The population structure of the European flying squid Todarodes sagittatus was studied using data of about 5000 squid caught in waters off the western Sahara between 1969 and 1997. The bulk of the population consisted of winter-spawned squid, which occurred as juveniles of 80–120 mm mantle length (ML) over the slope in spring, and as immature squid of 160–180 mm ML both on the shelf and slope in summer. In autumn, the squid attained 220–280 mm ML, matured, and shifted to the slope, where the spawning was supposed to occur in winter. Age and growth of T. sagittatus was studied using statolith ageing techniques. Assuming daily production of putative growth increments within statoliths, as well as sizes and proportions of immature and maturing females, the lifespan of the west Saharan populations of T. sagittatus lasts ∼1 y. Todarodes sagittatus is a fast growing squid at juvenile and immature ontogenetic phases. Early maturation (at ages 220–230 d in males and 250–260 d in females, respectively) and subsequent decrease of somatic growth rates caused rather small modal sizes of mature squid (250–300 mm ML) compared with those of their northern counterparts (350–420 mm ML). Both hatching dates and seasonality in occurrence of mature females shows that in waters off the western Sahara T. sagittatus spawns throughout the year with a well-pronounced winter peak.

The common cockle Cerastoderma edule is intermediate host to several species of digenean trematodes. However, little is known about the factors influencing the settlement of trematode larvae in cockles as well as their effects on the host. Aspects of the transmission ecology, behaviour and effects on juvenile host specimens of trematode larvae belonging to the genus Himasthla and utilizing mudsnails Hydrobia ulvae as their first intermediate host and various waterbirds as their definitive host have been studied. Cercariae of Himasthla spp. (more than 90% of the metacercariae were identified as H. continua post-experimentally) exhibited a host size-dependent selection within the host size range from 2 to 6 mm. Infection efficiency was reduced by the presence of substratum allowing cockles to burrow, suggesting that the foot and visceral region may be attacked by cercariae. No increased mortality due to parasite infections could be demonstrated within 5 d after infestation. The metacercariae within experimentally infected cockles were primarily located in the connective tissue within the foot and visceral region. Although some cockles were completely filled with metacercariae only small functional effects were detected, such as a slightly prolonged burrowing time of infected specimens.

This paper presents the first record of Ceratothoa steindachneri from Cornwall, making it the first resident species of the fish–parasitic isopod family Cymothoidae in Britain. The host is Echiichthys vipera (Trachinidae) the lesser weever fish, the isopod attaching to the host tongue. A complete redescription and reillustration for C. steindachneri is given, and a neotype is selected for the species Ceratothoa parallela. A key to the north-east Atlantic and Mediterranean species of Ceratothoa is included, with a brief illustrated account for each species.

Stomach contents of Todarodes sagittatus caught by trawlers working from 100 to 800 m depth in the Balearic Sea (western Mediterranean) were studied. From the 348 stomachs examined (153 males and 195 females) 33.62% were empty (39.21% in males and 29.74% in females). The diet of the squid was composed of 58 different prey items belonging to four major groups: Osteichthya, Crustacea, Cephalopoda and Chondrichthya. Osteichthyes, crustaceans and cephalopods were the most common prey, with a frequency of occurrence value of 84.85, 48.92 and 29.87% respectively. A change in the diet as the squid grows was observed, since juveniles feed basically on fishes while adults prey more actively on crustaceans. Analysis of the diet by size-classes reflected an ontogenetic migration to deeper waters since, parallel to the increase of size, a raise in the percentage of prey species inhabiting deeper waters was detected. Cannibalism was quite frequent, since T. sagittatus was the second most common cephalopod prey. Females had higher fullness-weight index and lower emptiness index than males, which reflects their major energetic demand for egg production.

The egg mass of the diamond-shaped squid, Thysanoteuthis rhombus (Oegopsidae: Thysanoteuthidae) was sighted in surface waters off south-east Sulawesi. It was a sinuous hollow tube-like structure about 2 m long and 0·15 m diameter. It was estimated to contain in the order of 180,000 purple eggs of 1 mm diameter with little or no yolk. Development of the embryos from early differentiation to hatching took between 47 and 57 h at about 28°C.

