The effect of food concentration on the reproductive success of the copepod Centropages typicus (Copepoda: Calanoida) was studied in the laboratory. Three different regimes of food were tested: absence of food, natural food conditions and a food media enriched with an algal culture. The results showed significant differences in egg production rate between regimes of food, but no significant differences in egg viability. A rapid response (24 h) in egg production rate to increment in the quantity of food was noted. Hatching success was not affected by food conditions prevailing during the incubations.

In order to induce metamorphosis in cyprids of the parasitic barnacle Loxothylacus panopaei (Gissler) (Cirripedia: Rhizocephala: Kentrogonida), we tested a number of compounds (ZR-512, 20-hydroxyecdysone, 3-isobutyl-l-methylxanthine and phorbol-12,13- dibutyrate) all known to cause metamorphosis in thoracican barnacles. Only one agent, phorbol-12,13-dibutyrate, had an effect and induced cypris larvae to complete metamorphosis without previous attachment. This suggests that diacylglycerol-activated protein kinase C plays a role in the metamorphosis of kentrogonid rhizocephalans.

Rhizocephalans are highly specialized crustaceans adapted for parasitic life on decapods. The juvenile parasite passes through an internal growth stage, where a root-like trophic organ invades the tissue and haemocoelic fluid of the host (for detailed information on rhizocephalan life history, see Haeg, 1992). As in free-living barnacles, a cyprid larva is the settling stage, and in thoracicans a juvenile barnacle is formed underneath the carapace of the cyprid larva. However, the rhizocephalans develop a so-called kentrogon, which accomplishes the injection of the primordial parasite (Glenner & Høeg, 1995). The degree of specialization towards a specific host means that the cypris larvae of rhizocephalans are extremely selective in their choice of substrata. They will not settle unless a specific host or part of a host, e.g. the gills, is offered. For this reason, the study of settlement and metamorphosis of these species has met with great difficulties.

Isolated embryonic membranes (i.e. the outer cuticular membrane, the fibrous layer, the inner cuticular membrane and the hatching membrane) and homogenates of incubated, decapsulated cysts of 16 populations from five Artemia species (Crustacea, Anostraca) were examined by sodium dodecyl-sulphate polyacrylamide gel electrophoresis. Characteristic differences in major polypeptides between 45 and 205 kD were seen. These differences might be used as markers for identification of different Artemia species. The validity of this approach in characterizing Artemia populations is discussed.

Ferritin crystals and calcium granules are reported from the ventral ceaca of Steleuthera ecoprophycea (Amphipoda: Stegocephalidae) collected from the Snake Pit hydrothermal vent, Mid-Atlantic Ridge (3520 m).

In a series of earlier papers (Moore & Rainbow, 1984, 1989, 1992; Moore et al., 1994), the authors described the widespread occurrence of intracellular, octahedral crystals of ferritin in the ventral caeca of a range of stegocephalid amphipod species from the continental shelf epibenthos and oceanic plankton. The discovery at 3500 m of a new Steleuthera species (S. ecoprophycea), from a hydrothermal vent on the Mid-Atlantic Ridge was announced recently by Bellan-Santini & Thurston (1996), and a complete description is provided therein.

Oceanic ridge sites are notable for their tectonic activity and the presence of a diversity of trace metals at high concentrations is to be expected in hydrothermal plumes emanating from such regions (German & Angel, 1995). The detoxification of accumulated trace metals in the ventral ceaca of stegocephalid amphipods from uncontaminated environments is now relatively well known (see above), so it was of interest to investigate whether a vent stegocephalid showed an atypical presence of trace metals in detoxified form in cells of the ventral caeca. The results following from an opportunity to investigate this are reported herein.

Material was derived from a dive made by the submersible ‘Alvin’ at Snake Pit hydrothermal field, Mid-Atlantic Ridge (23°23′N 44°56′W), 3520 m, on 16 June 1993 (see Bellan-Santini & Thurston, 1996). Steleuthera ecoprophycea was preserved in 70% alcohol. Subsequently to dissection, the single pair of ventral caeca from each of the four damaged amphipods investigated were post-fixed in 4% glutaraldehyde. For electron microscopy and x-ray microanalysis in STEM mode, ventral caecal tissues were then dehydrated through 95% and absolute ethanol, cleared in propylene oxide, embedded in TAAB resin, sectioned at 0·5 μm (semi-thin sections) on a Reichert OmU2 ultramicrotome and examined without staining in a JEOL 100C electron microscope equipped with LINK system EDX energy dispersive x-ray microanalyser.

