Cytologia 50: 507-512, 1985

Cytological Studies of Certain Desert of Saudi Arabia 3. The Karyotype of aethiopicus

A. A. AI-Saleh and M. A. Khan

Zoology Department, College of Science, King Saud University, Riyadh, Saudi Arabia

Accepted January 24, 1984

The mammalian fauna of Saudi Arabia is much more diverse and interesting than most realized and many new and interesting discoveries will certainly be made as it is studied. Cytogenetic surveys of the fauna, which have not been conducted so far in Saudi Arabia, are particularly of great importance in deciding the true systematic position of the individual and in evaluating the merits of these animals with reference to the desert ecosystem. Presently our paper deals with karyotype analysis of the Paraechinus aethiopicus which is of common oc currence in Saudi Arabia. This study is one among the series of surveys of desert mammals of Saudi Arabia (Al-Saleh and Khan 1984 a, b). Except the hedgehog amurensis (2n=44) the diploid number of 48 chromosomes is seen in the various species of the well known genera, Erinaceus, and Aethechinus (Painter 1925, Bovey 1949, Gropp and Geisler 1966, Gropp et al. 1966, Jordon 1966, Geisler and Gropp 1967, Kral 1967, Hsu and Benirschke 1968, Borgaonkar 1969, Gropp et al. 1969, Natarajan and Gropp 1971, Sharma et al. 1971, Gropp and Natarajan 1972, Matthey 1973 and Sharma et al. 1975). To the best of our knowledge there is only one report about the karyotype fo Paraechinus aethiopicus from Iraq (Bhatnagar and El-Azawi 1978). Our study of the hedgehog Paraechinus aethiopicus utilized a simple banding technique to ensure proper pairing of homologous chromosomes and to determine the morphology of the sex chromosomes.

Materials and methods

Six male collected from Al-Qaseem region, about 500Kms north west of Riyadh, the capital of Saudi Arabia, were used in this study. The animals were injected intraperitonially with 0.1ml of colchicine (1mg/ml in distilled water) per body weight and two to three hours later they were killed by anaesthetization with chloroform. Femoral marrow was extracted in hypotonic solution (0.075M

KCl) and treated in it for 30 minutes including 20 minutes of treatment at 37•Ž.

The marrow cells were then fixed in 3:1 absolute alcohol-glacial acetic acid fixative and spread on cold slides and dried on hot plate. The slides were then rinsed for

5 minutes in hot distilled water (60•Ž) and stained with Giemsa. The preparations were examined and several favorable metaphases had been photographed under

Karl-Zeiss photomicroscope. The measurements of long and short arms of chro- 508 A. A. Al-Saleh and M. A. Khan Cytologia 50 mosomes, relative length and centromeric index were calculated according to the system proposed by Levan et al. (1964).

Fig. 1. Karyotype of male Paraechinus aethiopicus.

Fig. 2. Diagram of the banded karyotype for Paraechinus aethiopicus .

Results The diploid number of chromosomes in Paraechinus aethiopicus is found to be 48, while the fundamental number (FN) is 96 and fundamental number of autosomes (FNa) is 92 (Figs. 1 and 2). Bands have been obtained by hot water treatment and the banding pattern is further elucidated by idiogramatic representation (Fig. 2). The classification of chromosomes into various groups has been done by following the nomenclature proposed by Levan et al. (1964) and the chromosomes are divided 1985 Cytological Studies of Certain Desert Mammals of Saudi Arabia 3 509 into three groups (Fig. 3). Group 1. Includes fourteen pairs of metacentric autosomal chromosomes. They are numbers 1, 3, 5-9, 12-17 and 20. Group 2. Consists of nine pairs of submetacentric autosomal chromosomes, numbers 2, 4, 10, 11, 18, 19 and 21-23.

Fig. 3. An idiogram of Paraechinus aethiopicus chromosomes constructed on the basis of the position of the centromere.

Group 3. Has one pair of metacentric sex chromosomes, X and Y. The chro mosome (X) is relatively medium sized and the (Y) chromosome is relatively small or microchromosome. 510 A. A. Al-Saleh and M. A. Khan Cytologia 50

Secondary constrictions and subtelocentric chromosomes are not seen in Paraechinus aethiopicus.

Discussion

The chromosome number of 48 as established by this study is the same found in other hedgehogs, Erinaceus, Hemiechinus and Aethechinus (Gropp 1969, Gropp et al. 1969, Gropp and Natarajan 1972 and Sharma et al. 1975). Although the previous report of Paraechinus aethiopicus is in general agreement, minor differences do exist in the present karyotype. Bhatnagar and El-Azawi (1978) state the karyo type consists of 17 pairs of metacentric, 6 pairs of submetacentric autosomes, a me dium sized metacentric X chromosome and medium sized submetacentric Y chro mosome. The present study classifies the autosomes as 14 pairs of metacentric, 9 pairs of submetacentric chromosomes, a medium sized metacentric X chromosome and a small metacentric Y chromosome. Thus this report is supported by the banding pattern, it clearly contradicts the findings of the above authors in the number of metacentric, submetacentric chromosomes and most important of all in the nature of Y chromosome which is small and metacentric and not medium sized submetacentric as described by them. The validity of our finding is closely checked by comparing the results of the karyotype of Hemiechinus auritus reported by Bhatnagar and El-Azawi (1978) with the observation of Sharma et al. (1975) on the karyotype of the same species. Al though the method of Levan et al. (1964) has been used by these different authors for the classification of the chromosomes, there is a clear contradiction with regard to the telocentric chromosomes. Bhatnagar and El-Azawi have reported the pre sence of 3 subtelocentric chromosomes, a pair of autosomal and single sex chromo some (Y), while Sharma and his colleagues have indicated that there are no subtelo centric chromosomes in H. auritus. Furthermore, our observation of the X being medium and metacentric and the Y small metacentric, finds similarity with the results obtained on Aethechinus algirus (Gropp and Natarajan 1972), Hemiechinus auritus (Sharma et al. 1975) and Erin aceus concolor (Giagia and Ondrias 1980). Thus we consider that misnomenclature of autosomal chromosomes as reported by Bhatnagar and El-Azawi (1978) may be a matter of erroneous calculation in the measurements of the chromosomes , but their classification of the sex chromosome (Y) has no strong basis. An explanation for this discrepancy may be that intraspecific Y chromosome polymorphism exists in the Aethiopian hedgehog as has been described in Syrian hamsters (Lehman et al. 1963) and in some strains of laboratory rats (Hungerford and Nowell 1963).

Summary

The karyotype of Paraechinus aethiopicus consists of 48 chromosomes compris ing 14 pairs of metacentric, 9 pairs of submetacentric and a pair of metacentric sex chromosomes, X and Y. The fundamental number is 96 and the fundamental number of autosmes is 92. Secondary constrictions and subtelocentric chromo- 1985 Cytological Studies of Certain Desert Mammals of Saudi Arabia 3 511

somes are not seen in this .

Acknowledgements The authors express their thanks to SANCST for supplying them with checklist of references and the Research Centre of the College of Science, King Saud Uni versity, Saudi Arabia for supporting this project . Our thanks are due to Dr. N. A. ElAsgah, the Head of Zoology Department for his continuous encouragement.

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