KARYOTYPIC STUDIES OF SEVEN SPECIES OF AFRICAN MEGACHIROPTER AN (MAMMALIA: PTEROPODIDAE)

Karyotypes of seven species of megachiropterans from Africa are described. Epomops franqueti, Hypsigncithus monstrosus, Lissonycteris angolensis, and Myonycteris torquata have a 2n = 36 and karyotypes that are similar to each other in morphology. Micropteropus pusillus (2n = 35) is similar to the above four, but possesses what ap-pears to be an X/YxY2 sex-determining system. Scotonycteris ophiodon (2n = 34, FN = 62) and Megaloglossus woermanni (2n = 34, FN = 62) are respectively distinctive from the other taxa studied, but may share several chromosomal characteristics with the other species.


Introduction
The family Pteropodidae is a diverse assemblage of species and is widely distributed in the Old World. The family consists of two subfamilies, 38 genera, and approximately 150 species (Koopman and Jones, 1970). Karyotypic studies within this family have been limited  (Table 1). Most species studied thus far appear to be chromosomally  conservative  and  are  characterized  by  similar  diploid  and  fundamental numbers.
In this study, the karyotypes of seven species, representing new data on six genera, are presented and discussed. The karyotype of Epomops franqueti has been described previously (Peterson and Nagorsen, 1975) from females. We illustrate the karyotype of a male. Our results are consistent with the majority of the chromosomal data reported thus far.

Materials and Methods
All karyotypes were obtained from bone marrow preparations made in the field by the in vivo incubation method as described by Robbins and Baker (1978). Diploid number determinations were based on counts from a minimum of 10 mitotic spreads. Nomenclature of chromosome morphology used is that of Patton (1967). All specimens examined were prepared as standard museum skins and skulls and are housed at the Carnegie Museum of Natural History (CM).

Specimens Examined
All specimens were collected in Cameroon unless otherwise noted.

Results
The karyotypes of seven species (representing seven genera and two subfamilies) are presented in Figs. 1-3. Table 1 is a summary of the known karyoptypic data for the family, including those reported herein. A brief description of each karyotype is given below. lustrated here is like that reported by Peterson and Nagorsen (1975).
The autosomal complement consists of 13 pairs of metacentric or submetacentric elements, ranging in size from large to small, and four pairs of medium-sized elements which have a submetacentric or subtelocentric centromere placement. The fifth pair of the complement possesses a secondary constriction proximal to the centromere (marker chromosomes) which is found in other species as well (see below, Dulic and Mutere, 1973;Peterson and Nagorsen, 1975;Yong and Dhaliwal, 1976). The X is a medium-sized subtelocentric and the Y is a small subtelocentric.
Hypsignathus monstrosus , 2n = 36, FN = 68, Fig ranging from large to small in size and five pairs of subtelocentric or acrocentric elements. The X is a medium-sized submetacentric and the Y is a small acrocentric. The karyotype of this species is distinctive in several respects. First, the marker pair with the secondary constriction is absent or at least not apparent. Second, the largest subtelocentric chromosome was not found in the complements of other species. If this pair is homologous to the largest pair of the other species, then it has undergone a pericentric inversion. is one additional pair of large metacentric chromosomes and one of the small metacentric pairs is lacking. The X is a medium-sized metacentric and the Y is a small metacentric.

Discussion
The karyotypes of the seven species reported here agree well with the general karyotypic trend thus far reported in the family Pteropodidae (Table 1). The works of several authors (Pathak, 1965#, 1965(Pathak, 1965#, b, 1966(Pathak, 1965#, , and 1972Dulic and Mutere, 1973;Peterson and Nagorsen, 1975;Yong and Dhaliwal, 1976) Dulic and Mutere (1973) for Rousettus aegyptiacus only in the morphology of the Y chromosome (which may be an artifact of preparation). These three genera have been considered closely related or congeners (Andersen, 1912;Rosevear, 1965) (Rosevear, 1965;Ellerman et al., 1953). Simpson (1945) had regarded these as congeners but the work of Ellerman et al. (1953) Dulic and Mutere (1973) are indistinguishable from those of Epomops franqueti (Peterson and Nagorsen, 1975; and this paper) and Hypsignathus monstrosus, and further supports the contention of a close relationship.
Micropteropus pusillus is similar to Epomops and Hypsignathus but is chromosomally distinctive. This species does possess the 13 pairs of metacentric-submetacentric elements, but it is lacking one pair of medium-sized subtelocentric chromosomes. Additionally, the males vol. 49   (Baker, 1970(Baker, , 1973(Baker, , 1979. The widespread occurrence of similar karyotypes was taken as an indication of shared homology between taxa. That this is not the case was demonstrated by studies utilizing G-and C-banding (Patton and Baker, 1978;. G-banding allows for the more accurate identification of homologous segments and it has been demonstrated that although the number and general morphology of linkage groups (chromosomal arms) may be similar in many taxa, they have been derived independently and are not homologous (Patton and Baker, 1978).
In the megachiropterans, the high incidence of diploid numbers of 34-36 and fundamental numbers of 58-68 may be misleading in that the homology suggested by overall similarity of karyotypes may be lacking. G-banding will allow a more accurate assessment of homology which will be of utility in systematic studies within this family. Comparisons of G-band homology will be of systematic importance in the study of relationships between species and higher taxa and should provide insight into the types and sequences of rearrangements involved in the evolution of megachiropterans.