Biochemical and Cytogenetic Analysis of Cutthroat Trout Populations in Northwestern Wyoming

Transcription

1 University of Wyoming National Park Servie Researh Center nnual Report Volume nd nnual Report, 978 rtile iohemial and Cytogeneti nalysis of Cutthroat Trout Populations in Northwestern Wyoming Eri J. Loudenslager University of California Follow this and additional works at: Reommended Citation Loudenslager, Eri J. (978) "iohemial and Cytogeneti nalysis of Cutthroat Trout Populations in Northwestern Wyoming," University of Wyoming National Park Servie Researh Center nnual Report: Vol., rtile 6. vailable at: This Yellowstone National Park Report is brought to you for free and open aess by Wyoming Sholars Repository. It has been aepted for inlusion in University of Wyoming National Park Servie Researh Center nnual Report by an authorized editor of Wyoming Sholars Repository. For more information, please ontat sholom@uwyo.edu.

2 Loudenslager: iohemial and Cytogeneti nalysis of Cutthroat Trout Populatio -- IOCHEMICL ND CYTOGENET IC NLYSIS OF CUTTHROT TROUT POPULTIONS IN NO RTHWEST ERN WYOMING Eri J. Loudenslager Fisheries iology Researh Faility Department of nimal Siene University of California Davis, California Objetives Prior to 9 utthroat trout (Sa l mo larki ) inhabi ted most drainages of the intermountain west inludi ng the Columbia, South Saskathewan, Missouri, Colorado, rkansas, Rio Grande, and South Platte Rivers and the Great asin. eause of overfishing, introdut ions of nonnative fish, and areless use of water resoures, 99% of the original populations of Salmo larki are believed to have gone extint (ehnke, 97). Reently, however, management agenies have beome inreasingl y aware of the prearious situation the utthroat trout is in and hav e implemented speial regulations to help restore these f isheries. One problem faing fisheries managers is to identify pure populations of utthroat tourt; another is to assign these populations to the proper subspeies. The problem of subspeies designat ion is partiularly diffiult beause meristi variation an be a s g reat within a subspeies as between them. Moreover, Pleistoene glaiation i nfluened the dispersal patterns of the existing subspeies ompliating our understanding of their zoogeography. During the past three summers I have studied the distribution of hromosomal and protein variants among Salmo larki subspeies. The objetive of my work within Yellowstone National Park and Teton County, Wyoming, is to: reassess the subspeies status of utthroat trout in the Snake, Yellowstone, and Missouri drainages; develop base line riteria for determining the purity of utthroat trout populations; and assess the purity of suspeted hybrid populations. Proedures Po ulations studied. During the summers of 976 and 977, Le Hardy's Rapids Yellowstone drainage), Pelian Creek (Yellowstone drainage) and Sedge Published by Wyoming Sholars Repository, 978

3 University of Wyoming National Park Servie Researh Center nnual Report, Vol. [978], rt Creek (Yellowstone drainage) from Yellowstone National Park and Dime Creek (Snake drainage), Snake River (Snake drainage), laktail Ponds (Snake drainage), ar -C Spring Creek (Snake drainage), Skull Creek (Snake drainage), and Spread Creek (Snake drainage) from Teton County, Wyoming, were examined eletrophoretially and ytogenetially. In the summer of 978, Casade Creek (Yellowstone drainage), Sylvan Lake (Yellowstone drainage), Little Thumb Creek (Yellowstone drainage), Thumb Creek (Yellowstone drainage), Cougar Creek (Missouri drainage), Gibbon River (Missouri drainage), Firehole River (Missouri drainage) and Ted Creek (Colorado River drainage) were sampled and are being examined eletrophoretially and ytogenetially. These samples represent three subspeies of Salmo larki, S.. lewisi, S.. bouvieri, and S.. pleuritius; and possible hybrids between Salmo larki and Salmo gairdneri. Cytogeneti methods. Chromosome preparations followed the method of Gold (974) with modifiation. riefly, after 6 hours of in-vivo inubation in olhiine, homogenized anterior head kidney was treated with a.7 N KCl hypotoni solution and fixed in Carney's solution (3: methanol :glaial aeti aid). One or two drops of the fixed ell suspension was dropped onto old, wet mirosope slides whih were then plate dried. Slides were stained in dilute (4-6%) Giemsa in phosphate buffer or C-banded using the a(oh) tehnique (Salamana and rmendares, 974).. Eletrophoreti methods. Samples of blood, heart, skeletal musle and liver were removed from freshly killed speimens or frozen arasses and stored in iquid nitrogen. Tissue extrats, prepared by homogenization and high speed entrifugation, were analyzed eletrophoretially in horizontal starh gels. The enzymes studies are latate dehydrogenase (LDH), malate dehydrogenase (MDH), alpha-glyerol phosphate dehydrogenase (agpdh), sorbitol dehydrogenase (SOH), xanthine dehydrogenase, (XDH), esterase (EST), aspartate-amino-transferase (T), superoxide dismutas~ (SOD), and reatin kinase (CK), as in previous years. In addition, phosphohexose isomerase (PHI), phosphogluomutase (PGM), fumerase (FUM), mali enzyme (ME), isoitrate dehydrogenase (IDH), and alohol dehydrogenase (DH) were added to the study. Geneti loi were onsidered polymorphi if the frequeny of the predominant allele was less than.99. Geneti heterozygosity was estimated by alulating the expeted heterozygote frequeny from the observed allele frequenies. Results Chromosome numbers in somati ells of utthroat trout from several loations in Yellowstone National Park and Teton County, Wyoming, are presented in table. lntraindividual variation is believed to be a4sed by hromosome loss during preparation and ounting errors. Table presents a omparison of the karyotypes of various utthroat trout subspeies. Two distintly different karyotypes are found within the Yellowstone Region. The first karyotype is observed in fish from the Yellowstone and Snake River drainages and is haraterized by a n hromosome number of 64

