Supralittoral rockpools form an extreme environment due to severe fluctuations in salinity, temperature and oxygen concentration. The only seaweed species in supralittoral rockpools around Great Cumbrae, Firth of Clyde was the green alga Enteromorpha intestinalis. Only two animal species were recorded permanently over a three year period in this environment; the orange harpacticoid copepod, Tigriopus brevicornis, and the chironomid larva, Halocladius fucicola. The present study demonstrates the role of the hollow thallus of E. intestinalis in the lifestyles of T. brevicornis (adults and nauplii) and H. fucicola. The thallus provides a moist refuge reducing desiccation when the rockpools completely dry out. Several hundred individuals of T. brevicornis have been observed in a single E. intestinalis thallus. This observation may explain how the species can successfully recolonize completely evaporated supralittoral rockpools after several weeks. The study also raises questions about the reliability of previous population estimates of Tigriopus spp. in light of this constantly overlooked refuge.

Anonyx sarsi (Crustacea: Amphipoda) is a widely distributed scavenger and predator in shallow waters of northern seas. It was caught, often in large numbers, in baited traps in the intertidal in Iceland, especially during mid-winter. Although hitherto only sporadically recorded from the intertidal, the species is undoubtedly among the most important carrion feeders there, and probably an important predator as well.

During the winter of 1996, a heavy storm crossed the coasts of the Azores. A comparison of wave-exposed and wave-sheltered samples of the intertidal planktonic developing periwinkle Littorina striata (Mollusca: Caenogastropoda), collected before and after this storm revealed: (1) an overall difference in relative and absolute aperture area between wave-exposed and wave-sheltered samples; and (2) depending on the technique used a storm (MANOVA/CDA/1994 vs 1996 nested ANOVA) or no storm (1992, 1993, 1994, 1996, nested ANOVA) effect was noted. Preference should be given to the latter analysis as it is more correct in the present context. Nesting of the factor ‘year’ in the factor ‘storm’, allows detection of the true storm effect, disentangling it from other year exposure interactions, while the inclusion of more than one pre-storm sample allows differentiation of storm effects from ‘normal’ temporal variation.

Laboratory based experiments, carried out on Littorina neglecta collected from the barnacle zone at Ravenscar, north-east England, showed that this marine prosobranch displays size assortative mating. Males prefer to mate with larger, more fecund females, but they do not necessarily choose the largest available. It is suggested that such size assortative mating may act as a barrier to reproduction between L. neglecta and L. saxatilis. No relationship was found between either male or female shell size and the length of copulation.

Morbihan Bay, France, is an important spawning area and nursery grounds for young cuttlefish. The eggs and the young cuttlefish are subjected to predatory species of fish. These were identified by analysing the stomach contents of 26 species and two species of cephalopods. Five fish species were found to be predators of young cuttlefish. The Balistes carolinensis feeds on the eggs, and Dicentrarchus labrax, Labrus bergylta, Spondyliosoma cantharus, and Conger conger eat young cuttlefish, from 8 mm (hatching cuttlefish) to 61 mm in mantle length (cuttlefish about 4-months old).

Investigation of the fecundity in Abralia veranyi from the Mauritanian slope showed that potential fecundity of this species is 10,000–26,000 including 1200–2400 (mean 1900) yolk oocytes and ripe eggs. Up to 1000 ripe eggs of 0.7–0.8×0.8–0.9 mm (mean weight 0.30 mg) were found in oviducts. In mated females there were found 13–226 (mean 71) spermatangia. Spawning is intermittent.

A single maturity classification key applied to five common chaetognath species of the eastern Mediterranean is presented. The efficiency of the key was tested using biometrical data: body length (BL), ovary length (OL) and seminal vesicle width (SVW). For each species the key proved easy to use and efficient in the distinction of the maturity stages providing a satisfactory size separation between them.

The growth bands in the plates of the echinoid Spharechinus granularis settled on the Algerian coast were analysed. Two distinct groups of sea urchins were identified with different growth patterns related to the period of recruitment, i.e. spring or autumn. The growth rate of the autumn cohort was higher over the year following the first winter after settlement. From the second winter there was little growth difference between the two cohorts. Compared to populations from Atlantic sites, the Algerian population has a lower growth rate and reduced longevity.

The reproductive cycle, development and spatial organization of the gonads of an exotic ascidian, Styela clava, were studied in Cork Harbour, Ireland. Monthly histological samples enabled the division of gonad development into six main stages, ranging from `inactive' to `regression'. Gonad development was asynchronous in the population, with more than one stage being found within some months. Gametogenesis was observed from February–November, but peaked between August–October. Spawning took place in September–October, followed by gonad regression in November–December.

Effects of external cation concentrations on larval metamorphosis in the ascidian, Halocynthia roretzi were examined. Metamorphosis (tail resorption) was induced by 20 mM and 50 mM K+ but, interestingly, was suppressed by 30 mM K+. Low concentrations of Ca2+ (1–5 mM) induced metamorphosis, while high concentrations did not, in contrast to findings in other invertebrates. Moreover, BAPTA-AM, an intracellular Ca2+ chelator, induced metamorphosis. This suggests that a decrease in intracellular Ca2+ of certain cells initiates larval metamorphosis in H. roretzi.

A specimen of the oilfish, Ruvettus pretiosus, was captured from the northern Adriatic (Gulf of Trieste) and represents the northernmost extension in range of this species in the Adriatic Sea.

The present study is the first record of twinning in Delphinus delphis. The first foetus was a female of 72 cm total length which had a curved caudal area. This animal was located in the left uterine horn, very close to the genital aperture. The second foetus was a male of 46 cm total length and its external morphology was deformed. It was located in the uterus and the nose was shorter than the female foetus. Documented incidences of twinning in cetaceans are rare.

Histological sections of the gonad of Bathymodiolus azoricus from the Lucky Strike and Menez Gwen hydrothermal vent fields (Mid-Atlantic Ridge) demonstrated a spawning event in this species in May 1994, synchronous between the two vent fields located 60 km apart, and a sexual pause in gametogenesis. As reported for other vent mytilid species, B. azoricus from Lucky Strike and Menez Gwen could exhibit hermaphroditism.