Polar benthic communities are subject to a range of disturbance levels from a variety of sources, principal amongst which is ice. This occurs in four main forms: the ice-foot, ice scour, anchor ice and fast ice, each of which influences benthos in a very different temporal and spatial manner. The four described forms of ice disturbance are all seasonal, but combined, influence communities throughout the year. The magnitude of ice mediated disturbance is often catastrophic and as a result both dominates benthic community structure and makes recolonization and development rates critical. This disturbance extremity results in high temporal and spatial heterogeneity, very low intertidal zone diversity and in places low mid–sublittoral diversity. It may also, however, be important in generating and maintaining the typically high sublittoral zone diversity observed at many polar localities. Intermediate frequencies or magnitudes of disturbance have been controversially discussed as important in maintaining diversity by prevention of space monopolization by overgrowth dominants in such environments as the deep sea. The shelf areas examined to date certainly suggest intermediate disturbance is important in maintaining polar sublittoral zone diversity. The combination of slow colonization and development with high frequencies of disturbance means most polar nearshore environments that have been described are permanently in a state of change or recovery.

The duration of residence at identifiable refuges in separate territories was assessed over an 800-d period for the goldsinny, Ctenolabrus rupestris, a territorial labrid (Osteichthyes: Perciformes: Labridae), on the west coast of Scotland. Goldsinny (N=12; seven male, five female) were taken from, tagged and returned to, marked refuges using anaesthetics applied underwater. Over the whole study period two goldsinny (one male, one female) moved between adjoining territories, but most (eight out of the ten recaptured or observed) remained in the refuge in which they were released.

The swimming and swarming behaviour of Tritodynamia horvathi (Brachyura: Pinnotheridae) has been considered to be a seasonal activity related to summer mating. However, little information has been available regarding other seasons of the year as the crabs have not been observed at the sea surface in the cool months from October until May. This is the first report of swimming behaviour observed during this low temperature season. The swimming individuals were observed in March 1991 in Yatsushiro Sound, Japan. Tritodynamia horvathi were observed swimming at a depth of 15 m, using their maxillipeds to feed. The crabs also swam in the aquarium and caught Artemia nauplii in the same manner. These findings suggest that their swimming behaviour is not a seasonal mating activity as previously believed, but a habitual behaviour associated with feeding.

Spectral reflectivity and transmission of the iridescent cuticle of six species of male Sapphirina (Poecilostomatoida: Copepoda) were measured by microspectrophotometry. Sapphirina angusta and S. opalina showed two spectral peaks of reflection, one at about 420 nm and the other at wavelengths longer than 750 nm. Sapphirina auronitens and S. gastrica had dominant peaks at wavelengths longer than 500 nm. Sapphirina ovatolanceolata had peaks between 430 and 600 nm, while S. metallina had various peaks along a wide range of wavelengths. The peaks at the longer wavelength in S. angusta and S. opalina may be related to the red pigments in the subcuticular layer of the species, or a result of a second-order effect of the multilayer system. The spectra of transmitted light were complementary to those of reflected light, indicating that the iridescence is caused by the interference of light by the integumental multilayer structure. The present results are also consistent with the hypothesis that the iridescence has a role in increasing the contrast of males against the ambient light conditions in the daytime distributional depth of the species.

Density and spatial distributions on an intermediate scale of two flatfishes—marbled flounder Pleuronectes yokohamae, and the brown sole Pleuronectes herzensteini (Pisces: Pleuronectiformes) within large (10,000–100,000 m2 patches of homogenous substratum (sand and silted sand)) were studied. Both species dominated in the demersal fish community. Densities of brown sole, were significantly higher in both types of habitat. Flatfish distribution was highly patchy and the mean fish densities in groups were as much as ten times higher than the mean fish densities in the area. More than 85% of all recorded flatfish were found within groups. Mixed groups with both species were most prevalent. The number of flatfish in one group ranged from 2 to 20. Brown sole was more abundant in the area and dominated in mixed groups. Levels of contacts between group members and densities within groups were inversely related to visibility condition. It is suggested that flatfish form a group and stay in the group, attracted by foraging movements of other flatfish and by plumes of upset particles caused by their bottom digging movements.

