In the field, both covering materials and shelters are commonly available to sea urchins. The behavioural decision between covering and sheltering thus obviously exists. However, no information is available on the preference between the two natural behaviours. Two conditions were designed with covering and sheltering materials to comparatively describe the diel trade-off between covering and sheltering behaviours in male and female Strongylocentrotus intermedius. In the present study S. intermedius had an obvious diel trade-off between covering and sheltering behaviours, preferring covering over sheltering when both behaviours were possible. Sex did not significantly affect the trade-off between the two behaviours, no matter whether covering materials were inside or outside the shelters. The rhythm of covering behaviour was not well correlated with intensity of light in the trade-off with sheltering behaviour. The present study provides new insights into behavioural ecology of sea urchins.

Morphometric characteristics of the periotic–timpanic bone complex in the middle ear of cetaceans, are effective characteristics in evaluating systematics. However, they have not been used for studies of geographic variation regarding dolphins of the genus Sotalia. This study aimed to compare the periotic–timpanic of Sotalia guianensis from four distinct locations, considered here as different operational taxonomic units, Amapá/Pará (AM/PA), Maranhão/Piauí (MA/PI), Ceará (CE), and Rio de Janeiro (RJ), using 21 morphometric measurements. Multivariate analysis showed significant distinction mainly between the units of northern (AM/PA and MA/PI) and south-eastern (RJ) Brazilian coast. The timpanic bone showed variation, reaching larger sizes in the Brazilian south coast unit, corroborating current molecular data on the geographic variation of S. guianensis.

Despite alterations caused by anthropogenic activities in Singaporean coral reefs, the sponge communities are quite diverse and Xestospongia testudinaria is one of the most common sponge species. In the present study, we used 16S rRNA gene barcoded pyrosequencing to characterize and compare bacterial communities from different biotopes (sponge, seawater and sediment) and to identify dominant bacterial symbionts of X. testudinaria in a Singaporean coral reef ecosystem. Our results showed that biotope appears to affect the richness, composition and abundance of bacterial communities. Proteobacteria was the most abundant phylum in sediment and seawater whilst Chloroflexi was more abundant in X. testudinaria. Members of the order Caldilineales (fermentation of organic substrates), Chromatiales (purple sulphur bacteria), Rhodospirillales (purple non-sulphur bacteria) and Syntrophobacterales (sulphate-reducing bacteria) were relatively more abundant in X. testudinaria samples.

Light and electron microscopy showed the same distribution of glycogen. The peritoneal cells contain large amounts in all three body regions investigated: the forepart, metameric region and postannular region. Glycogen is present in most epidermal cells and is very abundant in some, particularly in the postannular region, but the cells which secrete the chitinous and proteinaceous components of the tube are almost devoid of glycogen.

A combination of photography and subsequent image analysis of the photographs has been used to measure maximum length, perimeter length and total area of fronds of tagged Fucus serratus L. as part of a study of the growth of this species on the Yorkshire coast. Maximum mean growth rate of 0·26 cm d-1 was observed during June–July. Minimum mean growth rate of 0·01 cm d-1 was observed during October-March. The method is relatively quick and convenient, and has the advantage that in addition to apical growth of the longest and/or other branches, lateral growth and total growth in surface area can all be recorded, while loss of tissue can also be determined. A further advantage is that a photographic record is obtained of the history of each individual plant.

Space is one of the primary limiting resources for organisms on the intertidal rocky shore. This paper examined the effect of reduced density on key traits (mortality and growth) on the intertidal barnacles, Chthamalus montagui and Semibalanus balanoides, on the mid-shore in Plymouth, UK. Intra- and interspecific treatments comprising of C. montagui and S. balanoides were manipulated to reduce densities at two similar sites. Changes in mortality and operculum growth were assessed over an 8-week period using digital photography. Covariates of growth included nearest neighbour distance, competition between closest pairs and initial size. Conflicting patterns were observed when comparing growth rates between treatments and sites. At Site 1, interspecific treatments had a lower growth rate than intraspecific treatments, whereas at Site 2, interspecific growth rates were higher. ANCOVA showed that nearest neighbour distance had no significant effect on growth, but when comparing differences in growth of closest neighbouring pairs, C. montagui treatment showed evidence of competition whereas S. balanoides did not. ANCOVA analysis indicated no difference in growth between each outcome of pair competition, suggesting winners are initially bigger than losers. Comparisons of mortality between treatments indicated mortality over time with no significant differences observed between treatments, but response surface methodology (RSM) revealed no effects of competition on mortality of S. balanoides, but negative effects of both intra- and interspecific competition on C. montagui survivorship. Examination of natural populations of barnacles in the mid-shore indicated there was strong spatial variation in growth rates, perhaps driven by small-scale differences within sites.

