ALBERT

Notes: Defined media are described that support 14-20 h generation times for Acanthamoeba castellanii and A. rhysodes in monolayer cultures. the media differ in minor ways from previously described media, but the growth rates are greatly improved over previously reported values. Maximum growth rates were observed for A, castellanii in a complex medium containing 21 amino acids, but near-maximum rates could be achieved in relatively simple media containing 9 amino acids. Growth occurred with 6 amino acids, as reported by others, but generation times exceeded 30 h. Amitosis was a common problem during early subcultures in defined media, but became infrequent after repeated transfers. Synchronous encystment resulting in 70-80% cyst formation could be induced in the defined media by glucose and acetate starvation. the rate of encystment varied with cell density at the time of starvation and was optimal at initial densities of 400-800 amebae/mm2.

Notes: Herbage dry-matter yields of sown plots of white clover were greatly reduced by a natural infection of clover rot (Sclerotinia trifoliorum), the extent of the reduction being related to the level of infection. Examination of seasonal yield patterns suggested that although the plants apparently recovered from the disease it re-exerted its influence later in the season. No effects on seed yield could be detected but effects on the development of inflorescences and the proportion of ripe heads surviving to harvest were noted. Marked differences between varietal types existed for some of the characters examined.

Notes: Historical records demonstrate that the Lake of Tunis, Tunisia, was an open bay that became separated from the Mediterranean by an accreting barrier spit, forming a lagoon. Closure of the lagoon was caused by increased sedimentation as a consequence of Roman deforestation of the Medjerda River drainage basin to the north and subsequent accelerated longshore transport. The separation of the lagoon from the Mediterranean was completed in the early 1500s. At present, the 48 km2 lagoon averages less than 1 m in depth and reaches eutrophic conditions in the late summer. Consistent with the historical records, the lagoon sedimentary column shows three distinct successive environments of deposition: (1) an arid continental environment; (2) an open marine bay; and (3) the present brackish to hypersaline lagoon. These depositional environments are represented by the lower grey layer, which is less than 0-5 m thick, the middle olive-grey layer, which varies from 1 to 5 m in thickness, and the upper black layer, which is 1 m thick. All of the strata are predominantly silt plus clay, but usually contain at least 10% sand. The lower grey layer consists of pitted quartz sand, with very few abraded, broken molluscan fragments and benthic foraminifera with thick tests. An arid, subaerial depositional environment of latest Pleistocene time best explains these sediment and fossil assemblages. In the middle olive-grey layer, coral, coralline algae, open marine graeses and the dominance of foraminifera over ostracods (expressed as a low percentage of ostracods/ostracods plus foraminifera) attest to a depositional environment of an open marine bay. A sharp increase in the percentage of ostracods/ostracods plus foraminifera and organic carbon from the middle olive-grey layer to the upper black layer signifies a major change in depositional environment. The predominance of ostracods over foraminifera, abundance of gastropods characteristic of eutrophic conditions, high organic carbon content and absence of macro-fossils characteristic of open marine conditions clearly indicate that the upper black layer was deposited in a brackish to hypersaline, eutrophic lagoon which has persisted to the present. Seismic records indicate a karstic bedrock surface underlying the lagoon. The surface is marked by considerable relief, and shows a linear depression which may represent an early sixteenth century ship canal. Heavy metal analyses of total samples in five cores demonstrate that Mn and Fe vary randomly, and are apparently derived from natural sources only. Cd, Cr, Pb, Cu and Zn are typically highest in the uppermost unit, which reflects levels of human contamination since closure of the lagoon.

Notes: 17β-oestradiol, testosterone, 11 -ketotestosterone and calcium were measured in plasma of female rainbow trout over the course of a single spawning season. The patterns of rise and fall of the levels of 17β-oestradiol and calcium during sexual maturation were similar to those demonstrated by other workers. Very high levels of testosterone were found in plasma of sexually mature fish—mean level 211 ng ml-1 in November and 115 ng ml-1 in January. Ovulation occurred from December to February.

Notes: Measurements were made of plasma 11-ketotestosterone and testosterone in control and sex-reversed male rainbow trout, before and during their first spawning season (winter 1978/1979). Plasma concentrations of both androgens (in both groups) were 2–3 ng ml-1 in January 1978 (apart from some precocious spawners), rose slowly to 9–11 ng ml-1 in April and July and then increased rapidly to 100–150 ng ml-1 in November. From this time, testosterone levels declined but those of 11-ketotestosterone continued to rise to a peak of 260 ng ml-1 in February 1979. No significant differences in hormone levels were found between control male and masculinized female fish.

Notes: A study of the epideictic behaviour patterns of male Xiphophorus helleri Heckel was made, and the social rank of individual fish in 12 groups of three was assessed over a ten-day period. Straight-line hierarchies were established in most groups. An anatomical study was made to locate the adrenocortical tissue, and the adrenocortical activity of each fish was assessed by measuring mean nuclear diameter of 25 adrenocortical cells. Although results were somewhat variable, the highest-ranking fish in 7 out of 12 groups showed the least adrenocortical activity. The remaining two fish showed no significant difference from each other in adrenocortical activity, though their rank was in most cases clearly distinguishable on behavioural grounds.

Notes: Several aspects of salmonid sperm have been critically reviewed: structure, density, volume, chemical composition, metabolism, fertilisation techniques, motility, dilution, activation, storage at temperatures above and below 0deg; C and cryopreservation.

Notes: A direct comparison of plasma cortisol levels and mean nuclear diameter of adrenocortical cells in the same fish was carried out, to determine whether nuclear diameter could be used as a valid criterion of adrenocortical activity in Coregonus lavaretus (L.). Specimens were caught and killed by a variety of methods and at different seasons, providing a range of plasma cortisol concentrations, which were measured by gas-liquid chromatography. The head-kidneys of the same fish were immediately fixed and the diameters of 20 adrenocortical cell nuclei measured in 7 μm sections of each, prepared by strictly standardized methods. The correlation coefficient was 0·54, so that nuclear diameter cannot be regarded as an accurate criterion of adrenocortical activity.