was also lower at 10° C at the end of the experiment than at the beginning and it is suggested that this might have been due to an increase in the fat contents of the fish. The feeding rate of the fish was measured and showed a Q10 of 2.08 for the temperature range 5–15° C. The annual cycle of activity of A. marinus is discussed in relation to seasonal changes in food availability, light and temperature, and in the fat content of the fish. It is concluded that after spawning in the December–January period the fish remain buried in the sand until April, because of the limiting effect on swimming and feeding activity of the environmental factors in the intervening period. The proportion of fish available for capture at the start of the fishery in April is related mainly to temperature, but food (as measured by numbers of copepods) light intensity and photoperiod are by then increasing rapidly. After July the fishery ceases and it is thought that this is because the fish have entered an overwintering stage, during which they remain buried in the sand. This phase is also thought to be associated with the maturation of the gonads in readiness for the winter spawning. The factors causing the fish to enter this stage are as yet undetermined but may be related to the attainment of a certain level of fat content.

Notes: Food intake, growth and food conversion of young, O-group herring were studied at two temperatures and feeding regimes over a period of 19 weeks. The food intake of fish fed to satiation twice daily showed considerable variation. Food intake per fish at 14.5° C was about three times that at 6.5° C, and was generally much higher than in most other species of fish studied. The mean increase in wet weight over the 19-week period was 0.581 g/week at 14.5° C and 0.236 g/week at 6.5° C in fish fed to satiation and 0.094 g/week at 6.2° C and a ration of 1.3% of the body weight. Growth depensation was found to occur even in fish fed to satiation. The changes in specific growth rate, that is the percentage increase in weight/day, showed similar trends at different temperatures and food regimes. The mean conversion efficiency of fish on a ration of 1.3% at 6.2° C was higher than that of fish fed until satiation, at 14.5 and 6.5° C. The conversion efficiency of fish fed to satiation at 14.5° C showed a distinct decrease with increasing weight while at 6.5° C such a clear trend was not observed. In general, the conversion efficiency of young herring were found to be much lower than that of most other species studied. The weight exponent of the quantitative relationship between food intake and body weight at 14.5° C was 0.744. The total metabolic expenditure at 14.5° C, calculated using Winberg's (1956) ‘utilization coefficient, gave a weight exponent of 0.773.

Notes: Spawning Atlantic salmon, Salmo salar (L.), brown trout, Salmo trutta (L.) and rainbow trout, Salmo gairdneri (Richardson) were held in tanks for four weeks and then injected with filtrates from lesions of salmon naturally infected with UDN. In some cases prednisolone acetate was included in the inoculum. Water temperatures were recorded daily and the time of appearance of the lesions was noted. Passage experiments using extracts of these lesions were carried out.

Notes: Observations on the natural spawning of Alectis indicus (Rüppell) and Caranx ignobilis (Forsk.) were conducted in their natural habitat. Spawning occurred in pairs at daytime between ebbing and flooding tides. The spawning area was a shoal of 35–45 m, located in a deeper channel between two islands. The transparent eggs of C. ignobilis are pelagic.

Notes: The diet of the siluriform fish Bagrus docmac (Forsk.) is described in relation to various localities in Lake Victoria, East Africa. Invertebrates which are the principal food of young fish, but generally of little significance in adults, are particularly poorly represented in fishes from Tanzanian waters and most important in those from the Kavirondo Gulf where the ontogenetic changes in diet differ from those found elsewhere in the Lake. B. docmac starts feeding piscivorously at about 10 cm standard length with the transition from a principally invertebrate to a primarily piscivorous diet occurring at 15 cm S.L. In adult B. docmac fish are found in over 95 % of individuals with food. Haplochromis is the all important food type, and Tilapia, the most valuable commercial fish in the lake, is not preyed upon at all. Bathymetric changes with respect to the invertebrate food are noted, and it is shown that piscivorous feeding occurs mainly by day and invertebrate feeding by night. Quantitative estimates of consumption of Haplochromis by B, docmac are computed from the results of a series of 24 h fishing surveys and found to exceed published data from elsewhere. The formula for the computation of a daily ration is given as Log R=2.973 Log L—3.36089 and it is calculated that the mean annual consumption of Haplochromis by B. docmac is approximately 75% of the mean standing stock of the prey fish, as compared with a commercial catch of about 5% of the mean standing stock.

