_??_1995 The Japan Mendel Society Cytologia 60: 39-41, 1995

Karyotypic Analysis of Plecotus mexicanus (Chiroptera: Vespertilionidae)

Ricardo Lopez-W., Gerardo Lopez-O., Ma. Angeles Aguilar* and Elizabeth Arellano

Departamento de Biologia, *Departamento de Ciencias de la Salud, Universidad Autonoma Metropolitana-Iztapalapa, Apdo. Postal 55-35, Mexico, D. F., CP 09340

Accepted February 7, 1995

Plecotus mexicanus is a Mexican endemic species restricted to the high areas of the Sierra Madre Oriental, Sierra Madre Occidental and Eje Volcanico Transversal though there are two reports in the peninsula of Yucatan (Hall 1981). This species has been regarded as unusual and its biology is not well known (Burton and Pearson 1987); from the Taxonomy point of view, it has been considered as a subspecies of Plecotus townsendii (Hall and Kelson 1959) and as a monotypic species (Handley 1959). During the last 30 years, several studies have been realized in order to know the karyotypes and the chromosomal relationships among the species of genus Plecotus. Several authors (Fedyk and Fedyk 1970, 1971, Baker et al. 1974, Ando et al. 1977, Zima 1978, Fedyk and Ruprecht 1983) have worked on the karyotypes of the European species P. auritus and P. austriacus; the karyotypes of the American species, P. rafinesquii and P. townsendii, have also been described by other scientists (Baker and Patton 1967, Baker and Mascarello 1969, Williams et al. 1970, Anthony and Kitchin 1976, Bickham 1979a, Stock 1983). In this paper, the karyotype of P. mexicanus is described for the first time and it is compared with the karyotypes of the other species of genus Plecotus.

Materials and methods Nineteen adult P. mexicanus, 10 males and 9 females, were collected in a tunnel, 10 kilometers E Tlaxco, Tlaxcala, Mex., between 1984 and 1987. The skin and skull of all specimens were deposited in the Coleccion Mastozologica of the Universidad Autonoma Metropolitana-Iztapalapa (Numbers: UAMI 4754, 4756, 4793-4796, 4806-4813, 4820, 4825 4827, 4933). Mitotic figures were obtained from bone marrow cells following Tjio and Whang's procedure (1962); for karyotyping, chromosomes were arranged according to Anthony and Kitchin (1976) and classified into meta, submeta and acrocentrics using Levan's et al. criterion (1964).

Results

The karyotype of P. mexicanus shows a diploid number of 2n=32 (15 pairs of autosomes and one sex pair) and a fundamental number (FN) of 52; with regards to centromere position, nine pairs of the complement are metacentrics, one pair is submetacentric and the other six are acrocentrics, including the sex chromosomes (Fig. 1). 40 Ricardo Lopez-W. et al. Cytologia 60

Fig. 1. Karyotype of Plecotus mexicanus. •~1280.

Discussion

Chromosomal studies carried out with vespertilionid bats show that intergeneric variation is a common phenomenon while intrageneric karyotypic diversity is small (Bickham 1979a, b). The genus Plecotus is not the exception since all of its species present a diploid number of 32 and NFa of 50. Conventional karyotypes are the same for the three species of the New World which differ from the Palearctic ones only in the morphology of the X chromosome, being acrocentric in the first case and submetacentric in the second one (Fedyk and Fedyk 1971, Stock 1983). Fedyk and Ruprecht (1983) reported that the first 10 pairs of autosomes in P. auritus and P. austriacus are metacentrics while the results of this paper show that pair 10 of PAmexicanus is submetacentric. This result is consistent with the karyotypes shown by Baker and Patton (1967), Baker and Mascarello (1969) and Anthony and Kitchin (1976) for P. townsendii and P. rafinesquii in wich pair number 10 is submetacentric. If the three American species of the genus Plecotus show the submetacentric chromosome 10, this could be considered as a distinctive character among the American forms and the European ones. This idea agrees with that proposed by Fedyk and Ruprecht (1983) with regards to the differentiation of the genera of the Plecotine group from the chromosomal rearrangements of pair 10 as it has occured in other groups of vespertilionids as a source of variation (Stock 1983, Volleth 1985).

Summary

In this paper the karyotype of Plecotus mexicanus, a Mexican endemic species, is described and compared with those of the other species of the genus. It was found that P. mexicanus shares several features with P. townsendii and P. rafinsesqui such as diploid number 2n=32, a fundamental number of 52, acrocentric sex chromosomes and the submetacentric chromosome pair 10; the last is a new distinctive character between the American and European forms of the genus Plecotus.

Acknowledgements We are indebted to Family Armas (Tecomalucan, Tlax., Mex.) for their kind assistance during field work. This work was partially supported by CONACYT and Direccion General de Investigaeion Cientifica de la SEP. 1995 Karyotypic Analysis of Plecotus mexicanus (Chiroptera: Vespertilionidae) 41

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