ALBERT

Description: A model is presented which tests the representation of the maturity process in terms of gonadosomatic indices (GSI) in chokka squid Loligo vulgaris reynaudii. It assumes that the true maturation process is reflected by the results of histological investigation, which cannot be used in large-scale ecological work in the field. However, the maturity scales used in ecological studies define some morphological categories which can be linked directly to microscopic development. Therefore, the overlap of GSI ranges for each morphological maturity category may be used to judge how well the GSIs represent the histological stages. Results have shown that the overlap is large and that GSI cannot be recommended as adequately reflecting the maturation process in squid. A morphological scale of maturity with possible broad applications in exploited families of squid is proposed as a better representation of the maturation process than GSI.

Description: Morphological differences between paralarvae of two loliginid squid species common in southern African waters (Loligo vulgaris reynaudii and Lolliguncula mercatoris) are described. The differences are: Loligo — "cheek patches" consisting of four dark chromatophores, nine large dark dorsal chromatophores on the mantle, tentacular clubs broad and much wider than tentacle stalks, proximal row of three club suckers with others tetraserial, suckers large enough to appear crowded on the club surface; Lolliguncula — "cheek patches" with three dark chromatophores, two pairs of" large, dark dorsal chromatophores on the mantle, tentacular clubs narrow, proximal club suckers arranged in three pairs, suckers small, not particularly crowded. Relationships with other myopsids are briefly discussed.

Description: The mean pressures required to collapse gas vesicles in turgid cells of cyanobacteria from the Baltic Sea were 0·91 MPa (9·1 bar) in Aphanizomenon flos-aquae, 0·83 MPa in Nodularia sp. collected from the main deep basins and 0·34 MPa in Nodularia from shallower coastal regions. The gas vesicles were strong enough to withstand the depth of winter mixing, down to the permanent halocline (60 m in the Bornholm Sea, 90 m in the Eastern Gotland Sea) or to the sea bottom (30 m or less in the shallow Arkona Sea and Mecklenburg Bight). The cyanobacteria had low cell turgor pressures, within the range 0·08–0·18 MPa. The colonies were highly buoyant: the Aphanizomenon colonies floated up at a mean velocity of 22 m per day and the Nodularia colonies at 36 m per day. The colonies remained floating when up to half of the gas vesicles had been collapsed. In summer the cyanobacteria were mostly restricted to the water above the thermocline and in calm conditions their concentration increased towards the top of the water column. A series of colony concentration profiles indicated that, following a deep mixing event, the population of colonies moved upward with a net velocity of 22 m per day, similar to the colony floating velocity. This demonstrated that the buoyancy provided by gas vesicles would give a selective advantage to populations of cyanobacteria by enabling them to float into the higher irradiance of the near-surface water.

Description: In this study the antifouling activity was investigated of a series of chemically related, halogenated furanones isolated from Delisea pulchra (Greville) Montagne, a red alga which is rarely fouled in the field. The metabolites were tested in laboratory assays against representatives of the three major groups of fouling organisms, the barnacle Baianus amphitrite amphitirite Darwin, the macroalga Ulva lactuca Linnaeus and a marine bacterium (strain SW 8). Settlement of barnacle cyprid larvae was strongly inhibited, with an EC50 of 〈 25 ng·mr1 (25 ppb) for some compounds. The settlement and growth of algal gametes was also strongly inhibited, in some cases at concentrations as low as 25 ng·cm-2 • Growth of the marine bacterium SW8 was inhibited more strongly than by the common antibiotic gentamicin. Overall, activity of the D. pulchra metabolites was comparable to that of the heavy metals and biocides currently used in antifouling paints. However, no single compound was most active in all tests and some metabolites effective against one organism showed Iittle or no activity a·gainst the others. The high but variable level of activity of the D. pulchra metabolites, coupled with their small size, relative stability, and ability tobe synthesized suggest their potential use as active ingredients in antifouling coatings.