Divisional morphogenesis of the marine hypotrichous ciliate, Tachysoma ovata was investigated based on protargol impregnated specimens. Its morphogenesis reveals the following peculiarities: (1) there is a definite period during which the anterior part of the newly formed adoral zone of membranelles (AZM) in the opisthe connects with the parental AZM which remains unchanged during the morphogenesis. (2) The anlagen of left and right marginal rows do not develop simultaneously. (3) The replication processes of macronuclear segments are not recognizable during cell division. It is likely that the replication takes place during the interphase. (4) The origin of the fronto-ventral-transverse (FVT) cirral anlagen in the opisthe is characteristic: in other Tachysoma spp. these primordia are generated either from differentiated parental ciliatures (or are orientated by pre-existent organelles), or by division of the proter's FVT-cirral primordia. (5) The primordium of the undulating membranes in the proter always keeps the form of two streaks (so-called ‘semi-anlagen’). There is no conspicuous dedifferentiation or reorganization of the undulating membranes. A morphogenetic comparison with other species of this genus was carried out.

Sexual maturity in brachyurans is often associated with an allometric change in the relative growth of the animal. Maturity of Liocarcinus depurator was examined by analysing the monthly percentages of mature females (determined by the stage of gonad maturation and the presence of brood and sperm plugs) by size-class and the relative growth of different body parts: length and width of the carapace, length, height and width of the cheliped propodus; width of the abdominal segments in females and length of the first pleopod in males. Using the reproductive criteria the size at the onset of sexual maturity (carapace width at which 50% females are mature) in females of L. depurator is around 30–34 mm cephalothorax width. Principal component analysis (PCA) showed that the main source of morphometric variation for both sexes was due to heterochelia and allometric changes in growth. Morphometric variables were fitted using different regression techniques to one and two-phase growth models. The length of the first pleopod and the propodus of the right cheliped in males, and width of abdominal segments in females showed two clearly differentiated phases. Estimated maturity size (carapace width) corresponding to 50% mature animals was greater in males than in females. In males, size at the onset of maturity ranged between 31.4 and 35.7 mm, depending on the methods and variables used. The size at the onset of maturity in females ranged between 25.5 and 31.5 mm. In the Ría de Arousa, the size at maturity in females of L. depurator estimated using reproductive criteria is considerably greater than the size found based on morphometric criteria. The size at maturity based on morphometric criteria is greater in males than in females.

An experiment was carried out to estimate the rate of indirect fishing mortality on juvenile Spisula solida due to the exposure time on deck. Samples were collected using a dredge from a site off Vilamoura, south coast of Portugal, during July 1994. Length of deck exposure is directly related to mortality of juveniles. It was estimated a fishing mortality rate of 0.00335 per min, due to length of exposure.

The estuary of the River Crouch, south-east England, as sampled annually by beam trawl between 1987 and 1989, and again in 1992. The aim of an initial transect survey was to describe and quantify the subtidal epifauna at a time of high ambient tributyltin (TBT) concentrations, arising from the use of tin-based anti-fouling paints on the hulls of moored pleasure craft. Subsequent surveys at representative stations sought to examine the progress of any changes with time in animal populations in relation to a decline in concentrations of TBT in the environment, following a ban on the use of tin-based paints for smaller vessels in July 1987.

