The malacologicalsocietymalacological society of Japan A Chromosome Survey in Sixteen Species of Nudibranchs* Akihiko INABA and Yasuko SAiKi (Mukaishima Marine Biological Station) RR rw ff 16 (aj cr) ll:f ts 1?lg bl 3E -fii' ･ ts E[]x tt la on Er, OA-i45d"?Empe}fiMCfitKrfi],4tzaiMVI-･wt)VD (mpEff Plates II-III; tc 1-2) Abstract The chromosome numbers in 16 species belonging to 7 families of nudibranchs are here. The chromosomes so far reported reported by preceding investigators are shown in Table 1, and those by the present authors are in listed Table 2. These numbers are uniformly 13 in haploid without exception, and in spite of the remarkable difference in their external rnorphology, these nudibranchs have the similar karyotype, The sperma- togonial chromosomes are regarded as of metacentric nature, The sexual difference of chromosomes is not observed, In Japanese nudibranchs, the chromosomes of 13 species were observed by INABA and HiRoTA (1958)and INABA b, 1961a). (1959a, Recently, MANcJNo and SoRDi (1964a, b, 1965) reported the chromosomes of 16 Mediterranean nudibranchs, and BuRcH and NATARAJAN (1967) reported the chromosorne numbers of 2 nudibranchs from Eniwetok Atoll. These results are listedin Table 1, with some other previous reports. In this paper, the chromosomes of 16 nudibranchs in opisthobranchiate gastropods are described, and these results are discussed with other investigations. Before going further,the authors express their cordial thanks to Dr, R. HiRoTA, Mukaishima Marine Biological Station, and Mr. H. MuKAi, graduate student of Hiroshima University, for their aids in collecting the materials. Materials and Methods In this study, 16 species belonging to 7 families of Nudibranchs were used for the materials, as follows: CLASS GASTROPODA Subclass Euthyneura Order Nudibranchia Suborder Doridoidea Superfamily Cryptebranchia 's-6I ' * '" " Contributions from the Mukaishima Marine Biological station,No, 8 NII-Electronic LibraryMbrtiry Service The malacologicalsocietymalacological society ofJapanof Japan INABA and SAIKI: Chromosome of 16 nudibranchs 9 Family Dorididae Aldisa sanguinea Discodoris concimza Hoinoiodoris 1'aPonica Superfamily Phanerobranchia Family Okeniidae Coniodoris stt.oashimae Superfamily Porostomata Family Dendrodorididae Dendrodoris rubra itigrontacztlata Suborder Dendronotoidea Family Dotonidae Doto betla Suborder Eolidoidea Superfamily Acleioprocta Family Eubranchidae Et{brancltusntisaleieitsis Eubranchzts inabai Eubranchopsis vizg2'nalis Family Cuthonidae Ctttlzona futairo Catriona PttPillae Catriona Puny>ureoanitlata Catriona signijletra Superfamily CIeioprocta Family Facelinidae Ht'rviella a.ainis Rizxolia lineata Fumily Aeolidiidae Lime'nandra fztsij'ormis Eolidoidean nudibranchs live mostly on algae, mainly on Sargassum, They were ' collected by washing off Sargassum weeds in the vesseL others The inhabitingin the tide or on the rocky shore were collected pool at the low tide. Those materials were all collected from the vicinity of Mu kaishima Marine Biological Station in different seasons. The materials were fixed and stained aceto-orcein by squash method. Ob- servation was made under the Olympus and microscopes Nikon using a 100 × oil im- mersion objective and 15-20 × oculars. The magnification of all the figures and the photographs was 3300 times. Results of Observation ].) Aldisa sanguinea (Co6pER, 1862) A common medium size. Body-length doris in is about 25mm. The back is thickly covered with tiny rounded granules. General body-colour is vivid orange-red sprinkled everywhere with minute and indistinct black dots. It has 2 (or 1 or some- times 4) black spots on the back in the middle line. This species was obtained from rock reefs at an the islet near Mukaishima in July, 1966, The early metaphase of the lst spermatocyte wus examined. There were 13 chromosomes on the haploid nucleus plate. Some of them were ring-shaped (Pl, III, Fig. 1). NII-Electronic Library Service The malacologicalsocietymalacological society of Japan 10 VENUS: 26 Cl) 1967 2) Discodoris concin"a (ALDER et HANcocK, 1864) covered up to The body is very soft and the back is A large specie$ 80mm. of back is ashy brown and everywhere with granules. General ground-colour the The underside of the body is overlaid with dark brown mottle of varying intensity. specimen was collected also ashy brown irregularly spotted with dark brown. This 1966. In the lst diakinesis, from the rock reefs at an islet near Mukaishima in July, chromosomes III, Fig. 2). there were 13 chromosomes containing some ring-shaped (Pl. 3) llomot'odoris J'oponica BERGH, 1881 This is a very common doris. Body length of this species is about 50-60mm. General The back is covered with globular tubercles of varying sizes, ground-colour and maculated with black here and of the back is bluish yellow to bluish green is vicinity of the Station there. This species was obtained from the rock reefs in the were ob- in April, 1966. In each of the lst spermatocyte nucleus, 13 chromosomes served (PL IIL Fig. 3). 