Marine sessile invertebrates with outer skeleton constitute additional substrate for a diverse group of epibiotic organisms. Colonial hydroids are no exception. Large numbers of motile and sessile organisms use hydroid colonies covered with chitinous perisarc for permanent or temporal attachment. Such epibiotic associations between colonial hydroids and microorganisms are poorly studied and mostly known for subtropical regions. There are no data about the development of such epibiotic association and type of its specificity yet. The present paper for the first time describes the epibiotic association of the colonial thecate hydroid Dynamena pumila from the high latitude sea. We reconstruct the spatial and temporal development of such epibiotic community and analyse the organization of the multicomponent biofilm covering the hydroid colony. Comparison of the epibiotic community in different seasons indicates for holding out of the basal features and components of the community during the whole year. Ultrastructural investigations revealed that components of the biofilm affect the outer skeleton of the hydroid colony that results in penetration of the microorganisms into the skeleton and even soft tissues. Our data allow supposing that association of hydroid D. pumila with a microorganism community has features of a symbiotic system.

Austinixa aidae inhabits burrows of the ghost shrimp Callichirus major at Perequê-açu beach, Ubatuba, Brazil. We described the host-use pattern and sexual dimorphism of A. aidae to test for monogamy given the generality of this mating system in the subfamily Pinnothereliinae (family Pinnotheridae) to which A. aidae belongs. Against expectations, A. aidae lives as solitary individuals within burrows more frequently than expected by chance alone. Additional observations suggested that A. aidae exhibits a polygynandrous mating system with males moving among burrows in search of receptive females. First, only 21% of the burrows harboured heterosexual pairs of crabs and the body size of paired crabs was poorly correlated. This suggests pair instability and frequent shifts among burrows by male and/or female crabs, as reported before for other symbiotic crustaceans in which the body size of paired crabs is poorly correlated. Second, males paired with females that were sexually receptive (without embryos) or that have been receptive recently (carrying early embryos) were found more frequently than expected by chance alone. The above agrees with that reported for species in which sexual pairing does not last long. Third, sexual dimorphism in terms of claw size and coloration was evident. Claws were larger in males than in females, a condition that argues in favour of male–male competition in A. aidae. In addition, the body coloration of males was more similar to the sand grains of the beach than that of females. This sex-specific coloration suggests that males are ‘better adapted' than females to roam on the surface of the beach in search of burrows because their coloration should diminish the risk of detection by predators. Experiments are needed to reveal the details of the polygynandrous mating system herein inferred for A. aidae and to understand those conditions favouring particular reproductive strategies in symbiotic decapod crustaceans.

A new bathyal leucothoid amphipod, Leucothoe cathalaa sp. nov., is described and illustrated based on specimens collected at the Le Danois Bank (‘El Cachucho’ Marine Protected Area), southern Bay of Biscay. This species can be distinguished from the other species of the genus Leucothoe by the hardly visible eyes (translucent ocelli, in preserved specimens); antenna 1 with minute accessory flagellum; coxae 1–3 with 2 serrations on posterodistal margin; epimeron 3 posterodistal corner produced, bifid, with one seta between blunt lobes and telson apex pointed without accessory teeth. In live specimens, the eyes are easily visible, each represented as a rounded whitish-pigmented spot. The new species has been found living on fine sandy soft-bottoms between 486 and 574 m depth at the top of the bank. An identification key to the deep Atlantic European species of Leucothoe is provided, as well as ecological and biological comments.

Seasonal changes in spatial structure of biomass of submerged aquatic vegetation (SAV) and environmental variables were evaluated in Celestun Lagoon, an estuarine habitat in Mexico. Geostatistical techniques were used to evaluate spatial autocorrelation and to predict the spatial distribution by kriging. The relative contribution of 11 environmental variables in explaining the spatial structure of biomass of SAV was evaluated by canonical correspondence analysis. Spatial partitioning between species of SAV was evident: the seagrasses Halodule wrightii and Ruppia maritima dominated the seaward and central zones of the lagoon, respectively, whereas the green alga Chara fibrosa was constrained to the inner zone. The spatial structure and seasonal variability of SAV biomass were best explained by organic carbon in the sediments, salinity and total suspended solids in the water column. Analysis at different spatial scales allowed identifying the importance of spatial structure in biotic and abiotic variables of this estuarine habitat.