Larval fish and hydrographic data were collected in Kavala Gulf (northern Aegean Sea) across a fine scale grid of 17 stations in two surveys, carried out in the beginning of July 2002 and 2003. Despite the different taxonomic resolution and excluding the unidentified larvae, 22 taxa were caught in 2002 and 27 in 2003. Seventeen taxa were present in both years' collections. A total of 833 larvae were collected during the two samplings. The adults of several larvae caught, although sometimes at very low concentrations, are species with high commercial value or represent a major proportion of the captured production of the northern Aegean Sea. The larvae of European anchovy (Engraulis encrasicolus) were most abundant in both years followed by the brown comber (Serranus hepatus), the gobies (Gobius sp.) and, only for 2003, round sardinella (Sardinella aurita). Maximum anchovy larval densities reached 4145/10 m2 and 13852/10 m2 in the 2002 and 2003 surveys, respectively. The spatial extent of anchovy larvae was also high as they were collected at 12 stations in 2002 and at 15 in 2003. Besides water circulation, the spatial distribution of fish larvae was largely influenced by temperature, salinity and dissolved oxygen.

Coastal lagoons are highly variable environments that may act as hotspots of genetic diversity as a consequence of their ecological role as nursery habitats of marine species with both ecological and fisheries importance. The edible cockle (Cerastoderma edule) is a commercially important shellfish resource inhabiting coastal lagoons in Europe and their fisheries management urgently needs genetic studies to design appropriate strategies to promote the recovery of exploited populations. The aim of this study was to assess the C. edule genetic diversity and population structure at a small geographic scale, inside Ria Formosa coastal lagoon (southern Portugal) using mitochondrial cytochrome oxidase I sequences in six locations. Outcomes pointed to a common pattern of high haplotype diversity and non-significant genetic structuring inside the Ria Formosa lagoon. A high level of gene flow was detected between all localities and the presence of a single stock from a genetic point of view may be considered for fisheries management purposes. The existence of a high number of haplotypes and high values of haplotype diversity of C. edule in Ria Formosa lagoon could be consistent with the hypothesis that higher genetic diversity is expected in populations occurring in coastal lagoons, suggesting that lagoons could increase standing genetic variation and an adaptive potential of lagoon populations as an ecological response to a highly variable environment.

INTRODUCTION

The results of bottom line fishing have shown that significant catches can be made down to 3000 m depth at several positions on the continental slope off south-west England (Forster, 1968). But when hooks were lifted off the bottom either deliberately or accidentally very few fish were taken. The chances of catching bathypelagic fish in mid-water by baited hooks therefore seemed slender. In 1966 when thin white lines were tried, they were bitten through several times, always at about 1100 m depth. Trials with baited hooks set on thin wire lines in 1967 showed that the black scabbard fish Aphanopus carbo could be taken at this depth. In 1968 and 1970 during the course of short voyages on R.V. ‘Sarsia’ further vertical line hauls were made, taking Aphanopus regularly and also two species of deep-water squaloids.

Morphological and genetic investigations have led to the identification of Spiophanes adriaticus sp. nov. (Polychaeta: Spionidae) from the North Adriatic Sea (Central Mediterranean). A total of 81 specimens were recorded along the sublittoral zone between 8 and 27.5 m of depth. This species differs from other congeners by having: two pairs of black eyes, a cirriform occipital antenna, dorsal ciliated organs as thin bands usually extending to chaetigers 11–12, dorsal ciliated crests from chaetiger 14–17, undulate glandular opening on chaetigers 5–7, unhooded hooks from the 15th chaetiger and Y shaped tubes. A detailed description and illustrations are provided for the new species. Through DNA barcoding results and comparison of DNA sequences of the new species with those of other congeners available in the GenBank database, the validity of the new finding was confirmed. Spiophanes adriaticus sp. nov. represents the eighth species of Spiophanes recorded for the Mediterranean Sea. A key for the identification of Mediterranean Spiophanes species is also provided.