Notes: The distribution, specificity and pathogenicity of the acanthocephalan Pomphorhynchus laevis (Müller) were studied in the River Avon, Hampshire. The parasite occurred in every fish species, but three categories of hosts could be distinguished. Using growth and maturation as criteria of specificity, only chub Leuciscus cephalus (L.) and barbel Barbus barbus (L.) were recognized as its preferred hosts. Parasites occasionally matured in trout Salmo trutta (L.) and dace Leuciscus leuciscus (L.), but none grew or matured in other host species. Changes in the abundance of P. laevis along the river were related to changes in the abundance of both the intermediate host, Gammarus pulex, and the preferred hosts, and its occurrence in fish to the importance of G. pulex in their diet. In the upper reaches of the River Avon and in other localities populations could be maintained at a low level by parasites maturing in trout, and presence and abundance at any site depended upon the presence and abundance of both intermediate and definitive hosts especially and upon the dietary preferences of the latter. The absence of P. laevis from many parts of Britain is nevertheless still inexplicable. The parasite caused local damage to the intestinal wall of fish, the extent of which varied from species to species, but did not affect host growth rate or cause direct mortality and P. laevis cannot be regarded as an important pathogen in the River Avon or any other British River.

Notes: Ciliary aggregations have been found to occur on the olfactory epithelium of Gadus morhua (L.) and Melanogrammus aeglefinus (L.). The fine structure of ciliary aggregations is constant, consisting of 9 +2 complexes enclosed by a single membrane, though the number of complexes may vary within any ciliary aggregation. It is suggested that ciliary aggregations are motile structures associated with the sensory epithelium and may assist in the circulation of fluid between lamellae.

Notes: Two-hundred and nine fish of 13 species from Laurel Creek, Ontario, were examined for parasites between May and October 1973. Eighty-four species of parasites (22 of Protozoa, 24 of Monogenea, 17 of Digenea, 11 of Cestoda, 4 of Nematoda, 1 of Hirudinea, 1 of glochidia, and 4 of Crustacea) were collected and are listed and discussed.

Notes: The scales of Tilapia mossambica Peters* from Lake Sibaya show clear rings formed by broken, widely-spaced circuli in the anterior field. In order to determine the rate and time of scale ring formation, the number of circuli in the marginal increment was determined. Five scales from the pectoral region of 2223 fishes caught at regular intervals over two years were examined. When plotted as histograms, the number of circuli in the marginal increment showed a sharp movement to the left in September–October and again in January, indicating that the rings were formed during these months in the majority of fish examined. Pre- and postbreeding feeding migrations, and increases in condition factor, were associated with scale ring formation. Otoliths and opercula were also examined for age determination. Annual length increments were calculated for 450 T. mossambica collected throughout the year, and growth curves plotted. T. mossambica from Sibaya reach maturity after one year at a standard length of about 8 cm in females, and after two years at 10 cm in males. The breeding population had a standard length mode of 11–12 cm in females and 17 cm in males. The maximum final size was about 24 cm.

Notes: Data on the migratory behaviour of salmonids were collected at a gauging weir by means of a restivity fish-counter which triggered a motor-driven 35 mm still camera to provide photographic records of passing fish. A clear bimodal seasonal pattern of movement was observed in three consecutive years with peaks during June–August and October–December. Daily variations in the rate of movement could not be correlated with changes in discharge or temperature. Salmonids tended to move at discharges lower than those generally available. This contrasts with other published work and was attributed to the more equitable flow-pattern of chalk rivers. There was no optimal temperature associated with movements. Some evidence suggested that the largest fish moved earlier in the year but this was not marked. In clear water most movement occurred during the hours of darkness but during floods, when the river was turbid, the diurnal pattern tended to be reversed with greatest movement during the hours of daylight. Most fish negotiated the weir close to the bottom, well below mean velocity, and took a central path through the flume. Although analysis of upstream migratory behaviour was hindered by the lack of data on the numbers of fish available below the counting point it was concluded that the basic pattern of migration is established by time (season). Changes in discharge, light intensity and other parameters may then play a secondary role in modifying the details of the pattern but attention is drawn to records of movements in regulated flows where a remarkably constant pattern is shown from year to year.

