Cytologia 38: 731-736, 1973

A Comparative Study of the Karyotype in the (Pisces, )

P. Raicu, Elena Taisescu and P. Banarescu

Department of Genetics, University of Bucharest and Department of and Evolution, Institute of Biology, Bucharest, Rumania

Received July 27, 1972

The subfamily (Pisces, Cyprinidae) includes 84 represented by 20 genera, a single one of which, Gobio has a Palaearctic range, occurring through the northern part of East Asia, Siberia, Europe and parts of West and Central Asia, while the remaining genera are restricted to East Asia (Banarescu and Nal bant 1972). The genus Gobio is represented in Europe, Anatolia and the Caucas by seven species, one of which, G. gobio, has a wide Palearctic distribution, a second one, G. albipinnatus, is distributed from the Danube to Volga river, while the five other species are restricted to a single or to a few drainages. Four species live in Rumania: G. gobio is rather ubiquitous, occurring in many biotopes though it is absent from the Danube R. itself; and G. uranoscopus, G. albipinnatus and G. kessleri, occur in a peculiar biotype, although they are quite frequent in some localities specially for the two last-named ones. Considering that only a few cytogenetical studies were carried on fishes, and that there are many unsolved problems in taxonomy of the family Cyprinidae and of the Gobioninae subfamily, we considered necessary to make a comparative study on the karyotype of the Gobio species occurring in Romania. This became possible by elaborating a laboratory method for demonstrating the chromosomes in fishes (Raicu and Taisescu 1972) which gave very good results.

Materials and methods

The following species belonging to the genus Gobio (subfamily Gobioninae, family Cyprinidae, Pisces) provided material for this study: G. gobio (subgenus Gobio) from the Baneasa lake, Bucharest; G. kessleri banaticus (subgenus ) from Timis river, Uliuc village; G. albipinnatus vladykovi (subgenus Romanogobio) from Timid river, Uliuc village; and G. urano scopus (subgenus Rheogobio) from Arges river, Buda village. The method of Raicu and Taisescu (1971) was used for this study. It con sisted of the following procedure: the kidney, spleen, gills and liver, were removed from 2 hours after colchicine injection and after minced, they were intro duced in a hypotonic solution of natrium citrate for 45 minutes at room temperature on an electromagnetic agitator. Then, the specimen were centrifuged for 15 minutes 732 P. Raicu, Elena Taisescu, and P. Banarescu Cytologia 38

at 1500 r.p.m. and the sediment was submitted to 3 to 5 succesive fixations with absolute ethanol-glacial acetic acid (3:1). Between two fixations the specimens were kept for half an-hour in the refrigerator. Smears were made on very clean and frozen slides from the last cellular suspension, after the flame drying method. The smears were coloured in 15% Giemsa solution for 20 minutes. Through the above method were obtained well-hypotonized cells, with well-coloured and wells-cattered chromosomes. Microphotos and 3 to 5 karyotypes were prepared for each species, except in which were made 10 karyotypes and the idiogram. It was aimed to determine the following parameters: the absolute chromosomes length, the arms length and the ratio of the arms, as well as the relative length of the chromosomes, considering that the total length of the chro mosomal complement is equal with 1000.

Results and discussion

A comparative study of the karyotype in four species of the genus Gobio showed firstly the absence of the heterosomes and secondly a distinct karyotype for each species. Gobio gobio had 2n=50 chromosomes. There were 11 metacentric, 12 sub metacentric, one submetacentric and one acrocentric pairs. The identification of the autosomes was made on the basis of measurements and by establishing of the arms ratio (long/short), according to the nomenclature by Levan, Fredga and Sandberg (1964). Thus, the chromosomes in which the arms ratio is included between 1.0 and 1.7 are considered as metacentric (m), those with the arms ratio between 1.7 and 3.0 as submetacentrics (sm), those with the arms ratio between 3.0 and 7.0 as subtelocentrics (st) and those with an arms ratio exceeding 7.0 or in which an arm is missing, as acrocentrics (a).

