Application of fluorescent substance to the analysis of growth performance in Antarctic bivalve, Laternula elliptica

The shells of the Antarctic bivalve, Laternula elliptica, contain considerable information about their growth history and environmental changes. Growth rate determination in Laternula elliptica was attempted using a fluorescent substance, tetracycline, as a growth marker. The specimens were exposed to tetracycline solution of 200mg/ι for periods of 18 to 30h at about 0-2℃ without food. A distinct and narrow yellow fluorescent line was identified from the umbonal part to the ventral margin in all animals examined. This is the first success of fluorescent substance marking under the condition of low temperature and in Antarctic species. In the umbonal region, especially in the chondrophore, relatively rapid growth was observed. In the central part, a lower growth rate was observed. The growth rate of this species is not necessarily low in comparison with the temporal or tropical species. The combination of fluorescent marker and growth increment analyses will provide a powerful tool in estimating the benthic animal production, which is important information to understand the Antarctic ecosystem

Shell growth rate measurements of euthecosomatous pteropod Limacina helicina juveniles collected in the coastal Okhotsk Sea

第2回極域科学シンポジウム　共通セッション「海氷圏の生物地球化学」 11月16日（水） 統計数理研究所 3階リフレッシュフロ

Shell structure characteristics of the thecosomatous pteropods in the Indian sector of the Antarctic Ocean

第2回極域科学シンポジウム　共通セッション「海氷圏の生物地球化学」 11月16日（水） 統計数理研究所 3階リフレッシュフロ

Application of fluorescent substance to the analysis of growth performance in Antarctic bivalve, Laternula elliptica

Abstract: The shells of the Antarctic bivalve, Laternula elliptica, contain considerable information about their growth history and environmental changes. Growth rate determination in Laternula elliptica was attempted using a fluorescent substance, tetracycline, as a growth marker. The specimens were exposed to tetracycline solution of 200 mgll for periods of 18 to 30 h at about 0-2"Cithout food. A distinct and narrow yellow fluorescent line was identified from the umbonal part to the ventral margin in all animals examined. This is the first success of fluorescent substance marking under the condition of low temperature and in Antarctic species. In the umbonal region, especially in the chondrophore, relatively rapid growth was observed. In the central part, a lower growth rate was observed. The growth rate of this species is not necessarily low in comparison with the temporal or tropical species. The combination of fluorescent marker and growth increment analyses will provide a powerful tool in estimating the benthic animal production, which is important information to understand the Antarctic ecosystem. key words: fluorescent substance, shell, growth rate, bivalve, Laternula elliptic

Species richness of polydorid species (Polychaeta: Spionidae) in the English Channel (France) and on the Pacific Coast of Tohoku District (Japan)

International audienceSuccessive polychaete inventories have reported polydorids in the English Channel and there are some reports describing polydorids from the Pacific coast of Tohoku District, Japan. Species Richness in both areas is compared and discussed. Moreover, in March 2018, French-Japanese collaboration led to the collection of polydorid species from the shells of feral and cultured oysters Crassostrea gigas（THUNBERG, 1793）along the western coast of Normandy, France. Some species were also extracted from coralline algae and other calcareous substrates. Eight species were recorded belonging to four genera: Boccardia, Boccardiella, Dipolydora and Polydora. The two species Polydora hoplura Claparède, 1868 and Dipolydora giardi（Mesnii, 1893）were previously known in Normandy, along with another member of the genus Dipolydora that has not been identified to the species level. Boccardia proboscidea Hartman, 1940, Boccardiella hamata（Webster, 1879）and Polydora websteri Hartman in Loosanoff & Engle, 1943 represent new records in Normandy, while both Boccardia pseudonatrix Day, 1961 and Polydora onagawaensis Teramoto, Sato-Okoshi, Abe, Nishitani, Endo, 2013 are new species for European waters. We point out that collaboration with polychaete specialists to study well-known seas such as the English Channel would allow us to discover new species, expanding the list of species actually present. This study also highlights the need to continue this partnership further identify which polychaete species infest English Channel oysters

Polydorid species (Annelida: Spionidae) associated with commercially important oyster shells and their shell infestation along the coast of Normandy, in the English Channel, France

