One of the most problematic fishing methods in terms of by-catch and discarding is prawn-trawling. This paper analyses the incidental catch of an artisanal trawl fleet during two discrete Artemesia longinaris fishery seasons (2002 and 2004). The fishery season of A. longinaris operates monthly and it takes place in the surrounding area of the Barra do Rio Grande. Sampling was carried out during the fishing season (April–December) always on the same artisanal trawl boat. An observer was included on-board to avoid loss of information due to discards made by the fishermen at sea. Fifty species were caught: 38 fish and 12 crustaceans. Discrete fauna abundance and composition were recorded in analysed years, with higher by-catch ratios associated with elevated rainfall and low salinity. The overall discard ratio was 1:5.6, with values ranging from 1:11.3 in 2002 to 1:2.5 in 2004. The most striking differences between both years analysed were observed during autumn (1:75 in 2002 and 1:11.30 in 2004) and winter (1:16 in 2002 and 1:0.97 in 2004), while spring presented similar values (1:8 in 2002 and 1:4 in 2004). The discard ratio estimated in terms of number showed a different pattern, presenting overall values of 1:2.24 in 2002 and 1:0.5 in 2004. Higher estuarine runoff may have increased biomass production in the surrounding area of Patos Lagoon during 2002, sustaining higher abundance of estuarine-related and marine species in the area, as well as higher mean trophic level and abundance of top-predators. Conversely, A. longinaris production was consistently lower, since this marine species does not tolerate marked reductions in salinity. In 2004, salinity was higher, associated with low rainfall and favouring A. longinaris abundance in the area. During this dry year, the target-species was dominant in samples resulting in very low by-catch ratios, especially in winter (1:0.97). The catch was mainly composed of juvenile fish, since fishery is performed in nursery grounds.

The nucleus diameter/cell diameter (N/C) ratio and morphological characteristics of the haemocytes of the snail Babylonia areolata were studied using microscopy. Our results revealed two major types of haemocytes, namely granulocytes and hyalinocytes. In granulocytes, the cytoplasm was purplish red with Wright's staining, but it was blue in hyalinocytes. Hyalinocytes were smaller than granulocytes and had a higher N/C ratio. The granulocytes were sub-categorized into type I granulocytes and type II granulocytes based on the shape and the number of granules. Hyalinocytes were sub-categorized into large and small hyalinocytes based on the diameter and N/C ratio. Snails with a shell length from 2.7 to 3.3 cm showed no differences in the abundance of haemocytes.

Feeding habits of the toothed flounder Cyclopsetta querna caught in the south-east Gulf of California were studied. Specimens were collected via demersal fish surveys. Results of this study show that C. querna is a predator that focuses on fish inhabiting the bottom and in particular on tonguefish (Symphurus sp.), midshipman fish (Porichthys sp.) and moray eels (Muraenidae). The diet of the toothed flounder did not vary significantly throughout the period of study, and neither size nor sex-related variations in diet composition were observed. Simpson's index indicates a limited trophic niche breadth with a diet dominated by a limited number of taxa. The estimated TROPH value for C. querna is similar to that estimated for other demersal top predators from the studied area; therefore, the toothed flounder can be considered a top carnivore from the demersal community in the Gulf of California.

Larvae of eight sea spiders from three families (Ammotheidae, Pycnogonidae and Phoxichilidiidae) are described for the first time. The external morphology of the first larval stage of each species is presented in detail using scanning electron microscopy photographs in order to determine the mode of postembryonic development. Three types of larval development are apparent in the species examined. The species Achelia gracilipes, Eurycyde spinosa, Pycnogonum rickettsi and Pycnogonum stearnsi (families Ammotheidae and Pycnogonidae) have larval morphologies indicative of an ‘ectoparasitic’ development. Morphological characteristics of Achelia simplissima and Achelia chelata (family Ammotheidae) larvae suggest an ‘endoparasitic’ development, while larvae of the species Anoplodactylus viridintestinalis (family Phoxichilidiidae) have traits implying an ‘encysting’ postembryonic mode of development. Larvae of the species Nymphopsis spinosissima have unusual morphological characteristics that may be indicative of a new developmental mode.