Notes: Encapsulated fish hooks were found free in the stomachs of Plectropomus maculatus (Bloch). The tissue surrounded only the ferrous part of the hooks which in each case was badly corroded, the brass swivel and plastic sleeve were undamaged. Histological examination showed that the hooks were first surrounded by dense collagen and then by vascularized smooth muscle.

Notes: (1) The Na, K, Ca, Mg concentration of blood serum have been studied in nearly 60 fish species from various waterbodies (the Neva, Lake Dal'nee, the Volga, Lake Baikal, the White Sea, the Black Sea, the Barents Sea etc.). In fishes (Cyprinidae, Percidae, Siluridae etc.) from fresh water (Lake Dal'nee, the Baikal, the Neva) with low 0.18–0.24 mEq/1 Na concentration Na content in blood serum was lower than in closely related species from fresh water (the Volga, Lyutoga River) with larger Na concentration–nearly 0.5–1 mEq 1. Blood serum of marine teleosts Na concentration (156–210 mEq/1) was higher than in migrating and freshwater species (90–174) mEq/1) and it did not depend on seawater salinity: Barents Sea–465, White Sea–255, Black Sea–227 mEq/1.(2) Rather a considerable specific variation of ion concentration was found in blood serum of fishes from different families living in the same water body (Lake Baikal: Cyprinidae 90–95 mEq/1, Percidae 114 mEq/1, Salmonidae 126–129 mEq/1 etc.; the Volga: Siluridae 139 mEq/1, Percidae 142–150 mEq/1, Clupeidae 174 mEq/1).(3) No relation has been detected between K, Ca and Mg concentrations in blood serum of fishes and the concentrations of these ions in the environment.(4) Na concentration in the blood serum of sockeye salmon juveniles (101 mEq/1) migrating seaward was less than in adult fishes (132 mEq/1) returning to the lake to spawn. Na concentration in the blood of non-migrating salmonids (Oncorhynchus nerka adult residual 104 mEq/1, Salvelinus alpinus juvenile 140 mEq/1, adult residual 141 mEq/1) changed insig- nificantly during life history. Notable hypopotassemia was observed in spawning time in Salmonidae.(5) The comparison of blood serum ion concentration in males and females of fishes from different taxonomic groups (Acipenseridae, Salmonidae, Cyprinidae) showed no significant variation.

Notes: This study was undertaken to discern the effects of cortisol and human chorionic gonadotrophin (HCG) on ovulation in ayu, Plecoglossus altivelis (Temminck & Schlegel), with special reference to water and ion changes. Cortisol as well as HCG was very effective in inducing ovulation of ayu. The best response was obtained with 10 mg of cortisol. In combination of cortisol and HCG, the effective dosage of cortisol was less than when cortisol was used singly. In fish which received cortisol and/or HCG, both the gonadosomatic index (GSI) and the percentage increase in body weight were significantly greater when compared to the control. The increase in body weight appeared to be due to an ingestion of water in fish treated with hormone, as described in our previous report. At ovulation there was a high sodium content in the ovary of fish treated with hormone, whereas a low sodium content was seen in the muscle. It appears that the fish imbibes some water resulting in hydration of the oocytes with concurrent ion movement during maturation and ovulation. These results suggest that gonadotrophin and cortisol may exert their initial effect on the oocytes in a direct or indirect manner, possibly acting to affect the sodium transport system or to alter passive permeability of the egg membrane.

Notes: The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated at light intensities of 1, 10, 100 and 1000 lux, using a photographic method of recording activity. The level of swimming activity was high at 1000 and 100 lux, declining to a very low level at 1 lux. It was concluded that this was due to the limiting effect of light on feeding. The threshold light intensity for swimming activity in the tank was estimated as being approximately 20 lux but it was considered that in the area of the sandeel fishing grounds the threshold might be higher than this, in the region of 100 lux. The number of hours light per day above 20 and 100 lux at a depth of 15 m in the area of the Outer Dowsing sandbank (53°30′N, 01°00′E) was estimated for the various months of the year. It was shown that during the winter the light intensity does not normally reach 100 lux and only exceeds 20 lux for a few hours each day. It is suggested that this could limit swimming activity and accessibility at this time of year. Measurements were made of the penetration of light into sand and it was concluded that fish which are buried might be able to detect light, possibly via the pineal gland.