The city of São Sebastião (SS), in south-eastern Brazil, is one of the hotspots for marine research since the establishment of the Centre of Marine Biology of the University of São Paulo in the 1960s. The SS region experienced intense transformation during the past 50 years, including increasing urbanization and construction of maritime facilities. Ascidian surveys during the past 50 years have found 62 species, eight of which were described as new and 12 are introduced. Didemnidae and Styelidae are the most speciose families in São Sebastião Channel, with 20 and 15 species respectively. Phallusia nigra, Didemnum psammatodes, Trididemnum orbiculatum, Botrylloides nigrum and Symplegma rubra are the most common ascidians. Most of the species are of tropical origin and São Paulo is their southern geographical limit. Comparisons of reports of the ascidians from different time periods allowed detection of species introductions and shifts in assemblage structure in terms of both species composition and abundance. Additionally, we discuss the main taxonomic issues regarding ascidians from south-eastern Brazil and identify profitable areas for future research. We believe that the temporal data compiled here will serve as a baseline for monitoring and management of ascidians in SS. Additionally, this study provides one of the most detailed datasets of ascidian diversity from the south-western Atlantic Ocean.

Sponges (phylum Porifera) are important components of the benthic marine fauna known for their interactions with vertebrates and a large sort of invertebrates seeking for food, shelter or substrate for attachment. Studies on this subject, however, were restricted only to the macrofauna inhabiting sponges of the class Demospongiae. In the present work, we describe the macrofauna associated with a calcareous sponge in Brazil, Paraleucilla magna. Individuals of this allegedly non-native species were monthly collected during one year in Rio de Janeiro (Brazil). Fifty taxa representing 10 animal phyla were found associated with P. magna. The most frequent and abundant taxa were Crustacea, Mollusca, Polychaeta and Bryozoa, while echinoderms, cnidarians, ascidians, nemerteans, platyhelminthes and sponges were less frequent or even rare and less abundant. Juveniles of several taxa and pregnant females of Crustacea were found associated with P. magna, but these associations were not exclusive. The macrofauna associated with P. magna did not present a clear seasonality, although it was possible to observe a change in the community composition alongside the year. The volume of the sponges was significantly related to the diversity index (H′) and number of taxa, but not with evenness (J′) and number of individuals. Our results show that P. magna is used as a substrate for attachment and/or shelter by its associates and that most of these associations are just opportunistic. The data presented here reiterate a previous proposal that sponges are important biodiversity reservoirs and that they should be seriously considered in conservation programmes.

The harbour porpoise is seriously depleted and threatened with extinction in the Baltic Sea. It is usually assumed that Baltic porpoises form a separate population unit, although the evidence for this has been disputed lately. Here, a 3-D geometric morphometric approach was employed to test a number of hypotheses regarding population structure of the harbour porpoise in the Baltic region. 277 porpoise skulls from Denmark, Sweden, Finland, Germany and Poland were measured with a suite of 3-D landmarks. Statistical analyses revealed highly significant shape differences between porpoises from the North Sea, Belt Sea and the inner Baltic Sea. A comparison of the directionalities of the shape vectors between these units found differences that cannot be attributed to a general, continual shape trend going from the North Sea to the inner Baltic Sea. These vectors indicate a morphological adaptation to the specific sub-areas. Such adaptation may be the result of the topographic peculiarities of the area with variable topography and shallow waters, e.g. in the Belt Sea porpoises, there may be a greater reliance on benthic and demersal prey. The present results show that isolation by distance alone is an unlikely explanation for the differences found within the Baltic region and thus support previously reported molecular indications of a separate population within the inner Baltic Sea.

This study aims to describe the epibiota of the spider crab, Schizophrys dahlak with special reference to epizoic diatoms. Specimens were collected from the Suez Canal between autumn 2008 and summer 2009. Macro-epibionts consisted of the tube worm Hydroides elegans, the barnacles Balanus amphitrite and B. eburneus, the bivalve Brachidontes variabilis and the urochordate Styela plicata. Total coverage of macro-epibionts was greater on females' carapaces than those of males with apparent seasonal variations. The highest coverage was noticed in spring and winter for both males and females. Sixty-five diatoms taxa were recorded as epibionts belonging to 25 genera. The maximal total averages of cell count were observed during summer and spring with the highest average of 10.9 and 4.4 × 103 cells dm−2 for males and females, respectively. A single diatom taxon, Fragilaria intermedia, comprising 73.5% of all epizoic diatoms, was the most dominant species during spring, whereas Amphora coffeaeformis and Cocconeis placentula were the dominants during summer. The masking behaviour of S. dahlak was discussed in terms of the significant role of epizoic diatoms.