Japanese Journal of Ichthyology 魚 類 学 雑 誌 Vol.29,No.31982 29巻3号1982年 Geographic Distributions and Karyotypes localities,and the existence of polyploidy has of Cobitis takatsuensis and been demonstrated(Kobayasi,1976;Takahasi Niwaella delicata(Cobitididae) and Oka,1976;Ueno and Ojima,1976;Ueno et al.,1980).The remaining species have been either unstudied(C.takatsuensis)or studied Yoshiteru Kimizuka,Hiromu Kobayasi and Nobuhiko Mizuno with materials from limited localities(N.delicata: Hitotsumachi et al.,1969;Takahasi and Oka, (Received May 11,1982) 1976;M.angullicaudatus:Hitotsumachi and Sasaki,1967).In this study we examined The cobitidid subfamily Cobitidinae are karyotypes of C.takatsuensis and N.delicata represented by five species in Japan,i.e.,Cobitis from many localities to determine whether or taenia Linnaeus,C.biwae Jordan et Snyder,C. not there is chromosomal polymorphism in takatsuensis Mizuno,Niwaella delicata(Niwa) these species.For the sake of convenience in and Misgurnus anguillicaudatus(Cantor).For developing arguments,C.taenia is not divided the first two species,karyological studies have into subspecies in this paper. been made on extensive materials from various Fig.1.Geographic distribution of Cobitis takatsuensis,•œ,collecting localities in the present study;••, published records,specimens examined by us;(+),unpublished records(Takada;personal communica- tion),specimens examined by us;•›,published records,specimens not examined by us;*,unpublished records(Ohtake;personal communication),specimens not examined by us.Broken lines indicate principal watersheds.A,Go-no River system;B,Takatsu R.;C,Abu R.;D.Kakebuchi R.;E,Ohta R.;F,Nishiki R.;G,Saba R.;H,Shigenobu R.;I,Hiji R.;J,Iwamatsu R.;K,Shimanto R.;L, Mina R.;M,Iyoki R.;N,Onga R.1,Shiroidani River;2,Shigeyamadani R.;3,Ninotani R.;4,Daibo R.;5,Suginokawachi R.;6,Shigenobu R.(upper);7,Shigenobu R.(lower);8,Hoba R.;9, Katsuradani R.;10,Kuro-kawa R. ―305― 魚類学雑誌 Japan.J.Ichthyol,29(3),1982 systems in the Chugoku,Shikoku and Kyushu Materials and methods districts(Fig.1). Field surveys for the distribution of Cobitis Incorporating the present collection and takatsuensis were conducted from September published records(Mizuno,1970,1972,1978; 1977 to April 1981,in a total of 74 localities in Fujioka,1973;Gotomyo and Miyamoto,1975; 30 river systems in the Chugoku district of Fujioka and Katayama,1977;Naito,1977, Honshu,the western half of Shikoku and north- 1982;Ito and Mizuno,1978;Nagamine,1978; ern Kyushu.Collection of fishes was made Ehime Prefecture,1979;Nagai,1980),the mostly by scoop nets.Twenty-nine individuals geographic range of Cobitis takatsuensis en- from 11 stations in eight river systems were compasses the San-in province of Chugoku examined karyologically. district of Honshu,westward from the Go-no Niwaella delicata was collected from 10 River,the San-yo province of the same dis- stations in eight river systems in the Chubu trict,east from the Ohta River west to the Saba and Kinki districts of Honshu from April 1977 River,the western half of Shikoku east from the to May 1979,by scoop nets.Twenty individuals Shigenobu River on the Seto Inland Sea slope from all stations were used for chromosomal and the Shimanto and Mina Rivers on the examination. Pacific slope,and the Onga River drainage in For karyotype analysis each fish was given an northern Kyushu(Fig.1).The specimens from intraperitoneal injection of colchicine(0.5 or the Shimanto River system first reported as C. 1.0 %)or colcemid(0.5 %),two to three hours biwae by Kochi Prefecture(1979)and Ochiai prior to sacrifice.Gill and kidney tissues et al.(1980)and later identified as C.takatsuensis were removed,minced,treated with hypotonic or a closely related species by Ochiai(1981)and solution,and fixed in Carnoy's solution.Slide Ochiai et al.(1982)(KA(Department of Cultural preparation was made by means of the routine Fisheries,Faculty of Agriculture,Kochi Uni- flame-drying and Giemsa-staining methods.The versity)1383•`1442,62 specimens)were re- classification of chromosomes followed Levan et examined by us and tentatively identified as C. al.(1964).Specimens used in the present study takatsuensis. will be registered in the Yokosuka City Museum, Habitat.Cobitis takatsuensis occurs almost Kanagawa Prefecture,Japan. exclusively in the upper reaches of the rivers. In larger streams it is observed in deep,slow- Results flowing pools,particularly along their sides,and Cobitis takatsuensis stony bottoms of comparatively slow-flowing Geographic distribution.Cobitis takatsuensis portions,frequenting rapid-running portions was collected from 14 stations in eight river only when population density is high.In Fig.2.Karyotype of Cobitis takatsuensis from the Daibo River of the Kakebuchi system.Scale in- dicates 5 pm. ―306― Kimizuka,Kobayasi and Mizuno:Cobitidid Karyotypes small branches it inhabits stony bottoms of swift-as well as slow-flowing portions. In upper reaches C.takatsuensis occurs in small populations which are isolated from each other.Exceptionally,the