C 2001 The Japan Mendel Society Cytologia 66: 133-137, 2001

Karyological Study of the Banded , fasciatus fasciatus Gray (; Reptilia)

V. C. Ejere* and J. A. Adegoke

Department of Zoology, Obafemi Awolowo University, Ile-Ife, Nigeria

Accepted February 5, 2001

Summary Mitotic chromosomes were studied from the bone marrow of male and female, H. fas- ciatus fasciatus. A diploid chromosome number of 2n =40 was recorded for the with a chro- mosome fundamental number (NF) of 50. The karyotype is divisible into 2 main size groups namely, chromosome pair, number 1 which is the longest and chromosomes 2-40 which fairly intergraded in size. Neither microchromosomes nor heteromorphic pairs were observed. Possible mode of inheri- tance of chromosome variation in the genus, Hemidactylus also received some comments.

The Gekkonid fauna of Nigeria is very rich with about 7 genera and 15 species so far de- scribed (Dunger 1968). The genus, Hemidactylus has about 7 species, out of which karyotypic in- formation is available for only 1 species, H. brookii angulatus (Adegoke 1985). H. fasciatus fascia- tus is by far the most conspicuous of the Hemidactylus species in Nigeria because of its fairly big size and possession of characteristic dorsal chocolate bands from head to tail. It also enjoys a wide distribution in the forest region of Nigeria.

Karyotypic data accumulated so far for Hemidactylus species suggest a range in diploid chro- mosome numbers from 2n =40 (Bhatnagar 1962, De Smet 1981, Adegoke 1985) to 2n =46 (Makino and Momma 1949). However, diploid chromosome number as high as 2n =70 has also been report- ed in a parthenogenetic species, H. garnotti (Kludge and Eckardt 1969 in Gorman 1973). These past studies brought to limelight the distinct deviation of the Hemidactylus karyotypes from the typ- ical Gekkonid karyotype in possessing an appreciable number of biarmed chromosomes. The varia- tions in chromosome morphology exhibited by members of this genus can be utilized as an interest-

ing taxonomic parameter (Gorman 1973, Adegoke 1985). In the present communication, the kary- otype of H. fasciatus fasciatus has been described. Data obtained showed that this species exhibits a

specialized karyotype that is strikingly different from those of other Hemidactylus species known in literature.

Materials and methods

The used were collected at various times from residential houses within the Obafemi Awolowo University, Ile-Ile (Lat. 07•‹28'N, Long. 04•‹33'E) campus. Specimens were identified

using the identification keys of Dunger (1968). Sexes were determined by the careful examination

of the precloacal scales or after dissection. A total of 9 males and 3 females were used for chromo- some studies. Voucher specimens were kept in 10% formalin in the laboratory of one of us, JAA. Three hours prior to sacrificing, 0.05% colchicine solution (0.1 ml/10 g body weight) was in- jected intraperitoneally into each individual lizard. Chromosome extraction, spreading and staining techniques are as described earlier (Adegoke and Nadesan 1986, Adegoke and Ejere 1991). The

chromosome lengths were determined from at least 5 complete complements from the slides direct- ly using an eyepiece graticule. The individual measurements were converted to percentages of total

* Corresponding author . Present address: Department of Zoology, University of Nigeria, Nsukka, Nigeria. 134 V C. Ejere and J. A. Adegoke Cytologia 66 lengths of the chromosome complement. Terminology employed in the description of the cen- tromeric position follows that of Abraham and Prasad (1983).

Results and discussion For male and female H. fasciatus fasciatus, over 40 well spread metaphase and prometaphase chromosomes were scored from the bone marrow. No heteromorphic chromosome pairs were ob- served in the 2 sexes (Fig. 1A, B). The results of the centromeric indices, chromosome nomencla- ture as well as the fundamental number (NF) are shown in Table 1. The karyotype and the idiograms illustrating the centromeric location and length variations are as shown in Figs. 2 and 3. A diploid chromosome number of 2n =40 was recorded for the species with a fundamental number (NF) of 50. Testes spreads showing cells in diakinesis also gave 20 bi- valents (Fig. 1C). The karyotype of the species is divisible into 2 main size groups on the basis of the individual chromosome length. Group 1 consists of only chromosome pair number 1, which is by far the largest in size and is terminal in shape (Table 1). Group 2 comprises of chromosome pair numbers 2 to 40, which were always clearly visible in all spreads. They showed an intergrading of sizes as well as a manifestation of variable centromeric locations (Table 1, Fig. 3a). This group comprises of a median chromosome pair (number 20), 4 nearly subterminal chromosome pairs (numbers 15, 17-19), while the remaining 14 chromosome pairs (numbers 2-14, 16) were terminal. Karyotypic analyses of Gekkonid species have elucidated 2 prominent features. Firstly, majori- ty of the species possesses a karyotype that is more or less a graded series of telocentric chromo- somes with no visible distinction between the macro- and micro-chromosomes (Gorman 1973, King 1984). Secondly, there is the near absence of large metacentric chromosomes in the family with majority of the biarmed elements possessing subterminal centromeres (King and Rofe 1976,

