The bryozoan Cigclisula sp., is a heavily calcified erect species which occurs abundantly in the shallow sublittoral coral reef at Quilaluia Island, Quirimba Archipelago, northern Mozambique. It grows in an arborescent bilaminate form termed adeoniform on the undersides of coral heads or other available bioconstructed hard substratum. The geography and bathymetry of the area results in periodic high and complex current regimes often carrying water borne debris. If this periodic force overcomes the structural integrity of Cigclisula sp. either the outermost branches break or the colony topples at the base. The local population was dominated by young individuals: nearly 40% of the sample population had ten branches or fewer and less than 10% had more than 50 branches (these could be ascertained as young due to the lower proportion of damaged colonies with ≤10 branches; Figure 1). The only size group with no damaged specimens (branch breakage) were those with ≤5 branches. The mean proportion of branches broken significantly increased with increasing colony size. After one year a population of Cigclisula sp., initially comprising 30 colonies (encompassing the entire size spectrum of colonies), consisted of just one small specimen.

Six juvenile sperm whales were observed visually and acoustically in the confined waters of Scapa Flow, Orkney Islands during March 1993. General visual behaviours observed included slow travelling, head-outs, logging and side fluking but there were no observations of tail fluking within the confines of Scapa Flow. Recordings of the whales' vocalizations through hydrophones revealed a remarkably wide repertoire including clicks, rapid clicks, gunshots, chirrups, creaks, short trumpets, pips, squeals and clangs. Selected examples of these sounds were digitized and analysed as spectrograms. Clicks, rapid clicks, gunshots and clangs all showed a characteristic impulsive broadband signature. Chirrups, short trumpets and creaks were composed of rapid sequences of broadband impulses, although creaks were invariably faint and were difficult to illustrate well. Chirrups, short trumpets and clangs showed strong spectral peaks and pips were particularly unusual sounds with impulsive narrowband signatures composed of harmonically spaced peaks. Squeals exhibited prolonged, narrowband swept frequency signatures often with slight oscillation. All types of vocalization with the exception of clangs were heard from sperm whales during pure observation, minimum disturbance encounters in the field. Two attempts were made to remove the whales from Scapa Flow, the first being an enticement operation to lure the whales to open water with the use of underwater playback of sounds of socializing female sperm whales and the second a shepherding operation to drive the whales with a flotilla of vessels. The enticement operation was unsuccessful but the shepherding operation was successful, although the whales showed considerable reluctance to navigate a narrow channel to the open sea. During the shepherding operation there was a distinct change in the nature of the whales' vocalizations, with clangs predominating over other forms.

The stomach contents of 344 four-spotted megrim, (Lepidorhombus boscii) and 159 megrim (Lepidorhombus whiffiagonis), off the eastern coast of the Gulf of Valencia (Spain), were analysed. The two species examined do not appear to have very similar diets, based on the species composition of prey. The vacuity coefficient is not high for any of the species, the main food being Crustacea (Decapoda and Mysidacea). Also Amphipoda and Teleostei are components of the diet. Variations in the food of both fish related to their length show few small crustaceans as prey of the major specimens. Finally, there was evidence for seasonal variation of the quality and quantity of the food consumed. There was no great dietary overlap between these two species.

Interbreeding between two populations (Estero de Punta Banda, Baja California, Mexico (PB) and Mission Bay, California, USA (MB)) was tested using the live progeny (nauplii) of the marine calanoid copepod Acartia californiensis, in a male to female ratio of 3:1. The laboratory conditions were 18±2°C and a 12:12 h L:D cycle, during an experimental period of one week. The first filial progeny (F1) present in the replicates were used in four combinational experiments (non-hybrids: PB-PB and MB-MB, and hybrids: PB-MB and MB-PB). To investigate the production of the F2 generation, males and females were selected from F1 and 16 combinational experiments were conducted with five replicates each (non-hybrids: PBPB-PBPB and MBMB-MBMB, and hybrids: PBPB-MBMB, PBPB-PBMB, PBPB-MBPB, MBMB-PBPB, MBMB-PBMB, MBMB-MBPB, PBMB-PBPB, PBMB-MBMB, PBMB-PBMB, PBMB-MBPB, MBPB-PBPB, MBPB-MBMB, MBPB-PBMB and MBPB-MBPB). Statistical analysis for F1 showed no significant differences of the mean for live progeny between the non-hybrids and hybrids and between non-hybrids, but a significant difference between hybrids was found. For F2, the mean live progeny between non-hybrids and hybrids, between hybrids and between non-hybrids was found to be non-significant. These results show successful interbreeding between the populations studied.