Notes: The behaviour of the lesser sandeel, Ammodytes marinus (Raitt), has been investigated using a photographic method of recording activity. Three main states of activity were recognized: (1) swimming, (2) partially emerged from the sand, or (3) completely buried in the sand. When food was present there was a basic diurnal rhythm of activity; during the dark period most of the fish remained buried in the sand and in the light period they emerged to swim and feed. In the absence of food the level of swimming activity during the light period was extremely low, while the level of partial emergence activity increased. The fish appear to be visual feeders and those which were buried in the sand did not appear to be able to detect the presence of food in the water by means of olfaction. There was usually a low level of partial emergence activity during the dark period, which tended to increase in the few hours before the lights were switched on. The timing of this increase was thought to be related to an internal clock. The basic diurnal rhythm of activity shown in the laboratory experiments is discussed in relation to the marked diurnal variation in the catch of sandeels in the fishery. It is concluded that the failure to catch sandeels at night is due to their remaining buried in the sand.

Notes: One hundred and sixty eight species of parasite are listed from 36 species of freshwater fish from Britain and Ireland, and notes on their distribution are provided. A list of hosts together with the parasites recorded from them is also given. Although almost twice as many species are listed as in the most recent published reference list, the parasite fauna of Britain appears to be considerably poorer in number of species than that of mainland Europe, and that of Ireland poorer still. The distribution of most species, apart from two endemic species and a very few which have clearly been introduced into Britain in recent years from America or the mainland of Europe, appears to show no peculiarities and is probably contiguous with that of their hosts.

Notes: Mummichogs, Fundulus heteroclitus (L.) accumulated Cd 115m (NO3)2 from synthetic seawater solutions during a period of 25 days, but the rate of whole body accumulation decreased with increasing concentrations of stable Cd2+ in the medium. Viscera were the major repository of Cd 115m during uptake, especially gastrointestinal tract and to a lesser extent liver. Loss in whole body radioactivity over a post-treatment interval of 180 days in cadmium-free seawater was about 90%, with gallbladder and especially liver most influential in the excretion processes; this pattern was unchanged by the level of stable Cd2+ present in the medium during uptake. The significance of this and other observations in terms of field monitoring of cadmium utilizing teleosts as indicators is discussed.

Notes: Mirror carp (Cyprinus carpio L.) infected with sublethal doses of Ichthyophthirius multifiliis, were free of parasites 21 days after infection. Fish remained free of parasites for at least 8 months when maintained in an infective environment. Such fish were refractory to reinfection with numbers of parasites that killed all normal, previously unexposed fish. Serum from fish recovered from previous infections with sublethal doses of parasites, immobilized free-swimming stages of I. multifiliis to a dilution of up to 1: 1024. The rise in serum-immobilization titre occurred between the 10th and 22nd days of infection, the period during which parasites disappeared from the body surface of the fish. Infective stages of the parasite were unable to penetrate the mucus body covering of resistant fish.

Notes: A brood stock of Fundulus heteroclitus (Walbaum) minnows was established at theJohnson Space Center in Houston, Texas. By use of the aquarium maintenance systemdescribed in this report the fish were induced to produce fertile eggs throughout the year.Additional data is presented to confirm that F. heteroclitus found in the vicinity of Beaufort, North Carolina produce eggs which lack chorionic fibrils, making them especially suitablefor use in embryo development studies.

Notes: Measurements were made of urine flow rates and haematocrit of rainbow trout exposed to hypoxic conditions (3 mg O2/1) for 3, 4, 5 or 24 h. Elevated urine flow rates during short time exposure and concomitant increased haematocrit, followed by lower than normal urine flow rates on return to normal aerated water, suggest that haemoconcentration is the initial response to anoxia. Results from longer exposure to hypoxic conditions suggest that the initial period of haemoconcentration is followed by a period of water retention and a return of the blood volume to normal; the sustained elevated haematocrit is thought to be derived from release of erythrocytes from storage organs. During prolonged exposure rainbow trout also become more permeable to water.

Notes: The River Sirhowy, a trout river of the Ebbw System in south-east Wales still subject to sporadically high levels of suspended solids derived from the coal mining industry, was investigated over a three year period to assess its importance in the recolonization of a fishless river, the Ebbw Fawr, which is expected to recover from the effects of steelworks effluents discharged near its headwaters. Eight species of fish were recorded. Spawning areas for brown trout (Salmo trutta L.) were limited by industrial and urban developments and the discharge of suspended solids. Small numbers of native trout were produced in the system and the growth of these fish was poor in the main river, confirming the need for regular stocking. Movements of stocked trout were limited except in the lower reaches of the river where the presence of a native population, high levels of suspended solids and flash floods may have increased the numbers of fish moving into the recovering Ebbw Fawr.

