Yoshikazu NAGATA’s research while affiliated with Osaka Kyoiku University and other places

The Japanese rose bitterling, Rhodeus ocellatus kurumeus, is an endangered cyprinid species. The main reason of drastic diminution of R. o. kurumeus has been suggested to be due to hybridization between this subspecies and R. o. ocellatus introduced from China. Both RFLP analysis of mitochondrial DNA and RAPD-PCR analysis of genomic DNA were performed to elucidate the genetic introgression of R. o. ocellatus into R. o. kurumeus. The two subspecies were distinguished in the D-loop region of mtDNA by six restriction endonucleases. Rhodeus o. kurumeus had eleven subspecies-specific RAPD markers and R. o. ocellatus had two. Except some R. o. kurumeus populations, most of the populations of R. ocellatus in Japan were hybrids, equipped with subspecies-specific RAPD markers for the two subspecies, respectively. The genetic constitution of these markers in hybrids, however, greatly differed among populations. The R. o. ocellatus mtDNA was predominantly observed in hybrid populations, except two populations with mtDNAs of the two subspecies. Judging from the genetic dominance of morphological and physiological characters of R. o. ocellatus against R. o. kurumeus, hybrids probably have the same ecological dominance as R. o. ocellatus against R. o. kurumeus. Therefore, it is considered that R. o. kurumeus not only has its genetic property spoiled by hybridization with R. o. ocellatus, but also is expelled by R. o. ocellatus and hybrids. The replacement of mtDNA and genomes of R. o. kurumeus with those of R. o. ocellatus in hybridization might be accelerated by the backcross between hybrids and R. o. ocellatus.

Four new bitterlings, Acheilognathus tabira erythropterus subsp. nov., Acheilognathus tabira tohokuensis subsp. nov., Acheilognathus tabira jordani subsp. nov. and Acheilognathus tabi- ra nakamurae subsp. nov., were described on the basis of more than 600 specimens from 26 locali- ties in Japan. Acheilognathus tabira erythropterus, A. t. tohokuensis and A. t. jordani, formerly all included in a single undescribed subspecies of Acheilognathus tabira, differ from other subspecies of A. tabira in having a red-edged anal fin in nuptial males. Acheilognathus t. erythropterus, dis- tributed on the Pacific Ocean side of eastern Honshu, is distinguished from A. t. tohokuensis and A. t. jordani by having shorter ellipsoidal eggs (ratio of major axis to minor axis: 1.4-2.2 vs. 2.0-3.3 in A. t. tohokuensis and A. t. jordani). Acheilognathus t. tohokuensis, distributed on the Japan Sea side of eastern Honshu, is distinguished from A. t. jordani in lacking a black blotch on the dorsal fin in juveniles. Acheilognathus t. jordani, distributed on the Japan Sea side of western Honshu, is distinguished from A. t. erythropterus and A. t. tohokuensis by having a black blotch on the dorsal fin in juveniles. Acheilognathus t. nakamurae, distributed in the Kyushu area, differs from all other subspecies by the following combination of characters: edge of the dorsal fin in males red, anal fin in nuptial males edged with white, a conspicuous black blotch on the dorsal fin in both juveniles and small adult females, and long ellipsoidal eggs (ratio of major axis to minor axis: 2.3-2.9). Acheilognathus t. tabira Jordan and Thompson, 1914 differs from the 4 new subspecies by having more branched dorsal fin rays (10 vs. 9), the edge of the dorsal fin in males (grayish vs. red) and shorter ellipsoidal eggs (ratio of major axis to minor axis: 1.4-1.7 vs. 1.4-3.3). A key is provided for all Japanese species and subspecies of Acheilognathus.

Comparison of meristic characters (pored lateral line scales, vertebrae, and fin rays), and PCR-RFLP analysis in the D-loop and ND1 regions of mitochondrial DNA were performed to estimate the genetic diversity in local populations of the Japanese rosy bitterling, Rhodeus ocellatus kurumeus. In terms of meristic characters, the Fukuoka population was the largest in both range and variance of the number of pored lateral line scales and vertebrae (abdominal and caudal), and Osaka was the second, whereas the Kagawa population showed the smallest range and variance in these characters. In PCR-RFLP analysis, 11 haplotypes (3 in Fukuoka, 2 in Okayama, 2 in Kagawa, and 4 in Osaka) were observed, and nucleotide sequence divergence (NSD) was approximately two times larger in ND1 (mean, 0.61%) than in D-loop (mean, 0.31%). In the neighbor-joining (NJ) tree, based upon the NSD value in ND1, haplotypes were arranged into four clades, which corresponded to the locality of each haplotype. The Fukuoka population was conspicuously apart from the other populations (mean, 0.90% in NSD), but the remaining three showed a similar genetic distance with each other (mean, 0.48%–0.52% in NSD). In haplotype diversity of mtDNA, half the stations in Osaka and all in Kagawa were monomorphic. Especially, two haplotypes endemic to Kagawa were randomly distributed, irrespective of drainages. Rhodeus o. kurumeus in Fukuoka inhabits small rivers and creeks (open water systems), while that in Kagawa and Osaka lives in small ponds (closed water systems). Taking the information of morphology, mtDNA, and habitat into consideration, the low genetic diversity in Kagawa and Osaka populations of R. o. kurumeus is thought to be mainly the result of the isolation of their habitat.

