A NEW SPECIES OF OPHIUROIDEA FROM THE COAST OF KII PENINSURA, JAPAN

No species belonging to the genus Ophiolepis of Ophiuroidea has hitherto been recorded from the coast of Japan, but only two species, O. cincta and O. annulosa, from the Okinawa Islands. Recently I received a littoral ophiurid specimen from Prof. H. UTINOMI, Seto Marine Biological Laboratory of Kyoto University. The specimen was collected in the vicinity of Seto by one of the students visited the laboratory for the marine biological course in August, 1967 and handed to Prof. UTINOMI for identification. As a result of the study, the specimen is considered to be a new species of the genus Ophiolepis. Before going further, I wish to express my sincere gratitude to Prof H. UTINOMI for his kindness in offering this valuable specimen to me for examination, and to Dr. T. TOKIOKA, Seto Marine Biological Laboratory of Kyoto University, for his kind advices in preparation of the manuscript

When Ontogeny Matters: A New Japanese Species of Brittle Star Illustrates the Importance of Considering both Adult and Juvenile Characters in Taxonomic Practice

<div><p>Current taxonomy offers numerous approaches and methods for species delimitation and description. However, most of them are based on the adult characters and rarely suggest a dynamic representation of developmental transformations of taxonomically important features. Here we show how the underestimation of ontogenetic changes may result in long term lack of recognition of a new species of one of the most common ophiacanthid brittle stars (Echinodermata: Ophiuroidea) from the North Pacific. Based on vast material collected predominantly by various Japanese expeditions in the course of more than 50 years, and thorough study of appropriate type material, we revise the complex of three common species of the ophiuroid genus <i>Ophiacantha</i> which have been persistently confused with each other. The present study thus reveals the previously unrecognized new species <i>Ophiacantha kokusai</i> sp.nov. which is commonly distributed off the Pacific coast of Japan. The new species shows developmental differentiation from the closely related species <i>Ophiacantha rhachophora</i> H. L. Clark, 1911 and retains clearly expressed early juvenile features in the adult morphology. Another species, <i>Ophiacantha clypeata</i> Kyte, 1977, which had been separated from <i>O</i>. <i>rhachophora</i>, is in turn shown to be just a juvenile stage of another North Pacific species, <i>Ophiacantha trachybactra</i> H.L. Clark, 1911. For every species, detailed morphological data from both adult and juvenile specimens based on scanning electron microscopy are presented. A special grinding method showing complex internal features has been utilized for the first time. For all three species in this complex, a clear bathymetric differentiation is revealed: <i>O</i>. <i>rhachophora</i> predominantly inhabits shallow waters, 0–250 m, the new species <i>O</i>. <i>kokusai</i> lives deeper, at 250–600 m, and the third species, <i>O</i>. <i>trachybactra</i>, is found at 500–2,000 m. The present case clearly highlights the importance of considering developmental transformations, not only for a limited number of model organisms, but as part of the taxonomic process.</p></div

Adult disk spines and oral frames of <i>Ophiacantha kokusai</i> sp.nov. (A–B, holotype), <i>Ophiacantha rhachophora</i> H.L. Clark, 1911 (C–D, NSMT E–1540) and <i>Ophiacantha trachybactra</i> H.L. Clark, 1911 (E–F, NSMT E–7543).

<p><b>SEM of uncoated specimens using Keyence VHX-D510</b>. ap, adoral shield papillae; as, adoral shields; dp, dental plate; gs, genital slit; j, jaws; op, oral papillae; os, oral shield; th, teeth; red asterisks indicate absence of the adoral shield papillae in adult <i>O</i>. <i>rhachophora</i> and <i>O</i>. <i>trachybactra</i>. Scales bars, 0.1 mm.</p

<i>Ophiacantha trachybactra</i> H.L. Clark, 1911, type material, external views.

<p><b>A,</b> holotype USNM 25649, 12.7 mm dd, off Cape Terpeniya, Sakhalin Id., Okhotsk Sea, dorsal view; <b>B,</b> same, ventral view; <b>C,</b> paratype USNM 25694, Shumagin Bank, Alaska, 7.2 mm dd, dorsal view; <b>D,</b> same, ventral view; <b>E,</b> same, proximal arm segments, dorsal view; <b>F,</b> same, latero-ventral view, SEM. as, adoral shields; gs, genital slit; j, jaws; op, oral papillae; os, oral shield; red asterisks indicate the absence of the adoral shield papillae. Scales bars, 0.5 mm (F), 1 mm (A–E).</p

<i>Ophiacantha rhachophora</i> H.L. Clark, 1911, holotype USNM 25630, 5.6 mm dd, details, SEM.

