No abstract

Several new symbiotic associations involving Syllidae (Annelida: Polychaeta) are reported. The number of known host sponge species infested by Haplosyllis spongicola is updated to 36, with seven hosts being reported for the first time (i.e. Aplysina corrugata, Aplysina sp., Cliona sp., Cliona viridis, Phorbas tenacior, one sponge from Iran, one sponge from Cambodia). Two infestation patterns (a few worms per host cm3 in temperate waters and 10s or 100s in tropical waters) are identified. The taxonomic and ecological characteristics of the species are discussed. Five associations occurring between four syllid worms and decapod crustaceans are fully reported for the first time. Syllis cf. armillaris, S.ferrani and S.pontxioi occurred inside gastropod shells occupied by hermit crabs as well as Pionosyllis magnifica, which was also found inside the branchial chambers of the giant crab Paralithodes camtschatica. The description of Pionosyllis magnifica is emended on the basis of the new specimens found, while some taxonomic remarks on Syllis cf. armillaris are given. In addition, further evidence of sexual (P.magnifica) and asexual (S. cf. armillaris) reproduction in symbiotic syllids is provided.

Summary The red king crab Paralithodes camtschaticus (Tilesius, 1815) was introduced in the Barents Sea from the North Pacific in 1961–1969 to establish a fishery. Currently the crab inhabits an area from Kolguyev Island in the east to Sørøya in the west, and the total number of adults exceeds 40 million. The crab is a large generalist predator, so its potential impact on native bottom communities is expected to be high. The goal of this study was to review our publications related to the possible impact of the red king crab on the shallow water benthic communities of the Kola Peninsula inlets. First, we reviewed field and experimental data on feeding ecology of different size groups of the crab. Secondly, we examined the data on the benthic communities’ structure in the bays. Finally, assess possible changes in the community structure caused by the red king crab predation. The crab diet includes about 100 species of invertebrates, algae, and fish remnants. Diet of juveniles varied in three studied areas, but bivalve and gastropod mollusks dominated. Experiments on the juvenile feeding showed their positive selection for ophiuroids. Caught prey was usually not completely consumed. Food losses decreased from 50 to 60% in crabs with 35–40 mm carapace width (CW) to 25% in crabs with 70–80 mm CW. Within and between bays trends in the benthic community structure related to the crab density were revealed. Generally, proportion of the stations with disturbed community structure decreased eastward from 80% in the Kola Bay to 18% in the Dolgaja Bay and it was negligible in the Dal’nezelenzkaja Bay. This pattern coincides with the juvenile crab density decreasing eastward. On a smaller scale in the Kola Bay we observed a negative correlation between biomass of macrozoobenthos and juvenile crab density, which was likely related to the crab predation. Comparison of the new data obtained in 2006 with the detailed survey of soft bottom macrobenthos conducted in 1990 in Dolgaja Bay showed a decrease of the diversity of soft bottom communities as well as in species richness, density and biomass of bivalves. Our data demonstrate that the proposed impact of the crab on the bottom communities of the Barents Sea is not as dramatic as have been expected from its high feeding activity and wide diet. We hypothesize that the crab omnivory distributes its predation pressure among various groups of organisms and prevents elimination of particular species or taxa.

Haplosyllis spongicola is probably the most representative symbiotic syllid harboured by sponges and has been widely reported from tropical, subtropical and temperate seas. Its external morphology seems to be very well adapted for its life-style, with all chaetae being simple and having two small teeth and a large main fang. However, the species has been the subject of a long-lasting taxonomic controversy, which gave rise to more than 15 synonymies, with hundreds of records worldwide. The present paper is based on the study of more than 28 populations obtained from around the world. These populations have been carefully analysed using different approaches (morphometry, morphology and biology). As a consequence, the existence of a pseudo-sibling species-complex within the so-called cosmopolitan H. spongicola has been revealed. The most relevant characters (as well as their variability) that will allow a future identification of the species involved in the complex are fully described, illustrated and analysed.