Japanese bitterlings in the Rhodeinae have been classified into five genera (Okada, 1960), four genera (Aoyagi, 1957;Nakamura, 1963) or a single genus (Miyadi et al., 1976) on the basis of morphological characters of adult fishes.Recently, Miyadi et al. (1976) and Arai (1978) made phylogenetic discussions of Japanese bitterlings on the basis of morphological and karyotypic results which had been obtained by many authors.Arai (1978) emphasized the validity of minute scaly tubercles on the surface of the yolksac of rhodeine fish in prolarval stages.In the paper, however, he did not mention about morphology of the tubercles. The present authors microscopically confirmed that there are tubercles in all six species, which makes possible classification into two groups and/or four types by morphology of the tubercles.Although prolarvae of both Acheilognathus lancolata and A.limbata have been regarded to have a nearly smooth body surface, our observations showed that they have many tubercles (the major and the minor axises are about 20μm and 15μm, and the height 20-30μm).The former species tends to differ from the latter in having sharper and higher tubercles, but the tendency is not clearcut. Other species of Acheilognathus have very large ellipsoid tubercles of which the posterior part forms a ridge. A.cynaostigma and three subspecies (see Nakamura, 1963) of A.tabira have tubercles of an equal size (the lengths of both the major and the minor axises are 30-45um and 20-35 um, and the height is about 20 um).A.rhombea has more round tubercles, and tubercles of unequal sizes coexist in A.lognipinnis. Classification of rhodeine species by the morphology of tubercles well supports the phyletic relationships among them suggested by Miyadi et al. (1976).

The present paper gives the detailed illustration of morphological changes of the bitterlings, Rhodeus ocellatus ocellatus during development. This subspecies shows a peculiar breeding habit that female deposites eggs into gill-cavities of bivalve. The morphological change is discussed in relation to the habit. 二枚貝内に産卵されたタナゴ類の卵は鰓腔内で授精し,前仔魚期の末期まで発生する。今回はシャーレ内で人工媒精したタイリクバラタナゴの卵の発生を水温22±1℃で観察し,前仔魚期までの発生段階表を作製した。そして,その際に見られた形態的変化を特異なタナゴ類の産卵習性との関連から若干の考察を加えてみた。

Some characteristics of the fins in each subspecies of bitterlings (Rhodeus ocellatus ocellatus and R. ocellatus smithi) and in the hybrids between them were examined. The former was imported from China in 1942, and latter was supposed to be native in Japan. Whitish coloring appears in the ventral fins of the former, but not in that of the latter. In the hybrid this coloring was frequently recognized in male but seldom in female. The ray numbers in the dorsal and anal fins were found to be distributed within a same range regardless of the difference of the subspecies, although they have long been thought to be different for each subspecies. Distribution pattern in the ray number of the hybrid showed just between. Discussion was made on the problem of the changing distribution of these fishes which the present results seems to give a basic clue to.

小・中学校の理科の教科書は，いくつかの単元で溜池に生活している生物がとりあげられている。溜池は児童・生徒が接する身近な自然の中でも最も一般的な対象である。しかし、溜池を多数の生物が生活するまとまりのあるかたちで取り扱われてはいない。ここでは，このような取り扱いの可能性を検討する目的で，生物どうしの関係について，種間及び種内関係の具体例と学習上の問題点について述べた。 Pond is one of the most familiar objects among natural environments to all children.Organisms living in ponds are selectively and frequently used as teaching material for each subject of studies in the series of the science textbooks.Ponds is the place where many organisms are able to live and to continue alteration of generations with inter- and intraspecies relationships.In the level of schood education,however,there has been scarcely payed an attention to seek the pond in this point of view.In this paper,typical cases ofinter- and intraspecies relations are taken up to see the possible way how to give pupils and students the correct understanding on the ecosystem of the pond.

