The reflected patterns and colours of terrestrial animals often show a sexual dimorphism associated with visual display, mate recognition and selection. In the sea the structures associated with bioluminescence may also show a marked sexual dimorphism. Some apparent bioluminescent dimorphisms (e.g. differences in photophore numbers) are probably secondary functions of sexual differences in size. A role in sexual communication is much more likely where specific photophores are developed or enlarged in mature specimens of one sex only but the presence of light organs in female anglerfishes (but not in males) is complicated by a significant size dimorphism. Dimorphisms in dragonfishes and lanternfishes primarily involve the relative enlargement of particular photophores in the males. A sexual role is assumed, but the morphological differences are often small. Most male ponyfishes have enlarged light organs; behavioural observations of free-swimming animals have clearly demonstrated that the males use them to generate bioluminescent sexual signals.

This study evaluates the role of protozoa in larval fish feeding by describing protozoa in larval fish diets and testing the hypothesis that, in the Irish Sea, larval fish feed on protozoan prey at rates that potentially sustain their food requirements. Gut contents of 11 taxonomic groups of larval fish were examined, and protist prey occurred in the diet of all of them. Protozoan prey were identified, which provided an insight into their trophic role. Most of the protozoan prey were autotrophic or mixotrophic. In general, larval fish diets were constant over the spring/summer period, regardless of prey availability in the field and the composition of larval fish assemblage (taxonomy and size). A laboratory experiment on ingestion rates of flounder larvae as a function of ciliates concentration was conducted. Combined laboratory and field data showed that, in the Irish Sea, it is unlikely that ciliates are often the primary food source of flounder larvae, and, by implication, other larval fish as well. However, ciliates and other protozoa could be a substantial component of the larval fish diet, and they may potentially prevent food limitation.

The competition for space among fluorescent and nonfluorescent Anemonia species was monitored in the Mediterranean Sea in order to see whether the fluorescent species A. sulcata var. smaragdina was a better competitor in shallow water habitats. Over a period of 11 years, A. sulcata var. smaragdina convincingly out competed the nonfluorescent A. rustica. We thereby found support for the notion that the GFP-like pigments may increase competitive ability in anthozoans.

The life cycle of a species of the genus Bougainvillia (Cnidaria: Hydrozoa), found in the southern Mediterranean Sea, Italy, is here described. Hydroid colonies produced immature medusae with two tentacles and two ocelli per bulb and four unbranched oral tentacles. The number of tentacles and ocelli, which remained constant during the entire life cycle, are here considered diagnostic characters to identify the present as a new species. Female medusae lived up to 47 days (with an average of 30 days) when reared at 17°C, while males, reared at the same temperature, were short-lived, concluding their life cycle in no more than 15 days. The medusa of this species resembles B. ramosa var. nana described by Hartlaub in 1911 on the basis of few specimens and no polyp stage. After the complete life cycle has been observed, and given its peculiar medusa stage, Hartlaub's subspecies (variant) must be promoted to species rank as Bougainvillia nana.

This study presents a comparison of distribution and abundance of dominant megafaunal species at the TAG hydrothermal mound on the Mid-Atlantic Ridge from 1994 to 2004. A geographical information system (GIS) database was compiled from georeferenced observations of faunal abundances at 534 locations on the TAG hydrothermal mound, determined by image analysis of ROV dive footage from November 2004. These data are compared with observations from submersible dives in 1994 to assess changes in the extent and population density of aggregations of the shrimp Rimicaris exoculata at the central black smokers of TAG. The GIS database was also used to assess changes in abundance and distribution of the anemone Maractis rimicarivora by simulating the path of a biotransect conducted in 1994 and 1995. There was no evidence of a decline in the extent of shrimp aggregations at the central black smokers of TAG between 1994 and 2004. This result indicates that occasional exposure to high-intensity submersible lighting, which took place during several scientific expeditions in the intervening period, does not pose an immediate conservation threat to populations of R. exoculata. Similarly, there were no significant differences in the distribution and abundance of anemones between 1994 and 2004. These results indicate a constancy in the identity, distribution and abundance of dominant species at TAG that contrasts with other vent sites where quantitative time-series have been established. The reproductive pattern of R. exoculata was also examined by dissection and direct measurement of oocytes from females collected in September 1994 and November 2004, providing the first comparison of reproductive development in samples from different months for this species. There was no significant difference in oocyte size–frequency distributions of females collected in these samples, indicating a lack of seasonal reproduction in R. exoculata.

