A new species of Hymenomonas Stein, Hymenomonas lacuna sp.nov. from San Juan Island, Washington, U.S.A. is described using light and electron microscope techniques. The cells normally occur in non-motile clumps growing on the sides of the culture vessel. Each cell has a body covering composed of a single layer of coccoliths of unusual construction and several layers of circular unmineralized rimless scales. Occasional small elliptical scales are sometimes found.

The general cytology of the cells is discussed with special attention paid to the unusual pyrenoid and the role of the Golgi body in scale and coccolith production.

The relationship of this species to H. roseola Stein is discussed.

Population growth and concentration factors for 65Zn and 137Cs have been measured for Achnanthes brevipes Agardh, Carteria sp. Diesing, Chlamydomonas sp. Ehrenberg, Dunaliella salina Teod., Nannochloris atotnus Butcher, and Phaeodactylum tricornutum Lewin subjected to factorial combinations of eight temperatures (6–40 °C) and ten salinities (3.5–44.0 p.p.t.). Regression coefficients were calculated for polynomial models describing response surfaces for growth and radionuclide concentration. Salinity was more important than temperature in describing population growth for Carteria, Dunaliella, Nannochloris and Phaeodactylum. No independent variable was consistently of primary importance in describing 137Cs concentration factors, while temperature accounted for more variation in 65Zn concentration factors than salinity or population growth in all algae except Dunaliella. Concentration factors for 65Zn were uniformly higher than 137Cs concentration factors.

A new flagellate alga is described which has the flagellar apparatus characteristic of the genus Pavlova, but not the external particles on the cell body. The minute particles on the long flagellum contain acid polysaccharide. Paramylon and polyphosphate occur as vacuolar inclusions. A peroxide resistant layer is present in the superficial cisterna. The opposite membranes of the superficial cisterna differ considerably in structure. A diagnosis is given and taxonomic relationships are discussed.

A new member of the Haptophyceae, Corymbellus aureus gen. et sp.nov. is described. The cells of this species are aggregated into motile colonies which are more or less spherical at first, but which become annuloid as their size increases.

Individual cells are large and rather irregular in overall morphology with two heteroor homodynamic flagella and a short non-coiling haptonema arising from an anterior apical groove or furrow. Two types of oval body-scale are present; the larger, with upturned rim and a short central spine, are generally distributed, whilst the smaller, lacking such ornamentation, are confined to the apical groove.

The specific growth rate of Dunaliella tertiolecta was unaffected by mercury II concentrations of at least 2.03 μg at/1. At 10 μg at/1, it was eventually reduced by 84% but growth continued, giving a final level of cell material only 13% below that in a mercuryfree control. At this concentration, however, growth was largely uncoupled from division and giant cells were produced, probably due to the effect of mercury upon the production of methionine which is known to be implicated in the process of cell division.

The basis of the mercury tolerance was investigated in terms of (1) mercury detoxication in the culture medium by complex or compound formation between the metal and metabolites produced by the cells, (2) the concentration of sulphydryl groups both within the cells as possible sequestration sites and in the cell membrane where any molecular disruption and permeability changes produced by the metal first occur, (3) the absence of cellular potassium leakage and (4) the resistance of the cell membrane to the uptake of mercury II ions. Where possible, the results were compared with those from determinations of the same properties of the mercury-sensitive species Isochrysis galbana. The experiments indicated that the mercury tolerance of D. tertiolecta is partly related to the slower rate of mercury accumulation by this species, but is largely due to the detoxication of the mercury within the cell possibly by the precipitation of a highly insoluble mercury compound

The yolk nucleus of Antedon bifida is a large, intensely basophilic structure located in the cytoplasm of small to medium-sized oocytes. Electron microscopy reveals that this yolk nucleus is a conglomeration of hundreds of dense clumps. Each clump, which is a micrometer or two in diameter, consists of finely fibrogranular material in which are embedded ribosome-like particles. Also present in the oocyte cytoplasm are perinuclear dense granules, which may well be the precursors of the clumps making up the yolk nucleus. The yolk nucleus does not appear to participate directly in the elaboration of the yolk granules.

The defensive behaviour of 11 species of sea anemone when attacked by the nudibranch Aeolidia papillosa is described. An attempt is made to correlate their defensive responses with the habitat, and with the food preferences of Aeolidia. Actinia equina responds first by tentacle and column retraction, and then by inflation of the column, pedal locomotion, and detachment from the substrate. Anthopleura elegantissima responds in similar ways, but Anemonia sulcata, which has much longer tentacles, uses these in active defence against the eolid. Anemonia also crawls away but it does not detach.

