In order to control the spread of the invasive Caulerpa taxifolia (Chlorophyta) in the Mediterranean, in situ experiments were conducted with the specialized predator Lobiger serradifalci (Mollusca: Ascoglossa=Sacoglossa). An unexpected effect of L. serradifalci on C. taxifolia was observed. Instead of destroying the algal frond, the ascoglossan cut fronds into tiny living fragments capable of regenerating. Thus, L. serradifalci may facilitate C. taxifolia dispersal instead of controlling it.

Over a four year period, gonad index, examination of gonad tubules, and histology were used to study the reproduction in the sea cucumber Actinopyga mauritiana. This species reproduced annually during the warmer months of the year in Solomon Islands. This annual reproductive cycle progressed through five maturity stages: recovery, growing, mature, partly-spawned and spent. The recovery stage (March–May) was marked by initiation of gametogenesis and coincided with decreasing day length. The growing stage (June–September) was characterized by development of gametes through to the mature stage (October–December). Spawning occurred October through December and coincided with increased water temperature and day length. Spent gonads (January–March) contained a few unspawned gametes or completely lacked gametes. Although A. mauritiana had annual reproduction, individuals lacking or having indeterminate gonads were present year-round. Macroscopic examination of gonad tubules after biopsy provides a practical tool for assessing maturity condition of broodstock in the field during the reproductive season.

Prevalence of the parasite Hemioniscus balani (Isopoda: Cryptoniscidae) was determined in intertidal barnacles Semibalanus balanoides collected from north-east England during winter 1989–1990 and March 2000. Infection by female and male stages of the parasite were low (0·0–13·6% and 0·0–9·9%, respectively). Female stages were usually more prevalent lower down the shore, and were more common among larger barnacles. The observed rates of parasitism are similar to those recorded in the region 40–50 years ago.

Virus-like particles (VLPs) were observed in thin sections of the plumose anemone, Metridium senile, collected from seawater off the west coast of Sweden in 1969. The VLPs were observed in the nucleus of spiroblasts and amoebocytes; they were either pentagonal or hexagonal in section, indicating an icosahedral structure. Virus-like particles were ∼60 nm in diameter, with an electron-dense core 40 nm in width; they had no apparent tail. This is the first substantial report of viruses observed in sea anemone cells.

The breeding season of Nerophis lumbriciformis (Pisces: Syngnathidae), has not yet been determined for the southernmost part of its range. A total of 863 individuals was examined between March 1997 and November 1999. In Portugal, the breeding season of this species occurs throughout the year, with a marked reduction during summer and autumn, whilst in Britain it occurs from May to September. Despite these temporal differences, the water temperature at which breeding takes place is similar in the two areas (13–16°C). Together with preliminary laboratory observations with animals kept at different temperatures, these data support the hypothesis that the decrease in breeding activity during summer and autumn in Portugal is due to an inhibitory effect of high water temperature.

Mitochondrial dehydrogenases, antioxidant enzymes, transaminases and cytochrome P450 activity have been studied from the digestive gland of Mytilus galloprovincialis, reared in a non-polluted area of the Mar Grande of Taranto (Ionian Sea, Mediterranean).

A new mechanism of demosponge spicule formation was recognized during taxonomic studies of bioeroding sponges (Porifera: Demospongiae: Clionidae). To date different spicule types have been explained by matching structures to their organic matrix, the axial thread. Bulbous structures, however, do not have an organic counterpart. Immature spicules of Cliona tinctoria and Pione caesia have irregular, rough heads. Higher magnification during scanning electron microscopy shows that silica granules are deposited regionally to form bulbs. Later silica secretion smoothens the bulb surface. Silica deposition in form of granules rather than in layers appears to be a structuring tool in tylostyles.