A study was made of the efficiency of a commercially available hydraulic dredge design in use on the west coast of Scotland and of the annual biomass production of two different razor clam (Ensis spp.) beds within the Clyde Sea area. These two parameters, viz fishing efficiency and population annual production, are fundamentally important to any proper attempt to assess the long term sustainability of a fishery. The hydraulic dredge used in this study was found to have an absolute efficiency of 90.1% when expressed in terms of the collected wet weight biomass, representing the first time that the efficiency of a hydraulic dredge of this nature has been measured rather than simply inferred from track width. This indicates that this dredge design has the potential to remove the majority of a clam population, including undersized immature individuals, within a 45 cm swath in a single tow. Annual production estimates were also made for two separate razor clam beds. One population of Ensis siliqua was located in Irvine Bay and the other two populations (one E. siliqua and one E. arcuatus) occurred in a mixed bed on Hunterston Sands. Each location was sampled quantitatively on a regular basis using the same hydraulic dredge. Dredged areas were measured by SCUBA divers so that the population densities could be calculated for each sampling event. Size-classes within each population were identified from siphonal shell breadth measurements and production estimates were calculated using a size-cohort analysis procedure designed for stocks exhibiting recruitment but that do not have separable age-classes. Production of all three populations was low during the study (1.82–18.08 g AFDW 10 m-2) as were the production/biomass estimates (0.01–0.11). These data indicate that populations of Ensis spp. on the west coast of Scotland are slow-growing and typical of K-selected species. These data highlight the conflicting pressures facing any razor clam fishery: the design of extremely efficient hydraulic gear and the slow-growth of the target species. It is clear that the future commercial exploitation of these species will need very careful management to ensure sustainability and avoid fishery over-depletion.

Latreutes pymoeus is a poorly studied tropical and sub-tropical shrimp species that mainly lives on sea grass beds. Samples were collected from sea grass beds of Inhaca Island, Mozambique, during August 2005 at neap/spring and low/high tides. Specimens were identified, sexed, counted and morphometric measurements were made. Ovigerous females were classified as small (carapace length (CL): 2.7–3.2 mm), medium (CL: 3.3–3.8 mm) and large (CL: 3.9–4.4 mm). Embryo masses were carefully removed from the pleopods with forceps, eggs staged and counted. On average, about 20% more males were found than females (0.64 ±0.25 and 0.56 ±0.28 ind m-2, respectively), but males were significantly smaller (2.25 ±0.32 and 2.60 ±0.47 mm CL for males and females, respectively). At 3.1 mm CL at least 50% of the females found carried embryos in the pleopods. Average (±SD) brood size increased significantly with female length (76 ±18, 133 ±64 and 205 ±61, for small, medium and large ovigerous females). The number of embryos decreased significantly over the incubation period for each size-class of the shrimp. Brood loss from embryonic Stage I to Stage IV for small, medium and large shrimp were 19.8%, 36.5% and 41.8%, respectively. Although an increase in brood loss was observed with increasing shrimp size, senescence did not seem to occur since larger shrimps carried a higher number of embryos and negative allometry was not recorded. Mean embryo volume, in the same development stage, was not significantly different among the small, medium and large shrimp, increasing significantly from 0.014 mm3 to 0.029 mm3 from the first to last embryonic stages.

