Studies on the Chromosomes of Nandus Nandus and Badis Badis from the J and K State, India
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Cytologia 49: 73-79, 1984 Studies on the Chromosomes of Nandus nandus and Badis badis from the J and K State, India . P. Sharma, and N. K. Tripathi Department of Biosciences, University of Jammu, Jammu (J&K) India-180001 Received March 27, 1982 Family Nandidae includes 7 genera and 10 species of fishes (Nelson 1976). This family has been split in various ways by past authors. Barlow et al. (1968) in a de tailed and comprehensive study, erected a new family for Badis badis and concluded that it has descended from a proto-anabantoid stock. Gosline (1971) recognized three families-Badidae, Nandidae and Pristolepidae, and placed them at the start of Percoidei. He believed them to be related to the Anabantoidei and suggested their placement with them. Liem (1970) in a detailed myological and osteological study with a functional analysis of the feeding apparatus, argues convincingly that Nandi ds and Anabantoids show no phylogenetic affinity and considered Nandids to re semble relatively advanced members of Percoidei. The present cytological studies on Nandus nandus and Badis badis of the family Nandidae were taken up with a view point of finding their cytotaxonomic status. Materials and methods Both Nandus nandus and Badis badis were collected from the side pools of the New Khul at Gho-Manasan, Jammu (J and K; India), with the help of hand net and casting net gears. During collection trips only males of N. nandus were encounter ed. Fishes were brought alive to the laboratory. N. nandus specimens received an injection of 0.5% colchicine solution at the rate of 1ml/100g body weight for 3 hrs, whereas B. badis individuals being quite small in size, were allowed to swim in a dilute solution of colchicine (0.005%) for 6-8 hrs. Testes and different somatic tissues like gill and kidney used for chromosomal preparations, were kept in 0.075 M KCI for 20 to 30 minutes and later fixed in Carnoy's fixative (3 parts ethanol: 1 part glacial acetic acid). The slides were prepared using air-drying Giemsa staining technique. The chromosomes were classified following Levan et al. (1964). Meta-, sub meta-, and subtelocentrics were taken as biarmed and telocentrics as mono-armed for purposes of calculating the fundamental arm number. Results Eight specimens of Nandus nandus and ten of Badis badis were employed for karyotypic analysis. Best results were obtained from both testicular as well as soma tic tissues (kidney and gill). O 74 Sharma, O. P. and Tripathi, N. K. Cytologia 49 In case of male N. nandus a diploid count of 48 chromosomes has been recorded which included 4 metacentric, 18 submetacentric, 14 subtelocentric and 12 acrocen tric elements with NF=84 (Figs. 1, 4). The absolute chromosome length varied from a maximum of 2.6,q to a minimum of 1.3ƒÊ. At spermatocyte metaphase-I (Fig. 3) 24 bivalents have been observed without any indication of the sex-chromo somes. Certain somatic polyploid cells of hexaploid level (6n=144) have also been recorded from the testicular material (Fig. 2). The male and female somatic metaphase complements of Badis badis (Figs. 5, 6) revealed the presence of 46 chromosomes which comprised 6 metacentrics and 40 Figs. 1-4. Male of Nandus nandus. 1, somatic metaphase complement (2n=48) from kidney. 2, polyploid spermatogonial metaphase complement (6n=144). 3, A spermatocyte metaphase-I cell with 24 bivalents, 4, male karyotype (4m+18 sm+14 st+12 t). telocentrics. The chromosomes formed 23 homomorphic pairs (Figs. 7, 8) without any indication of sex-element or heterogamety both in the male and the female in dividuals. The fundamental arm number has been calculated to be 52. The absolute chromosome size varies from a maximum of 2.0ƒÊ to a minimum of 0.6ƒÊ in the males and 2.7ƒÊ to 1.2ƒÊ in the females of B. badis. At spermatocyte metaphase-I 23 biva lent. (Fig. 9) have been recorded, thus confirming the diploid number of 46 observed at somatic metaphase. Certain somatic polyploid cells of 12n level (Fig. 12) and some meiotic polyploids of the order of 4n (Fig. 10) and 6n (Fig. 11) have been ob served in the testicular tissue of B. badis. The sex-chromosomes could not be identi fi ed in both the species. 1984 Studies on the Chromosomes of Nandus and Badis from India 75 Discussion As far as the chromosome number 2n=48 in Nandus nandus is concerned, pre sent observations are in complete agreement with those of Kaur and Srivastava (1965) and Manna and Prasad (1977). Kaur and Srivastava (1965) reported all acrocentric chromosomes in the diploid complement of N. nandus studied from Dt. Kheri (U. P.), India, while Manna and Prasad (1977) described the haploid chromo Figs. 5-8. Badis badis. 