No abstract

Associations between scale-worms and giant mussels are common constituents of hydrothermal vent and cold seep ecosystems, but very little is known about their nature and ecology. Here, we analyze the ecological characteristics of the associations between Branchipolynoe seepensis, an obligate symbiotic polychaete, and their host mytilid mussels Bathymodiolus puteoserpentis and B. azoricus inhabiting hydrothermal vent fields on the Mid-Atlantic Ridge. Infested mussels generally harbored a single symbiont (<4% had two to six worms). Infestation rate varied from 7.2% to 76.5%, increasing with mussel size, and was significantly lower for B. puteoserpentis. Symbiont density at Lucky Strike ranged between 1071 and 1191 individuals m )2 . Female symbiont size was always positively correlated with host size, while only males and juveniles from small mussels showed the same trend. This suggested a relatively long-lasting host/symbiont association for females and short-lasting association with successive reproductive migrations for adult males. The sex ratio of symbionts was always biased in favor of females. Males were smaller and more slender than females and had one mode in their size distributions, whereas females typically had three or more modes, suggestive of a longer life span in females. Between 59.1% and 72.2% of mussels had damaged soft tissues with substantially higher incidence of trauma in infested ones, suggesting that symbionts may cause trauma. The symbionts also induce tunnel-like structures among the ctenidia, indicating fidelity to a particular location inside the host. Based on our data, together with the fact that infested mussels became relatively wider than non-infested ones, this association is considered parasitic (likely kleptoparasitic). Our data, together with those from previous studies, allowed us to define the main life-history traits of B. seepensis: (i) the relationship with their host is parasitic, (ii) the association begins at the smallest mytilid size classes, (iii) there is sexual dimorphism in body size, (iv) sex ratio deviates from 1:1 in favor of females, (v) fertilization occurs through temporal pairing and pseudocopulation, (vi) sperm are stored by females, (vii) eggs are large (likely lecithotrophic or with direct development), (viii) females have a longer life span than males, (ix) adult males may be semalparous, undertaking reproductive migrations followed by a short period of pairing and then death, and (x) females have a semi-continuous iteroparous reproductive cycle.

Background: The aim of the research was to study the gastropod assemblage associated with a planted mangrove consisting of Rhizophora apiculata in Dam Bay (Tre Island, Nha Trang Bay, central Vietnam). Long-term changes in species composition, density, and biomass of gastropod assemblages in a planted mangrove were compared to those associated with natural mangroves. Results: The gastropod assemblages in one planted and two natural mangrove associations were studied. Long-term monitoring (2005 to 2013) of assemblages associated with planted mangroves was also carried out. In total, 53 gastropod species in 21 families were recorded. This is comparable or even higher than in other areas of SouthEast Asia. In planted mangroves, R. apiculata trees were planted in mid (in 2004) and lower (2007) intertidal zones. Composition of gastropod fauna during the early period of observations (2005 to 2006) differed significantly in species richness, biomass, and abundance from the later period (2008 to 2013). Initially, the values of these parameters were low in the upper, and mid-intertidal zones and negligible in low intertidal zone. In 2008 to 2013, the values increased in the upper and mid-intertidal zones. R. apiculata planting in mid-intertidal zone and changes in its gastropod assemblage strongly affected those of upper intertidal zone as well. Comparison of gastropod fauna in planted mangroves and natural associations revealed significant differences. In planted mangroves, gastropods were mostly represented by eurybiotic species, also found in other not mangrove intertidal habitats, while in natural association many species were predominantly mangrove inhabitants, e.g., Potamididae, Littorinidae, and Ellobiidae. The fact that mangrove plantations in Dam Bay are highly dominated by opportunistic species, together with a paucity of predominantly mangrove-associated gastropods, suggest that the whole ecosystem is not balanced yet. Conclusions: The gastropod assemblage found in a 9-year old mangrove plantation differed from natural mangrove associations in that the former is dominated by opportunistic eurybiotic gastropod species. This could mean that the ecosystem of planted mangroves is unbalanced and is still in a transitional state.

Haplosyllis spongicola is probably the most representative symbiotic syllid harboured by sponges and has been widely reported from tropical, subtropical and temperate seas. Its external morphology seems to be very well adapted for its lifestyle , with all chaetae being simple and having two small teeth and a large main fang. However, the species has been the subject of a long-lasting taxonomic controversy, which gave rise to more than 15 synonymies, with hundreds of records worldwide. The present paper is based on the study of more than 28 populations obtained from around the world. These populations have been carefully analysed using different approaches (morphometry, morphology and biology). As a consequence, the existence of a pseudo-sibling species-complex within the so-called cosmopolitan H. spongicola has been revealed. The most relevant characters (as well as their variability) that will allow a future identification of the species involved in the complex are fully described, illustrated and analysed.