Investigations conducted off the Algerian coast between 1996 and 2001 resulted in the collection of 201 blue sharks, Prionace glauca, including 144 females and 57 males. Prionace glauca is mainly captured off the central area and lesser in the eastern area from the Algerian coast. The central area is probably a mating site of the species. The sex ratio changes are calculated according to specimen sizes and seasons. The recent abundance of the species in Mediterranean areas is discussed.

Examination of a small sample of Podocerus chelonophilus found clustered around mucus-exuding epidermal lesions of juvenile loggerhead turtles (Caretta caretta) collected off Madeira revealed the presence of fibrous material in the gut contents. The absence of planktonic remains suggested that these amphipods had been exploiting turtle material directly.

With the exception of the Cyamidae (whale lice), rather few amphipod taxa consistently live in association with marine vertebrates. Sea turtles, however, have been recorded carrying gammaridean and caprellidean epibionts by Caine (1986), who reported eight gammaridean species (including two domicolous fouling species) from nesting loggerhead turtles in Florida.

Relationships between size, wet weight, dry weight, carbon and nitrogen content were determined in Ophiothrix fragilis (Echinodermata: Ophiuroidea). Such relationships appeared very useful when studying dynamic processes such as nutrition, growth, excretion or reproduction, considered as fluxes of carbon and nitrogen in the ecosystem.

Relationships between size, wet weight, dry weight, ash free dry weight, carbon and nitrogen content of organisms are of fundamental interest in ecological studies of ecosystems. They allow us to understand and quantify the role of a species as it stores, consumes or produces organic matter during its life cycle. Determination of conversion factors are time-consuming but very useful for estimating flows in the ecosystem (Brey et al., 1988). Some compilations of conversion factors have been published (Båmstedt, 1981; Rumohr et al., 1987).

Ophiothrix fragilis (Abildgaard) is the dominant species of the ‘pebbles with sessile epifaunal community’ (Davoult, 1990), located in the Dover Strait (eastern Channel), where tidal currents are very strong. It is considered as an efficient suspension feeder (Roushdy & Hansen, 1960; Warner, 1971) and lives in dense populations (1000–2000 individuals m-2; Davoult, 1989) which are assumed to have a significant effect on the fluxes of organic matter from the pelagic to the benthic system and on the fluxes of ammonium to the water column (Davoult et al., 1991).

Individuals were sampled in May and June 1991 off the Cape Gris-Nez (50°55′N 1°35′E). Two-hundred individuals were measured (diameter ±01 mm, after Guille, 1964), dried at 60°C for 48 h, weighed (±0·1 mg), burnt at 520°C for 6 h (Anonymous, 1986), and the ash weighed (±0·1 mg). Total organic carbon and nitrogen content were determined with a CHN element analyser (Carlo Erba 1106): after a flash combustion in a helium stream temporarily enriched with pure oxygen, quantitative combustion was achieved by passing gases over Cr2O3 after a transfer through a reduction reactor to eliminate the excess of oxygen; components were separated in a chromato-graphic column, eluted, then measured by a thermal conductivity detector. Thirty-eight dried ophiuroids were ground with a micro-grinder, then two sub-samples (except for individuals <2 mm) were weighed at ±1 μg (76 measurements).

The aim of the present study is to test the resource economic monopolization hypothesis and the hypothesis of monogamy using the shrimp Alpheus estuariensis as a model. The shrimps were collected in two areas in the Vaza-Barriz estuary, north-east Brazil, from August to November 2016. The average abundance of refuges was obtained through 30 random replicates. The shrimp presented a random distribution in both areas. Males and females found together showed a weak relation between their sizes, with males being larger than females. In addition, the cheliped of males grows proportionally more than that of females. The great abundance of refuges present in the environment, added to the aforementioned results, do not support the idea of refuge-guarding behaviour or monogamy. These results, which are in disagreement with those already found for some shrimps of the same family, genus, and even species, reinforce the idea that Alpheidae can be used as a model in the study of how environmental conditions are capable of shaping the social behaviour of a species.

