Megadenus atrae n. sp., an endoparasitic eulimid gastropod (Mollusca) from the black sea cucumber Holothuria atra Jaeger (Aspidochirotida: Holothuriidae) in the Indo-West Pacific
Megadenus atrae n. sp., an endoparasitic eulimid gastropod (Mollusca) from the black sea cucumber Holothuria atra Jaeger (Aspidochirotida: Holothuriidae) in the Indo-West Pacific
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DOI：
10.1007/s11230-017-9731-7
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发表时间：
2017-07-01
影响因子：
1.3
通讯作者：
Kano, Yasunori
中科院分区：
文献类型：
--
作者：
Takano, Tsuyoshi;Waren, Anders;Kano, Yasunori
一种真腹足类动物，巨腹虾。例如，内寄生于黑海参HolothuriatraJaeger的泄殖腔中的一种，描述于日本的冲绳，为该属的第五种。在印度东南部、澳大利亚东北部和新喀里多尼亚也发现了同种的标本。属的归属是合理的存在（i）厚，长的长鼻承担一个大的折叠（pseudopallium）附近的基础和一个衣领状结构在中间，（ii）薄，球状的壳，是由pseudopallium覆盖，和（iii）性别二型性与女性通常大于男性。该新种与先前描述的四个同类的区别在于其釜形的假皮，吻的中度发达的衣领和圆形的壳基唇。的大小和性别的单独和成对的个人的比较支持以前的假设，即Megadenus罗斯，n，1910年的物种是环境性别决定的先雄的。本物种大多数发生为一夫一妻制的对，尽管其非常低的人口密度，这意味着一个同种个体的存在作为幼虫定居的线索。这两种机制将增加个人的繁殖成功率在这样的永久性寄生虫与低流行率和丰富的物种的Megadenus。
An eulimid gastropod, Megadenus atrae n. sp., endoparasitic in the cloacal chamber of the black sea cucumber Holothuria atra Jaeger is described from Okinawa, Japan, as the fifth species of the genus. Conspecific specimens have also been found from southeast India, northeast Australia and New Caledonia. The generic assignment is justified by the presence of (i) a thick, long proboscis that bears a large fold (pseudopallium) near the base and a collar-like structure at the middle, (ii) a thin, globose shell that is covered by the pseudopallium, and (iii) sexual dimorphism with the female generally larger than the male. The new species is distinguishable from the four previously described congeners by its cauldron-shaped pseudopallium, moderately-developed collar of the proboscis and rounded basal lip of the shell. The comparisons of the size and sex of solitary and paired individuals support a previous hypothesis that the species of Megadenus Ros,n, 1910 are protandrous with environmental sex determination. The present species occurs mostly as monogamous pairs despite its very low population density, implying that the presence of a conspecific individual acts as a cue for larval settlement. Both mechanisms would increase individual reproductive success in such permanent parasites with low prevalence and abundance as the species of Megadenus.