Actinia, Anthopleura and Anemonia are the preferred foods of Aeolidia. They commonly live in dense colonies where locomotion and detachment are likely to result in escape. Tealia felina is less preferred and is much less responsive when attacked by Aeolidia.

Anemones which possess acontia normally eject these when they are attacked by Aeolidia. Although Aeolidia does occasionally eat acontian anemones, evidence is presented which suggests that acontia have some deterrent effect on this predator. Although most acontian anemones are probably able to move by pedal locomotion and to detach from the substrate, these responses are much less frequently given than by Actinia equina.

The occurrence of Mytilicola intestinalis in populations of mussels in south-west England is recorded and compared with previous data. Since 1955 there have been two main changes in the distribution of Mytilicola: (a) it has invaded all the major estuarine mussel populations on the Bristol Channel coast, and (b) many previously uninfested open-coast populations all round the peninsula are now lightly infested. It is suggested that differences in infestation levels between estuarine and open-coast populations of mussels are due primarily to differences in the degree of exposure to wave action although factors such as size, population density and location of the hosts also influence infestation. The chance of the establishment of breeding pairs of Mytilicola depends on the parasite population size and its distribution through the host population

In laboratory tanks as well as in the sea Arctica islandica shows a pattern of intermittent burrowing activity. Periods spent at the surface of the deposit alternate with periods buried several centimetres beneath the surface of the sand, during which the animals respire anaerobically. There is no obvious rhythmicity to this behaviour; the duration of periods spent beneath the surface is very variable even in the same animal, but normally lasts between 1 and 7 days.

On the return to aerobic conditions both the heart rate and oxygen consumption areincreased but decline gradually during the following 20–25 h. This increased oxygen uptake is caused primarily by an increase in oxygen utilization but there is little change in ventilation rate. Both the initial rate of oxygen consumption and the duration of the recovery period show a correlation with the duration of the period of anaerobiosis. The concentration of alaninc in the blood of Arctica is high immediately after the return to aerobic conditions but declines during the recovery period. The similarity in the time taken for the concentration of alanine in the blood and the oxygen consumption of Arctica to return to normal levels suggests that at least part of this increased oxygen demand is associated with the metabolism of end-products of anaerobiosis.

The filtration rate of Mytilus edulis was measured in a flowing system by estimating the particulate matter concentrations at the inflow (C1) and outflow (C2) of the experimental chamber and immediately surrounding the bivalve (C0). Filtration rate was calculated as R1 = F(C1 – C2)/C0…(1), where F = flow rate through chamber. This formula differs from that previously used in flowing systems (R"t = F(C1 – C1/C2)…(2), by accounting for dilution of inflowing water as it enters the experimental chamber. Formula (1) was used to show that flow rate through the experimental chamber has a negligible effect on filtration rate whereas the use of formula (2) indicates erroneously that flow rate and filtration rate are positively correlated. The particulate matter concentration around the bivalve is also shown to have a negligible effect on filtration rate within the limits tested of approximately 2000–20000 particles ml-1.

Adult female Calanus helgolandicus Claus immersed for 24 h in sea-water solutions of [1-14C]naphthalene accumulated a detectable quantity (3.6 pg/animal) from concentrations as low as 0.10 μg/1.

Feeding experiments using barnacle nauplii or diatoms as foods showed that the dietary route of entry was more important quantitatively than direct uptake from solution in that in order to ensure that the same quantity of radioactivity in the animals was attained by the two routes the level of hydrocarbon in solution had always to be far greater than that present as paniculate food. Relevant to these observations was the further finding that after naphthalene had been accumulated directly from solution in sea water depuration was rapid and only a small fraction, less than 5%, of the original radioactivity could be detected after 10 days: by contrast, when the hydrocarbon was taken up by way of the food depuration was much slower, so that at the end of 10 days about a third of the original level of radioactivity still remained in the animals. Short-term experiments in which Calanus were fed on labelled diets for 24 h under bacteria-free conditions showed that at the end of this period over 90% of the radioactivity in the animals was present as unchanged naphthalene. However, more than two thirds of that released by the animals was in some form other than the hydrocarbon, a finding consistent with the view that Calanus is able to metabolize it.

The salinity preferences of the amphipods studied were found to correlate with distribution. Marinogammarus marinus, a marine species, showed a strong preference for higher salinity levels, the estuarine Gammarus duebeni showed little avoidance of any particular sea water concentration, and the freshwater Gammarus pulex displayed strong preference for dilute media

Tolerance experiments showed that the preference behaviour of M. marinus was not caused by lethal effects of salinity.

Observations on M. marinus suggested that the behaviour involved components of both preference and avoidance.

In M. marinus the choice is made on the basis of total osmolarity of the medium, not on its organic or ionic content alone.