The invasive species Caulerpa racemosa var. cylindracea represents a serious threat to the diversity of benthic assemblages in the Mediterranean Sea. In the present study, a removal experiment was carried out to test whether, after 18 months of C. racemosa var. cylindracea exclusion, the macrophyte assemblage resembled a non-invaded assemblage. The results show that in the assemblage invaded by C. racemosa var. cylindracea the number of species, macrophyte cover, Shannon diversity and Pielou's evenness were lower than in the non-invaded assemblage. Erect perennial species were particularly affected and other introduced species were significantly reduced or completely excluded. After 18 months of removal/exclusion of C. racemosa var. cylindracea, only partial recovery of the macrophyte assemblage could be observed. Species numbers, total cover and erect perennial species cover were still significantly lower than in the non-invaded plots. However Shannon diversity and Pielou's evenness had reached comparable levels. In contrast to native macrophytes, the total cover of other introduced species reached a level comparable to the non-invaded plots. In summary, the present study revealed that after 18 months of C. racemosa var. cylindracea exclusion: (i) only partial recovery of the macrophyte assemblage occurred; and (ii) the development of other invasive species was favoured by the absence of C. racemosa var. cylindracea (Sisyphus effect).

A new species, Endeolophus skeneae sp. nov., epibiotically associated with the gastropod Skenea profunda, is described from light microscope and scanning electron microscope observations. The new species is characterized by homogeneous ornamentation of the cuticle with annules with very fine and numerous longitudinal ridges, equally distributed around the body, subcuticular discontinuity in cuticle pattern along the lateral sectors of the body, relatively long body (1.1–1.6 mm) and relatively long tail (141–188 μm, c' = 7.5–11.4), short (19–22 μm) L-shaped spicules with ventrally bent blade and simple plate-like gubernaculum without apophysis. Symbiotic associations between aquatic nematodes and molluscs are discussed, with special emphasis on Dreissena polymorpha, zebra mussels. It is suggested that nematodes find food and shelter in the mantle cavity of the bivalve molluscs, and in the umbilicus and aperture of the gastropods, but to reveal the exact mechanisms of symbiotic associations of nematodes with aquatic molluscs requires further research.

Eight species of Yoldiella (Yoldiella biguttata Allen, Sanders & Hannah, 1995; Yoldiella similis Allen, Sanders & Hannah, 1995; Yoldiella extensa Allen, Sanders & Hannah, 1995; Yoldiella aff. jeffreysi (Hidalgo, 1877); Yoldiella sp.1; Yoldiella sp. 2; Yoldiella sp. 3 and Yoldiella sp. 4) from the continental slope off Rio de Janeiro were used to test if quantitative morphometric measurements of shell shape and hinge plate could effectively discriminate among them. Thirty specimens of each species were sampled, and a total of 25 variables were established and utilized as input data to perform a discriminant analysis. The percentage of correctly classified cases was never less than 80%. The hinge plate variables were always relevant, and the most important one was the width of the posterior hinge plate. On the other hand, shell shape variables, when present, were secondary. Considering that the variation in the shell of Yoldiella species is subtle, and also the findings of this study, we can state that the hinge plate morphometry has good potential to improve species discrimination.

Effect of epibenthic algae as species-specific coral settlement inducers was examined by laboratory experiments using six Acropora species. When epibenthic algae grew on artificial plates at three depths (shallow, middle and deep) on a reef slope over a period of two months, there was no effect as species-specific inducers. However, when the growth period was prolonged to five months, the larvae of Acropora digitifera which dominates on the shallow reef slope mainly settled on the plates that were conditioned at the shallow depth, while the larvae of A. muricata which dominates on the middle slope concentrated on the plates that were conditioned at the middle depth. These results indicate that epibenthic algae may act as a cue for the habitat selection of Acropora corals as a settlement inducer. However, the fact that there was no preference for specific plates in other species suggested that epibenthic algae do not act as a sole indicator in selecting a suitable settlement place for Acropora larvae.