4) Coniodoris sztgashimae BABA, 1960 in size. Body length is about 2e mm General body- This species is rather small here and there with dark colour. colour is pale yellowish brown shaded or maculated the back and sides. The speci- It is covered with clusters of opaque white dots on ascidians on rocks or algae near the mens were collected on some compound the metaphase show 13 chromo- Station in April and June, 1966. The lst diakinesis and size being ring-shaped (Pl.II, somes as haploid, one or two of comparatively large Figs. 1, 2). 1913) 5) Dendrodoris (Dendrodoris) rubra, var. nigromaculata (EL[oT, General body-colour is orange- This is also a common large doris, up to 70mm black blotches irregularly. The yellow, the back is smooth and covered with bold reefs at an near Mukaishima in June, specimens were obtained from the rock islet The haploid complex 1965. The early metaphase of the spermatocyte was examined. them were ring-shaped (Pl.II, of this species consisted of 13 bivalents. Some ef Fig. 3). 6) Doto (Doto) bella BABA, 1938 is small in size and lives on Sa?lgtissum Body length is 5-10mm. This species and Genera! body-colour is golden yellow The branchial papillae are pinecone-shaped. near the Station with This specimen was collected in May, 1960 spotted dark green. 26 chromosomes in the spermatogonial metaphase, from Sargasszt]n weeds. There were Iarge The others were not strongly bent but several pairs of them were V-shaped. metaphase, 13 chromo- were all metacentric (Pl. II, Fig. 4). In the lst spermatocyte II, Fig. 5). somes were observed. Some of them were ring-shaped (Pl. 1960 7) Eubranchus misakiensis BABA, is about 5mm. The branchial papillae This is a very small eolis. Body-length a subapical ring and bluish green liver-vein. General are long fusiform, with yellow on white, with chocolate-brown spots scattered everywhere ground-colour is yellow NII-Electronic Library Service The malacologicalsocietymalacological society of Japan INA}tA and SATK[: Chromosome of 16 nudibranchs 11. of the the bodv. This species was collected from Sailgassum weeds in the vicinity diakinesis Station in June, 1965. There were 13 bivalents in the lst spermatocyte (Pl. IL Fig. 6). 8) Ettbranchus inabai BABA, 1964' a very small eolis and first discovered near the Mukaishima This species is also is stoutish, Marine Biological Station CBAB,N, 1964). Body-length is about6mm. Body opaque white markings The back and sides are deep reddish brown and a series of from weeds Iies on the back in median line. This species was collected Sargtissz{m In the lst spermatocyte dia- in the shallow water near the Station in October, 1965. III, Fig. 4). kinesis, there were 13 bivalents and some of them were ring-shaped (Pl. 9) EttbranchoPsis i)irg･inctlis BAB.A, 1949 is about 1?mm. The branchialpapillae, This species is a small eolis. Body-length body-colour is olive- faintly vermilion-tinted, are long and fall off easily. General of deep blue on the back, sides, yellow and beautifully ernamented with round spots from SargassuTn weeds in the vicinity papillae and tentacles. This species was obtained bivalents in the diakinesis nucleus of the Station in October, 1965. There were 13 of the lst spermatocyte CPI. II, Fig. 7). 10) Cztthona fzttairo B,xB,x, 1963 mm. General body-colour is orange-yellow and the branchial Body-length is 20--30 This species with a dark vein and a white tip. papillaeare orange-yellow, green near the Station in May, 1966. was eollected on Sargassttm weeds in shallow water 13 dot-shaped bivalents II, Fig. 8). The lst spermatocyte metaphase contained CPI. BABA, 1961 11) Catriona PuPiltae 3-5 mm total length. Cephalic tentacles and rhino- Animal is always small and in below the tips and liver-veinsare dark phores marked with an opaque white band in the shallow water around brown. Thi$ species was collected on Sai:gassum weeds lst spermatocyte, 13 bivalents the Station in March, 1960. In the diakinesis of the one or chromosomes showed the ring-shape (Pl. II, were observed. Frequently two Fig, 9). 12) Catric)na PztvPetrc.oav･tttlata BABA, 1961 are long. The This is a smaH eolis und 6-10mm in length. Branchial papillae a band below the tip of each. coloration of branchial papillae is distinctive with purple tentacle and rhinophores. The specirnens Two bands of purple occur also on cephalic water around the Stationin August, were obtained on Sargassttm weeds in the shallow II,Fig.10). 1965. In the lst diakinesis, there were 13 bivalentswhich varied in size (Pl. 196] 13) Catriona sig'nifera BABA, of animal is 5-8mm. This species is This is a very small eolis. Total length with an ovoid dark brownish or black-green marking behind very distinctive green Liver branches within the branchial papillae are dark the rhinopheres on the back. on Sargassttmweeds in the shallow water around green, The specimens were obtained in October and November, 1965.