4 Loudenslager: iohemial and Cytogeneti nalysis of Cutthroat Trout Populatio -7- with a hromosome arm number of 4. This karyotype onsists of metaentri hromosomes, two of whih often have satellites, small submetaentri hromosomes, and 4 aroentri hromosomes. The seond karyotype is observed in native utthroat trout from the Missouri River drainage and is haraterized by a n hromosome number of 66 with 4 hromosome arms. This karyotype onsists of 34 metaentri hromosomes, 4 small submetaentri hromosomes, subteloentri hromosomes, and 6 aroentri hromosomes. The two karyotypes differ by a n hromosome number of two, without a hange in hromosome arm number. The simplest explanation for this is the fusion or fission of aroentri or subteloentri hromosomes termed a robertsonian rearrangement. There is also a differene in the number of small submetaentri hromosomes. In addition, the n=66 karyotype ontains several subteloentri hromosomes whih are absent in the n=64 karyotype. Eletrophoreti analysis is ompleted for all the populations sampled in 976 and 977. In addition, 978 samples from Ted Creek, Cougar Creek and Sylvan Lake have been analyzed and the results are presented in table 3. Casade Creek, Thumb Creek, Little Thumb Creek, Gibbon River and Firehole River are urrently being analyzed. The Ted Creek population whih represents the subspeies S.. pleuritius exhibited no eletrophoreti variation within the sample Tn=3). This population was divergent from Yellowstone utthroat trout (S.. bouvieri) at the SOH lous. nd divergent from west slope utthroat Ts.-. lewisi) at the SDH, IDH, ME and PHI-l loi. - - The Sylvan Lake population is polymorph i for T, MDH (,) and PHI-3. The T polymorphism is idential to the T polymorphism desribed in Yellowstone Lake and River (Loudenslager and Kithin, 979). The low frequeny MDH polymorphism was not deteted previously in any Yellowstone populations. However, the detetion of the variant allele may have been failitated by an improved separation tehnique. Currently it is unknown if this is a widespread polymorphism throughout the Yellowstone drainage. If it is ommon, we should detet it in the Casade Creek, Thumb Creek and Little Thumb Creek populations. PHI is a new enzyme system, and a low frequeny variant was found. eause this enzyme was not examined previously, no data is available on the geographi distribution of the variant. gain, final analysis of Casade Creek, Thumb Creek and Little Thumb Creek should give some indiation of how widespread this polymorphism is. The Cougar Creek population is polymorphi for low frequeny variants at the ME, SDH, PHI and LDH loi. In addition, the Cougar Creek population is differentiated from populations in the Yellowstone drainage at IDH, ME, PHI-3, SDH and an EST lous (see table 3). Disussion omparison of the karyotypes and eletrophoreti profiles of the populations sampled within Yellowstone National Park and Teton and Carbon Published by Wyoming Sholars Repository, 978 3