The spatial distribution of the subtidal crustacean assemblages of the Guadiana Riverestuary was studied previous to the building of the Alqueva Dam (the biggest dam inEurope). The differences between an estuarine and marine environment seem to be the mainreason responsible for the composition and distribution of the crustaceans along the studyzone. The Guadiana estuary has shown high number of species in comparison with othernearby estuaries and this richness seems justified by the scarce influence of pollutants(most of them have shown low or moderate values) and their hydrodynamic and granulometriccharacteristics (76 species were found, 39 in the estuarine area). A gradient ofenrichment and structuring of the assemblages was shown from the upstream to the marinezones and a spatial segregation of species was found along this estuarine environmentalgradient, e.g. the amphipod Corophium multisetosum and the isopodCyathura carinata in the upper estuary; the amphipodBathyporeia cf. pilosa and the isopodsLekanesphera levii and Saduriella losadoi in themiddle estuary; the amphipod Melita hergensis in the mouth; and a highnumber of species in the marine area. Since the Alqueva Dam will reduce the riverdischarges and may cause changes in the abiotic characteristics such as granulometry ofsediments or salinity, this study establishes a baseline against which a monitoringprogramme or follow-up studies could measure any significant effects of the dam or relatedimpacts.

Water drift and tidal rise make the use of bonding mechanisms beneficial for small benthopelagic or interstitial marine animals. Chemical adhesives for attachment are very common in molluscs; however, only a few cephalopods have glue producing organs. The family Idiosepiidae is characterized by an epithelial adhesive organ (AO) located on the posterior part of the dorsal mantle area. Previous morphological and histological studies described three non-glandular cell types (basal, interstitial and fusiform cells) and three glandular cell types (goblet, columnar and granular cells) containing protein and carbohydrate components. However, these studies provide different information about the nomenclature and characteristics of the cell types. The present ultrastructural analyses and a 3D reconstruction of the AO of Idiosepius pygmaeus and Idiosepius biserialis therefore serve to investigate the cell distribution, the fine structure of the cells and possible interactions between the cells.We found that basal cells form a continuous cell layer along the basal membrane, overlapped by the other epithelial cells. Embedded in microvilli-covered interstitial cells the glandular cells are more or less evenly distributed within the AO. Goblet and granular cells are solitary glandular cells without conspicuous morphological characteristics, whereas the columnar cells are arranged in dense aggregations of 5–15 cells. Each columnar cell is enclosed by a narrow supporting interstitial cell which contains dense longitudinal filament strands. The secretory process of the cells in the aggregation is synchronized. Each columnar cell aggregate bears approximately two ciliated sensory fusiform cells. The fusiform cells are connected to a neuronal network, aligned along the epithelium base.The results suggest that the bonding system is affected by two secretory cell types (granular and columnar cells). Both are similar in content, synthesis and secretory process but columnar cells are embedded in a particular cell environment. It is unclear in what way this arrangement is associated with the function of the AO. The neurons in several parts of the AO point to a neuronal control of the bonding mechanism. Comparisons with the AO cells of other cephalopods provide no indications for a morphological relationship between the adhesive systems.

The settlement and recruitment of the small brachyuran crab Halicarcinus planatus from the central area of Golfo San Jorge, south-western Atlantic Ocean, was studied. Three different artificial collectors were evaluated: smooth-surface panels, panels covered with synthetic lawn and ballasted plastic boxes filled with remains of fishing nets. In addition, plankton samples were taken monthly and water salinity and temperature were recorded. Between July 2006 and June 2007, the collectors were deployed monthly in the subtidal zone of two nearby localities and collected two months later. The recovered crabs were classified into four stages: settlers, recruits, advanced juveniles and mature crabs. There were differences in the presence of stages among collector types and seasons but not between localities. Settlers and recruits were abundant on the panels with synthetic lawn, while late juvenile and mature females were more frequent in the boxes. Larval stages occur between July and February, and only zoeas I and II were found. The males, which were only represented by early juveniles, were exclusively found on the panels with synthetic lawn, from where they would subsequently migrate to cryptic habitats such as the holdfast of Macrocystis pyrifera. Settlement occurs between September and April. Settlers showed a peak in abundance during November–December, while the recruits showed two peaks, one in December and the other in February–March. For late juveniles, the maximum abundance was recorded in April–May. Ovigerous females were found between May and September, when the experiment ended. Settlement and recruitment of H. planatus in Golfo San Jorge occur over a prolonged period. Individuals may undergo shifts in microhabitat use during this period, probably related to the search for food and shelter, and avoidance of predation and cannibalism.