The predatory action of the pink shrimp (Farfantepenaeus brasiliensis and Farfantepenaeus paulensis) trawling fishery in south-western Brazil affects populations of some benthic species and Hepatus pudibundus is an abundant by-catch in this fishery. Individual growth and mortality of H. pudibundus were studied by taking monthly samples for a year from the by-catch of the pink shrimp fishery in the Ubatuba region. The von Bertalanffy growth model described growth of H. pudibundus (K=2.73 y-1, CW∞=82.97 mm; K=2.62 y-1, CW∞=66.72 mm, for males and females respectively). Modal progression of the monthly average sizes was related to increasing values of relative condition index. The instantaneous coefficients of total, natural, and fishing mortality were: males, Z=7.62 y-1; M=1.80 y-1; F=5.83 y-1; females, Z=7.36 y-1; M=1.80 y-1; F=5.56 y-1. Length composition and mortality analysis suggest that H. pudibundus in the Ubatuba region might be overfished.

Chasmagnathus granulatus is a semiterrestrial intertidal burrowing crab that inhabits both the unvegetated mudflats and the cordgrass (Spartina densiflora) salt marshes in Mar Chiquita Lagoon (Argentina), where it is considered the ecologically key species. The mass of C. granulatus eggs incubated by females is colonized by epibiotic micro-organisms and accumulates detritus. The type of epibionts that use eggs as a substrate, the infestation degree, the maternal care behaviour and the protection of the incubation chamber were compared between females living on mudflats and on Spartina-dominated areas. In both places, the epibiosis by bacteria and filamentous fungi and peritrichid colonial ciliate was significantly higher in the periphery than in the centre of the brood mass. The accumulation of detritus was higher in the periphery in mudflat females but not in salt marsh females. Moreover, the level of detritus was significantly higher in mudflat than in salt marsh females only in the periphery of the brood. The infestation level of bacteria and fungi, and peritrichids, increased throughout the embryonic development only in mudflat females. The periphery of the brood mass was significantly more contaminated in mudflat than in marsh females, while the central region of the brood mass did not differ between habitats. The pleopods were significantly more contaminated by bacteria and filamentous fungi and peritrichid colonial ciliates in premoult females than in postmoult females, independently from the collection site. The percentage of females with abnormal embryos was significantly higher in mudflats (26.7%) than in marshes (12.3%). Females with late embryos spent more time flapping the abdomen and probing the embryos with the chela. Non-ovigerous females did not perform specific maternal care activities. The volume of brood mass both in early or late stage of development is greater than that of the incubation chamber and, consequently, peripheral embryos are more exposed.

Ucides cordatus is the most commercially important mangrove crab in Brazil. In spite of its economic importance, there are few studies of its reproduction, in particular the female reproductive system. The present study describes the histology and histochemistry of the spermathecae of U. cordatus. Adult females were caught monthly from July 2004 through June 2005, at Iguape, State of São Paulo. The crabs were anaesthetized, and their spermathecae removed and fixed in Davidson's fluid, following the histological routine for paraffin. The slides were stained with HE, xylidine Ponceau, PAS, alcian blue (pH 1.0 and 2.5), Sudan black B and picrosirius-haematoxylin. Histologically, the spermathecae possesses a capsule of conjunctive tissue, rich in collagen fibres, which surrounds the secretory columnar epithelium. In the lumen, individual sperm packets are not observed; the spermatophores are intermixed with the seminal fluid and secretions of the spermathecae itself. A large proportion of the free spermatozoids and spermatophores are arranged in homogeneous masses in the proximal part of the spermathecae. The secretion produced by the columnar epithelium appears to promote the movement of the gametes to the fertilization chamber, in a ventral position, allowing fertilization of the oocytes. Histochemically, the secretion produced by the columnar epithelium was strongly positive for neutral polysaccharides, positive for acid polysaccharides, and weakly positive for proteins and lipids. This secretion forms a glycoprotein matrix which is associated with maintenance of the spermatophores, which can remain stored for long periods.