Description: Simulations with an ocean general circulation model and a hybrid coupled model reproduce well the observed principal spatial mode (PSM) of variation of the tropical Pacific ocean/atmosphere system. The model results show the origins of the PSM to be a coupled ocean/atmosphere mode and suggest this phenomenon is not a natural mode of the tropical Pacific Basin alone. Air-sea interactions amplify the mode variability by a factor of 5–6 over the strength it would have in a purely random atmosphere and so it obtains climatological importance. These same interactions introduce the PSM to the atmosphere. The PSM of interannual variability is not directly driven by the annual cycle. But its time scale does depend importantly on the fact that the ocean-atmosphere coupling strength varies with respect to the annual cycle. The mode appears to be rather sharply peaked in wave number space but broadbanded in frequency space so that identifying it with a temporal designator, as has been done in the past is apt to be misleading.

Description: Megafauna on bioherms (large biological structures) of the scleractinian coral Lophelia pertusa at 240-290 m depth in the Haltenbanken- Fmyabanken area was investigated by video-recording. Sixteen transects from soft bottom with scattered patches of stones below bioherms to top of bioherms were analysed. Fauna patterns were related to the near-bottom currents. The orientation of the gorgonianParamuricea placomus was used as an indicator of the direction of the main currents at the bioherms. The bioherms were 2 to 31 m high, and had a basal area ranging from 1 500 to 50 600 m2. 36 taxa were identified, of which five taxa only occurred on the bioherms, and five only on the soft bottom with scattered stones. The diversity, H', was highest in the zone of dead Lophelia, and lowest on the silty clay. None of the 26 taxa observed on stones were spesific for this habitat, but occurred also on the bioherms or the soft bottom. The area with Lophelia rubble, near the basis of the bioherms, had the lowest number of taxa (15), but the highest average density of individuals (7.92 ind./1Om2). Different sponges, gorgonians (Paragorgia arborea, Paramuricea placomus, Primnoa resedaeformis), squat lobsters (Munida sarsi), redfish (Sebastes spp.) and saithe (Pollachius virens) dominated in terms of individuals per area. Diversity, density of sponges and density of gorgonians were highest on the down-current side of the bioherms. Saithe were observed with highest densities near the basis of the bioherms, on the up-current side, while redfish had highest densities on the parallel-current side of the bioherm top. These results indicate that near bottom currents and turbulence are factors affecting the fauna on Lophelia bioherms.

Description: There have traditionally been strong ties between physiology and ecology and between ecology and systematics. Although the connection between physiology and systematics has not been adequately realized, there are important reasons to strengthen it. Much of physiology has been based on the comparative method, which implies a knowledge of evolutionary relationships. Systematics, on the other hand, relies on the distribution of characteristics among groups of organisms, and should include characteristics of their lifestyles, including performance. Lifestyle characteristics, which are studied by physiologists, ecologists, or behavioral scientists, may be comparatively recent adaptations or may be constrained by evolution similarly to the morphological characters traditionally studied by systematists. Working together, these disciplines can provide better explanations of adaptations and evolutionary constraints about which not much is known for the great majority of cephalopod taxa.

Description: The morphological and physiological adaptations that the cephalopod sensory organs and nervous system underwent during the course of evolution are briefly summarized. Special emphasis is paid (i) to the vertebrate‐like lens eyes with their complex extraocular eye muscle system, (ii) to the vestibular analogue statocysts with hair cell receptor systems for linear and angular accelerations and an elaborate afferent and efferent nerve supply, (iii) to the epidermal head and arm lines which are analogous to, and as sensitive as, the lateral lines of fishes and aquatic amphibians, (iv) to the giant fibre system for escape jetting, and (v) to the highly centralized brain which is capable of different forms of learning and memory.

Description: Statolith microstructure was studied in eight specimens of the boreal sepiolid Rossia pacifica (mantle length ranging from 45to 90mm) caught on the continental slope of Northwest Bering Sea. Growth increments were presented in all ground statoliths and were narrow and uniform width (average 3.2 - 3.3µm). They were grouped into inner opaque and outer translucent growth zones. The total number of growth increments within the statoliths of mature males (75-78) was lower than of mature females (95-117 increments). Assuming growth increments to be laid down daily, the life span from hatching to death of R. pacifica in the Bering Sea may be 4-5 months.

