Hamatani, Iwao

Publications of the Seto Marine Biological Laboratory

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TitleA NEW SPECIES OF VOLVATELLA PEASE, 1860,FOUND IN THE "CAULERPAN MICROFAUNA" IN THEPROVINCE OF KII, MIDDLE JAPAN(OPISTHOBRANCHIA : SACOGLOSSA)Author(s)Hamatani, IwaoCitationPUBLICATIONS OF THE SETO MARINE BIOLOGICALLABORATORY (1972), 21(1): 13-20Issue Date1972-12-01URL http://hdl.handle.net/2433/175800RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityA NEW SPECIES OF VOL VAT ELLA PEASE, 1860, FOUND IN THE "CAULERPAN MICROFAUNA" IN THE PROVINCE OF KII, MIDDLE JAPAN (OPISTHOBRANCHIA: SACOGLOSSA)l) IwAo HAMATANI Tennoji Senior High School of Osaka Kyoiku University With Text-figures 1-3 and Plates II-III In the "caulerpan microfauna", so called by Burn (1966), which is a group of small animals especially inhabiting the caulerpan colonies and essentially feeding on these green algae, shelled sacoglossan opisthobranchs are systematically very interesting. Gonor ( 1961) gave in a table all available records of shelled sacoglossan opistho-branchs which had ones been described by other researchers from various caulerpan species, when he showed the biology of Lobiger serradifalci (Calcara, 1840) collected from a mat of Caulerpa prolifera in the Harbor of Villefranche in September of 1960. Further, Burn ( 1966) described four species of shelled sacoglossan opisthobranchs, which were found in Octorber of 1964 living on the green alga Caulerpa racemosa, var. turbinata growing on the coral reef near the southeast of Suva, Viti Levu, Fiji. The present author also made an observation on the "caulerpan microfauna" at Cape Shionomisaki in the Province of Kii, Middle Japan in March of 1971 and found fourteen species of opisthobranch gastropods living on Caulerpa brachypus Harvey growing in the lower intertidal zone. They are: 1. A form of Cephalaspidea (probably a juvenile of Hydatina sp.) 2. Philine sp. (1) 3. P. sp. (2) 4. Chelidonurafulvipunctata Baba, 1938 5. Gastropteron sp. (probably a juvenile of G.fuscum Baba & Tokioka, 1965) 6. Runcina sp. (1) 7. R. sp. (2) 8. Cylindrobulla japonica Hamatani, 1969 9. Volvatella sp. 10. Oxynoe viridis (Pease, 1861) 11. Lobiger (Lobiger) sagamiensis Baba, 1952 l) Contributions from the Seto Marine Biological Laboratory, No. 565. Publ. Seto Mar. Biol. Lab., XXI (1), 13-20, 1972. (Article 2) 14 I. HAMATANI 12. Phyllobranchillus oriental is (Kelaart, 1858) 13. Hermaea dendritica (Alder & Hancock, 1843) 14. A form ofTritoniidae Of these, thirty-one specimens of Volvatella sp. were collected. All of them are seemingly conspecific and detailed examinations on them have revealed that the form represents clearly a new species, which is named ayakii in memory of Mr. Ayaki Y. Nakajima whose aid made the present author collect these specimens. Hitherto, no species of Volvatella has been known from any part of Honshu Island of Japan; although only a single species, V. vigourouxi (Montrouzier, 1861), has been recorded from the Amami Islands south to Kyushu (Baba, 1966) and from Okinawa further south of the Amami Islands (Habe, 1946). So far as the present author is aware, the following ten species are generally recognized at present as valid members of the genus Volvatella Pease, 1860 ( =Arthessa Evans, 1950). 1. V. fragilis Pease, 1860 2. V. cumingii (A. Adams, 1855) 3. V. vigourouxi (Montrouzier, 1861) 4. V. candida Pease, 1868 5. V. pyriformis Pease, 1868 6. V. cincta Nevill & Nevill, 1869 7. V. laguncula Sowerby, 1894 8. V. elioti (Evans, 1950) 9. V. evansi (Kay, 1961) 10. V. ficula Burn, 1966 Hawaii Puerto St. Elena, W. Columbia New Caledonia Polynesea Society Is. Ceylon Port Elizabeth Zanziber Is. Hawaii Fiji Before going into the description, the author wants to express his hearty thanks to Mr. A. Y. Nakajima for his help in collecting the specimens and also to Dr. T. Tokioka of the Seto Marine Biological Laboratory for his kindness in reading the manuscript. Volvatella ayakii sp. nov. (Japanese name: Himetama-budoginu) Holotype: Collected on March 28, 1971 on the green alga, Caulerpa brachypus Harvey, growing on the rocky substratum in the intertidal zone near the low water mark in the neighbourhood of Cape Shionomisaki, Kii, Middle Japan. The specimen was fixed by 4% formaldehyde and preserved in 70% ethanol, and it is now in the custody by the present author. Paratypes: Paratypes Nos. 1 and 