fish occurs in the middle reaches of the Takatsu River where riverbed water springs out(Mizuno,1972), together with C.biwae and in the Shigenobu River(st.7 in Fig.1,present observation),to- gether with C.biwae and C.taenia.In these cases,C.takatsuensis inhabits stony bottoms, whereas C.biwae and C.taenia are seen on sand bottoms.Except for these two places,con- geners scarcely occur together with C.taka- tsuensis. Karyotype.Chromosome analysis was suc- cessful in 12 individuals from seven stations in four river systems(Table 1).The diploid chromosome number is 48.Karyotype from 36 well-spread metaphase plates from 10 in- dividuals comprises 12 metacentric,18 sub- Fig.3.Geographic distribution of Niwaella de- meta-subterocentric and 18 acrocentric chro- licata.•œ,collecting localities in the present mosomes(Fig.2).The only two metaphase study;••,published records,specimens examined by us;(+),unpublished records, plates available for karyotype analysis from two female specimens from the Shigenobu River. specimens examined by us;•›,published records(Niwa,1976;Okada and Kubota, (st.7 in Fig.1)show a reduced number of sub- 1956).Broken line indicates principal metacentrics by two and an increased number watersheds.A,Shiraiwa River system;B, of acrocentrics by two(Table 1).Polyploidy Jintsu R.;C,Kuzuryu R.;D,Sho-no R.; and sexual dimorphism were not observed. E,Yura R.;F,Sho-nai R.;G,Kiso R.;H, Niwaella delicata Ibi R.;I,Isuzu R.;J,Yodo R.1,Kado Geographic distribution.Specimens were col- River;2,Tochizu R.;3,Kumano R.;4, lected from 10 stations,five on the Pacific slope Hino R.;5,Sho-no R.;6,Ogawa R.;7, and the other five on the Japan Sea slope(Fig.3.) Makita R.;8,Nabari R.;9,Shigaraki R. The collecting localities in the present study and upper);10,Shigaraki R.(lower). ( Table 1.Karyotype of Cabitis takatsuensis from various localities.m,metacentric;sm,submeta- centric;st,subterocentric;a,acrocentric.For the localities,see Fig.1. ―307― 魚類学雑誌 Japan.J.Ichthyol.29(3),1982 the localities of the author's unpublished col- tions between Japan Sea slope and Pacific slope lection records fall within the geographic range populations of Niwaella delicata in the size of the species given by Niwa(1976)in terms of of the body,markings on the caudal fin and drainage systems(Fig.3). color pattern of the body.He futher suggested Habitat.Longitudinal distribution of the possibility of chromosomal dimorphism Niwaella delicata is generally restricted to the associated with such morphological variations upper reaches of the rivers.It inhabits stony Niwa,1976).However,the karyotypes from bottoms in rapid currents.No other cobiti- four populations from the Japan Sea slope dine fishes occur syntopically. (present study)and six populations from the Karyotype.Chromosome analysis was suc- Pacific slope(Hitotsumachi et al.,1969;Taka- cessful for 13 individuals of both sexes from hasi and Oka,1976;present study)show no four stations on the Japan Sea slope(st.1,2•`5 noticeable variations. in Fig.3)and four stations on the Pacific slope Combining the distributional patterns and (st.6•`8,10).The diploid chromosome karyological feature,it is of interest that Cobitis number is 50.The karyotype is composed of takatsuensis and Niwaella delicata,which have 6 metacentric,14 submeta-subterocentric and discontinuous distribution in mountain-streams, 30 acrocentric chromosomes.Polyploidy and show no chromosomal differentiation among sexual dimorphism were not observed. populations of each species,and C.biwae and C.taenia,which have continuous and wide- Discussion spread distributions in lowland waters,show Cobitis takatsuensis usually lives in stony- diverse chromosomal differentiation. bottomed mountain streams,concealing itself among bottom stones.It is therefore difficult Acknowledgments to detect the fish,and the geographic range We are grateful to Drs.Seibin Arasaki and given in this study may probably be extended in Takashi Hibiya of Nihon University,for their the future,particularly toward southern Shikoku kind guidance throughout the present study. and northern Kyushu. We also express profound gratitude to Dr. The collection data of the present study for Yasuhiko Taki,Tokyo University of Fisheries, C.takatsuensis combined with Mizuno's(1972) and Dr.Teruya Uyeno,National Science collection data for C.biwae and C.taenia Museum,Tokyo,for their valuable advice and indicate that there is habitat segregation be- the critical reading of the manuscript.We tween C.takatsuensis and the other two species are grateful to Dr.Akira Ochiai of Kochi Uni- of Cobitis,the former dwelling on stony bottoms versity,for allowing us to examine the specimens and the latter two on sandy bottoms.The from the Shimanto River.Our special thanks longitudinal distribution of Niwaella delicata is also go to Messrs.Hiroyuki Aizawa,Keisuke basically similar to that of Cobitis takatsuensis, Takada,Akihisa Iwata,Kazumi Hosoya,Junichi mainly occuring in the upper reaches of the Naito,Motoichiro Nagai and Tetsuo Ohtake,for rivers.