Notes: The plasma proteins of L. umbratus and L. capensis have been investigated by means of cellulose-acetate and polyacrylamide gel electrophoresis. Characteristic patterns were obtained for each specie although variations occur within a certain basic framework. Certain fractions were further isolated and approximate average molecular weights were found to vary between 55 000 and above 120 000 and isoelectric points between 5.78 and 4.2. Certain fractions were found to exist in dimeric form. It is concluded that the application of the human nomenclature to fish plasma protein fractions is of dubious value and that the fish fractions can only be classified after thorough biochemical investigation.

Notes: The reproductive cycle of Mormyrus kannume Forsk. was studied for one year, at two locations near the equator in Lake Victoria. Samples taken on a typical feeding-ground indicate that the species is monoestrous; ripe specimens being found from November to January, maturation taking place gradually over the remaining nine months of the year. Samples taken at a typical spawning-ground, however, contain ripe fish over a prolonged period, from October to May and possibly June, and the period available for maturation is correspondingly short. The difference in the reproductive cycles at the two localities appears to be the result of successive waves of immigration to the spawning ground by different populations within the lake, each having a 12-month annual cycle, but not in phase with each other.

Notes: Electrophoresis of haemoglobin in single erythrocytes of Labeo umbratus and Labeo capensis showed that haemoglobin behaved in three distinct ways in both species. The majority of cells contained haemoglobin which moved as a broad band towards the anode. In a few cells haemoglobin moved towards both the anode and the cathode and in even fewer cells, haemoglobin moved as a sharp band to either the cathode or anode. These results are discussed in relation to other observations.

Notes: The population structure and growth rate of Rhabdosargus holubi (Steindachner) in the closed West Kleinemond estuary in south east Africa, from 1971–973, are described. Juvenile R. holubi invade the estuary at a length of 1–2 cm but migrate back to the sea at a length of about 14 cm without attaining maturity in the estuary. Adult R. holubi are rarely encountered in estuaries. The annual growth increment of O group R. holubi was 6 cm, almost all occurring in summer. The growth of Lithognathus lithognathus (Cuvier) was also measured in the same closed estuary and O group fish of this species also grew 6 cm per annum although 1 + fish grew 8 cm per annum.

Notes: The haemoglobins and globins of the roach, Rutilus rutilus (L.) and the rudd, Scardinius erythrophthalmus (L.) have been studied by starch gel electrophoresis. At all stages of development studied, the roach and rudd haemoglobins give a similar electrophoretic pattern, the young fish of about 2 cm standard length possessing three separate haemoglobins, of which two bands only persist in the adult. The evolutionary significance of multiple haemoglobins in fishes is briefly discussed.

Notes: The pelagic larval stages and the demersal O-group stage of plaice were sampled in the immediate vicinity of Filey Bay, Yorkshire (54°12′N, 00°16′W), using a modified Gulf V high-speed plankton sampler and beam trawls. The distribution and movements of these fish were studied from the time of first settlement in May through the period of metamorphosis and the O-group stage. It was found that the larvae settled in water deeper than 5 m and moved into shallow water following metamorphosis. This established a typical distribution of larger fish in shallower water than the smaller fish. When the fish grew over 40 mm they moved out again into deeper water which leads to a reversal of the lengthdepth distribution. Further movements during the winter months and of the I-group fish were studied by tagging. It was found that emigration from the nursery ground did not occur until the I-group stage.

Notes: Young fry of salmon were distinguished from those of trout using electrophoresis of whole fry extracts on cellulose acetate sheets. The separation patterns were revealed by general protein staining. The method was found helpful in resolving the mixed salmon and trout fry of an upland stream.

Notes: Immature specimens of Opechona sp. are described from the stomach, pyloric caeca and intestine of larval and O-group haddock, Melanogrammus aeglefinus (L.), taken in the northern North Sea and to the west of Scotland. This appears to be a new host record and possible sources of infection are discussed, together with the occurrence of this normally intestinal parasite in the stomach. It is suggested that these infections may be worth taking into account when considering possible factors contributing to mortalities of haddock and other teleost larvae.