3-5 were collected together with the holotype. Para-type No. 2 was, however, collected on March 12, 1971 at the same locality and was dissected for the examinations of the radula, protoconch, spire and penis. The measurements of the types are as follows: A New Species ofVolvatellajrom Middle japan 15 Specimen Ani~al length, Type number man Shell length Shell breadth number extended state I Holotype 6.2mm 3.4mm 2 Paratype I 6.8mm 5.0mm 2.8mm 3 Paratype 2 7.0mm 5.0mm 3.0mm 4 Paratype 3 6.5mm 4.5mm 2.0mm 5 Paratype 4 5.2mm 4.5mm 2.5mm 6 Paratype 5 3.8mm 2.Umm Other specimens: Arriong these specimens (Sp. Nos. 7-22), three specimens (Sp. Nos. 7-9) were fixed by Bouin's fluid in sea water and sectioned into horizontal series and Sp. Nos. 10 and 13 into transverse series for future internal morphological studies, while Sp. Nos. 16 and 17 were dissected for observations of radular teeth. The soft-body in nine specimens (Sp. Nos. 11, 12, 14, 15 and 18-22) was in an imperfect con-dition to be studied. Sp. Nos. 23-31 were collected as empty shells, of which Nos. 23-25 were almost perfect, while others (Sp. Nos. 26-31) were broken considerably. Description: Living animals (Fig. 1; Pl. III, A-D) are whitish at a glance, as the soft-body of the animal extended out of the shell is milky white in colour, but specimens 2.5mm Fig. 1. Volvatella ayakii sp. nov. Dorsal aspect of a living animal, Paratype No. 2 (Sp. No.3). 16 I. HAMATANI preserved in alcohol (Pl. II, A-D) are yellowish orange. The soft-body can be invo-luted perfectly within the shell. A pair of rhinophore-like protuberances are visible on the head, though sometimes they may be only gentle inconspicuous elevations. Paired pure black eyes in the deep tissue are seen through the skin posterior and slight-ly external to the base of rhinophore-like protuberances. In contrast with Clyindro-bulla, no furrow is definable in the median line of the head-shield. The lateral edge of the head-shield is enfolded deeply to the base of the penis between the head-shield and the foot to form a groove on the lateral side of the head. Eyes are seen clearly 8 2mm Fig. 2. Voluatella ayakii sp. nov. Empty shell of the holotype (Sp. No. 1). A: dorsal side. B: ventral side. through the body wall in this groove at about the anterior one-third, the external ovi-duct furrow is running under this groove from near the mouth to the female orifice. The foot is small and rounded at anterior and posterior ends, the anterior end is slightly broader than the posterior. The body is furnished with numerous white opaque dots over the whole part under the shell and especially densely along the anterior border of the head-shield, on rhinophore-like protuberances, on the dorsal side of foot-corners, at the posterior end of the foot, in the area posterior to the gill-belt, and sometimes A New Species oJVolvatellafrom Middle japan 17 even on the penis, especially in its distal half. These white dots secrete copious white mucus at mechanical stimulation. The shell (Fig. 2, A and B) is nearly ovoid in shape, very thin and flexible, but extremely fragile. It is calcareous, but covered with the membraneous epidermis col-oured straw. In V. vigourouxi the epidermis is coloured ashy yellow with fine growth lines of dark brown (see Baba, 1966) and evidently more deeply than in the present species. The body whorl is rounded and slightly swollen in the middle, but contracted near the posterior end to form a spout. The anterior half of the aperture is dilated roundly and about a half as high as the shell, while the posterior halfbecomes narrower and extends somewhat linearly to the spout forming a narrow slit. The spire is com-pletely enveloped in the body whorl at about the posterior one-third of the shell length. The protoconch, which was born in the veliger stage, is retained on the spire. It is coiled sinistrally about 1-1/2 times and its type agrees with the "Shell-type 1" defined by Thompson (1961), which is corresponding to the"Types A & B" of Vestergaard and Thorson ( 1938). Visceral organs are blackishly seen through the shell, because it is only slightly translucent. A belt of gill-folds is seen on the liver-mass extending from the right middle to the left posterior fourth of the shell. The gill of the present species is of a pectinateshape, the primitive type common to Cylindrobulla (see Marcus & Marcus, 1956), Volvatalla (see Baba, 1966), Lobiger (see Hoffmann, 1940) and Ox_ynoe (see Eliot, 1906). The roof of the mantle cavity, to which the gill-folds are attached, corresponds to the tissue of the kidney. The radular teeth (Fig. 3, A; Pl. III, E) are uniserial and of a typical sacoglossan style as in Volvatella vigourouxi (see Baba, 1966), CylindrobullaJaponica (see Hamatani, 1969) and C. californica (see Hamatani, 1971). The radula consists of 8 teeth in the ascending and 19 teeth and a pre-radular tooth in the descending series in Sp. No. 16, while about 10 teeth in the ascending and 15 and a pre-radular tooth in the descending series in Sp. No. 1 7. Each tooth (Fig. 3, B and C) is blade-shaped, with a slightly hooked apex and with a series of about 25 (on an average, more than 30 at the max-imum and less than 20 at the minimum) somewhat slender denticles on each side of the blade which is broader in the present new species than in Volvatella vigourouxi. All these features rather resemble those in Cylindrobulla Japonica and C. californica. The tooth is almost transparent, though it is tinged very faintly yellowish. The pre-radular tooth is lod-shaped as in Cylindrobulla Japonica (see Hamatani, 1969) and C. californica (see Hamatani, 1971). In both Volvatella vigourouxi and V. ficula the pre-radular tooth has never been described. No penial stylet is found at the tip of the penis, by this point the present species is distinguished from V. vigourouxi. The rectum is short and slightly curved; the anus is situated slightly anterior to the middle and slightly displaced to the right from the median line on the dorsal surface of the visceral mass. The nervous system is almost 18 I. HAMATANI the same as in V. vigourouxi (see Baba, 1966). Other details of the internal morphology will be given in a future paper. Remarks: The shell of the present new species is very similar to that of Volvatella' cumingii (A. Adams, 1855), but in the latter the body whorl is much more dilated round-100f! Fig. 3. Volvatella ayakii sp. nov. A: Radular teeth ofSp. No. 16. B: An effective-tooth from Sp. No. 16, lateral side. C: A tooth of the ascending series from Sp. No. 17, ventral side. ly. V .. ficula Burn, 1966 from Fiji is also closely allied to the present new species in the form and size of the shell and living animal body. However, in V. ficula the spout is slenderer than in the present new species. Especially, the soft-body of the present new species shows no sign of a narrow orange band along the anterior mantle margin, A New Species ojVolvatellafrom Middle japan 19 which is very characteristic in V.ficula. In the general arrangement and morphology of radular teeth and respective tooth-blades, the present new species belongs to the group comprising V. vigourouxi, G_ylindrobulla japonica and C. californica, as ( 1) the rad-ula is of a uniserial sacoglossan type consisting of ascending and descending series, (2) each tooth has a series of slender denticles on each side, and (3) the tip of the tooth is hooked slightly. However, the present new species and the two species of Cylindro-bulla are separated very distinctly from V. vigourouxi, as the lod-like pre-radular tooth is existing at the end of the descending series in the former, but never defined in the latter. Summary 1. Volvatella ayakii sp. nov. described in this paper was collected from Caulerpa colonies growing in the lower intertidal zone at Cape Shionomisaki in the province of Kii, Mid-dle Japan, together wi~h Cylindrobullajaponica Hamatani, 1969 and some other opistho-branchs, forming the so-called "caulerpan microfauna". 2. Volvatella ayakii sp. nov. is defined mainly on the external appearance ofliving ani-mal body and the morphology of the shell and radular teeth, 3. Volvatella ayakii sp. nov. resembles very closely V. cumingii (A. Adams, 1855) from W. Columbia in the shell morphology, but the body whorl is more swollen in the latter than in the former. The present new species is also very similar to V .. ficula Burn, 1966 from Fiji in the appearance of living animal body, but the narrow orange band along the anterior mantle margin characteristic to the latter is quite missing in the former. 