Distribution of the 17;19 Robertsonian translocation in a herd of

by E.P. CRIBIU I, M. VASSART 2, V. DURAND ', A. GRETH 2, J.-F. AS MODE^, F. CLAR03 and S. ANAGARIYAH2

Institut National de la Recherche Agronomique, Centre de Recherche de Jouy-en-Josas, Laboratoire de CytogPnPfique, 78350 Jouy-en-Josas, France 'National Wildlife Research Center, P.O. Box 1086, Taz -'Museunt national d'Histoire naturelle, Parc Zoologique de Paris, 75012 Paris, France

Summary. - The cytogenetic survey of a captive population of Arabian Oryx (Oryx leucoryx) in Saudi Arabia has permitted the detection of a Robertsonian translocation involving chromosome pairs 17 and 19. This population has been constituted with animals from various arabian peninsula countries. The origin of this translocation is uncertain. Our results suggest that it originated from .

RPsumP. - L'Ctude cytoginetique d'une population d'Oryx d'Arabie (Oryx letlcoryx) ' en captivitt en Arabie Seoudite a permis de detecter une translocation robertsonienne impliquant les chromosomes 17 et 19. Cette population a kte constitute avec des animaux provenant de divers pays de la peninsule d'Arabie. L'origine de cette translocation est incertaine. D'aprks nos resultats elle pourrait avoir eu son origine B Qatar.

INTRODUCTION

A few years ago Saudi Arabia initiated a reintroduction program for various wild species extinct in their natural habitat ; a particular concern was devoted to the Arabian Oryx (Oryx leucoryx) that used to be present everywhere in the

Arabian peninsula. Originally, the Oryx was saved from total extinction by the , (( Operation Oryx n held in 1962. Nine individuals, the founders of the so-called cr World Herd D, were transported to the United States and were successfully bred (Grimwood 1988 ; Homan 1988 ; Mace 1988). Simultaneously, in Qatar, a herd was constituted with animals captured in the south of Rub A1 Khali in Saudi Arabia and Western Oman. Up to now, that population has remained completely isolated without any introduction of foreign animals, and therefore, this line is completely different from that of the American one. Therefore, a captive herd of Arabian Oryx has been established at the Natio- nal Wildlife Research Center (NWRC) located at Tai'f (Saudi Arabia). Recently, some animals were released in the Mahazat As Said reserve (Saudi Arabia). Cytogenetic studies have permitted to establish the standard karyotype for this species, using G- and C-banding techniques (Cribiu el al. 1989) and to find a 17;19 Robertsonian translocation in this herd (Cribiu et al. 1990). As a result, it was decided to karyotype all animals used for reintroduction. The present rapport outlines the results of that cytogenetic survey.

MATERIAL AND METHODS

I The NWRC herd (Saudi Arabia) has been established using animals from the Zoo (Saudi Arabia), the San Diego Zoo (U.S.A.), Qatar and various Arabian Gulf countries (Abu-Zinada et al. 1988). The Mahazat As Said herd (Saudi Arabia) has been constituted with Oryx from San Diego and . The Jordan herd (Shaumari Wildlife Reserve) has been created with animals from the San Diego Zoo and Qatar (Jones 1988). Karyotypes of 46 male and 44 female Arabian Oryx from NWRC and Mahazat As Said herds were made using lymphocyte cells (Grouchy et al. 1964). The chromosomes were banded using the G-banding method of Seabright (1971).

RESULTS AND DISCUSSION

The results of cytogenetic analysis of all animals examined are listed in Table 1. Out of the total of 90 animals, 81 had a normal karyotype, 2n = 58 similar to that previously described (Cribiu et al. 1989 ; Hsu and Benirschke 1977 ; Wurster and Benirschke 1968). All autosomal pairs except the largest which is submetacentric, were acrocentric. The X chromosome is the largest acrocentric with a minute but prominent short arm and the Y is a small acrocentric (Fig. I). The karyotype of 8 Arabian oryx (2 males and 6 females) appeared to include 57 chromosomes : two submetacentrics, 54 acrocentrics and one middle size meta-

TABLE l. - Number of animals carrying the 17;19 Robertsonian translocation.

I Females 1 Males I Origin Total number Nb. of 17;19 ~otalnumber Nb. of 17;19

Unknown 39 5 35 1

San Diego 0 0 4 0

Qatar 0 0 2 I

Jordan 5 2 5 0

Total 44 7 46 2 ROBERTSONIAN TRANSLOCATION IN ORYX

Fig. 1. - Karyotype of a male Oryx. centric chromosome (Fig. 2). A total of 56 chromosomes was found in one case. The karyotype of this female exhibited two middle size metacentric chromosomes. Recent familial cytogenetic studies have demonstrated that the metacentric chro- mosome, resulting from the fusion of chromosome 17 and 19, has a Mendelian co-dominant mode of inheritance (Cribiu et al. 1990). The origin of the translocation in the Saudi herd is uncertain, since this population is heterogeneous and has been constituted from animals coming from the United States and neighbouring Arabian countries. However, the absence of the translocation in animals from the San Diego herd (Ryder, personal commu- nication) and its detection in the herds from Jordan and Qatar strongly suggests that it originated from Qatar (Table I). The Qatar herd had been in a state of reproductive isolation since its formation and therefore, a member of the original breeding stock, captured in the Rub Al Khali, could have been a transloca- tion carrier. It is also possible that the mutation appeared de novo in the herd at the time of its formation. As a majority of Robertsonian translocatior~sfound in animal populations, the 17;19 translocation does not seem to be associated with phenotypic characteris- tics (Gustavsson 1969). In the absence of fertility records, a reduced fecundity in heterozygotes resulting from anaphase I nondisjunction and/or changes in the pattern of recombination in such individuals, cab not be excluded. An increased frequency of anaphase I nondisjunction has been reported in the laboratory mouse Fig. 2. - G-banded metaphase from a female Oryx with the 17;19 Robertsonian transloca- tion (arrow).

(Gropp and Winking 1981) and the most widely studied chromosome translocation in cattle, the 1;29 Robertsonian translocation, showed reduced fertility in daugh- ters of carrier bulls (Gustavsson 1969 ; Refsdal 1976). The nature of the advantage involved in the maintenance of Robertsonian variation is still unknown. Its magnitude should be sufficient to counterbalance the selective disadvantage of reduced fertility in heterozygotes. Reduced or sup- pressed recombination in the neighbourhood of the centromere in heterozygotes (Ford 1982) and/or preferential transmission in favour of Robertsonian metacen- tric (Gropp and Winking 1981 ; Searle 1986) are possible mechanisms for the maintenance of polymorphism. It is also. possible, that even chromosome mutations with a weak negative effect may become widely spread within a short time under restricted breeding conditions. In the present case, the distribution of the 17;19 translocation in the various herds could be attributed to genetic drift, genetic isolation and low selective pressures against the translocation. ROBERTSONIAN TRANSLOCATION IN ORYX 125

ACKNOWLEDGEMENTS The authors wish to thank H.R.H. Prince Saud Al-Faisal, managing director of the National Commission for Wildlife Conservation and Development in Saudi Arabia, to Prof. Abdulaziz Abu-Zinada, Secretary General of the Commission, and to Mr Jacques Renaud, director of National Wildlife Research Center for access to animals and moral support during our study. The collaboration of Dr. A. Bouvet (Post-doctoral Research Fellow, INRA) in the translation of the manuscript, is also gratefully acknowledged.

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