Previous studies on the ultrastructure of barnacle cypris larvae suggest that cypris morphology, especially the antennules which play a key role in selecting the final substratum for settlement, may show variations between species existing in different habitats. In the present study, the cypris morphology of the barnacle Fistulobalanus (Balanus) albicostatus, which predominantly lives on trunks of mangrove trees was investigated using scanning electron microscopy and compared with that of species from other habitats that have already been described. The antennular segments II and III of F. albicostatus each bear one post-axial seta. The third segment consists of an attachment disc surrounded by a thin cuticular velum and the fourth segment exhibits four sub-terminal setae and five terminal setae. The morphology of the cypris antennules of F. albicostatus is similar to other balanomorph barnacles which inhabit hard shores, revealing that the antennular morphology does not have diagnostic variations between species from the different intertidal habitats. The morphology of the caudal rami (used in the evaluation of the substratum microtopography), however, appears to vary among barnacles living on different substrata.

In this study we present results on epibionts on Zygochlamys patagonica from material collected during monitoring cruises in different areas in the Argentine Sea. We update the checklist of epibionts increasing the number of taxa from 19 to 41 and considering two species closely associated with the shells. The demosponge Iophon proximum was the most frequent and abundant epibiont (% presence and coverage). Polydora sp. was registered as a parasite of Z. patagonica in shells from the Beagle Channel, but it did not infest scallops from the commercial beds. Zygochlamys patagonica shells constitute conspicuous hard substrate available for the settlement of sessile organisms. This fact leads to an increased benthic richness in the continental soft-bottom areas of the Argentine Sea, where scallop beds are located.

The aim of this study is to analyse the co-occurrence of the encrusting sponge Iophon proximum and other sessile organisms on the shells of the Patagonian scallop, Psychrochlamys patagonica, and the relationship between scallop size and the presence of this sponge. Scallops were collected from four beds distributed along the 100-m depth isobath on the continental shelf off Argentina (south-western Atlantic). Statistically significant avoidance was observed between I. proximum and all other groups of sessile invertebrates. Co-occurrence of bryozoans, foraminiferans, folliculinid ciliates, hydrozoans, octocorals and spirorbid, serpulid and sabellarid polychaetes on valves not monopolized by I. proximum produced significant clumping, which, however, almost ceased to occur when only valves without this sponge were analysed. In Patagonian beds, valves monopolized by I. proximum were significantly smaller than those in which the sponge was absent (valve height, mean ±SE, with I. proximum: 54.1 ±1.74 mm, without I. proximum: 60.4 ±0.62 mm). This is the first study to report a significantly smaller size in sponge-covered scallops compared to those without sponges.

The predatory caenogastropod Hexaplex trunculus employed different methods to access different species of bivalve prey characterized by different shell thicknesses. Hexaplex trunculus drilled Callista chione and Venus verrucosa at their shell margins but the latter species also laterally. It also attempted to drill two species of Tapes but successfully penetrated these only after chipping the shell margin. Chipping, whereby a labral spine is forcibly pushed between the prey's valves, especially posteriorly, to break them followed by proboscis insertion, was typically applied to access the thinner shelled prey Cerastoderma glaucum whereas Modiolus barbatus and Mytilus galloprovincialis were either chipped or drilled. The pattern of M. galloprovincialis shell penetration appears related to predator and prey size. Small (40 mm shell height) H. trunculus tended to drill rather than marginally chip M. galloprovincialis. Medium sized (55 mm shell height) H. trunculus either chipped or drilled M. galloprovincialis in approximately equal proportions but also at the valve margin. Larger (70 mm shell height) H. trunculus tended to laterally drill average sized (35 mm shell length) and the biggest (65 mm shell length) M. galloprovincialis. When larger M. galloprovincialis are attacked it thus becomes increasingly more difficult for H. trunculus to chip and drill the shell margin, possibly because the periostracum is thicker here in such individuals, and the predator resorts to lateral drilling. This is possible because as the mytilid ages its surface periostracum becomes progressively eroded and thus thinner and easier to access. Scanning electron microscopy (SEM) identified shell microstructure damage which shows that the chipping and drilling behaviours of H. trunculus result from labral spine damage and dissolutional etching, respectively, rather than mechanical radula rasping. These observations have implications for the use of such predation marks to identify the predator taxon implicated from holes in either empty Recent shells or fossil material.