The analysis of the absolute length of the arms in the 25 pairs chromosomes

showed that it varied within rather wide limits (2.07 to 5.07ƒÊ) and the relative length, between 26.7% and 65.4%. The total number of the chromosomal arms

(NF) was 98 (Table 1). Gobio kessleri banaticus had 2n=50 and NF=98; among the autosomes there were 12 metacentric, 10 submetacentric, 2 subtelocentric and 1 acrocentric pairs. Gobio albipinnatus vladykovi had also 2n=50 and NF=98. The chromosomal complement consisted of 14 metacentric, 10 submetacentric and 1 acrocentric pairs. Gobio uranoscopus was found to be different from the three others both in the chromosome number (2n=52) and in the number of the chromosomes arms (NF=100). After a comparative analysis of the chromosome complement in the four species of the genus Gobio occurring in Rumania, we can remark firstly that the size of the chromosomes varies in very close limits, suggesting their common origin. Secondly, each species has a distinct karyotype, thus confirming also cytotaxonomi cally their specific independence. 1973 A Comparative Study of the Karyotype in the Genus Gobio (Pisces, Cyprinidae) 733

It was shown that the three species Gobio gobio, G. kessleri banaticus, G. albi pinnatus vladykovi, had the same number of chromosomes (2n=50) and of chromo some arms (NF=98). They differed by the distribution of the chromosomes in metacentrics, submetacentrics and subtelocentrics. All the three species have constantly only one pair of acrocentrics. This suggests that the evolution of the karyotype has occurred in the species as a result of duplication of some chromosomal segments or by translocation (Ohno 1970).

Table 1. The measurement of the chromosomes in Gobio gobio

The fourth species G. uranoscopus is much better individualized by the chro mosome number (2n=52) as well as by the chromosome arms (NF=100). It is otherwise the only species having 2 acrocentric pairs among them. This allows the establishment of the subgenus Rheogobio which includes 3 species, among which G. uranoscopus, was cytotaxonomicaly justified (Banarescu 1961). Thus it is possible to note that the genus Gobio includes 14 species covering 3 subgenera which occur in North and East Asia and in Europe and it is cytogenetically poly 734 P. Raicu, Elena Taisescu, and P. Banarescu Cytologia 38

Figs. 1-2. 1, karyotype of Gobio gobio. 2, karyotype of Gobio kessleri ssp. banaticus. 1973 A Comparative Study of the Karyotype in the Genus Gobio (Pisces , Cyprinidae) 735

Figs. 3-4. 3, karyotype of Gobio albipinnatus ssp. vladykovi. 4, karyotype of Gobio uranoscopus.

Figs. 5. A metaphase plate (a) and idiogram of Gobio gobio (b). 736 P. Raicu, Elena Taisescu, and P. Banarescu Cytologia 38

morpic, the Rumanian species being well individualized with respect of the chro mosome complement in accordance to the taxonomical classification. On the other hand we must underline that the Gobio species belong quite pro bably to the diploid group of the family Cyprinidae in which some species of Barbus (Puntius), Tinca, Leuciscus etc. are also included. All these species have 2n=48 -52, as against the tetraploid species of the same family which have 2n=100-104 and in which same species of Barbus, Cyprinus, Carassius etc. are included (Ohno 1970). The comparison of the karyotype of these three species do not suggest any closer cytotaxonomic relationships between two of them. The Danube drainage subspecies, G. albipinnatus vladykovi, described for the first time by Vladykov (1931) as hybrid between G. kessleri and G. gobio. The comparative study of the karyotype do not suggest a hybrid origin.

Summary

A cytogenetical study of four species of the genus Gobio that live in Rumania results in that 3 species, G. gobio, G. kessleri banaticus and G. albipinnatus vladykovi have the same number of chromosomes (2n=50) and chromosomal arms (NF=98), in despite of their distinct chromosomal complement. The fourth species, G. uranoscopus is different in the number of chromosomes (2n=50) and chromosome arms (NF=100), thus justifying the establishment of the subgenus Rheogobio.

References

Banarescu, P. 1961. Weitere systematische Studien fiber die Gattung Gobio (Pisces, Cyprinidae), insbesonders in Donaubecken. Vestn. Cesko-Slov. Zool. Spolecn, Praha, 35 (4): 3/8 -346. - and Nalbant, T. 1972. Gobioninae (Pisces/Cyprindiae). Das Tierreich, Walter de Gruyter and Co., Berlin. Levan, A., Fredga K. and Sandberg, A. 1964. Nomenclature for centromeric position on chromo somes, Hereditas 52: 201-220. Ohno, S. 1970. Evolution by Gene Duplication. Springer Verlag. Raicu, P. and Taisescu, Elena. 1972. Metoda pentru studiul cromozomilor la pesti. In Vol. Genetica, Soc. St. Biologice. Buc. 7-12. Vladykov, V. 1931. Les poissons de ]a Russie souscarpathique (Tchecoslovaque). Mem. Soc. Zoologique France, 29: 1-375.