Propithecus Verreauxi Coquereli (Primates, Indriidae)

International Journal of Primatology, Vol. 4, No. 4, 1983 The Banded Chromosomes of Coquerel's Sifaka, Propithecus verreauxi coquereli (Primates, Indriidae) P. A. Poorman ~ Received September 9, 1982; revised November 30, 1982 The karyotype of Propithecus verreauxi coquereli is described in this report using G-, Q-, and C-banding and silver staining for nucleolus organizer regions. The banded chromosomes of P. v. coquereli (family Indriidae) are compared with those of Lemur fulvus fulvus (family Lemuridae), revealing few karyotypic similarities between the two groups and suggesting a well- established phylogenetic divergence between these families. KEY WOKD~: l-'roplthecus; Indriidae; banded karyotype; chromosomal evolution. INTRODUCTION The family Indriidae, composed of three genera, Propithecus, Indri, and Avahi, is included in the infraorder Lemuriformes, all of whose members are restricted to the island of Madagascar and the Comoro Islands. The anatomical and behavioral features of the indriids indicate that they form a cohesive group; however, their unbanded karyotypes differ in both diploid number and fundamental number (Rumpler, 1975). The genus Propithecus is represented by two known species, P. verreauxi (A. Grandidier, 1867) and P. diadema (Bennett, 1832), each with different unbanded karyotypes. The diploid number determined from unbanded preparations is 48 for P. verreauxi and 42 for P. diadema (Rumpler, 1975). In this study a banded karyotype is established for P. verreauxi coquereli. ~Department of Anatomy, Duke University Medical Center, Durham, North Carolina 27710. 419 0164-0291/83/1200-0419503.00/0 1983 PlenumPublishing Corporation 420 Poorman The banded karyotype of Propithecus might be expected to resemble more closely the banded karyotype of the Lemuriformes, of which it is a member, rather than the Lorisiformes. In order to look for karyotypic similarities between Propithecus and Lemur, the banded chromosomes of P. v. coquereli are compared with those of L. fulvus fulvus in this study. MATERIALS AND METHODS A 3-ml heparinized blood sample was drawn from one male P. v. coquereli housed at the Duke University Center for the Study of Primate Biology and History. The lymphocytes were cultured and processed using the procedures of Dresser and Hamilton (1979) and Poorman (1982). Slides were G-banded (Dresser and Hamilton, 1979), Q-banded (Miller et al., 1971; Poorman, 1982), C-banded (Schreck et al., 1977), or silver stained for nucleolus organizer regions (NORs) by the AgAS procedure (Goodpasture and Bloom, 1975). Six mitotic karyotypes were measured for relative lengths and arm ratios of the chromosomes using a Numonics graphics calculator (Moses et al., 1977). Metacentric, submetacentric, and acrocentric classifications are based on the centromeric nomenclature of Bender and Chu (1963). Chromosomes with arm ratios of 1.0-1.9 are metacentric, 2.0--4.9 are submetacentric, and greater than 5.0 are acrocentric. RESULTS The modal diploid number of P. v. coquereli is 48. The karyotype consists of 10 autosomal submetacentrics, 20 autosomal metacentrics, and 16 autosomal acrocentrics. The Y chromosome is a small acrocentric, and the X, a medium sized submetacentric. The autosomal fundamental number is 76. The largest chromosome pair, averaging 9.9 #m in early and midmetaphase spreads, is easily identifiable. The rest of the chromosomes show a serial reduction in length from 7.0 to 0.8 #m, with the X chromosome approximately 2.8 #m (falling in position 12) and the Y chromosome approximately 1.2 #m. G- or Q-banding allows the identifica- tion of each of the autosomal pairs and the sex chromosomes. Figure 1 shows one G- and one Q-banded chromosome for each pair in the karyotype of P. v. coquereli, together with an idiogram showing the bands typically seen at metaphase. The autosomes are ordered by relative length. C-banded preparations consistently show pronounced centromeric staining on each chromosome (Fig. 2). One of the small acrocentrics has Banded Chromosomes of Coquerel's Sifaka 421 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 X Y Fig. 1. Haploid mitotic karyotype of P. v. coquereli: G-banded chromosome (left), idiogram of G- and Q-banded pattern (center), and Q-banded chromosome (right). Bar = 10 ~tm. additional C-positive material in its long arlia and is most likely the Y chromosome since the acrocentric Y of Lemur also has additional C- positive material. Sequential AgAS staining after either G- or Q-banding reveals two pairs of NOR-bearing chromosomes, pairs 16 and 18. In each case, the NOR is adjacent to the centromere in the long arm of the chromosome. Only a few similarities exist between the G-banded Chromosomes of P. v. coquereli and those of L. f. fulvus (Hamilton and Buettner-Janusch, 1977). Propithecus chromosomes lq, 18, and 20 have banding patterns 422 Poorman Fig. 2. C-banded metaphase spread of P. v. coquereli. Three chromosomes appear to be almost completely heterochromatic, the Y chromosome