Biochemical genetic markers to identify two morphologically similar South African Mastomys species (Rodentia: Muridae)

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Abstract

The two common southern African mice species (Mastomys coucha and M. natalensis) are morphologically almost identical, making field identification impossible at present. Specimens from two localities were collected and tissue and blood samples taken. The habitat type of each locality was studied, and a distribution map compiled. A definite correlation between biome-type and species range was found to be present. Three isozyme markers were identified: glucose phosphate isomerase in liver, and two general (non-specific) protein coding loci in muscle. In addition, we also identified species characteristic haemoglobin components in both species. This is the first study to report genetic variation within, and differentiation between these species. Our results are of medical importance because Mastomys coucha carries bubonic plague and M. natalensis carries Lassa Fever.

Introduction

The Mastomys species complex of mice is widely distributed in South Africa, especially the so-called Multimammate mice, Mastomys coucha and M. natalensis. The limits of their distribution are only provisional at this stage (Skinner, 1990), but it is known that they are sympatric in some areas, and allopatric in others. Mastomys coucha acts as a reservoir for the Rickettsian Yersinia pestis, the organism causing Plague (Dippenaar et al., 1993).

At present, three diagnostic forms of plague are known: bubonic, primary pneumonic and primary Septicaemic. Bubonic plague, which is the most common type in epidemics, is fatal in about 25–50% of untreated cases. Pneumonic plague, a highly contagious (airborne) form, and Septicaemic plague, a generalised blood infection, are rarer forms, and usually fatal (Roberts et al., 1996). Apart from Bubonic plague, this species complex is also a reservoir for the Banzi and Witwatersrand viruses (Dippenaar et al., 1993) as well as a recently emerged disease in forested West Africa. Lassa fever is an infection caused by an arenavirus, and has a high mortality rate, even in patients with hospital care (15–20% fatal). Mastomys natalensis, being a documented carrier of Lassa Fever also carries a Lassa-like virus called Mopeia. Its effect on man is yet to be established or researched (Murray et al., 1995).

Morphologically, both species are almost identical in all visible characteristics, and were originally regarded as one (De Graaf, 1981) M. natalensis. However, Gordon (1984) has shown that, at the very least, both species are distinguishable by ethological and micro-morphological characteristics, by their chromosome number, and characteristic haemoglobin variations. More recently, Dippenaar et al. (1993) used multivariate analysis of cranial characteristics to distinguish between the two species. However, 50% of the specimens collected at a sympatric locality were identified differently according to the latter method.

In the present study, we examined new material of two allopatric populations of M. coucha and M. natalensis aimed at identifying species characteristic genetic markers. Allozyme and haemoglobin variations were analysed comparatively.

Section snippets

Materials and methods

Tissue extracts of 24 individuals of M. coucha caught at Montgomery Park, Johannesburg (26°09’22’’S, 27°58’58’’E) and 20 individuals of M. natalensis caught at La Lucia ridge in Durban North (29°44’44’’S, 31°03’09’’E), were analysed electrophoretically using standard horizontal starch gels and homogeneous polyacrylamide gels (Fig. 1). The localities were also studied to determine if there was a relationship between habitat types and the distribution of these two species (Fig. 2). Specimens that

Ecology and distribution

It was not previously possible to accurately describe the geographic distribution and habitat requirements of either species, as a result of the extreme morphological similarity of M. natalensis and M. coucha, and the fact that the genetic composition of only a relatively small number of individuals has been studied. It does however seem likely that differences in the habitat requirements of the two species do exist. Fig. 2 shows the localities of the M. coucha and M. natalensis populations

Acknowledgments

We thank Sasol far funding this project.

References (24)

  • L. Miribel et al.

    Electrotransfer of proteins following polyacrylamide gel electrophoresis — nitrocellulose versus nylon membranes

    J. Immunol. Methods

    (1988)
  • J.C. Avise et al.

    A Comparative Summary of Genetic Distances in the VertebratesPatterns and Correlations

    Evol. Biol.

    (1982)
  • F.J. Ayala

    Population and Evolutionary Genetics

    (1982)
  • G. De Graaff

    The Rodents of Southern Africa

    (1981)
  • N.J. Dippenaar et al.

    Diagnostic morphometrics of two medically important southern African rodents, Mastomys natalensis and M. coucha (Rodentia: Muridae)

    South African J. Sci.

    (1993)
  • Falk, T.M., Abban, E.K., Oberst, S., Villwock, W., Pullin, R.S.V., Renwrantz, L., 1996. A biochemical laboratory manual...
  • T.M. Falk et al.

    Heterogeneity and subunit composition of the haemoglobins of 5 tilapiine species (Teleostei, Cichlidae) of the genera Oreochromis and Sarotherodon

    J. Comparative Physiol. B

    (1998)
  • Ferreira, J.T., Grant, W.S., Avtalion, R.R., 1984. Workshop on Fish Genetics. CSIR Special Publications, Pretoria, p....
  • Gordon, D.H., 1984. Evolutionary genetics of the praomys (Mastomys) natalensis species complex (Rodentia: Muridae)....
  • H. Harris et al.

    Handbook of Enzyme Electrophoresis in Human Genetics

    (1976)
  • M. Nei

    Estimation of average heterozygosity and genetic distance from a small number of individuals

    Genetics

    (1978)
  • C.L. Markert et al.

    Lactate dehydrogenase isozyme patterns of fish

    J. Expl. Zool.

    (1965)
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