著者

Munakata Mizuho Tanaka Hayato Kakui Keiichi

出版者

Zoological Society of Japan

雑誌

Zoological Science (ISSN:02890003)

巻号頁・発行日

vol.38, no.3, pp.287-296, 2021-06

被引用文献数

7

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We describe the cypridoidean ostracod Heterocypris spadix sp. nov. from brackish water on Okinawa Island, Japan. The species closely resembles Heterocypris salina (Brady, 1868) but differs in that (1) the marginal infolds on valves are less developed, (2) the tubercles on the anterior margin of the right valve are completely covered by the selvage and invisible in inner view, and (3) the calcified inner lamella on the ventral margin of the left and right valves is scarcely evident in inner view, as the ventral margins of the valves bend inwardly. We determined partial sequences for the cytochrome c oxidase subunit I (COI; cox1) and 18S rRNA genes in H. spadix for future DNA barcoding and phylogenetic analyses. Our sample contained only females. A breeding experiment revealed that H. spadix females reproduce parthenogenetically. Another experiment showed that H. spadix has low tolerance to desiccation, with all individuals at 25°C dying between 1–2 hours after removal from water. We amplified and sequenced a partial 16S rRNA sequence for the endosymbiotic bacterium Cardinium from H. spadix. Infection by Cardinium may be related to the parthenogenetic reproductive mode we observed in H. spadix.

著者

Kakui Keiichi Munakata Mizuho Tanaka Hayato Hiruta Chizue

出版者

Elsevier

雑誌

Zoologischer Anzeiger (ISSN:00445231)

巻号頁・発行日

vol.293, pp.145-148, 2021-07

被引用文献数

1

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Ostracoda is a diverse group of tiny crustaceans. Although more than 9330 extant species have been described, whole-mitogenomic data were available for only five species. Here we present a complete mitogenomic sequence for an additional species, the parthenogenetic podocopan ostracod Heterocypris spadix. The mitogenome is 15,205 bp long and contains the typical animal mitogenomic complement of 13 protein coding, two ribosomal RNA, and 22 transfer RNA genes. In a mitogenome-based phylogenetic tree, Myodocopa and Podocopa were each monophyletic. Gene order in Podocopa was much more similar to the pancrustacean ground pattern than was gene order in Myodocopa. Gene order was invariant in the three myodocopan species examined, all in the family Cypridinidae. Within Podocopa, two species from different families (Fabaeformiscandona kushiroensis, Candonidae; H. spadix, Cyprididae) were identical in gene order and differed from the pancrustacean ground pattern by only a single recombination. In Cyprididae, however, Cypridopsis vidua differed from H. spadix by five rearrangements. These conflicting patterns—apparent gene-order conservation within (Cypridinidae) and between families (Cyprididae and Candonidae), but marked divergence within a family (Cyprididae)—suggest that the evolution of gene order in ostracods was more complex than that expected from the cypridinid data.

著者

Munakata Mizuho Tanaka Hayato Kakui Keiichi

出版者

Pensoft Publishers

雑誌

Zoosystematics and Evolution (ISSN:14351935)

巻号頁・発行日

vol.98, no.1, pp.117-127, 2022-04-05

被引用文献数

2

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We describe the cypridoidean ostracod Cavernocypris hokkaiensis sp. nov. from riverbed sediments in an alpine stream at an elevation of ca. 1850 m in the Taisetsu Mountains, Hokkaido, Japan. This species differs from congeners in having (1) the outer surface of the carapace smooth, with sparse, tiny setae, but without shallow pits; (2) the carapace elongate rather than triangular in lateral view; (3) the antennula consisting of seven podomeres; (4) first palpal podomere of maxillula with five dorsodistal and one ventro-subdistal setae; (5) the fifth limb lacking setae b and d; and (6) the fifth limb lacking a vibratory plate. We provided the key to the Cavernocypris species. We determined partial sequences for the cytochrome c oxidase subunit I (COI; cox1) and 18S rRNA (18S) genes in C. hokkaiensis. Our sample contained only females, and we obtained a partial 16S rRNA sequence for the endosymbiotic bacterium Cardinium from C. hokkaiensis, indicating the possibility that this ostracod species reproduces parthenogenetically. Our field survey and observations of captive individuals suggested that C. hokkaiensis may be endemic to the Taisetsu Mountains, with a low population density, narrow distributional range, and slow maturation to sexual maturity.