at 12:00 and the No. 23 chromosomes at center and at 9:00. The chromosome at 1:00, which appears to be a long acrocentric, is actually a submetacentric with the short arms folded under. Bar = 10~m. identical to those of L. f. fulvus chromosomes lq, 21, and 25. The Y chromosome in both species is a small acrocentric with a terminal band. P. v. coquereli has a submetacentric X chromosome which does not resemble the acrocentric X of L. fulvus or the submetacentric X chromosomes of other species of Lemur. C-bands in P. v. coquereli are similar to those in L. f. fulvus in being very prominent and present at all centromeres. DISCUSSION Comparative studies of banded chromosomes of prosimians can provide information about the evolutionary relationships of different but related species. The extent to which the karyotypes of two groups resemble each other is a measure of the closeness of their relationship in a phylogenetic sense. Correlation of the cytogenetic results with the classical morphological and geographical criteria, together with recent biochemical and immunological data, can help to resolve some of the conflicts in the taxonomic classifications of the prosimians. Although the precise relationship of the Indriidae with the other Lemuriformes and Lorisiformes is not clear, several lines of evidence have been used to construct cladograms which place the Indriidae among the other members of the Lemuriformes and Lorisiformes. In a systematic analysis of morphological and behavioral characteristics of the Strepsirhini, Eaglen (1980) constructed a cladogram in which the Indriidae are placed as Banded Chromosomes of Coquerers Sifaka 423 a sister group to the Lemuridae. This lemur-indriid dade then forms a sister group to the Lorisidae, Galagidae, and Cheirogaleidae. On the basis of Eaglen's results, the Indriidae would be expected to have some karyotypic similarities with the Lemuridae. TattersaU (1982) has constructed a cladogram primarily on the basis of craniodental morphology, in which an Indri group (composed of the Indriidae, their subfossil relatives, and Daubentonia) belongs to a lemur clade. In this scheme, the Indriidae would be expected to have more karyotypic similarities with Daubentonia and the Lemuridae than with other groups. Phylogenetic reconstructions using data from immunodiffusion tests (Dene et al., 1976; Goodman, 1975) show that Propithecus (Indriidae) is most closely related to the Lemuridae and that these two groups are closer to cheirogaleids than to Daubentonia. In turn, cheirogaleids, Daubentonia, Propithecus, and Lemur are closer to each other than to lorisoids. From these results, more karyotypic similarities would also be expected between the Indriidae and the Lemuridae than between the Indriidae and other groups. However, a comparison of the banded chromosomes of P. v. coquereli and L. f. fulvus reveals few karyotypic similarities. This is not what would be expected on the basis of the immunodiffusion tests and an analysis of morphological and behavioral characteristics. If Propithecus is more closely related to the Lemuridae than to any other group, the relationship based on a comparison of the banded karyotypes does not seem to be a very close one, suggesting a well-established phylogenetic divergence between the Indriidae and the Lemuridae. The Propithecus karyotype also differs to a similar degree from that of another of the Lemuriformes, Cheirogaleus medius. Most of the latter's chromosomes (27 of 32 autosomal pairs) are indistinguishable from those of L. f. fulvus, despite a few notable differences (Dresser and Hamilton, 1979). Thus, the chromosomes of Propithecus are more removed from those of Lemur than are those of Cheirogaleus. Propithecus has four small chromosomes which appear to be identical to chromosomes in C. medius (P. v. coquereli chromosomes 18, 19, 20, and 21 have the same G-banding patterns as C. medius chromosomes 22, 25, 28, and 27), two of which (chromosomes 25 and 27 in C. medius) are not present in L. f. fulvus. C. medius chromosome 1, which is thought to be primitive because it is acrocentric, is postulated to have given rise to L. f. fulvus submetacentric 1 by Robertsonian translocation to another acrocentric and loss of G-positive material (Dresser and Hamilton, 1979). 424 Poorman The long arm of this submetacentric in L. f. fulvus is identical to the long arm of P. v. coquereli 1. Thus, it seems that both may have arisen from ari ancestral homologue of C. medius chromosome 1. All three Lemuriformes, Propithecus, Lemur, and Cheirogaleus, are distinctly different from the lorisoid Galago CrasMcaudatus. A comparison of the banded chromosomes of C. medius and G. crassicaudatus reveals few karyotypic similarities (only five chromosome arms are the same; Poorman, 1982). The banded karyotype of P. v. coquereli is also very different from that of G. crassicaudatus but has at least 10 chromosome arms which are identical to arms in G. crassicaudatus, only 2 of which are also present in C.

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