<p><b>A–L, proximal segments. A,</b> lateral arm plate; <b>B,</b> same, inside view; <b>C,</b> ventral arm plate; <b>D,</b> dorsal spine; <b>E,</b> arm spine articulations; <b>F,</b> spine, ventral view; <b>G,</b> hollow dorsal spine, transversally sectioned at middle part; <b>H,</b> ventral spine; <b>I,</b> vertebra, dorsal view; <b>J,</b> same, ventral view; <b>K,</b> same, distal view; <b>L,</b> same, proximal view; <b>M–R, middle segments. M–N,</b> lateral arm plates showing spine-like protuberance; <b>O,</b> arm spine articulations; <b>P,</b> vertebra, dorsal view; <b>Q,</b> same, distal view; <b>R,</b> ventral arm plate. Red asterisks indicate the absence of the vertebral condyle (streptospondylous articulation) on both proximal and distal vertebrae. Scales bars, 0.05 mm (E, F, Q), 0.1 mm (A–C, G, H, J, K–R), 0.2 mm (D, I).</p

<i>Ophiacantha trachybactra</i> H.L. Clark, 1911, subadult specimen 6.8 mm disk diameter NSMT E–7557, sta. KT-93-15 (M 3), off Sanriku, northern Honshū, external views.

<p><b>A,</b> dorsal view; <b>B,</b> ventral view; <b>C,</b> proximal arm segments, dorsal view; <b>D,</b> proximal arm segments, ventral view; <b>E,</b> proximal arm segments, ventral view, SEM; <b>F,</b> proximal arm segments, ventral view, details, SEM. as, adoral shields; gs, genital slit; j, jaws; op, oral papillae; os, oral shield; red asterisks indicate the absence of the adoral shield papillae. Scales bars, 0.5 mm (F), 1 mm (A–E).</p

Comparison of the oral frame patterns in <i>O</i>. <i>rhachophora</i> H.L. Clark 1911 and <i>O</i>. <i>kokusai</i> sp. nov. and (specimen NSMT E–1540 and paratype NSMT E–7638 respectively) using the grinding method technique.

<p><b>A–C,</b> three consecutive sections of the disk of <i>O</i>. <i>rhachophora</i> showing placement of only three oral papillae (including distalmost one) emerging exclusively from the jaws; <b>D–F,</b> three consecutive sections of the disk of <b><i>O</i>. <i>kokusai</i> sp.nov.</b> showing placement of three oral papillae emerging from jaws and a fourth separate thorny papilla emerging from the adoral shield. ap, adoral shield papillae; as, adoral shields; dp, dental plate; gs, genital slit; j, jaws; op, oral papillae; os, oral shield; th, teeth; red asterisks indicate the absence of the adoral shield papillae in <i>O</i>. <i>rhachophora</i> (<b>A–C</b>). Scale bars, 1 mm.</p

Diagnostic characters of the <i>Ophiacantha kokusai</i>, <i>O</i>. <i>rhachophora</i> and <i>O</i>. <i>trachybactra</i>.

<p>Diagnostic characters of the <i>Ophiacantha kokusai</i>, <i>O</i>. <i>rhachophora</i> and <i>O</i>. <i>trachybactra</i>.</p

Main stages of the development of <i>Ophiura leptoctenia</i> H.L. Clark, 1911 (family Ophiuridae), a series from the locality in Okhotsk Sea (sta. 79).

<p><b>A, C, E, development of the dorsal disk characters. A,</b> adult specimen, 10 mm disk diameter, primary plates occupy a restricted area within the disk (ZMMU D–1051); <b>C,</b> juvenile specimen, 2 mm disk diameter, primary plates occupy a considerable area of the disk (ZMMU D–1051), SEM; <b>E,</b> early postlarval specimen, 1 mm disk diameter, primary plates occupy whole dorsal disk area (ZMMU D–1051), SEM; <b>B, D, F, development of the ventral oral characters, SEM. B,</b> adult specimen, 10 mm disk diameter, all oral papillae are spiniform, 2–3 adoral shield papillae; <b>D,</b> juvenile specimen, 2 mm disk diameter, both spiniform and block-shaped oral papillae present, 2 pairs of adoral shield papillae; <b>F,</b> early postlarval specimen, 1 mm disk diameter, only pair of block-shaped oral papillae present, and pair of adoral shield papillae. ap, adoral shield papillae; as, adoral shields; cpp, central primary plate; dp, dental plate; j, jaws; rpp, radial primary plates; op, oral papillae; os, oral shield; th, teeth. Scales bars, 0.1 mm (E, F), 0.3 mm (B, D), 1 mm (C), 5 mm (A).</p