The malacologicalsocietymalacological society of Japan llreVoLVEN L]S (Jup. Jovr. Malac.) 51. No. 4 (1992}:235 268 - IIi Jgit V) P, 1987 1988 as blA ll fe do> JtL eC .k Lt tZl ?flj ?gEE ifR ?fiE e5 b> t* #2 5 ak vaRma []i l9g {} rt., rtJ..Z- za ll (MSIil<XtcI}i: . H)as;iUJ:iF･lt\) from Bathyal Zone Noteworthy Gastropods Colleeted in Tosa Bay by the RIV Kotaka-MaTzL in 1987 and 1988 Takashi OKuTANI and Akiko IwAHoRl Tokyo 108 and (Tokyo Univesity of Fisheries, Konan, Minato-ku, Bunkyo-ku, Tokyo 112) Japan Women's University, Mejirodai, m) 18 Abstract: Among the gastropod specimens trawled from bat,hyal depths (450-780 tosaensis Neptunea kotakamaruae, species were identified. Four species, namely, Eosipho to be new species. Morphological Antiplanes delicatus, and Eipergo nipponensts are recognized of "rare'' species, e.g. Otukaia kiheiziebisu, characters, particularly radula, and distributions Ptychosinynx bisinua- Orectospira tectijbrmis. 7)'ephonopsis sayoae, Buccinum koshikinum, fauna in Tosa Bay seems to ta japonica among others are discussed, Bathyal gastropod and undercurrent. represent a mixture of faunlllae of intermediate (slope) water Introduction Nakayama, famous for a rich molluscan fauna 1960; Tosa Bay has been (Azuma, extended to shallow depths or 1965). However, more intensive collecting effort has been molluscan fauna in this bay has seldom at best to shclf zone than deep water, thus deepsea collections et al., 1963). The RfV been explored except a report of sporadic (Horikoshi made an in- Kotaka-Maru, Nansei National Fisheries Research Institute at Kochi, recently there tensive trawling down to 8oo m in Tosa Bay to clarify demersal finfish fauna (Horikawa et al., 1991). trawl samplings, interesting mollusks were incidentally caught During such series of for us through the courtesy of Mr. Hiroshi and many gastropod specimens were supplied a lightupon bathyal Horikawa of that Institute. The investigation on this material throws of soft facies. Among them, some molluscan fauna of Tosa Bay, particularly bottom "rare" species may noteworthy. Here, in- range extentions and mass occurrences of be depth of 450 m are reported. teresting gastropods collected from deeper than the NII-Electronic LibraryMbrary Service The malacologicalsocietymalacological society ofJapathof Japan 'vENUS: 236 Vol. 5t, Ne. 4 (1992) Materials Out of the KOtaka-Maru collection 'specimens 455 gastropod from nine haulstreatedmade in deeper than 450 m to 780 (down m) during 1987 and 1988 are selectively here (Fig. 1, Table 1). N 133` 13.l-E Koch; SHIKOKU 33"3or 33N Nif Asizuri Fig. 1 Sampling site of the RfV Kotaka-?Lclaru in Tosa Bay. area with depth contour from (Stippled 4oo to 800 m) Table 1. Date, depth and number of specimens gastropod under the present study (R/V Kbtdka-Mliru) ' ' Haul nuMber uSed Depth range Date Numbers of specimen in this paper of haul under examination 1 Sept, 2, 1987 630-670m 96 2 OcL 6, l987 450-500 15 3 Nov. 17, 1987 600 50 4 Nov. 24, 1987 780 151 5 Jan. 26, 1988 700 15 6 May 14, 1988 7oo 30 7 June 21, 1988 700-720 32 8 Sept, 13, 1988 750 62 9 Sept. 21, 1988 750 ' 1 tt ' NII-Electronic Library Service The malacologicalsocietymalacological society of Japan 237 Okutani･lwahori: Bathyal Gastropods from Tosa Bay Taxonomy Family TROCHIDAE Rafinesque, 1815 1. Bathybembix aeola (Watson, 1879) (Figs. 2-6) Materiai: 14 specimens from Haul 3 (600 m); 32 from Haul 4 (780 m); 16 from Haul 8 (750 m). The largest specimen measured 49.95 mm in length (height) and 38.7 mm in width. The ratio of LIW is 1.23 (N=10). The soft part has a small nuchal appendage behind the right eye. ti radula ribbon The radula is rhipidoglossate, co.3.1.3.eo (oo 19) (Fig. 4). The length of central is variable, but approximately 10(7b of shell length and bearing 40-50 rows. The tooth has a broad base with triangular lateral projections and a strongly incurved central cusp of which both lateral margins are serrated. The lateral teeth are also monocuspid and finely serrated in both sides (Fig. 5). The marginals are thin sickle-shaped and serrated (Fig. 6). Remarks: Among the radula of the Tribe Calliotropini Hickman & Mclean, 1990, this species may have a good size of rhachidian in comparison to, such as, CZitliotropis Seguen- za, 1903. Hickman (t981) discussed the functional morphology of radula of this species and assumed that B. aeota performs selective deposit feeding. Distribuiion: This species was originally collected from the HMS Challenger St. 232, off Enoshima Islet, Sagami Bay, 345 fathoms, and St. 235, the Sea of Enshu-Nada, southern the coast of Middle Honshu, 565 fthoms. Since then, this species has been known from Sea of