Caught in the act:phenotypic consequences of a recent shift in feeding strategy of the shark barnacle <i>Anelasma squalicola</i> (Lovén, 1844)

Anelasma squalicola is a barnacle found attached to deep-water lantern sharks of the family Etmopteridae and is the only known cirriped on fish hosts. While A. squalicola is equipped with mouth and thoracic appendages (cirri), which are used for suspension feeding in conventional barnacles, its attachment device (peduncle) appears to have evolved into a feeding device, embedded into the tissue of its host. Here we demonstrate, through comparisons of the feeding apparatuses between A. squalicola and conventional suspension-feeding barnacles, that mouthparts and cirri of A. squalicola are highly reduced, and incapable of suspension-feeding activities. We show that in conventional suspension-feeding barnacles strong symmetries exist within these vital trophic structures. In A. squalicola strong asymmetries are widespread, indicating that those structures have been uncoupled from natural selection. The digestive tract is consistently empty, suggesting that feeding via cirri does not occur in A. squalicola. In addition, comparisons of stable isotope ratios (δ13C and δ15N) between A. squalicola, its shark host, and a conventional suspending feeding barnacle indicate that A. squalicola is taking nutrition directly from its host shark and not from the surrounding water. Our results strongly indicate that this barnacle has abandoned suspension feeding and now solely relies on obtaining nutrition from its host by a de novo evolved feeding mechanism.publishedVersio

Two new cryptic and sympatric species of the king crab parasite Briarosaccus (Cirripedia: Rhizocephala) in the North Pacific

Rhizocephalan barnacles have been reported to parasitize a wide range of king crab species (Lithodidae). So far all these parasites have been assigned to a single species, Briarosaccus callosus Boschma, 1930, which is assumed to have a global distribution. Here we investigate Briarosaccus specimens from three different king crab hosts from the fjord systems of Southeastern Alaska: Lithodes aequispinus Benedict, 1895, Paralithodes camtschaticus (Tilesius, 1815), and Paralithodes platypus (Brandt, 1850). Using molecular markers and by morphological comparison we show that Briarosaccus specimens from these three commercial exploited king crabs are in fact morphologically distinct from B. callosus, and further represent two separate species which we describe. The two new species, Briarosaccus auratum n. sp. and B. regalis n. sp., are cryptic by morphological means and were identified as distinct species by the use of genetic markers (COI and 16S). They occur sympatrically, yet no overlap in king crab hosts occurs, with B. auratum n. sp. only found on L. aequispinus, and B. regalis n. sp. as parasite of the two Paralithodes hosts.publishedVersio

Infestation of parasitic rhizocephalan barnacles <i>Sacculina beauforti</i> (Cirripedia, Rhizocephala) in edible mud crab, <i>Scylla olivacea</i>

Screening of mud crab genus Scylla was conducted in four locations (Marudu Bay, Lundu, Taiping, Setiu) representing Malaysia. Scylla olivacea with abnormal primary and secondary sexual characters were prevalent (approximately 42.27% of the local screened S. olivacea population) in Marudu Bay, Sabah. A total of six different types of abnormalities were described. Crabs with type 1 and type 3 were immature males, type 2 and type 4 were mature males, type 5 were immature females and type 6 were mature females. The abdomen of all crabs with abnormalities were dented on both sides along the abdomen’s middle line. Abnormal crabs showed significant variation in their size, weight, abdomen width and/or gonopod or pleopod length compared to normal individuals. The mean body weight of abnormal crabs (type 1–5) were higher than normal crabs with smaller body size, while females with type 6 abnormality were always heavier than the normal counterparts at any given size. Sacculinid’s externa were observed in the abdomen of crabs with type 4 and type 6 abnormalities. The presence of embryos within the externa and subsequent molecular analysis of partial mitochondrial COI region confirmed the rhizocephalan parasite as Sacculina beauforti. Future in-depth descriptions of the life cycle and characteristics of S. beauforti are recommended as it involves a commercially important edible crab species and the effect on human health from the consumption of crabs is of crucial concern

Genome-wide SNP analyses reveal population structure of Portunus pelagicus alongVietnam coastline