4. In features of radular teeth Volvatella ayakii sp. nov. belongs to the same group as one containing V. vigourouxi (Montrouzier, 1861), Cylindrobullajaponica Hamatani, 1969 and C. californica Hamatani, 1971, if the existence or absence of the lod-like pre-radular tooth can be of a minor significance. LITERATURE CITED Adams, A. 1855. Monograph of the family Bullidae. Thes. Conch., vol. 2, p. 599. Baba, K. 1966. Gross anatomy of the specimens of the shelled sacoglossan Volvatella ( =Arthessa) col-lected from Okinoerabu Island, Southern Kyushu, Japan (Nudibranchia). Publ. Seto Mar. Bioi. Lab., vol. 14, no. 3, pp. 197-205. Baba, K. 1967. Supplementary notes on the anatomy of Metaruncina setoensis (Baba, 1954), (N. G.) (Opisthobranchia-Cephalaspidea). Publ. Seto Mar. Bioi. Lab., vol. 15, no. 3, p. 191 (Postscript 2). Burn, R. 1966. The opisthobranchs of a caulerpan microfauna from Fiji. Proc. malac. Soc. Lond., vol. 37, pp. 48-54. Evans, T.J. 1950. A review of Pease's genus Volvatella, together with a preliminary report on a new sacoglossan genus. Proc. malac. Soc. Lond., vol. 28, pts. 2-3, pp. 102-106. Gonor, J.J. 1961. Observations on the biology of Lobiger serradifalci, a shelled sacoglossan opisthobranch from the Mediterranean. Vie et Milieu, tome 12, fasc. 3, pp. 381-403. Habe, T. 1946. On some species of the Cephalaspidea fromJapan. Venus (Jap.Journ. Malac.), vol. 14, nos. 5-8, p. 184. (in Japanese). 20 I. HAMATANI Habe, T. 1950. Illustrated catalogue of Japanese shells. no. 3, p. 24. Habe, T. 1965. New illustrated encyclopedia of the fauna of .Japan. II. Mollusca. Hokuryukan, p. 168. (inJapanese). Hamatani, I. 1969. A new species of the rare shelled sacoglossan genus Cylindrobulla from Middle Japan (Opisthobranchiata). Pub!. Seto Mar. Bioi. Lab., vol. 17, no. 3, pp. 171-174. Hamatani, I. 1971. A new species of Cylindrobulla, sacoglossan opisthobranch, from California; with a comparison with C.japonica Hamatani, 1969. Pub!. Seto Mar. Bioi. Lab., vol. 19, nos. 2-3, pp. 111-117. Kay, A. 1961. A new opisthobranch mollusc from Hawaii. Pac. Sci., vol. 15, no. I, pp. 112-113. Kay, A. 1965. Marine molluscs in the Cuming collection, British Museum (Natural Histrory) de-scribed by William Harper Pease. Bull. Brit. Mus. (Nat. Hist.) Zoo!., Suppl. I, pp. 12-13. Marcus, Ev. & Marcus, Er. 1956. On the tectibranch gastropod Cylindrobulla. Ann. Acad. Brasil. Cien., vol. 28, no. I, pp. 119-128. Nevill. G. & Nevill, H. 1869. On some new marine gastropoda from the southern province of Ceylon. Journ. Asiat. Soc. Bengal, vol. 38, pt. 2, p. 67. Pease, W.H. 1860. Descriptions of new species of Mollusca from the Sandwich Islands. Proc. Zoo!. Soc. Lond., pt. 28, pp. 20-21. Pease, W.H. 1868. Descriptions of marine Gastropodae, inhabiting Polynesia. Amer. Journ. Conch., vol. 4, no. 2, pp. 73-74. Pilsbry, H.A. 1894. Manual of Conchology, vol. 15. Opisthobranchiata, pp. 382-385. Souverbie, S. M. 1861. Descriptions d'especes nouvelles de l'archipel Caledonien. Journ. de Con-chyl., vol. 9, pp. 271-272. Sowerby, G. B. 1894. Marine shells of South Africa. Journ. Conch., vol. 7, p. 373. Thompson, T. E. 1961. The importance of the larval shell in the classification of the Sacoglossa and the Acoela (Gastropoda Opisthobranchia). Proc. Malac. Soc. Lond., vol. 34, pt. 5, pp. 233-238. Vestergaard, K. & Thorson, G. 1938. Uber den Laich und die Larven von Duvauceliaplebeja, Polycera quadrilineata, Eubranchus pallidus und Limapontia capitata (Gastropoda, Opisthobranchiata). Zoo!. Anz., Bd. 124, pp. 129-138. EXPLANATION OF PLATES II-III Plate II. Volvatella ayakii sp. nov. The holotype, preserved specimen. Fig. A: Dorsal side. Fig. B: Ventral side. Fig. C: Right side. Fig. D: Left side. Plate III. Volvatella ayakii sp. nov. Figs. A-D. Living specimens. A: Sp. No.7, dorsal side. B: Sp. No.9, ventral side. C: Sp. No. 9, showing white opaque secretion from the spout at mechanical stimulation. D: Sp. No.9, left side in a slightly contracted state. Fig. E. Radular teeth of Sp. No. 16, reproduced in Fig. 3 A. Publ. Seto Mar. Biol. Lab., XXI (1), 1972. PLATE II I. HAMATANI: A New Species ofVolvatellafrom Middle Japan Publ. Seto Mar. Biol. Lab., XXI (1), 1972. PLATE III I. HAMATA NI: A New Species ifVolvatella fi"om Middle j aj1an 

A NEW SPECIES OF VOLVATELLA PEASE, 1860, FOUND IN THE "CAULERPAN MICROFAUNA" IN THE PROVINCE OF KII, MIDDLE JAPAN (OPISTHOBRANCHIA : SACOGLOSSA)

Iwao Hamatani

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A NEW SPECIES OF VOLVATELLA PEASE, 1860, FOUND IN THE "CAULERPAN MICROFAUNA" IN THE PROVINCE OF KII, MIDDLE JAPAN (OPISTHOBRANCHIA : SACOGLOSSA)

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