International audienceAbstract Polydorid species (Annelida, Spionidae), which inhabit the shells of the commercially important oyster Crassostrea gigas , were investigated along the coast of Normandy, France. Eight species, including five new records for Normandy ( Polydora onagawaensis , Polydora websteri , Boccardia pseudonatrix , Boccardia proboscidea , and Boccardiella hamata ) and two first records in European waters ( P. onagawaensis and B. pseudonatrix ), were identified based on morphological, molecular biological, and ecological characteristics. Polydora onagawaensis , which belongs to the Polydora ciliata / websteri complex, was discovered in the shells of wild and suspended cultured oysters, as well as in limestone substrates. In the phylogenetic analysis of mitochondrial COI gene sequences, specimens of P . onagawaensis collected from Normandy were grouped together with specimens from the USA into a single clade and were distinguished from the other three lineages that comprised Japanese and USA specimens. Polydora websteri inhabited shells of suspended cultured oysters. Polydora hoplura , Dipolydora giardi , and Dipolydora sp. were observed in shells from the sandy oyster culture grounds. Boccardiella hamata has been found in wild oyster shells from muddy oyster culture grounds. Boccardia pseudonatrix was observed in the shells of both the wild and cultured oysters. Adult and juvenile Boccardia proboscidea were observed in coralline algae, as well as in suspended cultured oysters. Mud tubes were observed to protrude from the outer surface of the shells, and abnormal black and calcareous deposits were secreted on the inner surface of the shells against polydorid penetration

Polycyclic Aromatic Hydrocarbons in Sediments and Bivalves on the Pacific Coast of Japan: Influence of Tsunami and Fire.

Surface sediments and at least one edible bivalve species (Ruditapes philippinarum, Mytilus galloprovincialis, and Crassostrea gigas) were collected from each of seven intertidal sites in Japan in 2013. The sites had experienced varying levels of tsunami and fire disturbance following the major earthquake of 2011. Eight polycyclic aromatic hydrocarbons (PAHs) were identified and analyzed by gas chromatography-mass spectrometry. Total sediment PAH concentration (CT), the sum of the average concentrations of the eight PAHs, was 21-1447 μg kg-1-dry. Relative to the average level of one type of PAH in sediments collected around Japan in 2002 (benzo[a]pyrene = 21 μg kg-1-dry), five of the seven sites showed concentrations significantly lower than this average in 2013. The CTs for the three bivalves (134-450 μg kg-1-dry) were within the range of the previous reports (2.2-5335 μg kg-1-dry). The data suggest that the natural disaster did not increase PAH concentrations or affect the distribution within sediment or bivalves in Tohoku district. Although PAH concentrations at the sites pose no risk to human health, the findings highlight that the observed PAH levels derive from pre- rather than post-quake processes

Phylogeography and genetic diversity of the Japanese mud shrimp Upogebia major (Crustacea, Decapoda, Upogebiidae): Natural or anthropogenic dispersal?

Upogebia major (De Haan, 1841) is known for forming huge burrows in sandy, intertidal areas that can extend to depths of over 2 m. Despite its widespread distribution in East Asia and Russia, the genetic relatedness of its regional populations remains uncertain, likely owing to difficulties in specimen collection. Therefore, to appraise the phylogeographic patterns, genetic diversity, and morphological variety of U. major, the mitochondrial DNA of specimens collected from Japan, Korea and China were subjected to molecular phylogenetic analyses of COI genes, alongside morphological assessment. As a result, we discovered four principal groups; of these, Group 1 consisted predominantly of Japanese specimens, while Groups 3 and 4 were interpreted as having originated from the continent. Group 2 exhibited genetic segregation from both continental and Japanese descent. Group 1 mostly comprising Japanese specimens implies that the planktonic larvae of U. major were disseminated north and south by ocean currents encompassing the Japanese archipelago. In contrast, individuals probably originating from the continent were discovered in Lake Notoro, Hokkaido and Matsukawa-ura, Fukushima in northeastern Japan, indicating possible introduction from the continent through ocean currents or unintentional introduction with other organisms imported. Additionally, one of the specimens collected from Matsukawa-ura exhibited significant genetic and morphological differences from other specimens, suggesting the possibility of being a subspecies. The outcomes of this study not only offer valuable insights into the origins of distribution of U. major but also introduce a novel challenge of assessing the coexistence of two routes: natural and anthropogenic dispersion