The blue swimming crab (Portunus pelagicus Linnaeus, 1758) is one of the commercially exploited crab fishery resources in Vietnam. This is the first study to provide a broad survey of genetic diversity, population structure and migration patterns of P. pelagicus along the Vietnamese coastline. The crab samples were collected from northern, central and southern Vietnam. Here, we used a panel of single nucleotide polymorphisms (SNPs) generated from restriction site-associated DNA sequencing (RADseq). After removing 32 outlier loci, 306 putatively neutral SNPs from 96 individuals were used to assess fine-scale population structure of blue swimming crab. The mean observed heterozygosity (Ho) and expected heterozygosity (He) per locus was 0.196 and 0.223, respectively. Pairwise Fst and hierarchical AMOVA supported significant differentiation of central and northern from southern populations (P<0.01). Population structure analyses revealed that P. pelagicus in the south is a separate fisheries unit from the north and center. Contemporary migration patterns supported high migration between northern and central populations and restricted genetic exchange within the southern population. In contrast, historic gene flow provides strong evidence for single panmictic population. The results are useful for understanding current status of P. pelagicus in the wild under an environment changing due to natural and anthropogenic stresses, with implications for fisheries management.publishedVersio

The Japanese oyster drill <i>Ocinebrellus inornatus</i> (Récluz, 1851) (Mollusca, Gastropoda, Muricidae), introduced to the Limfjord, Denmark

The predatory neogastropod Ocinebrellus inornatus was first reported from Europe in W France in 1995 and has since been detected at other sites in NW and N France and The Netherlands. It is native to the North Pacific where it preys on the Pacific oyster Crassostrea gigas. Here we report on the occurrence of the species in beds of European oysters (Ostrea edulis) in the Limfjord, NW Jutland, Denmark. The morphology-based identification has been confirmed by genetic analysis. The species was probably introduced with oysters imported from France in the 1970s and 1980s. The invasion is still relatively localized but as the species has established a reproductive population, it may eventually spread to other parts of the fjord and in time pose a problem to the oyster fishery. The species’ invasion history is reviewed

Expansion of the barnacle Austrominius modestus (Darwin, 1854) (cirripedia, Thoracica, Balanidae) into Scandinavian waters based on collection data and niche distribution modeling

The barnacle Austrominius modestus, native of New Zealand and Australia was introduced to the South of England around 1943 and has since spread to most coastal waters in Western Europe, including the southern North Sea. Apart from an ephemeral incursion into the Danish Wadden Sea in 1978, since 2010 it has established permanent populations capable of reproduction along the North Sea coast of the Jutland peninsula, the Limfjord, the north-western Kattegat, and the Skagerrak. It has probably invaded Danish waters by pelagic larvae originating in the German Wadden Sea. The species has since spread to other Danish localities, likely following the prevailing currents, but other means, as for instance transport by vessels, are possible. The barnacle inhabits stones, stone-reefs, mollusk shells, and live shore crabs in shallow waters. Based on hydrographical data from its native and recently invaded areas, we predict its future distribution to extend to most coasts of continental Europe except for brackish waters (< 20 PSU), and the Arctic seas. The northernmost distribution limit may include the Lofoten Islands of NorwaypublishedVersio

Induced metamorphosis in crustacean y-larvae: Towards a solution to a 100-year-old riddle

<p>Abstract</p> <p>Background</p> <p>The y-larva, a crustacean larval type first identified more than 100 years ago, has been found in marine plankton samples collected in the arctic, temperate and tropical regions of all oceans. The great species diversity found among y-larvae (we have identified more than 40 species at our study site alone) indicates that the adult organism may play a significant ecological role. However, despite intense efforts, the adult y-organism has never been identified, and nothing is therefore known about its biology.</p> <p>Results</p> <p>We have successfully and repeatedly induced metamorphosis of y-larvae into a novel, highly reduced juvenile stage by applying the crustacean molting hormone 20-HE. The new stage is slug-like, unsegmented and lacks both limbs and almost all other traits normally characterizing arthropods, but it is capable of vigorous peristaltic motions.</p> <p>Conclusion</p> <p>From our observations on live and preserved material we conclude that adult Facetotecta are endoparasitic in still to be identified marine hosts and with a juvenile stage that represents a remarkable convergence to that seen in parasitic barnacles (Crustacea Cirripedia Rhizocephala). From the distribution and abundance of facetotectan y-larvae in the world's oceans we furthermore suggest that these parasites are widespread and could play an important role in the marine environment.</p

First recorded occurrence of the parasitic barnacle (Anelasma squalicola) on a Greenland shark (Somniosus microcephalus) in the Canadian Arctic

A solitary Anelasma squalicola specimen was collected from the cloaca of a Greenland shark (Somniosus microcephalus), the first time this association has been recorded. The specimen's identity was confirmed through morphological and genetic assessment (mitochondrial markers: COI and control region). A. squalicola is a species typically associated with deep-sea lantern sharks (Etmopteridae) and, until the present observation, had never been observed at a sexually mature size in the absence of a mating partner. Given the reported negative effects of this parasite on its hosts, monitoring Greenland sharks for additional cases is recommended.publishedVersio