Santelmoa is diagnosed by the following characters: anterior portion of frontals fused; scapular foramen open; anterior ceratohyal–posterior ceratohyal (=epihyal) articulation interdigitating; cranium narrowed; supratemporal commissure and occipital pores absent; intercalar reaching the prootic; ascending rami of the parasphenoid wing high; palatal arch well developed; posterior hyomandibular ramus short; post-temporal ventral ramus well developed; six branchiostegal rays; vertebrae asymmetrical; pelvic fin rays ensheathed; scales, lateral line, pyloric caeca, palatine and vomerine teeth present. A new species of Santelmoa, Santelmoa elvirae sp. nov., is described on the basis of four specimens collected from the Bellingshausen Sea, Southern Ocean, at a depth of 1837 m. The new species can be distinguished from Santelmoa carmenae, the type species of the genus and the sole known Santelmoa species, by the following characters: mouth inferior; vertical folds on posterior end of the upper lip and on the lower lip lobe; oral valve nearly reaching the anterior edge of vomer; two posterior nasal pores; lateral line double with ventral and medio-lateral branches; single row of palatine teeth; dorsal fin rays 108–111; anal fin rays 93–94; pectoral fin rays 18–19 and vertebrae asymmetrical, 26–27 + 90–93 = 116–119.

The antifouling activity of a series of hexane, ethyl acetate, ethanol and aqueous extracts from 11 species of marine sessile organisms collected from the south-east coast of China was investigated. Settlement inhibition of cyprid larvae of the barnacle Balanus albicostatus was used to evaluate their antifouling efficacy. Screening of the 44 extracts showed antifouling activity in 90.9% of the hexane extracts followed by 90.9% of the ethyl acetate, 72.7% of the ethanol and 36.4% of the aqueous extracts. The hexane extracts of Tubularia mesembryanthemum, Notarcus leachii cirrosus and Styela canopus, the ethyl acetate extracts of Bugula neritina and N. leachii cirrosus, and the ethanol extracts of B. neritina and Anthopleura sp. were the most active in inhibiting the settlement of B. albicostatus, with EC50 values all below 50 μg/ml. At least one of the four extracts of each tested species exhibited antifouling activity, suggesting that all 11 marine sessile organisms contained antifouling substances and they may have evolved chemical defences against biofouling on their surfaces.

Two new species of free-living marine nematodes Paramarylynnia filicaudata sp. nov. and Paramarylynnia stenocervica sp. nov. from the Yellow Sea, China are described. Paramarylynnia filicaudata sp. nov. is characterized by a homogeneous cuticle with transverse rows of even dots; spicules boat-shaped, swollen in the middle and gradually tapering towards both ends; tail conical with a long filiform terminal portion and without subventral setae on the conical part. Paramarylynnia stenocervica sp. nov. is characterized by the marked narrower anterior part of the neck region; heterogeneous cuticle with transverse rows of punctations and the punctations of anterior contracted portion larger and more widely spaced than the remaining portion; spicules curved and cephalate proximally; gubernaculum boat-shaped, swollen in the middle and gradually tapering towards both ends, five small tubular precloacal supplements.

The trematode Parorchis acanthus is widely distributed and exhibits a broad host spectrum, with larval stages occurring in marine gastropods and adult flukes parasitizing on various seabird species. Unlike the majority of digeneans, its cercariae do not invade a second intermediate host but encyst on a substrate in the open. In a series of laboratory experiments, we investigated factors influencing cercarial emergence and settlement of P. acanthus. Emergence of cercariae from the gastropod intermediate host Nucella lapillus increased with increasing temperature, whereas cercarial encystment success decreased. Numbers of emerged cercariae were highest in the presence of light and water. However, although in much lower numbers, cercariae were also released from N. lapillus and successfully encysted under relatively dry conditions. Cercariae were found to settle predominantly on filtering blue mussels Mytilus edulis, suggesting that cercarial concentration on the valves is largely facilitated by the bivalve's inhalation current. After being inhaled, cercariae actively emerged from the mussels using their suckers and subsequently encysted on the shells, preferably along the rim of the valves. Barnacle epibionts Semibalanus balanoides were observed to impair cercarial settlement on mussels, by disturbing or preying on cercariae. Whilst settlement success of cercariae on M. edulis increased with increasing mussel density, intensity of encysted metacercariae decreased. Furthermore, cercariae settled more efficiently on small than on large mussels. Our findings suggest that the transmission of P. acanthus cercariae is regulated by a range of abiotic and biotic factors, with filtering activity of mussels playing a key role by enhancing accumulation of cercariae on a substrate suitable for transmission to the bird final host.