Ontogenetic and seasonal variations in the diet were studied for a benthopelagic fish, the red cod Salilota australis (Pisces: Moridae) from the Falkland Islands shelf. The study revealed that small fish (<39 cm total length, TL) fed mainly on benthic gammarid amphipods, with squid Loligo gahi, Illex argentinus and the fish Patagonotothen spp. being of secondary importance. In medium sized fish (40–60 cm TL) the importance of fish in their diet increased, but benthic gammarid amphipods remained important, although their role decreased in the percentage by weight. Large fish (>61 cm TL) fed mainly upon Patagonotothen spp. which consisted of 90% by weight. Seasonal variations were analysed only for medium-sized fish. In February–June, S. australis fed mainly on benthic amphipods and Patagonotothen spp. In July–October, the squid Loligo gahi became the most common prey. In November–January benthic crustaceans reappeared in the diet, and Patagonotothen spp. became the most important prey item followed by benthic gammarid amphipods and the isopod Seriolis sp. The niche breadth was found to be similar in the different size groups (2·03–2·66), indicating that the fish fed on one to two abundant prey items in each group. The niche breadth of medium-sized fish varied seasonally reflecting the diversity of prey items utilized throughout the year.

A specimen of the deep-water, spatangoid urchin, Cystochinus loveni, wearing a costume of agglutinated protists, was collected from 3088 m in the Gulf of Alaska, north-east Pacific. Over 24 putative taxa of living and dead foraminiferans and xenophyophores, as well as a sipunculan, polychaete, tanaid, and two isopods, were collected from the dorsal surface of this single individual. This is the first report of a deep-sea urchin using rhizopod protists and it is proposed that the urchin acquires camouflage or benefits from increased specific gravity associated with the protistan cloak.

Five specimens of the penaeid genus Funchalia were found inside living Pyrosoma atlanticum taken off Tenerife. No such association has been noted previously. The largest of the Funchalia was an immature F. villosa; the other four were early post-larvae. Aspects of their morphology are described and compared with previous descriptions. They were probably also F. villosa.

A female Octopus macropus, the first ever observed spawning, attached eggs (4·0×1·2 mm, with a chorion stalk 4 mm in length) individually or in clusters to a hard substrate, and brooded them till hatching. Hatchlings measured 4·0 mm in dorsal mantle length, 5·5 mm in total length and were planktonic; their short arms had seven suckers each, the outer demi-branch of each gill had ten lamellae. The chromatophore pattern confirmed an earlier identification of young individuals from the plankton (Naef, 1923).

In this study, the indirect (i.e. boats not involved in dolphin viewing activities) impacts of boat traffic on the acoustic behaviour of Pacific humpback dolphins, Sousa chinensis, were assessed in Moreton Bay, Australia. Humpback dolphin acoustic behaviour is affected by transiting boat traffic. Boats' passage did not affect the rates at which dolphins produced click trains and burst pulse vocalizations. However, dolphins significantly increased their rate of whistling immediately after a boat moved through the area. This increase occurred only when boats were less than 1·5 km from the groups. Groups including mother–calf pairs showed an increase in whistles in response to boats' passage. Groups with no calves produced significantly fewer whistles. This evidence suggests that the noise from transiting vessels affects dolphins' group cohesion. Mother–calf pairs appear to be most disturbed by transiting vessels, and exhibit an increased need to re-establish vocal contact.

The diet breadth and diet overlap of two co-existing species of flatfish, plaice (Pleuronectes platessa) and dab (Limanda limanda) inhabiting a shallow bay in south-west Ireland are compared. They were shown to vary with the resource matrix, the gut region and the sample size. Diet breadth was calculated using Levin's index and diet overlap calculated using Horn's index. Values of diet breadth were considerably less for numerical abundance data when compared to percentage occurrence data. Similarly, diet overlap values were less for numerically derived data. In dab, diet breadths were significantly lower for stomach-only contents than for intestine-only or whole gut contents. In plaice, there were no significant differences in diet breadths between gut regions. Significantly lower diet overlaps for stomach-only data were also found. Reducing the size of sample to N=30 and N=10 resulted in increases in the calculated value of diet breadth, by as much as 0·13 and 0·34 respectively, these increases were frequently significant. The same reductions in sample size for diet overlap decreased overlap values by 0·02 and 0·13 respectively, significant only when sample reduced to N=10.