Notes: The annual reproductive cycle of the catfish, H. fossilis (Bloch) is divided into the preparatory period (February-April), the prespawning period (May-June), the spawning period (July-August) and the postspawning period (September-January). During the early postspawning period (September-November), the hypothalamo-hypophyseal-ovarian system shows a gradual regression. In January, the hypothalamic nuclei, the pars magnocellularis (PMC), the pars parvocellularis (PPC) of the nucleus preopticus (NPO), and the nucleus lateralis tuberis (NLT) show renewed activity, as shown by a significant increase in their nuclear diameters and an accumulation of neurosecretory material (NSM) in their cell bodies. The hypophysis and the ovary remain quiescent. During the preparatory period, all the hypothalamic neurons studied indicate decreased activity but simultaneously show an accumulation of NSM in their cell bodies. The number of granulated basophils in the proximal pars distalis (PPD) of the hypophysis remains low but ovarian weights increase, presumably due to the multiplication of oogonia. In the prespawning period, there is a marked accumulation of NSM in the cell bodies of the hypothalamic neurons and at the same time the number of granulated basophils in the PPD of the hypophysis dramatically increases with concomitant increase in vitellogenic activity in the ovary. During the spawning period, the hypothalamic neurons continue to store NSM in their cell bodies and simultaneously there is a tremendous increase in the number of granulated basophils in the PPD of the hypophysis and the ovary has a large proportion of yolky primary oocytes. Spawning is associated with a significant degranulation of the granulated basophils in the PPD of the hypophysis. The significance of the results is discussed in relation to the environmental and hormonal regulation of seasonal ovarian activity.

Notes: The mucus of the trout and char was found to contain only one sialic acid, n-acetyl neuraminic acid (NANA). The concentration of NANA in the epidermis is directly proportional to the mucous cell concentration. In both species the highest concentration of mucous cells occurs on the anterior regions of the body and there are significantly fewer cells on the fins. These findings are discussed in the light of our knowledge of the functions of fish mucus.

Notes: The numbers of adult trout in Loch Leven were estimated in April each year 1968–71 by tagging fish caught by seine net, and estimating the proportion of the total stock tagged from examination of the angling catch during June-August. The vulnerability of tagged fish before June and after August was higher than that of untagged fish. Tag losses, estimated by double marking, were 2.15 % over a whole angling season. The reporting rate of tag recaptures varied within and between years from 0.43 to 0.71. Differential mortality of tagged and untagged fish was unimportant, except in two subsidiary experiments when fish were tagged in June and August, when handling losses reached 2.7%. With adjustment for these measured errors, the stock of trout beginning their third or more years in the loch in April, fell from 126 665 in 1968 to 52 337 in 1971.

Notes: Some observations on the biology of Mastacembelus armatus (Lacepède) from Muzaffarnagar (U.P., India) have been made during the period July 1966 to June 1969. At a particular stage of maturity of the fish there is a close relationship between the gonad weight and the body weight which helps in determining the breeding period of the fish. Both male and female fishes mature simultaneously. The gonad weight influences the relative condition, while the visceral weight does not exert any significant effect on it. The development of the female gonads greatly affect the curve of relative condition, more than the development of male gonads, though the curve for male fish also shows a steady rise and fall in the seasonal variations of the relative condition. Seasonal fluctuations in relative condition correspond to its spawning season. In M. armatus, the presence of two peaks in the curve confirm two breeding seasons. The present studies have also elucidated to a certain extent the important aspect of the maturation and spawning habits of M. armatus in North India. The fish has two breeding seasons of short duration during June and July and again in November. The mature ovaries of each season contain slight maturing ova of next season along with mature ova of the present season. The entire stock of ova measuring 0.16 mm and above are shed during spawning.

Notes: The age of perch. Perca fluviatilis L. was determined from the annual bands laid down on the opercular bone. Year class monthly mean lengths were based on this ageing. The opercular bones have also been used for back-calculating growth. It was found that back-calculated mean lengths per age were similar to those calculated by direct measurement. There was little difference in growth between the sexes for the first 2 or 3 years of life. The investigation was too short for a correlation to be found between growth increments and degree days above 14°C although Slapton Ley was found to be warm in comparison to other British waters and the perch grew fast. Ford-Walford plots gave L∞= 22.0 cm for males and L∞= 25.0 cm for females. In length-weight relationships, fry and immature females were homogeneous between their monthly subgroups, and fry obeyed the cube law throughout. Mature males and females were heterogeneous between monthly subgroups. Growth has been expressed in weight form and instantaneous growth rates are given. These rates are higher for fry than older fish. Condition was closely related to gonad development in mature fish. Condition fell sharply after spawning and then rose rapidly in May and June. A sudden drop in condition was noted in males during August which cannot be fully explained.