Kashima-Nada (Taki and Otuka, 1942) in 60-100m (Kira, 1954). Okutani (1964) collected this species by the RfV Sqyo-Maru from Sagami Bay and the Sea of Enshu-Nada, at depths between 500 and 1,020 m. Although Kuroda et al. (1971) gave the range of "off Horikoshi this species Shikoku", the only precise locality data from Tosa Bay are by Hakuho-Mar". This et al, (1983) from Tosa Bay, 707-750m (40 specirnens) by the R!V south to Tosa Bay tending species thus ranged from off the Sea of Kashima-Nada down to deepen the habitat soytherly. Otukaia ktheiziebisu (Otuka, 1939) (Figs. 7-13) from Haul 6 700 m). Material: One specimen from Haul 5 and 7 specimens (both in numbers of spiral ribs mentioned Except for the size and a considerable variability NII-Electronic Library Service The malacologicalsocletyofmalacological society of Japan 238 VENUS: Vol. 51, No. 4 (1992) Figs.2-6.Bathybembix aeola (Watson) J'"U T] St"f:fi trJ ]tr"d 2, Shell length 49.9 mm; 3, SI. 33.4 mm; 4. A part of radula ribbon (scale=1oo "m); S. CentTal and lateral teeth, cnlarged (scale=50 ptm); 6. LaLeral and marginal teeth, enlarged (scale=1oo "m). 4-6 all from SL 21.35 mm. NII-Electronic Library Service The malacologicalsocletyofmalacological society of Japan Okutani.Iwahori: Bathyal Gastropods from Tosa Bay 239 Figs.7-13.Otukaia kiheiziebisu (Otuka) ce'xNl V'Jz ifJiL b"i 7. Shell length 26.7mm; 8. SL 26.5 mm; 9. Illustration in the original description by Otuka (1939); 10. A part of radula ribbon (scale=1 mm); 11. Central and lateral teeth, enlarged (scale=1oo ptm); 12, 13. Marginal teeth, enlarged (scale=IOO pm). 10 from SL 26.15 mm, 11, 13 from SL 22,8 mm, 12 frorn SL 20.05 mm. NII-Electronic Library Service The malacologicalsocietymalacological society of Japan 240 VENUS: Vel. 51, No.4(1992) below, the present materials well agree with the original description of Otuka (1939 as Calliostoma). The size of the specimens under examination ranged from 12.3 mm to 26.7 mm in shell length (height) and LIW from O.898 to 1.007 (mean O,966). The primary spiral keels, which are usually wealky beaded or finely crenulated, on the penultimate and body whorls are three including the basal peripheral one. In some specimens, such as the one from Haul 5 and 3 specimens from Haul 6 have strong secondary spiral ribs intercalated. Espe- cially, a specimen measuring 23.5 mm in shell length from the latter lot has 5 equally strong spiral ribs on the body whorl representing a different appearance from the typical form. In such a multi-ribbed specimen bears stronger secondary cords which are primarily emphasized tertiary cords. The base is ornamented by 18 to 20 strong spiral cords with narrow interstices. The radula isrhipidoglossate, co.4.1.4.oo (Fig. 10). The central tooth has a thin, strongly bent cusp which is finely serrated laterally. Lateral teeth are also strongly bent and serrated like the central tooth (Fig. 11). The marginal teeth may be ciassified into one innermost, 8 inner and about 35-40 outer marginal teeth. The innermost marginal tooth has rather robust shaft, thick base and 4-5 short cusps along the incurved distal portion. The inner marginals are thinner than the innermost marginal and tend to weaken outwardly and have 8 comb-like cusps on both sides. Thc outer marginals have a slender shaft and incurved cusp which is elaboratedly serrated (Figs. 12, 13). Remarks: This species was originally described by Otuka (1939) based on the specimen from a depth of 600 m in the Sea of Kashima-Nada. Although the type specimen (Reg. No. 500 Earthquake Research Institute, Tokyo Imperial University: Fig. 9) was destroyed during the war, the subsequent specim ¢ n in the Kawamura Collection, now stored in the National Science Museum Tokyo, which sN'as illustrated by Okutani (1983), was compared for identit'ication. Ikebe (1942) established Otukaia for this deepsea, thin-shelled, and sparsely ribbed Cal- liostomatin. The present study reports for the first time the radula of this "rare'' species and clarifies that it is typical for the Calliostomatinae Thiele, 1924 (Hickman & McLean, 1990).Distribution: "from Ikebe (1941) gave the occurrence of this species the Sea of Kashima- Nada, 6oo m deep and off Misaki, Sagami Bay, 50-60 fathoms'', However, the occurrence of this species in Sagami Bay has nor been verified since. The present discovery Figs. 14--17. Phanerotepida transenna (Watson) }7 VV'7.f>'Y g Ob"l 14. Shell length 25.3 mm; 15. Apart of half radula ribbon (scale=1oo pam); 16. A part of radula ribbon (scale=5oo ptm); 17. Central tooth, enlarged (scale=100 pam). 15-17 all fTom SL 25.3 mm. Figs. 18-20. 0rectospira tectijbrmis (Dall) Y lfJz.i7 7 )7 Jl:b;E V 7tr'1 18.