VENUS 62 (1-2): 11-18, 2003

A New species of Aperiovula (: ) Collected near the the Boso Peninsula, Japan

Yoshihiro Yoshihiro Omi

4-20-8 4-20-8 Sendagaya, Shibuya-ku ，あわ 10 151 0051, Japan

Abstract: Abstract: An ovulid gastropod collected from off the Boso P巴ninsula in Honshu, Japan, is is described as a new species Aperiovul α aurora. It is morphologically most similar to Aperiovula Aperiovula jeanae Cate, 1973, from which it can be distinguished by its thinner and transluc 巴nt shell and callously produced posterior terminal; the sharper and stronger denticles on on the n紅 rower outer lip; the wider aperture, and the lack of both a yellowish marginal line and and a funiculum.

Keywords: Keywords: Ovulidae, new speci 巴s, Aperiovula aurora, Boso P巴ninsula

Introduction

A considerable numb 巴r of ovulid species have been described and recorded in Japan. The ovulid ovulid fauna of southern Kii Peninsula has been examined by Cate (1970, 1973, 1978a, 1978b), Cate Cate & Azuma (1971), and Azuma (1974a, 1974b, 1974c, 1975, 1976a, 1976b). The Boso and Miura Peninsulae are considered to be the northern distribution limits of many ovulids. Their ovulid ovulid fauna was well investigated by Mase (1989), who emphasized the importance of mantle color color pattern and sculpture in recognizing species. The present author has had a chance to examine examine two ovulid specimens collected at 200-300 m depth off the Boso Peninsula that do not re re pres 巴nt any species hitherto known from Japan. Further comparison with worldwide ovulid species species led to the conclusion that th 巴y represent a new speci 巳s. In terms of external features, this new species is considered to be most closely r巴lated to Aperiovula jeanae Cate, 1973, and is described described here.

Taxonomy

Family Family Ovulidae Fleming, 1828

Genus Aperiovula Cate, 1973

Type species by original designation: Ovulum adriaticum Sow 巳rby, 1828.

Aperiovula Aperiovula aurora n. sp.

(Fig. (Fig. 2A 』 F)

乃•pe material: Holotype (NSMT-Mo 73529) from rocky sloping bottom at 200-250 m, off Namuya, Boso Peninsula, Chiba, Japan (35°03.9'N, 139°46.?'E), December 7, 2001, collected by T. Osato together with alycyonacean host in gill net set for Japanese lobster Metanephorops japonicus japonicus (Tapparone - Canefri); paratype (Omi collection) from sandy mud bottom at 250-300 m, off Hota, Boso Peninsula, Chiba, Japan (35 。08.l'N, 139 。47.0'E), April, 1998, collected by T. Osato Osato with pennatulacean host in gill net set for M. japonicus (Fig. 1). 12 12 Y. Omi

132 ・ 136° 140 ・ 144 ・E

42 ・N (/

~~ 百9 !<. () !<. ψ !l> 38 ・

．‘九、 ‘。 ~：正j、 凡 匂 ’b -

・oli ・oli 30 ・

35 ・ 26 ・ む

Fig. Fig. 1. Localities of Aperiovula aurora n.sp .

Description: Description: Shell moderately l紅 ge, pyriform, inflated in middle , attenuate anteriorly. Four wide reddish transverse bands crossing entire dorsum on slightly translucent pinkish ground color . Anterior and posterior ends yellow in color . Anterior terminal with well-developed whitish callus callus on left margin extending onto fossula through below terminal ridge on ventral side , but not not reflected dorsally. Right margin weakly angulated. Dorsum weakly incised at anterior and posterior posterior 1/8, but smooth in middle, except numerous delicate growth striations. Ventral side convex, convex, smooth, slightly thickened. Columellar lip straight with two weak columellar folds. Fossula Fossula edentate, weakly concave in middle, connected to terminal ridge. Labrum narrow, bearing bearing 27 sha 中， strong denticles . Aperture wide, almost equal in with throughout. Anterior siphonal siphonal canal slightly widened anteriorly. Posterior extremity well produced and slightly twisted. Funiculum Funiculum absent. Posterior canal thickened and completely closed by thick callus. . Animal. Mantle grayish to beige scatter 巴d by numerous black spots. Radula Radula (Fig. 3A-F) . Taenioglossate with formula 2:1 :1 :1:2. Rachidian tooth sectorial in shape with with large central cusp and 9 lateral denticles on both sides, 4th and 5th larger 出an others; mid- basal basal margin convex. Lateral teeth triangular, leaf-shaped, with elongate shaft; basal margin New Species of Aperiovula from Japan 13

