Description of a New Species of Astrophiura (Echinodermata : Ophiuroidea) from Tosa Bay, Japan, and Several of Its Remarkable Anatomical Characteristics

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Astrophiura wanikawa, new species, is the ninth in the bizarre and rarely collected genus Astrophiura to be named, and the second to be described from Japanese waters. Individuals cling to the valves of dead clams, Glycymeris (Glycymeris) rotunda, occurring at depths circa 300m. Relatively thick integument on the dorsal surface of the disk incorporates particles of sediment and may harbor a hydroid associate. Integument sheathes the tentacle pores, seals the corners of the oral slits, and connects the arm spines fringing the disk. Disproportionately large tube feet under the disk each terminate in a knob that is richly endowed with secretory papillae. The enlarged adhesive tube feet and the webbed peripheral disk spines presumably enable the ophiuroid to adhere tenaciously, and seal tightly against the substrate. A. wanikawa is gonochoric. Its gonads contain either moderately large oocytes, or round-headed sperm, and have a gonoduct connected to the ventral body wall of the disk. However, individuals lack bursal slit structures from which ophiuroids typically release gametes. The new species is distinguished from its congeners by prominent dorsal disk plates with raised edges. The pairs of long adoral shields of unequal length with proximal tips in contact but out of alignment, is another characteristic exclusive to A. wanikawa.
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