Morphometric characteristics and spatial distribution of Tontonia grandis sp. nov. were investigated in the northern East China Sea and the adjacent sea areas. Tontonia grandis has a large conical body shape, 113 μm (70–155 μm) in length by 55 μm (40–113 μm) in width, a caudal appendix, multiple macronuclei and 14 (13–16) anterior and 28 (24–33) ventral polykinetids. Some cells have numerous cortical platelets on the surface and others do not. These two forms showed different horizontal distribution, and hence the presence of cortical platelets might be influenced by the environment inhabited. However, various forms of caudal appendix were observed, which constitute a continuous series of their developmental stages. This result might suggest that the caudal appendix is replaced by new growth and repeats its developing and sloughing spontaneously.

Ptychodactiaria, currently recognized as an order equivalent to Actiniaria (sea anemones sensu stricto) and Scleractinia (‘true’ or hard corals) of cnidarian class Anthozoa, contains three monotypic genera, Dactylanthus, Ptychodactis, and Preactis, in two families, Ptychodactiidae and Preactiidae. Features that had been considered distinctive to the order among hexacorallian anthozoans were that gametes mature in protrusions from the mesenteries, as in octocorallian anthozoans, and that gametes do not mature embedded in mesogloea. However, we found that ptychodactiarian gametes develop in the mesenteries, surrounded by mesogloea, as in other sea anemones. We conclude that the three species constitute a clade, the most distinctive feature of which is medially fused mesenteries at the proximal end of the body. This clade merits subordinal status within order Actiniaria. We redefine Ptychodactiaria and its component taxa, moving Dactylanthus from family Ptychodactiidae to family Preactiidae.

Three macroalgae were studied: Enteromorpha sp. (Chlorophyceae), Hormosira banksii (Turner) Descaisne (Phaeophyceae), Corallina sp. (Rhodophyceae). Fractal dimensions (D) for the outlines of the three species were 1.24, 1.07 and 1.35 respectively in the step range 0.5–5.0 mm. All three species showed loss of epifauna on the falling tide; loss was greatest in Enteromorpha, least in Corallina. In Enteromorpha and Hormosira, most loss of epifauna was in the form of harpacticoid copepods; in Corallina loss was spread more evenly across the taxa. Epifaunal biomass and retention was much greater in Corallina than in the other two species, partially because of better water-retention properties. Enteromorpha and Hormosira both showed marked decreases in epifaunal diversity during emersion; Corallina did not.

Research into the feeding habits of cetaceans has traditionally relied on examining samples taken from the digestive tracts of commercially caught or stranded and by-caught animals. This depends on the identification and measurement of hard parts such as fish otoliths. Otoliths are often partially digested in the stomach, making quantitative estimates of fish size from otolith size biased.

As a preliminary attempt to quantify the size reduction of otoliths found in the stomachs of small cetaceans, an in vitro digestion experiment was carried out. Otoliths of herring, whiting, poor cod and haddock were digested at 37°C, pH=3·6, and measured every 60 min.

Linear regressions relating otolith size to digestion time and original size generally provided an adequate description of the time course of size reduction. The parameter that changed most rapidly due to digestion was otolith thickness. Differences in digestion rates between species reflect the general robustness and shape of the otoliths.

A simulation using actual dietary data showed that the overall diet composition was not radically changed by accounting for otolith digestion, although the apparent contribution of herring increased as the assumed digestion time is increased, because herring otoliths were the most susceptible to digestion.

Temporal patterns in metazoan parasite community diversity of Crassostrea gigas, (Lamellibranchia: Ostreidae) were studied in the Exe Estuary at monthly intervals over one year and in relation to host age-classes. A total of four metazoan species was found to parasitize C. gigas in the Exe Estuary: the turbellarian Paravortex sp., cercaria Lepocreadiidae, metacercariae of Renicola roscovita and the copepod Mytilicola intestinalis. Only R. roscovita and M. intestinalis were present in all months throughout the year and in all host age-classes. Analysis of the metazoan parasite community at individual host level revealed little variation in community structure with respect to season or host age, as only a slight increase in diversity values was observed during the summer months. However, community diversity does vary from year to year, as shown by comparison between host age group samples in three consecutive years. None of the parasites are specialist to oysters but all appear to be widespread and abundant parasite of other lamellibranch species.