5, somatic metaphase complement (2n=46) from gill of male. 6, somatic metaphase complement (2n=46) from gill of female. 7, male karyotype (6 m+40t), 8, female karyotype (6m+40t). 76 Sharma, O. P. and Tripathi, N. K. Cytologia 49 some formula as n=2m+ 18 sm+3 st+l t and NF=94 for N. nandus studied from West Bengal, India. Present studies, however, revealed a haploid chromosome formula, n=2 m+9 sm+7 st+6 t with NF=84 in the local population. The ob servations of Kaur and Srivastava (1965) on N. nandus reporting all acrocentric chromosomes seem to be a result of inadequate technique adopted by them. While Figs. 9-12. Male of Badis badis. 9, a spermatocyte metaphase-I showing 23 bivalents. 10, a polyploid spermatocyte metaphase-I cell with 48 bivalents (4n). 11, a polyploid spermatocyte metaphase-I cell with 84 bivalents (8n). 12, a polyploid spermatogonial metaphase complement (12n=276). the karyotype dissimilarities recorded in N. nandus between present population and that of West Bengal, India (Manna and Prasad, 1977) may be as a consequence of geographical isolation of the two populations and can be explained on the basis of Robertsonian fusion (or dissociation) mechanism. Badis badis has been worked out for the first time from India except a prelimi nary information on its haploid number (2n=24) by Post (1965). During present 1984 Studies on the Chromosomes of Nandus and Badis from India 77 studies 2n=46 has been observed in somatic metaphase cells. The existence of 23 bivalents at metaphase-I further confirms 2n=46 in this fish. Most of the karyologically studied members of Anabantoidei (Perciformes) are reported to have a diploid chromosome number in the range of 46 and 48. Gosline (1971) asserted that the group Anabantoidei is an early Perciform offshoot with some affinity with the Nandidae (which he suggested may best be placed in the Anabantoi dei). The two presently investigated species of Nandidae, N. nandus and Badis badis have been found to possess 2n=48 and 46 respectively, a karyotype feature very close to Anabantoidei, which further cytotaxonomically substantiates the view of Gosline (1971) of the placement of Nandids with Anabantoidei. Perciform fishes are mostly marine dwellers, leaving a few species which are freshwater. In Perciform fishes, the basic chromosome number has been considered as 48, since 2n=48 occurred in number of species studied (Post 1965, Nayyar 1966, Ohno et al. 1968, Chen and Ebeling 1971, Ueno and Ojima 1977, Ojima and Kashi wagi 1979). Abe (1976) stated that the karyotype of the freshwater species might have been derived from that of the marine species or less freshwater adopted forms in Perciformes. However, the cytogenetic features in the species having 2n=48 and 2n=40, are not in favour of the above view (Abe 1976). A number of fishes have been reported to have mitotic and meiotic polyploid cells in their testicular tissue of diploid species. In salmon (Salmo salar), perch (Perca fluviatilis), pike (Esox lucius), pike perch (Lucioperca lucioperca) and ruff (Acerina cernua) the polyploidy of tetraploid and octoploid level has been reported by Nygren et al. (1968a, b). The chromosomes in the meiotic polyploid cells of sal mon formed multivalents while in perch, pike, pike perch and ruff, the chromosomes exist in the form of bivalents only. The present studies on two leaf fishes have also revealed certain mitotic (6 n in N. nandus; 12n in B. badis) and meiotic polyploid cells (4n and 8n in B. badis). The chromosomes were present only in the bivalent form in the meiotic polyploid cells observed in the present species, however, no mul tivalent could be observed. According to Nygren et al. (1968b) the high chromo some number may be formed by endopolyploidy, a process which in many cases has been carried through with only some of the chromosomes in the set, thus giving plates with uneven numbers. Badis badis meiotic polyploid cells occurred in the approxi mate range of 4n (48 bivalents) and 8n (84 bivalents) with 2 bivalents more and 8 bivalents less respectively than the exact multiples. Its variability may be as a re sult of addition of stray elements in tetraploid cell and displacement of some ele ments in case of the octoploid cell. In addition to endopolyploidy the high chromo some numbers may also be formed by the fusion of the adjacent cells. White (1973) emphasized the need to determine the time at which the fusion of adjacent cells occur to achieve polyploidy, for the early fusion of cells possibly results in the formation of multivalents while the late fusion results in the bivalent formation. Thus, the present observations of the bivalents in all the meiotic polyploids cells in B. badis point to the possibility of late fusion of adjacent cells as a cause of origin of these aberrant cells.