著者

Kazutaka Takahashi Hiroshi Itoh Junya Hirai Kazuaki Tadokoro Koh Nishiuchi

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.358-368, 2022-11-30 (Released:2022-11-30)

参考文献数

31

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A new species of sapphirinid copepod, Sapphirina doliolettae n. sp. was described from the Kuroshio Extension region in the western North Pacific Ocean. The new species is similar to S. nigromaculata and S. scarlata with respect to the following characteristics: 5-segmented antennule, one inner marginal process on caudal rami, and slender endopods with two apical spines on leg 4. However, it can be distinguished from these congeners by a combination of the following characteristics: the relative length of each segment of the antennule and antenna in both sexes, the width of the fourth pedigerous somite in females, the shape of the anterolateral corner of the genital somite in males and terminal process length of 3rd endopodal segment of leg 2 in males. The mitochondrial cytochrome oxidase subunit I sequences of S. doliolettae showed high interspecific variabilities from other Sapphirina species, including S. nigromaculata (20.2%) and S. scarlata (21.6–21.8%).

著者

Sijun Chen Victor S. Kuwahara Tomoyo Katayama Fuminori Hashihama Kazuo Yabe Satoru Taguchi Kazutaka Takahashi

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.18, no.4, pp.214-224, 2023-11-27 (Released:2023-11-30)

参考文献数

53

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We measured the concentrations of photoprotective compounds, carotenoids and mycosporine-like amino acids (MAAs), in surface-dwelling copepods in relation to their vertical distribution patterns along a zonal transect in the subtropical North Pacific to better understand their adaptation to strong ultraviolet (UV) radiation. All the dominant copepod groups analysed had detectable levels of both photoprotective compounds, while the concentrations differed among taxonomic groups. Farranula spp. had high carotenoid and MAA content (mean carotenoids: 0.0656; mean MAAs: 0.0230 µg mg dry wt−1) and the accumulation of MAAs correlated positively with in-situ UV penetration, explaining their constant occurrence in the surface layer throughout the transect. Oncaea spp. and Acrocalanus spp. had higher levels of carotenoids than MAAs and showed variable vertical distribution patterns regardless of UV penetration, suggesting that carotenoids are used only temporally to mitigate the effect of UV radiation. In contrast, Clausocalanus spp. and Calocalanus spp. had the lowest concentrations of both photoprotective compounds (mean carotenoids: 0.0148 and 0.0209; mean MAAs: 0.0015 and 0.0029 µg mg dry wt−1). The mean weighted depth of Clausocalanus spp. showed a significant negative relationship with UV penetration, suggesting that they mitigated the harmful effects of UV radiation through behavioural responses. Calocalanus spp. may have adapted to subtropical surface waters with relatively low photoprotective compound concentrations. Our study demonstrated that surface-dwelling subtropical copepods exhibit taxon-specific patterns in photoprotective compound concentrations that are adaptations to intense UV radiation, which is crucial for understanding the high species diversity of copepod communities in subtropical open waters.

著者

Taketoshi Kodama Kazutaka Takahashi Ken-ichi Nakamura Shinji Shimode Takafumi Yamaguchi Tadafumi Ichikawa

出版者

日本プランクトン学会、日本ベントス学会

雑誌

Plankton and Benthos Research (ISSN:18808247)

巻号頁・発行日

vol.10, no.1, pp.75-79, 2015-03-25 (Released:2015-03-20)

参考文献数

25

被引用文献数

1 4

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Short-term variation in the ammonium excretion rate by Calanus sinicus during the post-capture period was evaluated in 1-h incubations. Incubation water volume (13 mL vs. 100 mL) did not significantly affect the excretion rate, and the overall mean excretion rate of C. sinicus was similar to reported values from congeneric species. However, the 24-h variations in the excretion rate denoted that acclimation stress decreased the excretion rates 1–2 h after introduction to a no-food condition. The effect of presence/absence of food was not significant up to 24 h after capture.