著者

Ryutaro Goto Yumi Henmi Yuto Shiozaki Gyo Itani

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.16, no.3, pp.155-164, 2021-08-06 (Released:2021-07-31)

参考文献数

42

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Ikeda taenioides (Ikeda, 1904) (Annelida: Thalassematidae: Bonelliinae) is the world’s longest spoon worm species, which possesses an extremely long tape-like proboscis with a striped color pattern and a large brownish red trunk. This species is endemic to the Japanese Islands and inhabits a deep vertical burrow in intertidal and subtidal sand flats. Their proboscis, which extends from its small burrow opening, has been frequently observed around Japanese coasts. However, sampling of the main body (i.e., trunk) has been extremely rare because it always stays within a deep part of the burrow. Here, we report the success of the sampling of two specimens of I. taenioides with trunks in two different localities of the Seto Inland Sea (i.e., Ohmishima and Hachi), Japan, in 2019 and 2020 using a yabby pump. This is the first sampling of the trunk of I. taenioides in 88 years after its last collection in Onomichi Bay in 1931. We described the trunk color and morphological characteristics of the two specimens, including the internal anatomy. The trunks of the two specimens showed different colors, that is, pale brown (Ohmishima) and deep brownish red (Hachi). However, they were not distinguished to the species level by the comparison of partial COI sequences, suggesting that I. taenioides has an intraspecific variation in trunk color. Despite the difference in the sampling seasons (Ohmishima: June, Hachi: February), both specimens included numerous ripe eggs. According to previous studies, those collected in November and December also included numerous ripe eggs. Taken together, I. taenioides may be reproductive throughout the year or have multiple reproductive seasons per year.

著者

Masanori Sato Naoto Jimi Gyo Itani Yumi Henmi Shuji Kobayashi

出版者

The Japanese Society of Systematic Zoology

雑誌

Species Diversity (ISSN:13421670)

巻号頁・発行日

vol.28, no.2, pp.147-163, 2023-07-25 (Released:2023-07-25)

参考文献数

83

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The monotypic polynoid genus Arctonoella Buzhinskaja, 1967 comprises solely the type species A. sinagawaensis (Izuka, 1912), which was originally described from Tokyo Bay (central Japan), and subsequently recorded from China and the Russian Far East. The six specimens we collected together with the burrowing filter-feeding spoon worm Urechis unicinctus (Drasche, 1880) from three intertidal-flat sites in the Seto Inland Sea represent a new report for the western Japan, and the second for the country. Our morphological observations reveal that the shape of the cephalic peaks in the frontal prostomial margin is variable even within a local population, although this character has been considered as diagnostic for Arctonoella. This genus is closely related with Hesperonoe Chamberlin, 1919, both morphologically and phylogenetically. Hesperonoe urechis Marin and Antokhina, 2020, collected inside a burrow of U. unicinctus in the Russian Far East, is hereby deemed a junior synonym of A. sinagawaensis. This species morphologically resembles Hesperonoe adventor (Skogsberg in Fisher and MacGinitie, 1928), which inhabits spoon worm (Urechis caupo Fisher and MacGinitie, 1928 and Echiurus echiurus alaskanus Fisher, 1946) burrows along the northeastern Pacific coast of America. Therefore, we conclude that the Arctonoella-Hesperonoe species complex requires to be reviewed to determine the proper generic arrangement. Additionally, we revise the available data on the symbiotic fauna living inside the burrows of U. unicinctus and U. caupo.

著者

Minoru Ijichi Gyo Itani Hiroshi Ueda

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.12, no.3, pp.145-150, 2017-08-22 (Released:2017-08-24)

参考文献数

26

被引用文献数

4

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The life cycle and precopulatory mate guarding behavior of the poecilostomatoid copepod Goidelia japonica associated with the spoon worm Urechis unicinctus (Echiura) are described based on specimens from 19 worms collected from western Japan. A total of 676 copepods were collected from the host’s rectum (494 copepods) and body surface (182 copepods). Copepod numbers were significantly correlated with host weight. Copepods in the rectum consisted almost completely of copepodids (35%) and adult males (65%), with only one non-ovigerous adult female recorded. In contrast, those on the body surface were all adult males (24%) or females (76%), of which 58% were ovigerous. No nauplii or CI occurred. In the rectum, 36% of the adult males guarded 67% of the copepodids, consisting of CII–CV. From these results, their life cycle is considered as follows: nauplii and CI live as plankton; just before or after molting to CII, they enter the host’s rectum and females are probably soon guarded by males; they grow up to CV there; CV females guarded by males move to the body surface just before the final molt; on the body surface females molt to adults and spawn eggs. Guarding the first symbiotic stage (CII) is a unique precopulatory behavior for symbiotic poecilostomatoid copepods. This can be explained from the viewpoint of evolutionary resolution of the intersexual conflict and advantage for early copepodids in precopula.