Fig. Fig. 2. Aperiovula spp. A-C, F. Aperiovula aurora n. sp. , holotype (NSMT-Mo 73529) , length 21.2 mm, width width 11.3 mm , height 9.5 mm. D, E. Aperiovula aurora n. sp. , paratype (Omi collection), length 20.2 20.2 mm, width 11.8 mm , height 9.5 mm. G. Aperiovula shikamai Cate , 1973, length 9.5 mm, width width 5.8 mm, height 4.3 mm. H-J. Aperiovula jeanae Cate , 1973, length 14 .8 mm, width 7.9 mm, height 6.4 mm . 14 14 Y.Omi

Fig. Fig. 3. Radula of Aperiovula auror αn， . sp. A. Dorsal vi 巴w of radular ribbon towards frontal end. B. B. Marginal teeth. C. Rachidian teeth and lateral teeth . D. Rachidian t巴巴 th ,enlarged . E. Lat 巴ral teeth , enlarg 巴d. F. Lateral teeth . New Species of Aperiovula from Japan 15 slender slender and projecting backward ; m 句or cusps remarkably large , slightly curved inwardly ; outer cusps cusps minute 5-6 in number, partly split on top. Inner marginal teeth narrow, triangul 紅 in shape , rake-like rake-like in appear 組問， wi 出 19 -23 denticles; partly split approximately 1/3 distally to 24 on top .

Outer Outer m 紅 ginal teeth na 町 ow triangular in shape, rake- like in app 巴arance, with 23-25 denticles extending extending approximately 115 distally, sometimes subdivided into 2-4 tiny denticles; outermost denticles denticles 3-4 times broader than others and split on top, overlapping inner marginal teeth. Dimensions: Dimensions: Holotype: Length 21.2 mm , width 11.3 mm , height 9.5 mm. Paratype: Length 20 .2 mm, width 11.8 mm, height 9.5 mm. Type Type locali 砂： Off Namuya, Boso Peninsula ,Japan , 200-300 m deep . E 砂mology :aurora ，“daybreak ” in Latin , for the rosy pink color of the shell .

Discussion: Discussion: The holotype of new species is an adult female, c紅 rying a fully developed ov 訂 y and and albumen gland . Therefore , it is evident that new species does not form distinct funiculum even even at maturity. There is great intraspecific variability in shell color in ovulids. The shell shape and the structures surrounding the aperture are thus more significant for identification. The dorsal dorsal striation and funiculum are considered to be the most important features in this family. The lack of these features is a peculi む ity of this new species. Cate (1973) created the genus Aperiovula Aperiovula with Ovulum adriati cum Sowerby, 1828 as the type species , citing shells that are often often translucent, fairly large and thin , and that have broad of apertures, and minimal thickening of of the outer lip. This new species is here placed in Ap eriovula based on the presence of all these these features. Ten species (A. all ynsmithi Cate , 1978 , A. jeana e Cate , 1973 , A. m の1eri αna Cate , 1973 , A. pontia Cate , 1975 , A . robertsoni Cate , 1973, A . shikamai Cat 巴， 1973, A. taka e Cat 巴， 1973, 1973, A. takaeopsis Cate, 1978, A. testudiana Cate , 1978 A. yukitai Azuma, 1985) have been recorded recorded in the genus Aperiovula in Japan. Aperiovula aurora is over 20 mm and relatively large

Fig. Fig. 4. Comparison of posterior ( A, B) and ant 巴rior (C, D) extremities of Aperiovula spp . A, C. Aperiovula Aperiovula jeanae , shell length 14 .8 mm . B, D. Ap eriov ula aurora , holotype, shell length 21.2 21.2 mm . 16 16 Y. Omi