This short note describes the in situ activity cycles of Galathea squamifera and G. strigosa (Crustacea: Decapoda) through SCUBA diving observations in south-west Ireland. Both species exhibited nocturnal activity peaks, although they were not exclusively nocturnal. Fluctuating tidal current strength and direction had no discernible influence on either species’ activity cycles. It is suggested that shelters, particularly in terms of both predator avoidance and as foraging areas, play an important role in the ecology of both species.

Both the anomuran decapod crustaceans Galathea squamifera Leach and G. strigosa (L.) are widespread throughout the rocky subtidal of the north-west European coastline. In contrast to the general body morphology and the structure of the mouthparts which have been well studied (Nicol, 1932; Pike, 1947), the biology and ecology of the genus Galathea remains poorly studied. These morphological studies have shown that the mouthparts are ill-adapted to living on muddy substrates, essentially restricting the distribution of both G. squamifera and G. strigosa to rocky areas, where their food is obtained by detrital deposit feeding and scavenging. Turner & Warman (1991) have studied the activity patterns of the genus Galathea at Lough Hyne, southwest Ireland and concluded that the genus exhibits nocturnal activity peaks. However, the different species were not distinguished, nor was the potential effect of the aberrant tidal patterns in the area considered. As at least three species (G. squamifera, G. strigosa, G. intermedia) are known to occur at the study site (Holmes, 1985), the present study was initiated to elucidate the activity cycles at a species-specific level.

Late premoult females from precopula pairs of male and female Carcimts maenas (Crustacea: Brachyura) moulted at times of expected high tide in constant conditions in the laboratory. The data presents for the first time evidence of endogenous, circatidal (−12·4 h) moulting rhythms in a crustacean.

Studies on the temporal patterns of moulting in crustaceans have elucidated rhythms of seasonal (annual or biannual), lunar (29·4 d), semilunar (14·7 d) and diel (24 h) periodicities (see Conan, 1985; Fernandez et al., 1994). Examples in the literature of so-called ‘tidal’ rhythmicity of moulting given by Conan (1985) are more correctly referred to as semilunar or neap/spring patterns. There appear to be no reported examples of true tidal (12·4 h) moulting rhythms. Also there is very little evidence in the literature that moulting rhythms phased to geophysical cycles are controlled endogenously. Most studies have been carried out in the field or under L:D cycles in the laboratory and only a few have been undertaken with animals in constant conditions (see Fowler et al., 1971; Bishop & Herrnkind, 1976; Nicol, 1989; Fernandez et al., 1994). Conan (1985) has reported moulting rhythms of circamonthly, circatidal (=circasemilunar) and circadian periodicities but his use of the prefix ‘circa’ is unusual since it more correctly describes free-running rhythms in constant conditions, not environmentally driven rhythms as in the examples quoted. In the present study we sought to determine whether moulting in the shore crab Carcimts maenas (L.) was tidally patterned and endogenous.

Over a period of several days in the summer of 1991 large numbers of premoult female Carcinus maenas were obtained by searching for specimens associated with males in precopular pairs.

The ‘Sea Empress’ oil tanker grounded outside Milford Haven (Wales, UK) in February 1996, spilling ~70,000 tonnes of crude oil and contaminating over 100 km of coastline, causing mass mortalities and standings of at least 11 mollusc species. Intensive field monitoring commenced after the spill, examining immunity and hydrocarbon levels in the mussel, Mytilus edulis (Mollusca: Bivalvia), a commercially-harvested species which can accumulate contaminants. Comparisons of mussels from oiled and reference sites revealed significant modulations in cell-mediated immunity. Elevations in blood cell (haemocyte) numbers and decreases in superoxide generation and phagocytosis were identified in contaminated animals. The immune response of contaminated mussels gradually improved and generally showed no significant differences compared with clean mussels after 11 weeks. By then, total hydrocarbon content in contaminated mussels had declined by 70–90%, while polycyclic aromatic hydrocarbon content had decreased by over 90%.