Phenoloxidase (PO) has been shown to be present in both invertebrates and vertebrates, yet little is known about the PO in Branchiostoma belcheri tsingtauense. The present study demonstrated that the PO activity existed histochemically the epithelial cells of the gill bar and intestine of adult animal, producing brown to black melanin deposits. Ultrastructural examination revealed that PO reaction products were localized in the cytoplasmic granules of the epidermal cells, the epithelial cells of gill bar and intestine and most of them were electron-dense and homogenous. Frequently, the PO reaction products were also observed in the secondary lysosomes.  The mucus from the body surface had little antibacterial activity against Escherichia coli, but it enhanced the antibacterial activity of L-dopa and the enhancement was suppressed by PTU, a PO specific inhibitor. This indicates that the active material inhibiting the E. coli growth in the mucus is PO.

Current flow regime, bathymetry and substratum angle were found to influence the density and distribution of the following anthozoan species at Lough Hyne Marine Nature Reserve, Ireland: Corynactis viridis, Alcyonium digitatum, Caryophyllia smithii, Anemonia viridis and Anthopleura ballii. Density variation was found on inclined, vertical and overhanging cliff surfaces for species found on hard substratum (Corynactis viridis, Alcyonium digitatum and Caryophyllia smithii). All species showed significant variation with increasing depth and between sites with different water flow rates.

Stomach contents of 382 Palinurus elephas collected in the Columbretes Islands Marine Reserve (north-western Mediterranean) were examined to study the diet and to assess ontogenetic and sex related differences in feeding regime. Molluscs, crustaceans, and sea urchins were the most common prey. Diet composition varied with lobster size but not with sex. Ontogenetic changes in diet were reflected in the progressive reduction of the contribution of gastropods and crustaceans and in the increased importance of other prey such as fish.

The Continuous Plankton Recorder (CPR) survey has collected plankton samples from regular tracks across the world's oceans for almost 70 y. Over 299,000 spatially extensive CPR samples are archived and stored in buffered formalin. This CPR archive offers huge potential to study changes in marine communities using molecular data from a period when marine pollution, exploitation and global anthropogenic impact were much less pronounced. However, to harness the amount of data available within the CPR archive fully, it is necessary to improve techniques of larval identification, to genus and species preferably, and to obtain genetic information for historical studies of population ecology. To increase the potential of the CPR database this paper describes the first extraction, amplification by the polymerase chain reaction and utilization of a DNA sequence (mitochondrial 16S rDNA) from a CPR sample, a formalin fixed larval sandeel.

Haloes of encrusting algae, mostly Hildenbrandia, and cyanobacteria were found on the home scars under the shell of Patella vulgata, beneath the pallial cavity. The presence and area of halo varied between sites. Area generally increased with limpet size and at one site was negatively associated with slope of the shore. It is suggested that the algae provide a resource and may, therefore, play a role in the foraging ecology of the limpet.

This study examined the inter-relationships between molluscs, heavy metal concentrations and trematode parasites. Littorina littorea (Mollusca: Gastropoda) were sampled seasonally from two sites in a tidal lagoon. Site A was close to the inflow of a polluted stream whilst site B was at the opposite end of the lagoon. The samples were analysed for lead, iron, copper and nickel. Metal concentrations in L. littorea varied with site, season and parasite infection, and exceeded comparative non-polluted concentrations for all metals in some samples. Parasitized periwinkles consistently had significantly lower levels of iron, copper and nickel than uninfected periwinkles.

The third record of the sharpnose seven-gill shark Heptranchias perlo (Selachii: Hexanchidae) north of the Bay of Biscay is reported. The 101 cm total length specimen, which was taken incidentally on a commercial bottom-set longline at a depth of 166 m, was an immature female. Beaks belonging to the short-finned squid Illex coindetii (Cephalopoda: Ommastrephidae) were recovered from the stomach, and an unidentified species of nematode was found parasitizing the stomach mucosa.