Through rearing known age individuals and maintaining chemically marked adults in captivity, this study explored the rate of increment formation in southern calamary (Sepioteuthis australis) statoliths over seasonal (summer and winter) and ontogenetic (hatchlings and adults) extremes. A ‘one increment–one day’ relationship was verified for captive-reared hatchlings up to 40 days post-hatching which remained stable across the seasonal extremes. This relationship, however, was not evident in the chemically marked adults as inconsistencies of up to 44 days were detected between the number of days elapsed post-stain and the increment count. No seasonal effect was detected in the ratio between increment count and days elapsed, however, the degree of underestimation was consistently greater for winter-caught adults by approximately 2.5 increments relative to summer-caught adults. This less-than-daily increment formation in adults may be due to: (1) the periodicity of increment formation changing throughout the squid's lifespan; (2) deleterious effects associated with rearing squid in captivity; and/or (3) compromised interpretation of the statolith microstructure as a result of the preparation method.

The understanding of the stock structure of a species is essential to effectively manage fisheries. Otolith shape analysis has been successfully applied in stock identification using the elliptic Fourier analysis. This method was used to assess possible differences in the otolith shape of Helicolenus dactylopterus caught around the Azores, Madeira and mainland Portugal. A total of 294 individuals ranging from 23 to 29 cm in total length, equally distributed by sex and area, were analysed. The multivariate analysis of variance performed on the otolith normalized elliptic Fourier descriptors (NEFDs) revealed significant differences for both area and sex, but no interaction was found between the two factors. In the canonical discriminant analysis an overall classification success of 69.4% and 66.7% was achieved for females and males respectively. These results suggest the usefulness of otolith shape analysis for stock differentiation of bluemouth from Portuguese waters.

To highlight the diversity of extracellular embryonic matrix (ECM) secreting structures in the gastrulae of the starfish Pisaster ochraceus the localization of antibody generated to hyaline layer, was studied. It was shown that hyaline layer epitope takes place in the cortical granules. Moreover, this material was revealed in secretory vacuoles and secretory vesicles which are situated in the apical parts of ectoderm cells. Besides, the same molecules were found in the yolk granules having loosened content. It seems likely that in P. ochraceus the ECM is secreted by four types of secretory structures.

The present paper is the first scanning electron microscope (SEM) description of a protonymphon larva of an Ammotheidae. The morphology of the first larval instar of Achelia assimilis is described in detail and illustrated for the first time. The morphological characters are compared to previous larval descriptions of other pycnogonid species. The larvae are integrated into Bain's classification of larval types within the pycnogonids (Bain, 2003a) as a ‘typical protonymphon’. Larvae were obtained from ovigerous males, caught in Punta Huinay, Huinay, Chile and analysed with light microscope and SEM. Descriptions of pycnogonid protonymphons at a species-specific level in the future will contribute to a deeper understanding of larval pycnogonid taxonomy at the level of differential diagnoses.

The small, monogeneric family of polychaetes known as Trochochaetidae has been exclusively collected in the northern hemisphere, mainly in temperate–cold environments. Nine species have been described so far including Trochochaeta mexicana sp. nov. described herein, while one species remains unnamed. Only two species had previously been recorded in the eastern Pacific, so T. mexicana sp. nov. is the first record for the family in the tropical Mexican Biogeographic Province. The new species is characterized by having a pair of eyes, acicular neurochaetae on chaetigers 2 and 3, a small knob-like antenna and a nuchal crest projecting through chaetiger 1. Trochochaeta mexicana sp. nov., together with Trochochaeta kirkegaardi, Trochochaeta diverapoda and Trochochaeta cirrifera are the only trochochaetids that have been found exclusively in warm environments.