Notes: The population dynamics and production of Daphnia hyaiina^ the dominant cladoceran i n Eglwys Nynydd, a shallow eutrophic reservoir in South Wales, were studied for 2 years against a background of limnological measurements. The appearance and development of successive generations from egg to adult could be followed from changing numbers in arbitrarily defined size classes. Seasonal variations in mean length, mean brood-size and proportion of gravid adults were recorded and mean brood-size was related to changing food and temperature conditions. Egg-development times for D. hyaiina were determined in culture and the population parameters finite birth (S), instantaneous birth (b′), instantaneous population change (r′), instantaneous death (d′) and finite death rates (D) were estimated from field data. Turnover and production estimates were calculated from finite death rates and biomass. The calculated potential rate of increase (b′) was nearly always greater than the observed rate of increase (r′): seasonal changes in death rate (d′) generally parallel changes in birth rate (b′) but remain somewhat out of phase. Population oscillations are probably due t o a delay in the expression of the effects of population density upon birth and death rates.The mean biomass of Daphnia in 1970 was 0-57 mg dry wt/l (0-88 g C/m2) and in 1971 0-32 mg dry wt/l (0.49 g C/m2). Annual production for Daphnia was 11-8 mg dry wt/l (18-2 g C/m2) in 1970 and 8-30 mg dry wt/l (12 8 g C/m2) in 1971. Information available on primary production in the reservoir suggests that the production of Daphnia accounts for less than 2% of gross primary production. However, the pattern of population growth of Daphnia in Eglwys Nynydd almost certainly reflects a food limited system. In summer, blue-green algae may be abundant but serve as a poor food source: throughout the blue-green bloom egg production remains low, at times remaining below 0-5 eggs/adult.

Notes: The development and use of an improved automatic system for the accurate measurement of dissolved organic carbon (D.O.C.) in fresh waters is described. The method, which covers the range 0-25 mgl−1 D.O.C., is based on the oxidation of organic carbon to carbon dioxide by U.V. radiation. The carbon dioxide produced is measured by a non dispersive infra-red gas analyser (I.R.G.A.). The I.R.G.A. is also used in the semi-automatic measurement of particulate organic carbon (P.O.C.) by a combustion method which allows very low concentrations to be measured using samples of 200 ml or less.Results of surveys of two river systems indicate that D.O.C. concentrations of less than 2.0 mg l−1 are typical in unpolluted chalk streams. D.O.C. concentrations of streams draining acid heathland were found to be significantly higher (3-5.5 mg l−1).D.O.C. concentration was found to increase rapidly during a spate, in a river draining areas of mixed underlying geology. The throughput of D.O.C. during the twenty-five to fifty spates which occur annually in the river could amount to 20-30% of the annual flux of D.O.C.P.O.C. concentration in chalk spring waters (0.03–0.04 mg l−1) were found to be higher than expected from preliminary estimates using membrane filtration techniques.The relevance of the measurement of D.O.C. and P.O.C. flux to estimates of the energy budgets of stream ecosystems is discussed and published methods for the automatic measurement of D.O.C. are reviewed.

