Herpetologica, 37(2), 1981, 92-95 © 1981 by The Herpetologists' League, Inc.

THE KARYOTYPE AND CHROMOSOMAL BANDING PATTERNS OF THE CENTRAL AMERICAN RIVER DERMATEMYS MAWII

John L. Carr, John W. Bickham, and Robert H. Dean

Abstract: Dermatemys mawii has a diploid number of 56 and a karyotype identical to that of a (Chelonia mydas). We hypothesize that D. mawii and C. mydas share the primitive karyotype for all non-trionychoid cryptodiran .

Key words: ; ; Dermatemys; Karyology; Reptilia; Testudines

The Dermatemydidae is one of The only living dermatemydid is Der- the oldestextant families of the suborder matemys mawii, a large river turtle from Cryptodira, with a fossil record extending southern and adjacent Central back into the Cretaceous (Gaffney, 1975). America (Iverson and Mittermeier, 1980). June 1981] HERPETOLOGICA 93

|l II 19 ti it mm

B II II II«•

mm* •■ mm

FlG. 1.—Standard karyotype of Dermatemys mawii with chromosomes arranged into groups: (A) meta- centric to submetacentric macrochromosomes, (B) telocentric to subtelocentric macrochromosomes, and (C) microchromosomes.

Dermatemys has been closely allied to in Tuxtla Gutierrez, , Mexico. the mud and musk turtles of the family Exact locality data were unavailable, but on the basis of serum pro the specimen was presumably from the tein electrophoresis (Frair, 1964, 1972), state of Chiapas. cranial morphology (Gaffhey, 1975), and penial morphology (Zug, 1966). Based Results upon pelvic girdle and hindlimb mor phology, Zug (1971) further proposed The standard karyotype of D. mawii that Dermatemys represents the basal (2n = 56) is presented in Figure 1. Chro stock of the kinosternids. Knowledge of mosomes are arranged according to Bick- the karyotype of D. mawii could provide ham (1975) into group A metacentric or an important test of the hypothesized re submetacentric macrochromosomes, lationship between kinosternids and der- group B telocentric or subtelocentric matemydids. Standard karyotype and macrochromosomes, and group C micro- banded chromsome data for D. mawii are chromosomes. There are 7, 5, and 16 presented here for the first time. pairs of chromosomes in groups A, B, and C, respectively. A heteromorphic pair of Materials and Methods sex chromosomes is not present in the Fibroblast cultures were initiated from male specimen examined. the heart tissue ofa single male D. mawii Figure 2 is a comparison of the G-band and grown in medium 199 enriched by ed macrochromosomes of D. mawii and twenty percent of original volume with a cheloniid (Chelonia my das). Chelonia fetal bovine serum. Standard karyotype, mydas has a diploid number of 56, with G-banded, and silver-stained prepara 7, 5, and 16 pairs of chromosomes in tions were made from cultured cells as groups A, B, and C, respectively (Bick- described in Sites et al. (1979&). ham et al., 1980), as does D. mawii. We The specimen (TCWC 57695) was a can detect no difference between the captive individual in the Parque Zoolo- G-bandedmacrochromosomes of Che gico of the Instituto de Historia Natural lonia and Dermatemys. The location of 94 HERPETOLOGICA [Vol. 37, No.2

FlG. 2.—G-banded macrochromosomes of groups A and B. The left element of each pair is that of Dermatemys mawii, the right element that of Chelonia mijdas.

the nucleolar organizing region in D. and Dermatemys have been mawii is on a group C microchromosome. hypothesized to be close relatives (see Pritchard, 1979). Discussion The location of the nucleolar organiz The only extant of the family ing region (NOR) is proximal to the cen Dermatemydidae, D. mawii, is charac tromere on a large, acrocentric micro- terized by a diploid number of 56. This chromosome. This is also true for che- same diploid number is also characteris loniid and emydine turtles, but it differs tic of two other cryptodiran groups, the from kinosternines, staurotypines, che- (Killebrew, 1975; Sites et lydrids, testudinids, trionychids and ba- al., 1979fo) and the (Bickham tagurine emydids (Sites et al., 1979a; et al., 1980). The cheloniids and the der- Haiduk and Bickham, 1982). matemydid share the 7:5:16 arrangement This study corroborates earlier find of chromosome pairs into groups A:B:C, ings indicating that slow rates of chro respectively, while the kinosternines dif mosomal evolution characterize crypto fer in having a 6:6:16 chromosomal ar diran turtles (Bickham and Baker, 1976, rangement. The difference can be ex 1979; Bickham et al., 1980; Sites et al., plained as a pericentic inversion in a pair 1979&). The fact that the two morpholog of group A chromosomes in the chelo ically primitive families compared herein niids and dermatemydid to create another possess identical karyotypes (at least at subtelocentric pair of group B chromo the levels examined) and that this karyo- somes in the kinosternines (Sites et al., type is directly comparable (see Bickham 1979b). et al., 1980) to that of emydids (probably The absence of heteromorphic sex the most derived family of turtles) leads chromosomes is interesting because the us to conclude that this may represent the only reported sex chromosome system in primitive karyotype for all of the Cryp- turtles is found in the Stauroty- todira, excluding the and pus, with males being the heteromorphic Carettochelyidae. Assuming this hypoth sex (Bull et al., 1974; Sites et al., 1979a). esis to be correct, nothing can be said June 1981] HERPETOLOGICA 95