A B

C

Fig. 1. Chromosome spreads of Hemidactylus faciatus faciatus. A) Mitotic metaphase spreads of male. B) Mitotic metaphase spreads of female. C) Diakinesis spread from the male. Bar is 5 sumeach. 2001 Karyological Study of the Banded Gecko 135

Table 1. Chromosome classification, nomenclature and fundamental number (NF) for H. fasciatus fasciatus. (i) is centromeric index derived from: length of short arm X 100/total length

a

b

Fig. 3. Idiograms of the karyotype of H. fasciatus fas- ciatus to show a) centromeric location, b) length variation. NF =50. (-) Indicates that centromere is away from terminal position.

Fig. 2. Representative karyogramme of male H. faciatus faciatus. Bar is 5 ƒÊm.

King 1984, Adegoke 1985). Generally, however, the incoherence in the evolution of diploid chro- mosome numbers vis-a-vis the fundamental number of arms, have rendered the family almost diffi- cult to study especially in any attempt to interpret the evolutionary sequence in their karyotypic in- heritance (Gorman 1973). Information documented from karyological studies of Hemidactylus species, portray enough variation to warrant cytotaxonomic differentiations. Although there had been a near conservative- 136 V C. Ejere and J. A. Adegoke Cytologia 66

Table 2. Diploid number and fundamental number (NF) variation among some Hemidactylus species

ness in diploid chromosome number of 2n=40-46 in the genus, the fundamental number of arms was variable, 44-80 (Table 2). Much more interesting, is the observation that the variability in the NF's occurred mostly among the 4 species with the diploid number of 40. It seems probable that the karyotype of 2n = 46 comprising exclusively of telocentric chromosomes recorded for H. bowringii (Nakamura 1932 in Gorman 1973), H. frenatus and H. flaviridis (Makino and Momma 1949) most closely represents the ancestral karyotype for the genus. Accordingly, the karyotype with 40 chro- mosomes must have arisen through the mechanisms of centric fusion coupled with pericentric in- version in 1 or 2 steps resulting in a reduction of the chromosome number. Though this opinion contradicts the view expressed earlier on the evolution of karyotypes in by Gorman (1973), it is noteworthy that similar mechanisms have also been reported in some gecko species especially the genus, Gehyra (King 1984). The variable chromosome numbers of 40 and 46 recorded for H. flaviridis (Table 2) create the impression that this was a case of misidentification. We strongly think that there is the need to revisit again the karyotype of this species as better cytogenetic techniques exist now for vertebrate cytotaxonomy. This will shed more light on the species true karyotype. De Smet (1981) reported a karyotype for H. brookii which was found to be morphologically different from that described for another subspecies. Such a variation informed the cytological corroboration of the classification of the subspecies as H. brookii angulatus (Adegoke 1985). The karyotype obtained for H. fasciatus fasciatus in the recent study, further attests to the karyotypic heterogeneity among Hemidactylus species. The possession of mainly telocentric chro- mosomes coupled with the fact that the relatively few biarmed chromosomes occurred among the small elements, nonetheless contrasts with the karyotypes described for H. flaviridis (Singh et al. 1970 in Gorman 1973), H. brookii (De Smet 1981) and H. brookii angulatus (Adegoke 1985). The karyotypes described for these species contained many biarmed chromosomes. However, the karyo- type of H. fasciatus fasciatus is Gekkonid in structure in that there is an intergrading in sizes of the chromosome elements although chromosome pair, number 1 is longer than others (Fig. 3).

Acknowledgements This work was supported in part by grant No. 1425FX made to JAA by the Obafemi Awolowo University, Ile-Ife, Nigeria.

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