61 Present status of the native parthenogenetic strain of Artemia sp. in the salterns of Tamil Nadu S. SIVAGNANAM 1 , V. KRISHNAKUMAR 2 , S. KULASEKARAPANDIAN 1 AND N. MUNUSWAMY 2 1 Central Institute of Brackishwater Aquaculture, No. 75, Santhome High Road R. A. Puram, Chennai – 600 028, Tamil Nadu, India 2 Unit of Aquaculture and Cryobiology, Department of Zoology, University of Madras Guindy Campus, Chennai – 600 025, Tamil Nadu, India e-mail : munuswamynm@yahoo.com ABSTRACT This article reports on a field survey conducted on the occurrence of the brine shrimp, Artemia in salt pans and lakes in Tamil Nadu, south-east coast of India during 2002–2003. A total of 15 salt pans in four regions were sampled; the maximum samplings were carried out from Tuticorin region. The reproductive performance of the locally colonized Artemia populations, both parthenogenetic and bisexual forms were assessed. Based on the available field data, a chart on the sources of native (parthenogenetic) and bisexual strains of Artemia in Tamil Nadu was prepared. Native parthenogenetic populations were found to occur in Vedaraniyam (VRM) and Nagercoil (NGC) regions, whereas bisexual populations of Artemia were predominant in Chennai (CHE) and Tuticorin (TCN) regions. The present study emphasizes the need for conservation of the native parthenogenetic strains by inoculating them in Artemia free salt pans. Keywords: Artemia, Cyst, Parthenogenetic strain, Salt pans, Sexuality, Tamil Nadu Introduction The brine shrimp, Artemia a well known hypersaline crustacean, is distributed worldwide in more than 600 localized geographically isolated areas such as inland salt lakes, coastal lagoons and natural and man-made salterns (Van Stappen, 2002). The genus Artemia is regarded as a complex of bisexual and parthenogenetic forms (Badaracco et al., 1987) and is defined by large criteria of reproductive isolation. All the parthenogenetic forms are grouped together as Artemia parthenogenetica. In India, parthenogenetic strain of Artemia sp. was reported to occur as pure natural population in coastal salt pans (Kulkarni, 1953; Baid, 1958; Royan et al., 1970; Achari, 1971) and inland salt lakes (Bhargava et al., 1987). Attempts were made to culture the brine shrimp, Artemia in salt pans for biomass and cyst production using the native strain (Bhargava et al., 1987; Gopalakrishnan et al., 1989; Kulasekarapandian et al., 1992; Kulasekarapandian and Ravichandran, 2003). Besides, exotic bisexual strain from San Francisco Bay (SFB) has also been introduced to meet the demand towards feeding in shrimp larval rearing at hatchery level (Royan, 1981a,b; Royan et al., 1992; Kulasekarapandian, 2004). However, impact of exotic strain introduction on the existing natural population is not well understood. Indian J. Fish., 58(4) : 61-65, 2011 The Artemia strains undergo either bisexual or parthenogenetic mode of reproduction. The selective advantages and costs of parthenogenesis and bisexual reproduction are explained extensively in the literature (Williams, 1975; Browne and MacDonald, 1982). Although parthenogenetic reproduction confers immediate advantages since it is more efficient, it also tends to promote low genetic variability (Abreu-Grobois and Beardmore, 1982). Bisexual reproduction maintains higher genetic variability among individuals, which would aid in dispersal to different habitats (Williams, 1975) and would presumably allow a more rapid evolutionary response to environmental challenge. Parthenogenesis in Artemia sp. predominates among Old World strains, whereas in the New World, only sexual reproduction has been reported (Bowen et al., 1980; Personne and Sorgeloos, 1980). In Old World strains, where bisexual and parthenogenetic populations overlap in their distribution, the bisexual strains tend to occur in inland salt lakes and parthenogenetic strains are found in coastal salterns (Browne and MacDonals, 1982). Artemia resources in India, especially with reference to the existence of native populations confined to Tamil Nadu are poorly studied. Therefore, the present study