among allied ovulids (exc 巴pt for Ovula and Phenacovolva spp.) of Japan. Mo 叩hologically the most similar species in the same genus may be Aperiovula jeanae Cate, 1973 (Fig. 2H-J) and Aperiovula Aperiovula shikamai Cate, 1973 (Fig. 2G). In A. shikamai Cate, 1973, shell is spherical, similar to A. A. aurora; however A. shikamai di 首位s in having a prominent funiculum and distinct transverse striations striations on the columella. There are also di 百erences in radula mo 中hology, i.e. A. shikamai has only only two outer cusps on the lateral teeth (Azuma, 1976: text-fig. 5), wh 巴reas A. aurora possesses five five to six smaller outer cusps. A. jeanae is similar in shape and distributed at almost the same vertical vertical range as A. aurora, but the latter can be distinguished from A. jeanae by the following features: features: (1) (1) The shell of A. jeanae is thicker, only slightly translucent, and purplish pink to white in color tinged tinged with yellowish orange at the marginal rim on dorsum. On the other hand, the shell of A. α urora is more inflated, thinner and translucent, and bears indistinct transverse red bands on reddish reddish pink ground color. (2) (2) A. aurora has a more pronounced and twisted posterior terminal than A. jeanae. (3) (3) A. jeanae has distinct funiculum callosity at the posterior end on ventral side (Fig. 4A). However, However, funiculum of A. aurora is almost absence (holotype; Fig. 4B) or exists only as a trace trace (paratype). 4) (4) In A. jeanae (Fig. 21), the labrum is thicker and more broadly developed, and the apert ぽ e is narrower. narrower. A. aurora (Fig. 2B, E) has very wide aperture and a narrower labrum. (5) (5) The columellar folds and labral denticles of A. jeanae are weak (Fig. 2J, Fig. 4C). However, A. aurora aurora has distinct columellar folds and sharp labral denticles (Fig. 2F, Fig. 4D). (6) (6) A. jeanae (Fig. 4C) has a prominent and convex fossula, whereas the same feature is weak and concave concave in A. aurora (Fig. 4D). Among the similar-looking ovulids hitherto known from Japanese waters, Crenavolva (SerratovuL α ）imitabilis Cate, 1973 also resembles A. aurora in general profile. However, the new species species differs by the lack of spines on the periph 巴ral edge of the outer lip, the closed outer edge of of the canal, the lack of defined dorsal striation, and the undeveloped funiculum.

Biological Biological note: Most ovulid species are usually associated with a single octcorallian host, such such as alcyonarians, gorgonians and antipatharians. However, the two type specimens were found on different hosts. The holotype of was found on Studeriotes sp. (Alcyonacea: Paralcyoniidae), while while the paratype was on a pennatulacean host (T. Osato, personal communication). Certain species species such as Primovula rhodia (Adams, 1854) are found not only on alcyonarians but also on gorgonians. gorgonians. A. aurora may also have a peculiar mode of parasitism. The holotype and paratype are are completely identical with each other in major shell features, but slightly different in color. Mase (1989) speculated that shell color variations in P. rhodia are aposematic depending upon the host host rather than food. The di 旺巴rence in host probably caused the color differ 巴nces in types of the present present new species as well.

Acknowledgements

I am grateful to Mr. Takashi Osato, Chiba, for giving me the opportunity to study the new species by by providing the invaluable specimen; Mr. Yukimitsu lmahara of Wakayama Natural History Museum, identification for identification of th 巴 alycyonac 巴an host ，阻d Mr. Naoki Adachi, Tokyo, for providing the scanning electon electon micrographs of the radula. I am also grateful to Dr. Takashi Okutani, the Emeritus Professor at Tokyo Tokyo University of Fisheries and Mr. Hitoshi Ikeda of Hayama Shiosai Museum in Kanagawa, for their valuable valuable comments on the manuscript. I also thank the following persons who helped me in various ways: ways: Dr. Shin Kubota of Seto Marine Biological Laboratory, Kyoto University; Mr. Kin ’ ya Mase in Kanagawa; Kanagawa; Mr. Shingo Habu in Wakayama, and Mrs. Hazel J. Yamada in Hawaii, U.S.A. New Species of Aper ・iovula from Japan 17

References

Azuma, M. 1974a. Two new sp 巴cies of the genus Phen α covolva Iredal 巴， 1939 from off Kii, Japan and Formosa (Gastropoda: Ovulidae). i令n川（ J.α panese Joum αl of Malacology) 32: 113 116. Azuma, M. 1974b. Systematic studies on the Rec 巴nt Japanese family Ovulidae (Gastropoda) - I. 怜 nus (Japanese (Japanese Journal of Malacology) 33: 65- 73. Azuma, M. 1974c. Systematic studies on the Recent Japan 巴S巴 family Ovulida 巴（ Gastropoda) II. iをnus (Japanese (Japanese Journal of Mal α cology) 33: 97-108. Azuma, M. 1975. Systematic studies on the Rec 巴nt Japan 巴se family Ovulidae (Gastropoda ）ー III. 1をnus (Japanese (Japanese Journal of Malacology) 34: 73 83. Azuma, M. 1976a. Systematic studies on the R 巴cent Japanes 巴 family Ovulidae (Gastropoda ）一 IV. i匂1US (Japanese (Japanese Journal of Malacology) 35: 106-117. Azuma, M. 1976b. Systematic studies on th 巴 R 巴cent Japan 巴se family Ovulidae (Gastropoda) - V. iをηus (Japanese (Japanese Journal of Malacology) 35: 185-204. Azuma, M. 1985. A new species of the genus Aperiovula Cate, 1973 (Gastropoda, Ovulidae) from Kikaigashima Kikaigashima Is. Japan. Venus (Japanese lour η al of Malacology) 44: 229-231.

