B. 



U 



X X 



il H M H n 



if IS II ti II 



II It II tt II It 



Figure 1. — Karyotype of the California gray wfiale, Gigi. The autosomes are arranged into four 

 groups based on centromere positron and relative size. Tfie provisional X ctiromosomes are 

 indicated. 



prepared by standard honiogeneou.s 

 staining techniques, advances in the 

 differential staining of chromosomes 

 have added another dimension to 

 tcaryotypic analysis by making it now 

 possible to individually characterize 

 each chromosome of the complement. 

 Consequently, and as part of a larger 

 cytotaxonomic study of marine mam- 

 mals, evaluation of the gray whale 

 karyotype by quinacrine mustard 

 fluorescent banding was undertaken 

 on Gigi. a captive female gray whale. 



MATERIALS AND METHODS 



Chromosome preparations were ob- 

 tained by blood culture (Kulu. Veo- 

 melt. and Sparkes. 1971). Exposure 

 of the cells to 0.075 M KCI for 8 

 minutes was the preferred hypotonic 

 treatment and cold, rather than tlame- 

 dried. slides were made. The slides 

 were stained with Giemsa for normal 

 karyotyping or with quinacrine mus- 

 tard (50 micrograms/ml buffer for 

 .^0-40 minutes) for fluorescent karyo- 

 typing. Photographs of fluorescent 

 metaphases were taken on Kitdak' 

 Tri-X film with an exposure time of 

 45-50 seconds. Ten Giemsa and eight 

 fluorescent karyotypes were analyzed. 



' Use of trade names m this publrcation does 

 not imply endorsement ot commercial products 

 by ttie National Marine Fistieries Servrce 



RESULTS 



Gigis karyotype (Giemsa) is illus- 

 trated in Figure 1. The autosomes are 

 provisionally arranged into four 

 groups (designated A, B, C. and D). 

 Group A is composed of five pairs of 

 large submetacentric chromosomes. 

 Group B of five pairs of medium-sized 

 submetacentrics. Group C of six pairs 

 of metacentrics, and Group D of five 

 pairs of acrocentric chromosomes. 

 Within each group the chromosome 

 pairs are arranged by decreasing size. 

 The presumptive .\ chromosomes are 

 indicated in the karyotype. 



The fluorescent karyotype of Escli- 

 ritiniiis rohuslus is presented in Figure 

 2. The arrangement of the chromo- 

 somes follows that of the standard 

 karyotype. The banding pattern of 

 each chromosome pair is distinctive 

 and in addition to allowing positive 

 identification of the homologues 

 makes it possible to characterize each 

 pair of the complement in order to 

 facilitate karyotypic comparison with 

 other species. The fluorescent banding 

 pattern of the presumptive X chromo- 



Dehorah A. Duftield is with the 

 Deparlmenl of Biology at (he 

 University of California at Los 

 Angeles, Los Angeles, C A 90024. 



some is the same as that exhibited by 

 the X chromosome of another of the 

 baleen whales, the sei whale. BaUwiiop- 

 icrii horcalis-, and a number of the 

 smaller odontocete cetacean species 

 (personal observation). 



DISCUSSION 



The karyotype of the California 

 gray whale appears to be very similar 

 in number and gross morphology to 

 that of a number of other cetaceans, 

 both mysticete and odontocete'' (Kulu. 

 1972: Arnason. 1972). The fluorescent 

 karyotype of the gray whale was ex- 

 amined in the hope that the resolution 

 of chromosome structure afforded by 

 fluorescent banding would indicate 

 differences between its karyotype and 

 that of other cetaceans not obvious by 

 regular staining methods. In order to 

 illustrate the level of karyotypic com- 

 parison made possible by fluorescent 

 banding, the larger submetacentrics 

 which comprise Group A (pairs 1-5) 

 in two mysticete and two odontocete 

 species are shown in Figure 3. While 

 there are certain similarities between 

 the banding patterns of all four species, 

 it is clearly possible to distinguish 

 between the overall banding pattern 

 of the mysticete (gray whale, sei 

 whale) chromosomes and that of the 

 odontocetes ['l'uisi<>p\ inincaius. Laf-- 

 cnorhyiu hits tihliqiiidciis). Less obvi- 

 ous differences are also present which 

 further distinguish gray whale from sei 

 whale and Tiirsiops from Lugeno- 

 rhyncluis. A detailed comparison of 

 the fluorescent karyotypes of these 

 cetaceans is beyond the scope of this 

 report; however, it can be concluded 



- Arnason (1972) tias reported ttiat ttie X ctiromo- 

 some of B boreahs is one ot ttie larger ctiromo- 

 somes of ttie complement, sucti as found in 

 other ot the balaenopteran whales However, 

 both standard and fluorescent karyotypes ot a 

 male sei whale, tissue from which was made 

 available to this author by the Richmond whaling 

 station in California, indicate that the X chromo- 

 some of 8. boreahs is of medium size and 

 similar both in relative size and banding pattern 

 to the provisional X chromosome of the odon- 

 tocetes (Kulu, 1972), 



■1 Of all cetaceans studied to date, only the 

 sperm, pigmy sperm, and killer whales are 

 karyotypically distinct by standard staining 

 techniques. 



26 