タナゴ類とそれらの産卵床となる二枚貝の種構成が異なる九州北西部の3小河川で,同所的に生息するタナゴ類の産卵生態,特に二枚貝の利用の仕方に関して比較した。調査した河川のうち2小河川に共通して生息するセボシタビラはカタハガイにのみ産卵した。また,バラタナゴのドブガイに対する強い正の選択性が認められた。同一貝内には複数種のタナゴ類の卵仔魚が確認され,貝内卵仔魚を発生段階別に区分することで,一度に産み込む卵数を推定した。同所的に複数種のタナゴ類が生息し,それらは特定の貝種に同時期に産卵している傾向があるものの,貝への選択性,一度に産卵する卵数,産卵時期のずれが認められ,このことが複数種のタナゴ類が同所的に生息することを可能にする要因であると考えた。 Females of bitterling spawn in gill chamber of freshwater mussles with their elongated ovipositor. The bitterlings and freshwater mussles were collected at three small creeks in Northwest Kyushu. All collection fish were fixed with 10 % formalin liquid, and freshwater mussels examined presence of eggs and larvae of bitterling in gills chamber. The bitterlings was dominant species in all creeks. Tanakia lanceolata and T. limbata were collected at three small creeks, but Acheilognathus tabira subsp. S did not collect in Gochoda Creek, and Rhodeus ocellatus and A. rhombeus did not collect in Sinkawa Creek. The mussels that bitterling spawned in each creek concentrated on a specified species, and A. tabira subsp. S spawn only Pseudodon omiensis in Sinkawa Creek and Horikawa Creek. The eggs and larvae of plural species of bitterlings and with different growth stages were found in a mussel. R. ocellatus was shown high selectivity toward Anodonta woodiana for deposition. Specific difference in selectivity of mussels and deposition time among the bitterlings may make sympatric existence of bitterlings in a small creek.

日本の固有種イタセンパラ（コイ科タナゴ亜科）は, その狭い分布域と絶滅の危機から, 天然記念物と絶滅危惧IA類に位置づけられている。本種を河川の中で保護・増殖するためには, 本種と本種が卵を産みつける二枚貝が繁殖する環境の特徴を明らかにする必要がある。そこで今回は, 淀川に生息するイタセンパラと生息環境に関するこれまでの研究をレビューした。また, 文化庁と環境庁の許可を得て, 本種の産卵, 貝内の卵・仔魚のはじめての写真を掲載した。本種は秋に産卵し, 仔魚はほぼ半年の間貝内で越冬した後に泳出する。淀川のイタセンパラの本来の繁殖場所は, 下流域に発達した河川内氾濫原に存在する池（通称ワンド）の中でも, 本流から隔離された小型の浅い池であることが示唆された。それらの池の水位は, 伏流水を通じて本流の水位と同調して変動する。そのため, 池には本流水が冠水し直接流入する時期（増水時）と氾濫原内に低水位で孤立する時期（減水時）が季節的に繰り返される。イタセンパラの繁殖に関する生態学的研究は, この観点にたって行なうことが重要である。 The Japanese endemic bitterling, Acheilognathus longipinnis Regan was designated as both a natural monument and a critically endangered species for the reason of its restricted distribution and a sense of crisis of extinction in Japan. It is evident that the investigations on habitats of A. longipinnis and mussels were necessary for the purpose of preservation of the bitterling. In this paper, we summarized the studies that were carried out at the Yodo River, Osaka Prefecture, Japan. The first photographs of egg deposition into a mussel and eggs／larvae in the mussel were also published by permission both of the Agency for Cultural Affirs and the Environmental Agency. A. longipinnis deposittheir eggs in autumn, and larvae swim out from the mussel in May and early June, after passing the winter in the mussel during a half year. It was suggested that A. longipinnis mainly reproduced in small and shallow pools in the floodplain formed in the lower reach of the Yodo River. The floodplain pools where isolated from the main channel were filled occasionally by river flooding mainly in early summer and autumn. On the other hand, a small water body was remained in the pools through groundwater seepage in the lower water state of the river in winter. We must reseach the habitats both of A. longipinnis and mussels from the viewpoint of seasonal fluctuations in water level of the floodplain pools.

兵庫県姫路市西部を流れる大津茂川の淡水魚類相と調査地点ごとの魚類の生息状況を明らかにした。今回の調査を通して，8科26種－亜種，総数7400個体の標本を得た。そのうち大津茂川において初記録となったのは，カワバタモロコAphyocypris　rasborella，ニゴイHemibarbus　labeobarbus，ウキゴリChaenogobius　urotaeniaであった。大津茂川において特徴的であったのは，近隣の他河川にはみられる渓流棲の淡水魚，および通し回遊魚を欠くことと，近縁種であるカワムツ2型Zacco　temmincki　two　typesとオイカワZ．platypusが同所的に生息していることであった。 Fish fauna of the Otsumo River,Hyogo Prefecture,was surveyed from in 1992.Throughout the present study,7400 individuals were caught and recognized 8 families,26 species and subspecies.Among them ,Aphyocypris rasborella,Hemibarbus labeo barbus and Chaenogobius urotanea were first recording fish from Otsumo River.Fish fauna of Otsumo River were lack of upper-middle dwelling fishes.Three members of genus Zacco were also distributed in Otsumo River.