Description: The distribution and abundance of six species of Sepia and one of Rossia were studied during six west coast and three south coast bottom trawl surveys off South Africa. The two most common species on both coasts were Sepia australis and S. hieronis. Both were most abundant on the northern West Coast (Orange River and Port Nolloth areas) and were sparsely ditributed over the rest of the region. The depths of greatest abundance were 60-190m (S. australis) and 110-250m (S. hieronis). The highest biomass indices were recorded on the species also peaked in May 1988 on the South Coast (803 tons). The environmental factors most influencial in the distribution of the two species were bottom oxygen concentrations between 1,5 and 3,5ml-l-1. The two species were most abundant at relatively low temperatures: on the West Coast catches peaked when the S. simoniana and S. typica) are usually found in shallow water (〈100m), mainly on the South Coast. Rossia enigmatica, a sepiolid, is most abundant in 400-500m of water, generally on the West Coast.

Description: A new type of epibenthic sledge is presented, which possesses an additional supranet above the epinet. Both nets are closed by an opening/closing device in the water column. The new construction allows a selective catch ofhigher suprafauna, which swims 1–1.33m above the seafloor, and a good discrimination between real suprafauna and epifauna. In total, 79581 Peracarida were sampled at 8 stations at about 75°N and 12°W, off Greenland. Of these, Isopoda were usually the most abundant group in the epinet, Amphipoda in the supranet. At the stations where suprafauna was abundant, the numbers of Mysidacea were usually higher in the epinet than in the supranet, probably due to differences in food supply, i.e. the enrichment of food in the benthic boundary layer.

Description: Observations of the dinoflagellate Dinophysis norvegica in the Baltic Sea during the summers of 1991–1993 indicate that maximal abundances (c 40–150 × 103 cells l-1) were found at the thermocline, typically at 12°C. Maximum densities were usually between 12 and 15 m where 2·9% and 1·5% of surface photon irradiances, respectively, were measured. No diel vertical migration was observed, and cell densities in the mixed layer were always low. Photosynthesis versus irradiance measurements with an oxygen electrode indicated that these populations had a P max of 2·47 [coefficient of variation (CV) 7·3%] and 3·4 (CV 4·7%) mg O2 mg Chl a -1 h-1, and compensation values of photon irradiance were 16·5 and 83 μmol m-2 s-1 in 1992 and 1993, respectively. Both oxygen electrode and 14C light/dark bottle measurements indicated that D. norvegica had very little net photosynthesis at the depths where it was most abundant; it would have had about 2·5-fold greater capacity at photon irradiances present closer to the surface. Calculated carbon doubling times via photosynthesis averaged 4–11 months. There was no observable diel rhythym of DNA synthesis, suggesting that either D. norvegica was not dividing synchronously (asynchronous division is common in heterotrophs) or not dividing at all. Electron microscopy did not reveal the presence of food vacuoles, but feeding and digestion could have been extracellular. The data suggest that this species is a mixotroph which received its primary nutrition via heterotrophic means during our observation periods in the summers of 1991–1993.

Description: Larvae of Siboglinum poseidoni were reared in the laboratory. About 6 weeks after recovery from the central Skagerrak the larvae develop a small tentacular bud. On the opposite side a stomodaeum is formed. Electron microscopy of suitable sections shortly in front of the tentacular bud reveals a ciliated opening and tract. In the trunk this tract is reduced to a small tube by bulging endoderm cells containing large amounts of yolk. The lumen is obscured by densely packed cilia. In more advanced stages extracellular symbiotic bacteria occur within this transient digestive tract. They appear to be taken in via the transient mouth. As development progresses the mouth and ciliated foregut close. In the trunk of adult specimens the space between the dorsal and the ventral vessel is occupied by bacteriocytes forming the trophosome. The lumen ofthe digestive tract is reduced to small ciliated spaces. The tentacle develops opposite to the transient mouth and hence dorsally, while the main nerve trunk is ventral. More advanced larval stages closely resemble an elongated annelidian metatrochophora. A relationship between Vestimentifera (Obturata) and Pogonophora (Perviata) is confirmed and the placement of both groups within the phylum Annelida suggested.