https://orcid.org/0000-0002-4606-7038
![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
ABSTRACT
Xenassiminea nana n. gen. and n. sp. is described from estuaries of temperate mainland Japan (central to western Honshū, Shikoku and Kyūshū). This species has a minute, colourless, translucent, depressed and helicoid shell and resembles some so-called skeneimorphs. However, the anatomical characters of the head–foot, radula and reproductive system indicate that this species belongs to the Assimineidae, in spite of the dissimilarity in shell features. The presence of basal cusps of the central radular teeth and the extremely rudimentary cephalic tentacles indicate that it should be assigned to the subfamily Assimineinae. The shell size (0.8 mm in length, 1.1 mm in diameter) is the smallest among known assimineids. It lives beneath stones deeply buried in sandy mud flats at the innermost parts of large bays and can be regarded as threatened by the rapid loss of these habitats in recent years.
和文摘要
本州中〜西部・四国・九州の河口域から Xenassiminea nana n. gen. and n. sp. カハタレカワザンショウを記載する。この種の殻は微小・無色半透明・螺塔低平な蝸牛形でいわゆるシタダミ様を呈するが, 頭部−腹足・歯舌・生殖器などの解剖学的特徴はカワザンショウ科に属すことを示す。歯舌中歯に下歯尖を持ち, 頭触角が極端に短いことからカワザンショウ亜科の一員である。殻の大きさ（殻長0.8 mm, 殻径1.1 mm）はカワザンショウ科の全既知種中で最小である。大規模な内湾最奥部の砂泥干潟に深く埋もれた転石下に棲み, 近年は棲息環境の急速な消失によって危機に瀕していると見做される。
ZooBank registration: http://www.zoobank.org/urn:lsid:zoobank.org:pub:46AB42CF-497C-47DE-AA67-87AC6712CAEC
Acknowledgements
I am grateful to Yoshimasa Hayase and Taichi Wada for the provision of several occurrence records and habitat information of the present new species. I also thank Winston F. Ponder, Bruce A. Marshall, and Donald J. Colgan for valuable comments on the manuscript. Alison Miller kindly checked the Queensland specimens in the Australian Museum, Sydney.
Disclosure statement
No potential conflict of interest was reported by the author(s).