Cate, Cate, C. N. 1970. A new species of Japanese Ovulidae. The Veliger 13 ：・ 181. Cate, Cate, C. N. 1973. A systematic revision of the Recent Cypraeidae family Ovulidae (: Gastropoda). Gastropoda). The 防 liger, supplement 15: 1-116. Cate, Cate, C. N. 1975. New cypraeacean species (Mollusca: Gastropoda). The Veliger 17: 255 261. Cate, Cate, C. N. 1978a. Recently discov 巴red n巴w sp 巴ci 巴s of Ovulidae chi 巴fly from Wakayama Pref. Japan. 防 nus (Japanese Journal of Malacology) 37: 191 204. Cate, Cate, C. N. 1978b. N 巴w species of Ovulidae and reinstat 巴ment of Margovula p γrulina. Nautilus 92: 160-167. 160-167. Cat 巴， C N. & Azuma, M. 1971. Sixteen new species and one new genus of Japanese Ovulidae. The Veliger Veliger 13: 261 268. Mase, K. 1989. Taxonomic significance of color pattering of the soft body in the family Ovulidae

description description of soft body of 26 species 目 1令nu 』・ (Japanese Journal of Malacology), Supplement 1: 75-120. 75-120. (in Japanes 巴 with English abstract) Sowerby, Sowerby, G. B. I. 1828. On the Recent species of the genus Ovulum, Zο oological loUJ ηα l 4: 145 162.

(Received (Received May 19, 2002 I Accepted May 2, 2003) 18 18 Y.Omi

房総半島沖で採集されたキヌハダヅツミ属の 1 新種

決見慶宏

要約

房総半島沖からキヌハダヅツミ Aperiovula 属の新種が発見されたので記載する。

Aperiovula Aperiovula aurora n. sp. アケボノウミウサギ（新称：曙海兎） 貝殻は卵型。背面から腹面にかけて半透明なピンク色で，背面には太い 4 本の赤色帯が横断し，前後 端はやや黄色くなる。貝殻は薄くわずかに透過性があるが，堅牢である。貝殻はふくらむが，前端に向 かつて長く細くなる。前端左方向に厚く滑層が発達し腹面側に回りこみ末端袋へと連続するが，前端の 縁には反転した滑層の形成は見られない。外唇縁は前端から後端にかけて弱く鍔状に縁取られる。背面 は，前後端 1/8 ほどの部分にのみ弱い縫合が形成されるが中央部にかけては背面の螺状脈は無く，微細 な髪すじ状の成長線が縦軸方向に多数刻まれる。腹面内唇側はよく膨らみ，背面より若干厚くなる。内 唇縦溝は滑らかで段差はない。内唇末端袋には弱い 2 歯の刻みが入り，末端裳はまっすぐ縦に長く発達 する。軸唇簡に歯列は無く，中間部がわずかに凹み，末端髪に連続する。外唇は発達せず幅が狭く，外 唇歯は 27 歯あり，刻みは下方に鋭く形成される。殻口は広く前端から後端までほぼ同間隔で開く。後端 は長く良く発達しているが，滑層癒（funiculum ）は痕跡程度で，後端内唇壁も形成きれない。後溝の溝 は終点で厚く閉じており，弱くねじれる。このねじれは背面側からも確認できる。殻長 21.2 mm ，殻幅 11.3 11.3 mm ，背高 9.5 mm （ホロタイプ）。 模式産地：千葉県内房富浦町南無谷沖，水深 200 ～250mo 分布：房総半島南部 本種は A jeanae Cate, 1973 オトメキヌハダヅツミに似るが，後端が弱くねじれる点，貝殻背面に赤色 帯または赤色紋が出現する点，外唇が黄色に彩色されない点，内唇の膨らみが強い点，滑層癌（お凶cul um) は消失または痕跡程度しか形成されない点，殻口が広く外唇幅が狭い点，外唇の歯列は明確で深く切れ 込み，先端が下方に鋭く発達する点，軸唇寓が弱く凹む点、などの違いにより識別される。 本種ホロタイプはウミトサカ Studeriotes sp. (Alcyonacea: Paralcyoniidae ）上から採集され，パラタイプ はウミエラ上から採集された情報を得ており（大里私信），広選択型の固着動物食性をもっ可能性が考え られる。