Ablation of the upper and/or lower antennae had no effect on salinity choice in M. marinus, and acclimation to 50% sea water did not alter the preference for full sea water.

It is suggested that behavioural responses which confine animals to areas well within their physiological salinity limits promote survival in aquatic environments which may undergo fluctuations in salt concentration.

Two new gammaridean amphipods, Crybelocephalus birsteini sp.nov. and Halicoides discoveryi sp.nov., and a new subspecies of hyperiid amphipod, Scina wagleri atlantis subsp.nov. are described from oceanic plankton samples taken off Fuertaventura, Canary Islands.

The acoustic measurements made during the SOND cruise are presented in the form of vertical profiles of relative scattering coefficient at day and night and its time dependence over sunrise and sunset for the four echo-sounders used. These profiles are compared with the scattering which is calculated would be returned from the vertical distributions of biological samples reported by other workers, but particularly from the distribution ofswimbladder fish analysed by Badcock. The similarities between the calculated and measured profiles support the assumption that swimbladder fish dominate the scattering due to their high target strengths, particularly at frequencies up to and including 36 kHz. By correlating fish sizes, daytime depth, migration behaviour and acoustic scattering several of the layers may be tentatively attributed to particular species. A calibrated echo-sounder in the frequency range up to 36 kHz is size selective, but can nevertheless be useful for looking at broad distributional features. However, because the numerically more abundant small planktonic animals are inadequately represented by the sounder the records are little more than a guide to net sampling programmes.

The spatial pattern of the ostracod Cyprideis torosa (Jones, 1850) is aggregated and can be described by the negative binomial distribution. The fit of the observed distribution to the negative binomial is less well for the total number of females because females that are not carrying eggs tend to be independently distributed from both females carrying eggs and males. The aggregations are roughly circular with a radius of about 13 cm and may be themselves aggregated. A method to picture the aggregations is described.

An oceanographic survey of Galway Bay was initiated in 1972. Plankton samples were collected on monthly cruises at selected areas in the bay.

Sagitta elegans and Sagitta setosa were found not to be entirely resident in the bay and recruitment of all stages occurred from outside the bay several times during the study. It has also been suggested that the younger stages, especially of S. elegans, were washed out of the bay in the upper layers.

S. elegans was breeding in Galway Bay in July, August and September 1972 and possibly April and May 1973. Breeding was observed in the S. setosa population in September 1972 and from August to November 1973.

The Galway Bay area was sampled quantitatively for plankton during 1972–3. The larvae and/or post-larvae of 67 species of fish were identified from the plankton. The recorded occurrence per m3 and the percentage occurrence of the individual species is presented and discussed, and reference is made to the concurrent occurrence of various chaetognath species and copepod species. The results of previous investigations of the plankton of the Galway Bay area are mentioned.

The histology and histochemistry of whiting skin was studied in larval, juvenile and adult fish. The adult specimens were obtained throughout the year but there was no evidence of seasonal variation in the areas of the body sampled. The skin of the whiting is considerably more complex than that of any other teleost fish which has been described in detail. The epidermis of the mature fish comprises five layers, consisting of Malpighian cells and a variety of other structures including large cystic bullae, which ultrastructurally and histochemically are relatively amorphous but comprise a major proportion of the epidermis. A reticulum of epidermal melanocytes occurs above these structures and two types of mucous cell are described. The major histochemical feature of the epidermis was the alkaline phosphatase reaction, similar to that found in higher animals. Succinic dehydrogenase activity was found at all levels. The epithelial mucins were mainly acid mucopolysaccharide with a small sialic acid component and a greater proportion of sulphated muco-substance. The dermis was morphologically similar to that of other scaled fishes. Mast cells were particularly prominent and occasional non-pigmented ‘melanophores’ were seen.

The mesopelagic alepocephalid fishes Xenodermichthys and Photostylus have unusual compartmented sub-dermal spaces filled with a fluid more dilute than sea water. The fluid is probably lymph, and contributes to the low density of the fish. The external layer superficial to these subdermal spaces consists of cells containing large intracellular paracrystals which form tubular arrays. This external layer is interrupted by numerous photophores (in Photostylus borne on stalks) which have a reddish-violet central core, and are backed by a reflecting layer. The reflector does not contain guanine, it is made up of a series of flattened cells, and reflects blue-green light. The cells of the central core are assumed to be photocytes and are in connexion with apparent nerve terminals, but in neither fish has luminescence of the photophores been observed.

The haematocrit for Prionace was found to be 22.3%, which is similar to values reported for other carcharhinid and sphyrnid species. Haemoglobin content and mean haemoglobin concentration were respectively 57 g/100 ml and 257%. Erythrocytes were generally larger than reported for other carcharhinids.