Notes: (1) Chaoborus anomalus and Chaoborus ceratopogones were found together throughout the year in Lake George, Uganda, the larvae forming 65-85% by number of the macro-benthos of the central lake area.(2) First and second instar larvae were wholly planktonic and third and fourth instar larvae mainly benthic during the day, migrating into the water column at night. A proportion of the third and fourth instar larvae were found in the water column during the day in the centre of the lake where light attenuation was greatest. C. anomalus showed a greater tendency to be benthic than C. ceratopogones.(3) Planktonic larvae were distributed in dense patches thought to be cohorts resulting from oviposition by swarms of adult females. The maximum density of planktonic larvae recorded was 31.7 × 102/m2 column. Third and fourth instar larvae were more evenly distributed in the benthos of the central lake area, the maximum density recorded was 79.9×102/m2.(4) First and second instar larvae occurred mainly in the inshore regions, very few were found in the centre of the lake. Oviposition is likely to take place inshore. The patches of planktonic larvae were not stationary. Dispersal of larvae away from the shore may be active or may result from complex oscillations of the water mass produced by storms. In C. ceratopogones the floating egg batches could he carried away from the north shore by currents produced by inflows and prevailing winds.(5) Adults of C. ceratopogones were more numerous during the rainy seasons than during the dry seasons. A similar, though less marked seasonality was found in the occurrence of C. anomalus adults. The biomass of benthic larvae of C. ceratopo-gones was estimated at 387.0 mg C/m2 in the dry season, June 1970, and 130 0 mg C/m2 in the rainy season, October 1970. That of C. anomalus was constant at 241.7 and 254.3 mg C/m2 in June and October, 1970 respectively.(6) No difference was found in the horizontal distribution of the larvae, or in the size and weight attained by the various stages.(7) Interspecific differences were found in the mean number of eggs per adult female (309, C. anomalus and 224, C. ceratopogones); in the nature ofthe egg batches; n i the morphology of the larval mouthparts and pharyngeal sphincters, as well as i n the vertical distribution of the larvae and seasonal occurrence of the adults. On the basis of these differences the co-existing species are thought not to be competing for the same resources.

Notes: Forty-three species of Plecoptera were collected from emergence traps in an Oregon woodland stream. Adults occurred during every month of the year, but the largest numbers and most species emerged from April to June. Temporal separation of con-generic species occurred within the suborder of Filipalpia, but not in Setipalpia. Some species of Nemoura had split emergence periods.The onset of emergence for a species from year to year generally varied by less than 2 weeks. Peak emergence occurred at least 1-2 weeks after the start ofthe emergence period.

Notes: Behaviour of Brachycentrus americanus was observed in a simulated stream in the laboratory every 2 h for 7 days in January, and in Lawrence Creek, Wisconsin, every half hour for 2 days in May. In the field, animals, algae, and detritus in the drift were sampled every half hour with an 800-μm and a 60-μm mesh net.The primary mutually-exclusive behavioural units were filtering, case building, and withdrawn when the larvae had their cases attached to the substrate, and crawling and holding when cases were not attached. Diel changes in behaviour were similar i n the laboratory and field. Almost 100% of the animals were filtering at night, whereas only about 60% were during day. Withdrawn, case building and unattached activities occurred more frequently during the day. While only 0-5% of the laboratory animals were unattached during the day, in Lawrence Creek 10-20% were unattached at that time and many moved across the substrate and grazed. Drifting, which was acyclic, did not correlate closely with the diurnal increase in unattached activity.Available drifting food in both nets increased markedly following rain. In the absence of rain, dry weight of detritus from the 800-μm net increased at night. Changes i n timing and method of feeding are discussed relative to gut contents, morphological adaptations, and energy expenditure of B. americanus, and to food availability.

Notes: Books Reviewed in this Article: Clark, R. B. and Wootton, R. J. (1972) (Eds.). Essays in Hydrobiology presented to Leslie Harvey.

Notes: Larvae of three species of the genus Hydropsyche with distribution patterns indicating they are associated with increasing ranges of flow rate and temperature in the sequence H. instahilis, H. pelhicidula, H. angustipennis, were selected for study. Experiments on frequency of ventilatory movements indicated that the larvae were increasingly tolerant to dissolved oxygen concentration, flow rate and temperature in the same sequence of species. Experiments on net-spinning indicated a corresponding order of preference for higher temperatures and a general preference for higher flow rates. During experiments on net-spinning the number of larval casualties, ascribed to encounters between individuals, showed marked contrasts between species. The significance ofthe behaviour ofthe larvae under experimental conditions is discussed with reference to their distribution in the field.

Notes: The relationship of total body length to formalin dry weight for individuals of Thermo-cyclops hyalinus and Mesocyclops leuckarti, from the tropical Lake George, Uganda, is given and shows that previous estimates of individual biomass and, therefore, of zooplankton standing crop and production based on them, were too high. The annual mean standing crop of total Crustacea, in 1969–70 was 828 mg (dw) m−2 and for T. hyalinus, the dominant species, 559 mg (dw) m−2 Biomass tended to be higher in the mid-lake area than inshore. The annual mean production of T. hyalinus is now estimated to be 44 mg (dw) m−2 day.