著者

Takumi Teraoka Kanako Amei Yutaka Fukai Kohei Matsuno Hiroji Onishi Atsushi Ooki Tetsuya Takatsu Atsushi Yamaguchi

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.17, no.4, pp.369-382, 2022-11-30 (Released:2022-11-30)

参考文献数

67

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Knowledge about the taxonomic and size composition of mesozooplankton is of critical importance for both fisheries and oceanography. In this study, we collected an annual time series of mesozooplankton samples in Funka Bay and analysed them using ZooScan to reveal the seasonal changes in taxonomic and size structure. Both zooplankton abundance and biovolume peaked in April and were dominated by an appendicularian Oikopleura labradoriensis which has been reported as being are being important food source for flatfish larvae. Furthermore, Noctiluca scintillans was abundant from September to December. The occurrence of this species may be related to the recent increase in the transport of Tsugaru Warm Current water into the bay. The Normalized Biomass Size Spectra (NBSS) was significant for 16 of 21 sampling dates. Insignificant NBSS, with an extremely flat slope, was observed for January–March. Significant NBSS with a flat slope was observed in April. Then, the relatively steep slopes of the NBSS were the case from mid-May to December. These seasonal changes in the slope of NBSS suggest that the energy transfer efficiency for higher trophic levels varied seasonally. The observed slopes of the NBSS in Funka Bay ranged from −1.09 to −0.30, which was flatter than the theoretical value (−1) and the previously reported values for the oceanic region of the western North Pacific. This suggests that the energy transfer efficiency to organisms at higher trophic levels in the Funka Bay is higher than in the adjacent oceanic region.

著者

Yoshinari Endo Yuma Sato Atsushi Yamaguchi Igor Dovgal

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.17, no.4, pp.393-405, 2022-11-30 (Released:2022-11-30)

参考文献数

54

被引用文献数

1

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This study investigated the host-epibiont relationship between calanoid copepods and suctorian ciliates collected widely from the northern North Pacific Ocean. Mid- and deep-water adult female calanoids without dormant stages were found to be infested with suctorians, probably because of their larger size, longer intermolt duration and longevity in comparison to males and surface water species. A total of 259 calanoids belonging to sixteen species were infested with five suctorian species. Among them, Candacia columbiae, Gaetanus minutus, Lucicutia bicornuta, Metridia similis, Pleuromamma scutullata, and Racovitzanus antarcticus were reported to be infested with suctorians for the first time in the present study. Ephelota coronata infested only Metridia pacifica and displayed a strong host preference, whereas the other suctorians displayed a weaker host preference. Any suctorian species that infested Metridia pacifica and M. similis attached almost exclusively to their urosome. Suctorians might avoid or could not stay attached to the anterior parts of these fast-swimming copepods. The attachment sites of Actinocyathula pleuromammae and Paracineta gaetani extended to the anterior part of the copepod body as the number of attached suctorians increased, suggesting they were obliged to attach to suboptimal parts that were exposed to faster flow speed.

著者

Yasuhide Nakamura Rei Somiya Noritoshi Suzuki Mitsuko Hidaka-Umetsu Atsushi Yamaguchi Dhugal J. Lindsay

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.12, no.2, pp.95-103, 2017-05-30 (Released:2017-06-06)

参考文献数

46

被引用文献数

3 15

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Optics-based surveys for large unicellular zooplankton were carried out in five different oceanic areas. New identification criteria, in which “radiolarian-like plankton” are categorized into nine different groups, are proposed for future optics-based surveys. The autonomous visual plankton recorder (A-VPR) captured 65 images of radiolarians (three orders: Acantharia, Spumellaria and Collodaria) and 117 phaeodarians (four taxa: Aulacanthidae, Phaeosphaerida, Tuscaroridae and Coelodendridae). Colonies were observed for one radiolarian order (Collodaria) and three phaeodarian taxa (Phaeosphaerida, Tuscaroridae and Coelodendridae). The rest of the radiolarian orders (Taxopodia and Nassellaria) and the other phaeodarian taxa were not detected because of their small cell size (< ca. 400 µm).

著者

Hiroshi Kajihara Atsushi Yamaguchi

出版者

The Plankton Society of Japan, The Japanese Association of Benthology

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.15, no.4, pp.337-341, 2020-11-18 (Released:2020-11-12)

参考文献数

31

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The three currently recognized species comprising the pelagic polystiliferous hoplonemertean genus Protopelagonemertes Brinkmann, 1917 are supposedly distinguishable chiefly with respect to the number of proboscis nerves: 29 (varying from 22 to 30) in P. hubrechti (Brinkmann, 1917); 19–21 (varying from 19 to 22) in P. beebei Coe, 1936; and 36 in P. joculatori Van der Spoel, 1988. A single specimen collected off the Pacific coast of Hokkaido, Japan, herein identified as P. beebei, was found to possess 19–23 primary proboscis nerves. In addition to the primary proboscis nerves, the material also possessed 12–16 secondary proboscis nerves, which are discernible from the primary nerves in that they coexist with putative glial cells. Although secondary proboscis nerves have been identified in some other species in the Pelagica, they have not previously been described for any members of the Protopelagonemertes. Our findings thus prompted us to question the validity of morphological species delimitation within this genus, given that the distinction between primary and secondary proboscis nerves has previously not been taken into consideration. Close examination of the specimen in the living state revealed that it is characterized by a pair of cephalic furrows, a structure commonly found in benthic representatives of the phylum, but herein confirmed for the first time among the Pelagica. A 658-bp partial sequence of the mitochondrial cytochrome c oxidase subunit I gene from the newly examined specimen was found to be identical to sequences derived from two other specimens previously collected in Sagami Bay, thereby indicating that P. beebei may occur commonly in Japanese meso- to bathypelagic waters.