Heart rate of the tropical limpet Cellana grata was monitored on the shore (Cape d'Aguilar, Hong Kong) and in the laboratory using a non-invasive technique. Individual field measurements performed on inactive limpets, in a variety of thermal conditions during a diurnal low tide, showed a general increase in heart rate with increasing body temperature. This relationship was not always evident when monitoring individual responses over a diurnal low tide period, since under some circumstances, heart rate of individuals decreased with increasing the temperature of the substrate and foot. A factorial laboratory experiment showed that heart rate was faster at higher temperatures but slower in larger animals. The combined evaluation of field and laboratory data suggests that limpets in some habitats may be able to regulate their metabolic rate when resting on hot rock substrates.

Different marine invertebrates have different tubular or vesicular systems within their locomotor muscle fibres. The siphonophores Chelophyes, Abylopsis and Muggeia have invaginated tubules which are the morphological equivalent of the vertebrate invaginated tubular system, but lack a sarcoplasmic reticulum. In Chelophyes the previous suggestion that Ca2+ channels in the extensive invaginated tubule system allow ingress of Ca2+ is shown to be incorrect. Contraction of the swimming muscles in Chelophyes is not blocked by 20 μM ryanodine, nor is it induced by 10 mM caffeine, hence intracellular Ca2+ stores appear absent. Contraction is, however, maintained by replacement of the greater part of the usual external Na+ by Li+ or by or N-methyl-D-glucamine, although action potentials can still be evoked. Hence we conclude that following contraction, internal Ca2+ is reduced by a Na/Ca2+ exchange mechanism.

The effects of surface roughness and microsolubility on fouling levels are examined using glass and acrylic samples. It is found that both of these, often overlooked, physical characteristics have a noticeable effect on the rate of fouling. The microsolubility of acrylic results in lower fouling than found on glass despite the higher hydrophobicity of acrylic and the resultant increase in initial attraction for fouling organisms. Fouling levels were found to increase with increasing surface roughness and therefore studies on the fouling susceptibility of different materials should report the roughness values of the samples examined.

A variety of methods are available to extract chlorophyll from epilithic biofilms using solvents. The relative efficiency of these has not been determined simultaneously and there is no recognized standard procedure. In this paper techniques for sample collection, storage, preparation and extraction are reviewed and compared experimentally.

Extraction of chlorophyll was incomplete unless biofilms were fully hydrated. This factor was highly significant for all the solvents tested, with at least three times more pigment being extracted from hydrated samples than from dry ones. Methanol was the most efficient solvent, releasing over 96% of the total chlorophyll during a single extraction; hot ethanol extracted 86%, while acetone extracted less than 50%. Sonicating samples during extraction did not release any additional pigment. Centrifuging to remove suspended material did not alter estimates and was not advantageous. Rugose rock surfaces released more chlorophyll than smooth ones. However, a simple method to quantify surface rugosity at an appropriate scale was not available.

Based on these observations, a standard method for chlorophyll extractions from epilithic biofilms using 100% methanol at room temperature (20°C) is proposed. This technique requires considerably less supervision than previously preferred methods and gave a chlorophyll extract which was stable for 15 h.

Two members of the scallop genus Pecten (Bivalvia: Pectinidae) occur in European waters. Pecten maximus is largely an Atlantic species whilst Pecten jacobaeus is almost completely confined to Mediterranean waters despite slight overlap of distributions in the western Mediterranean. Genetic distances between these species were estimated using both allozyme electrophoresis and mitochondrial DNA PCR–RFLP and shown to be of a similar magnitude to intraspecific values, considerably lower than expected for congeneric species. These data are discussed in the light of recognised morphological differences, hybrid rearing trials and previous studies examining genetic distance by allozyme methodologies.

Towed underwater TV observations at 440 m in the northern Evoikos Gulf, Greece, revealed a soft mud plain heavily bioturbated by the thalassinidean Calocaris macandreae, with Callianassa subterranea and Nephrops norvegicus also present. Ejecta mounds and feeding traces indicated the presence of a large echiuran, provisionally identified as Maxmuelleria gigas. The locality also supported a dense population of a second echiuran, Bonellia viridis, a species not previously recorded as an inhabitant of sedimentary environments.

Seasonal variations in reproductive cycle of Spisula solida were studied between June 1995 and June 1996 at a site off Vilamoura, southern Portugal. Sex ratio was found to be in favour of males. Both males and females showed a synchronism in gonadal development and spawning. Gametogenic activity started with decreasing temperature at the beginning of autumn. The onset of spawning took place in February when the seawater temperature began to increase. Spawning ended in May. It is possible that the white clam does not spawn at a definite temperature, rather responding to the increase in seawater temperature. Between June and September, the specimens were found to be in the resting stage and the condition index increased, probably due to the accumulation of reserves. Spisula solida reached maturity during the first year of life.

This paper analyses the age and growth pattern of the four-spotted megrim (Lepidorhombus boscii), collected in the north Aegean Sea. The otoliths of the species exhibit bilateral asymmetry. Our data indicates that males have shorter lifespans (0–6 y) than females (0–8 y) and reach lower asymptotic lengths. A significant difference in growth rate exists between the two sexes after the first year of life. Growth in length is greater in females than males, whereas males appeared to be heavier than females of the same size. The latter was also corroborated by the higher accumulation of lipids in the muscle of males in relation to females. The growth rate of the species in the Atlantic was higher than in the Mediterranean. The oligotrophic character of the study area seemed to have a negative effect on the growth of megrims.

