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The karyotype of Myotis levis dinellii (Chiroptera: Vespertilionidae) from South America.

Abstract. -- The karyotype of Myotis levis dinellii from Argentina was examined and determined to be 2N = 44, (fundamental number 50). Karyotypic variation within the genus Myotis is also reviewed.


Myotis levis (Geoffroy 1824) is distributed in central Argentina, Uruguay, Bolivia and southeastern Brazil (Redford & Eisenberg 1992; Koopman 1993) where it inhabits a wide variety of habitats ranging from transition forests, moist Chaco Serrano forests to Monte Desert scrub (Mares et al. 1995). The systematic status of Myotis levis has remained unchanged since the major revision of the Neotropical members of the genus Myotis by La Val (1973). La Val (1973) recognized two subspecies; M. levis levis occurs in the eastern areas of central Argentina and M. levis dinellii which is found in the western part of this species range.

Reviews (Baker et al. 1982; Zima & Horacek 1985; Bickham et al. 1986; Mc Bee et al. 1986; Reina et al. 1994; Volleth & Heller 1994) have focused on the karyology of bats of the genus Myotis throughout the world. In mainland South America, 12 species of Myotis are known (Koopman 1993), but among the species that inhabit this continent, karyotypes have been described only for M. nigricans (Schinz 1821) by Bickham (1979) and M. keaysi Allen 1914 by Baker & Bickham (1980).


A total of nine specimens of Myotis levis dinellii were collected with mist nets and by hand. The standard procedure of in-vivo colchicine mitotic arrest was used for obtaining chromosomes from bone marrow (Baker et al. 1982). In most cases the yeast stress method (Lee & Elder 1980) was used to obtain a higher mitotic index. Slides were produced by dropping the cell suspension from a height of 50-60 cm into a large drop of distilled water on the surface of the slide (Baker et al. 1982). Chromosome slides were observed and photographed, and the diploid number and chromosomal morphology were determined for each specimen. Karyotypes were prepared in which autosomes were arranged in decreasing order of size and the X and Y placed as the last members of the series. The Y chromosome was tentatively identified as chromosome banding procedures were not made. Voucher specimens are deposited with the collections of The Museum at Texas Tech University (TTU) and the mammal collection of the Museo Provincial de Historia Natural (RVP), Santa Rosa, La Pampa, Argentina. Frozen tissue samples are deposited with the collections at Texas Tech University (TK).


Material examined. -- Cordoba Province: Cruz del Eje Department, Palo Parado, one male specimen (TTU 64336-TK 40653); Rio Cuarto Department, Coronel Baigorria, Estancia San Gonzalo, five female specimens (TTU 64337-TK 40657, TTU 64338-TK 40658, TTU 64339-TK 40659, TTU 64341-TK 40662, TTU 64342-TK 40663). La Pampa Province; Caleu Caleu Department, Almacen El 52, three male specimens (TTU 64346-TK 27901, TTU 64347-TK 27902, RVP 180-TK 27903).


The karyotype of Myotis levis dinellii (2n = 44, fundamental number 50) is composed of three pairs of large metacentric elements characteristic of the genus (Bickham 1979; Reina et al. 1994), a small pair of metacentrics and seventeen pairs of acrocentrics. The smallest of the acrocentrics, the last three pairs, are barely discernable in their morphology. The X chromosome is a medium sized submetacentric and the Y chromosome is a small submetacentric (Figure 1).

This karyotype does not in general depart from those described for M. nigricans and M. keaysi except that M. levis has a Y chromosome that appears to be larger than the smallest pairs of autosomes and not the smallest chromosome as has been described for Myotis nigricans by Bickham (1979). Except for these minor variations, as found for the Y chromosome in the genus (Bickham 1979), Myotis levis further documents the chromosomal conservativeness characteristic of this genus and most of the Vespertilionidae (Baker & Bickham 1980).


Support for the author's stay at TTU was provided in part by the Direccion Nacional de Cooperacion Internacional, Ministerio de Cultura y Educacion, Argentina and the Universidad Nacional de La Pampa, Argentina. Locality Almacen El 52 was sampled as part of La Pampa Province Vertebrate Survey. R. J. Baker and S. Kasper critically reviewed and provided many helpful suggestions on the first draft of the manuscript. J. Bickham and K. McBee contributed to the manuscript's improvement through their constructive review.


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Sergio I. Tiranti

Department of Biological Sciences, Texas Tech University

Lubbock, Texas 79409-3131

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Author:Tiranti, Sergio I.
Publication:The Texas Journal of Science
Geographic Code:30SOU
Date:May 1, 1996
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