about the relationship between the Der- Staurotypus). Cytogenet. Cell Genet. 13:419- matemydidae and the Cheloniidae be 425. Frair, W. 1964. Turtlefamily relationships as de cause their karyotypes are completely termined by serological tests. Pp. 535-544. In C. plesiomorphic. The Kinosternidae pos A. Leone (Ed.), Taxonomic Biochemistry and Se- sess karyotypic apomorphies, but none of rology. The Ronald Press Company, New York. these is shared with either of the other . 1972. Taxonomic relations among chely- drid and kinosternid turtles elucidated by sero two familes, making a cladistic assess logical tests. Copeia 1972:97-108. ment of the relationships impossible. Gaffney, E. S. 1975. A phylogenyand classifi However, considering Dermatemys to cation of the higher categories of turtles. Bull. possess the primitive karyotype for the Am. Mus. Nat. Hist. 155:389-436. majority of the suborder does make it an Haiduk, M. W., and J. W. Bickham. 1982. Chro mosomal homologies and evolution of testudi- available ancestor from which the kino- noid turtles with emphasis on the systematic sternine and staurotypine karyotypes (as placement of Platysternon. Copeia 1982: in

well as the karyotypes of other families) press. can be derived. IVERSON, J. B., AND R. A. MlTTERMEIER. 1980. Dermatemydidae, Dermatemys. Cat. Am. Am- phib. Rept.:237.1-237.4. Acknowledgments.—We are grateful to Miguel Killebrew, F. C. 1975. Mitotic chromosomes of Alvarez del Toro of the Instituto de Historia Natural turtles. III. The Kinosternidae. Herpetologica in Tuxtla Gutierrez, Chiapas, for making the spec 31:398-403. imen of D. mawii available to us. We also thank Pritchard, P. C. H. 1979. , evolution, Alvaro Rodriguez, Manuel Lemus Kourchenko, and and zoogeography. Pp. 1-42. In M. Harless and Susana Lopez de Lara de la Fuente for encourage H. Morlock (Eds.), Turtles: Perspectives and Re ment and assistance in obtaining the specimen. search. John Wiley and Sons, New York. This research was supported, in part, by National Sites, J. W., Jr., J. W. Bickham, and M. W. Hai Science Foundation grant DEB 77-13467. duk. 1979a. Derived X chromosome in the turtle genus Staurotypus. Science 206:1410-1412. Literature Cited Sites, J. W., Jr., J. W. Bickham, M. W. Haiduk, and J. B. IVERSON. 1979&. Banded karyotypes of Bickham, J. W. 1975. A cytosystematic study of six taxa of kinosternid turtles. Copeia 1979:692- turtles in the genera Clemmys, and 698. . Herpetologica 31:198-204. Zug, G. R. 1966. The penial morphology and the Bickham, J. W., and R. J. Baker. 1976. Chromo relationships of cryptodiran turtles. Occas. Pap. some homology and evolution of emydid turtles. Mus. Zool. Univ. Mich. no. 647. Chromosoma 54:201-219. . 1971. Buoyancy, locomotion, morphology . 1979. Canalization model of chromosomal of the pelvic girdle and hindlimb, and systematics evolution. Bull. Carnegie Mus. Nat. Hist. 13:70- of cryptodiran turtles. Misc. Publ. Mus. Zool. 84. Univ. Mich. no. 142. Bickham, J. W., K. A. Bjorndal, M. W. Haiduk, and W. E. Rainey. 1980. The karyotype and Accepted: 20 January 1981 chromosomal banding patterns of the green turtle Department of Wildlife and Fisheries (Chelonia mydas). Copeia 1980:540-543. Bull, J. J., R. G. Moon, and J. M. Legler. 1974. Sciences, Texas AirM University, College Male heterogamety in kinosternid turtles (genus Station, TX 77843, USA