A new species of marine yeast Kluyveromyces penaeid (Saccharomycetoideae) was isolated from the heart tissue of a subadult shrimp Penaeus chinensis during tissue culture. The yeast grew well in seawater supplemented with 2% shrimp extract, but did not grow in chemically defined media. The vegetative cells reproduced by multilateral budding and formed rudimentary pseudohyphae occasionally. Asci were spheroidal and evanescent containing 2–13 smooth or oval ascospores. The best temperature for the yeast to grow was 20–25°C and 37°C was lethal. The yeast grew well in half to full strength seawater supplemented with shrimp extract, but did not grow in 25% strength seawater. The carbohydrate fermentation test was positive, the diazonium blue B and urea hydrolysis tests were negative.

Abiotic and biotic aspects of the covering behaviour of the purple sea urchin, Paracentrotus lividus (Echinodermata: Echinoidea) were systematically examined in situ and in the laboratory to analyse potential intra-population differences in the nature of this behaviour. In the field, significant differences in the occurrence of covering behaviour were found between age groups. Smaller P. lividus covered at higher frequencies than larger individuals. Higher proportions of individuals were also observed to cover during afternoon sampling periods. Significant differences in the types of covering material used were found between P. lividus observed in the laboratory and in the field. These findings suggest that the benefits and/or opportunities of covering behaviour may change with size and habitat.

The lengths of chthamalid cyprids collected during August 1996 on six rocky shores in County Cork, Ireland are reported. The lengths showed a bimodal distribution. The smaller length mode corresponded well with the length range of laboratory-reared cyprids of Chthamalus montagui (Crustacea: Cirripedia), whilst the larger length mode was greater than the length range reported for laboratory-reared C. stellatus. Size may be a useful means to identify Chthamalus cyprids in field investigations.

The effects of shell resource and interspecific competition on sexual size dimorphism of the hermit crab, Pagurus middendorffii (Decapoda: Paguridae), were examined from population comparisons. Degree of size dimorphism and mean shell size occupied by male and female P. middendorffii differed among adjacent sites, and there was a significant correlation between them. Although most large P. middendorffii occupied large Chlorostoma lischkei shells in both shell-limited and shell-unlimited populations, P. lanuginosus, a sympatric species, occupied large C. lischkei shells more frequently than P. middendorffii did in a shell-limited population. Environmental factors, shell availability and interspecific competition for shells, might play important roles in determining the degree of sexual size dimorphism of P. middendorffii.

Zooplankton biomass varies on temporal, horizontal and vertical scales. However, data sets which incorporate all these dimensions at high resolution are very rare. Two devices which measure all these aspects have recently been simultaneously deployed in the Celtic Sea, the continuous plankton recorder (CPR) and the Longhurst–Hardy plankton recorder (LHPR). This demonstrates that integrated biomass derived from the LHPR are not significantly different from those derived using the CPR. Values have, therefore, been combined for the first time to describe the vertical distribution of mesozooplankton biomass at the Celtic Sea shelf edge through an annual cycle. This suggests that the surface biomass peak is broader at the shelf break than in the open ocean and in the autumn the main biomass peak may be below the depth sampled by the CPR.

Some meiobenthic harpacticoid copepod species cannot be successfully cultured, therefore empirical models were developed to estimate their development times, using literature data, but taking into consideration several empirical rules previously formulated to model the development of planktonic copepods. The present models demonstrated the overwhelming influence of rearing temperature on egg development time, and of body length on total development time and indicate a capacity to adapt development rates to environmental temperature.

Oval squid Sepioteuthis lessoniana hatchlings originated from maternally identical egg strings were incubated under constant temperature and examined with special reference to statolith formation. Statoliths of a hatchling already had an adult-like shape, and some increments were observed. In spite of the maternally identical origin and constant incubation temperature (25°C), dorsal mantle length and statolith length of the hatchlings varied from 4.70 to 6.26 mm and 320 to 410 μm, respectively (N=14). These variations had a positive correlation with the embryonic duration ranging from 22 to 27 d, which means that the size of body and statolith becomes larger in hatchlings hatching later.

The polymerase chain reaction (PCR) was used to produce species-specific DNA markers (RAPDs) from two sibling cockle species and five other co-occurring intertidal bivalves. Amplification reactions with one single primer readily distinguished larvae and adults of Cerastoderma edule from larvae and adults of C. lamarcki, and from adults of Mya arenaria, Macoma balthica, Scrobicularia plana, Venerupis pulastra and Mytilus edulis. Random amplified polymorphic DNA (RAPD) is suggested as a simple and quick method to determine species identity in taxa that are difficult to identify on the basis of morphological characters alone, such as marine bivalve larvae.