Intertidal individuals of Mytilus galloprovincialis were exposed to anaerobiosis in laboratory at 22°C and a set of biochemical metabolites and survival potential determined. Differences in survival potential between individuals emersed or kept in oxygen-free seawater were residual according to ST50 values (survival time, P[asymp ]0.05) but emersed individuals survived significantly longer when considering ST90–100 values (P<0.05). Anaerobiosis was similarly activated under both emersion and incubation in anoxic seawater after 6 h according to a seven-fold increase in succinate. Longer exposure of individuals (up to 48 h) caused succinate (and propionate) to increase but in a higher magnitude under incubation with anoxic seawater. Propionate appeared in soft tissues after 24 h of incubation in anoxic seawater and after 48 h when individuals were emersed. Glycogen was not utilized after 6 h in any case, but was progressively used with longer exposure times and in a higher magnitude under incubation in anoxic seawater (48 h). Adenylate energy charge (AEC) was highly affected by both exposure time (P<0.001) and anaerobic treatment (P<0.01). Rapid breakdown of ATP and phospho-L-arginine (PLA) did occur during the first 24 h of anaerobiosis, the latter ATP drop was accompanied by slight increase of ADP but strong increase of AMP that accumulated in a higher magnitude under incubation in anoxic seawater. Biochemical results of the present study suggested a certain degree of aerobiosis for emersed M. galloprovincialis that in turn is linked to a slight but significant longer survival performance. Most significant biochemical changes occurred during the first 24 h of oxygen deprivation, but significant differences between treatments were observed after 24–48 h. These lag differences in biochemical metabolites together with more accurate survival analyses have to be considered when investigating the energy metabolism linked to the anaerobic performance of M. galloprovincialis.

The mating pattern of Littoraria flava, a typical grazer snail of the supralittoral zone and sometimes the midlittoral zone of boulder shores in tropical and sub-tropical regions, was examined to determine the occurrence of size-assortative mating and sexual selection on size. We also evaluated its reproductive behavioural mechanisms, as well as their implications for the evolution of the species. The population was investigated from May 2001 through April 2002, on an artificial rocky shore composed of a boulder wall at Flexeira Beach, Itacuruçá Island, Rio de Janeiro, Brazil (22°56′S 43°53′W). The current study showed that: (1) copulating pairs were observed only from November through March, indicating seasonal reproduction of the population; (2) linear correlation between sizes of copulating mates were weak but significant, characterizing assortative mating by size; (3) there was sexual selection for female size, i.e. large females were favoured as mating partners over small ones; however, sexual selection on size was not observed among males; (4) there were significant positive correlations between male and female shell sizes and the copulation time; (5) there were significant differences in copulation time among different types of copulating pairs; and (6) mating females were significantly larger than non-mating females, while there were no differences between the sizes of mating and non-mating males, indicating differential sexual selection between sexes. These findings may contribute to the evolution of sexual dimorphism in this species. Male choice behaviour plausibly explains the assortative mating and sexual selection on female size of Littoraria flava. As males chose larger mates because they benefit reproductively therefore large females have increased chances of mating and fertilization (sexual selection for size). Further evidence suggests that large females are more successful than small females in carrying out mating, because large females remain in copulation for a longer time than do small females.