In situ seasonal study of siphonal activity in Mya arenaria (ten individuals) was performed using a fixed video camera during nine complete submersion cycles between May and November 1996. Siphonal activity was described by exhalant and inhalant siphon simultaneous closure frequencies (EIC), pseudofaeces production frequencies (PFC) and both siphons opening state duration (OPE). A repeated measure ANOVA model showed a slight OPE increase between May and June and a strong OPE and EIC decrease from October. A non-linear probit model on the proportion of individuals showing PFC events during submersion cycles indicated a progressive decrease of this behaviour with time. The siphonal activity was relatively high until September and then decreased from October suggesting a marked reduction of the feeding activity.

The cercaria described here was found on 21 April 1936, in twelve out of sixteen specimens of Nucula nucleus (L.) from Cawsand Bay, Plymouth Sound. The parasite was found by Dr Marie V. Lebour, who kindly gave me the infested molluscs for examination. I have thought it advisable to publish these notes, incomplete as they are, as it may not be possible for me to obtain further specimens of infested Nucula for some time to come.

The trematode was found to parasitize the digestive gland and gonad. The cercariae develop in irregularly shaped parthenitae which each contain from, two to ten larvae in various stages of development. The parthenitae measure 0.9–2.0 mm. in length.

The cercaria is very large and has a long, forked tail (Fig. 1). The measurements on the left of Table I were made with an ocular micrometer when the living cercariae were slightly flattened under the pressure of a cover-slip.

The body is elongate in outline, with a slight constriction just behind the oral sucker, and reaches its greatest diameter opposite the ventral sucker. The pre-acetabular region of the body is highly muscular and capable of much. extension and contraction. Near the posterior border of the oral sucker there are two blunt processes, ventro-lateral in position. In section, the body is somewhat cylindrical, and consequently it is almost impossible to obtain true measurements from living cercariae because different individuals could not be subjected to the same pressure under a cover-glass. The measurements given on the right of Table I are of mature cercariae fixed in Bouin's fluid without pressure, and supplement those of living cercariae.

A new species, Longibrachium falcigerum, is described from seamounts in the North Atlantic Ocean, from depths of 495–695 m. Longibrachium falcigerum sp. nov. is unique among its congeners for possessing falcigers and spinigers in the lower chaetal bundle. Another member of the Rhamphobrachium complex, Rhamphobrachium (Spinigerium) brevibrachiatum, occurring with the new species, is briefly characterized.

Variation in the abundance of Barleeia unifasciata is compared in several red algal species between June 1978 and June 1980 at Cooskeen Cove, Bantry Bay, Ireland. Population abundance in all algae varied seasonally, exhibiting a cycle of late-summer to autumn maxima, with winter to early summer minima. Greatest abundance was recorded in those algae which formed compact turf-like growths suitable for the entrapment of diatoms and detrital material and provided greatest shelter from wave-crash. Length frequency data showed the main recruitment period to be late June-October with a peak in August with juveniles present in all months of the year. Maximum life span was shown to be 2 years or more with only 15 % of the population surviving into the second year. Sexual development and reproductive cycle was determined for 0 + and 1 + animals. Mature males produced sperm continuously throughout the year. Not all 0 + females spawned in their first year. Summer spawning 0 + females exhibited reduced sexual activity in October and spawned again in the following summer. Some 1 + females spawned in winter and spring. Delayed sexual development in some individuals of both sexes was related to late hatching.

While experimenting on the vertical distribution of plankton in comparatively shallow waters I found it necessary to devise a releasing apparatus for use with horizontally towed plankton nets. Under existing working conditions there were four circumstances for which the instrument had to be adapted:

Malacobdella grossa is recorded from a new host, Cerastoderma edule, and the association appears to be confined to the Shetland Islands. Infection rates were high at five of the seven sites studied and double infections were very common. The commensal population was dominated by large individuals.