5 University of Wyoming National Park Servie Researh Center nnual Report, Vol. [978], rt ounties, Wyoming, to those available for others. larki subspeies suggest some interesting affinities. The karyotype of the individuals examined from Cougar Creek are idential to that desribed from Salmo larki lewisi from the Joko River State Trout Hathery, rlee, Montana (Loudenslager and Thorgaard, 979). The eletrophoreti profile is similar to that of Salmo larki lewisi presented by Reinitz (977). Thus, Cougar Creek and presumably other native utthroat populations in the Missouri drainage are west-slope utthroat trout, Salmo larki lewisi, not Yellowstone utthroat trout, Salmo larki bouvieri. Salmo larki lewisi, both eletrophoretially (llendorf and Phelps, personal ommuniation) and karyotypially (Loudenslager and Thorgaard, 979), is more losely related to the oastal utthroat trout (Salmo larki larki) than other interior subspeies. Cutthroat trout populations from the Yellowstone and Snake River drainage are idential eletrophoretially and karyotypially. Their karyotype (n=64) is similar to other interior subspeies, inluding~ pleuritius, ~ utah, S.. henshawi and S.. seleneris. Eletrophoretially, Yellowstone utthroat trout an-be-differentiated from these subspeies but are very losely related to S.. pleuritius and S.. utah. The geneti similarities between Cougar-Creek utthroat trout-and west-slope utthroat trout and between Yellowstone-Snake River utthroat trout and onneville asin utthroat trout suggest that two well differentiated utthroat trout ineages have made postglaial invasions into the headwater streams on the eastern side of the Continental Divide. lthough the subspeies S.. bouvieri, S.. lewisi and S.. pleuritius are quite distint eletrophoretially, indiating geneti variability and differentiation among Salmo larki subspeies, my stuides have failed to detet extensive biohemial geneti variation within populations. Estimates of heterozygosity for Ted Creek, Cougar Creek and Sylvan Lake are.,.34 and., respetively. These values are in the range observed in other utthroat trout populations in the Yellowstone region (. to.6) (Loudenslager and Kithin, 979), but muh lower than other vertebrates. In addition, urrent studies with Salmo larki henshawi generally reveal a similar low level of geneti polymorphism. Stohasti effets ould aount for low variation in relatively small populations with homing tendenies. However, the evolutionary onsequenes of this monomorphism is unknown. knowledgments I wish to thank the U.S. Fish and Wildlife Servie personnel who have helped ollet fish, espeially Mr. John Varley. I also wish to thank G.. E. Gall for allowing me to ontinue my Yellowstone researh while in his laboratory at Davis, California. This study is being funded through a grant from the University of Wyoming-National Park Servie Researh Center to Dr. R. M. Kithin, The University of Wyoming. 4

6 Loudenslager: iohemial and Cytogeneti nalysis of Cutthroat Trout Populatio Literature Cited -9- ehnke, R. J. 97. The zoogeography, systematis and management of utthroat trout. Colorado Coop. Fish. Unit, Colorado State Univ., Fort Collins. 8 pp. Gold, J. R fast and easy method for hromosome karyotyping adult teleosts. Prg. Fish Cult. 36:69-7. Loudenslager, E. J. and R. M. Kithin Geneti similarity between two forms of Salmo larki in Wyoming. Copeia 979(4) :-. Loudenslager, E. J. and G. H. Thorgaard Karyotypi and evolutionary relationships of the Yellowstone and west-slope utthroat trout. J. Fish. Res. oard Can. :- (submitted Otober 978). Reinitz, G. L Eletrophoreti distintion of rainbow trout (Salmo gairdneri), west-slope utthroat trout (Salmo larki), and their hybrids. J. Fish. Res. oard Can. 34: Salamana, F. and S. rmendares C-bands in human metaphase hromosomes treated with barium hydroxide. nnl. Genet. 7:3-36. Table. Chromosome numbers in somati ells of utthroat trout. Population No Le Hardy s Rapids 3 Pelian Creek 7 Snake River 3 laktail Ponds Skull Creek 3 Spreak Creek Dime Creek 9 Casade Creek a Thumb Creek a Cougar Creek a Joko Hathery 4 all individuals are not yet analyzed Table. omparison of karyotypes of Salmo larki subspeies. Subspeies S.. larki S.. larki S.. lewis i S.. bouvieri S.. pleuritius S.. henshawi n NF is fundamental number or hromosome arm number; M is metaentri hromosome; SM is submetaentri hromosome; ST is subteloentri hromosome; and is aroentri hromosome Published by Wyoming Sholars Repository, 978

7 University of Wyoming National Park Servie Researh Center nnual Report, Vol. [978], rt Table 3. llele frequenies of variant proteins for 9 geneti loil. Enzyme llele TED CREEK S.. peuritius n=3 SYLVN LKE S.. bouvieri n=43 COUGR CREEK S.. ewi s i - -n=4 ME.7.93 (. 3) PHI-3 l (. 63)..9 (. 9) PGM.8. (. 3) SDH- D E SDH- D.9 (. 63). 9 MDH-3,4.98. (. 4) IDH- l. l..8. (.) IDH- l. l. T - H = (.).3. 7 (. ). (. ) (. 34) lnumbers in parenthesis are heterozygosity estimates for individual geneti loi (h=-l:x). h for monomorphi proteins is.. H=L:h/r; where r= number of loi examined and inludes monomorphi loi. 6