Corresponding author: Masaatsu Tanaka (
Academic editor: Chris Glasby
A new echiuran,
Echiurans are a small group of marine coelomates, previously classified as a distinct phylum, but now often included in the Phylum
The echiuran in the present study was first identified as
We have compared echiurans newly collected from a sandy flat near Onomichi Bay with the specimens deposited in the Tohoku University Museum (TUM), collected from the bay in 1931 and labeled as “
We collected new specimens from a sandy flat, named Hachi-no-higata, at the mouth of the Kamogawa River, Takehara, Hiroshima Prefecture, Japan in 2011. The specimens were relaxed with menthol, and minute pieces of proboscis were taken from the holotype and two paratypes and fixed with pure ethanol for future molecular analyses; all remaining material was fixed in 10% seawater formalin and then stored in 70% ethanol. Further materials have been retained at our Laboratory of Taxonomy, Toho University (LTTU), the Department of Zoology, University Museum, University of Tokyo (UMUTZ), or TUM. The type series, as well as the two non-type ones, are deposited in the National Museum of Nature and Science, Tsukuba, Japan (NSMT).
Observations, dissections, and drawings were made under a stereoscopic microscope. Trunk length (TL) and proboscis length (PL) were measured. General terminology was based on
Trunk up to 80 mm long in preserved specimens. Leaf-like gonostomal lips with smooth margins. Neurointestinal vessel unbifurcated. Ring vessel absent. Rectal caecum absent. Anal vesicles fastened basally to the trunk wall by mesenteries.
In life, trunk colored pinkish yellow and proboscis pale yellow (
In preserved specimens, TL ranging from 25 to 73 mm (n = 28) and PL ranging from 6 to 33 mm (n = 8). Proboscis, often detached from trunk, elongated and slightly expanded at its extremity, with its proximal end forming small lower cup around mouth. Trunk wall thickened and covered with numerous distinct papillae, especially prominent (up to 1 mm) at both extremities. Trunk musculature consisting of outermost circular, middle longitudinal, and innermost oblique layers, all of which continuous throughout.
Paired ventral setae of usual form, with strong interbasal muscle (
Paired gonoducts situated slightly behind ventral setae (
Long and convoluted alimentary canal, filled with sand grains and elliptical fecal pellets, ca 2 mm in long axis (
Vascular system composed of dorsal, neurointestinal, and ventral vessels, without ring vessel (
Paired simple anal vesicles, ca one-third of TL in holotype, while rarely attaining TL in other specimens, covered wholly with numerous microscopic ciliated funnels and fastened basally to trunk wall by some mesenteries (
The specific name is dedicated to the late Dr Hayao Sato who made a significant contribution to the taxonomy of echiurans, sipunculans, and priapulids in Japan and adjacent waters.
Hiroshima Pref. (Seto Inland Sea), Ikarise Islet at the entrance of Lake Hamana, and Misaki (Sagami Bay), Japan, intertidal to subtidal, sandy to muddy bottoms.
A comparison of all known species referred to the genus
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absent | absent | absent | smooth | body wall | Seto Inland Sea, Japan | This study | |
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absent | absent | barely detectable | with digitiform projections | body wall | Probably around Hokkaido, Japan | |
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absent | absent | absent | with digitiform projections | body wall | Monterey Bay, California, USA |
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absent | absent | absent | with digitiform projections | intestine | Dunwich, Queensland, Australia | |
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absent | absent | absent | with irregular serrations | unknown | Monterey Bay, California, USA |
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absent | present | absent | with irregular serrations | body wall | Puget Sound, Washington, USA |
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present | absent | unknown | with irregular serrations | intestine | Araça Beach, São Paulo, Brazil |
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present | unknown | unknown | smooth | unknown | Jiaozhou Bay, Shandong, China |
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Thus, the taxonomic identity of
Our cordial thanks are due to Drs S. Sato (TUM) and R. Ueshima (UMUTZ) for loan of specimens with permission to dissect; Mr K. Okada for help in collecting specimens; Dr M. Sato (Kagoshima University), Messrs Y. Kuwahara (Abashiri Fisheries Research Institute) and S. Kimura (Mie University) for materials; Dr T. Kon (Toho University) for helpful discussions; a reviewer for helpful comments on the manuscript; and to Enago (www.enago.jp) for English language review. This study was partly supported by a Grant-in-Aid for Field Research from Faculty of Science, Toho University to TN.