Egg capsules and intracapsular embryos of Rapana venosa were studied to determine the reproductive pattern of this invader species in the south-eastern Black Sea. Egg deposition of R. venosa in the laboratory at 25°C was described. Egg laying began in mid-June, reached a peak in July and ended in late August in 1996. The total number of the egg capsules per whelk ranged between 197 and 999 (mean 575 ±41). The mean length of the egg capsules was 13.26 mm. Each capsule contained between 124 and 1090 embryos with a mean of 555 ±10. Mean larval production per rapa whelk was about 392,931 ±42,731. The mean size of eggs produced was 213.8 μm. Five different stages of intracapsular development were observed. Embryos developed without nurse eggs. Veliger larvae completed their intracapsular development and hatched in 22 days at 25°C.

It has been claimed that most squid species in the genus Onykia may be immature stages of species in the genus Moroteuthis. To evaluate the generic status of Moroteuthis and Onykia and to identify paralarvae collected in northern Hawaiian waters, we performed morphological investigation and nucleotide sequence analysis of the mitochondrial cytochrome oxidase I (COI) gene. Of 42 Onykia paralarvae (1.8–8.5 mm dorsal mantle length, DML) examined, 41 had a nucleotide sequence identical to that of M. robusta and one (designated Onykia sp. A) could not be assigned to any known Moroteuthis species. Nucleotide sequence diversity estimates based on Kimura's two-parameter distances between Onykia sp. A and Moroteuthis spp. (0.109–0.150) fell well within the range of congeneric species, suggesting that Onykia sp. A is a member of the genus Moroteuthis. Molecular data supported the conclusion that the genus Moroteuthis is a junior synonym of the genus Onykia. Morphological investigation revealed that paralarvae of O. robusta (= M. robusta) <4.0 mm DML were distinct from other Onykia paralarvae in the chromatophore pattern on the mantle. The key characters for distinguishing O. robusta paralarvae from Onykia sp. A were the number and arrangement of chromatophores on the funnel.

Reproductive properties of Eledone moschata from the north-eastern Aegean Sea are reported for the first time. A total of 471 specimens was collected during monthly samplings from December 2004 to November 2005. The mantle lengths of the species were between 4.5 and 15.0 cm with an average of 8.1 cm ±0.15 for 204 males, and between 2.7 and 14.0 cm with an average of 7.8 cm ±0.12 for 267 females. The annual sex ratio (males: females) of the sampled specimens was 1:1.31. Maturity stages were recorded on a monthly basis in both sexes. The highest monthly percentage of mature females (21%) and males (46%) was recorded in January 2005 and June 2005, respectively. The monthly and seasonal gonadosomatic index (GSI) results indicated that E. moschata shows two annual reproduction peaks for each sex. For males, the first spring peak occurs in March–June and the second, autumn peak is in November. For females, the first summer peak occurs in May–June and the second, winter peak is in January, respectively. On the other hand, the reproductive season extends from November to July with two peaks in the Aegean Sea. Total oocyte stock varied from 273 to 2896 with a mean of 836 ±193 oocytes. The mean size of the oocytes was 6.26 ±0.10 mm. The maximum oocyte size found was 10.7 mm. The mean length of spermatophores was of 13.66 ±0.08 mm (range: 7.3–18.3) and their average number was 52 ±6 (range: 6–172).

First observations on reproduction of Neorossia caroli from the southern Sardinian sea are reported, based on the analyses of an egg clutch and specimens collected by bottom trawl on sandy and muddy grounds. The egg clutch, consisting of 13 white eggs of 9 mm length with embryos at an advanced developmental stage, was found at 1200 m depth, attached to a piece of hard substrate. Adult specimens were collected in a depth range between 400 and 1600 metres. DNA sequences indicated that embryos, spermatangia and adults belonged to the same species, the carol bobtail squid, N. caroli. Fecundity analysis made on 40 females showed a variable number of eggs (20–611) in the ovaries, with the combined presence of advanced and developing oocytes, and few smooth eggs ready to be spawned in the oviducts of mature females. Several sperm reservoirs (spermatangia) were embedded in the mantle of some of the females, in the anterior ventral area overlying the oviduct.