Genetic variation in sympatric populations of diploid and polyploid brine shrimp (Artemia parthenogenetica)

Abstract

We examined genetic variation in sympatric diploid and polyploid brine shrimp Artemia parthenogenetica from each of three populations (China, Italy and Spain). Italian and Spanish tetraploids are closely related (I = 0.964). Diploids and tetraploids within each of the two European populations are also closely related (mean I = 0.905). Most alleles found in diploids also exist in sympatric polyploids. In contrast, the asexual Artemia (2N, 4N and 5N) in our study share few alleles with their close sexual relative, A. tunisiana (mean I = 0.002). These results, as well as the work of other authors, strongly suggest that at least the tetraploid Artemia in our study have an autopolyploid origin.Clonal diversity of polyploid Artemia can be very high at least in some population. Both diploids and polyploids had low clonal diversities in the populations dominated by polyploids and high clonal diversities in the population dominated by diploids.The most common genotypes of sympatric diploid and polyploid Artemia frequently differed. Some alleles occurred only in diploids, while others were restricted to polyploids. These results suggest that polyploidy in Artemia has led to genetic divergence from diploid progenitors, and that ploidy-level variation must also be considered in developing an understanding of spatial and temporal allozyme polymorphism in asexual populations.

The marbled crayfish as a paradigm for saltational speciation by autopolyploidy and parthenogenesis in animals

“…It has been described in some asexual invertebrate families and a few vertebrate hybrids [26,68–71] and is mostly associated with allopolyploidy. Autopolyploidy is much less common and is usually not associated with parthenogenesis, perhaps with the exception of some high arctic ostracods and polyploid populations of the brine shrimp Artemia parthenogenetica [72,73]. Artificially induced autopolyploid shrimp and fish are usually sterile [74], making the combination of autopolyploidy and parthenogenesis in marbled crayfish rather unique.…”

Genetic variation and evolutionary origins of parthenogenetic Artemia (Crustacea: Anostraca) with different ploidies

“…This supposition was not supported strongly by data documented to date. Some studies have evidenced triploid and tetraploid parthenogenetic Artemia had lower genetic variation than diploids (Zhang & King ; Maniatsi et al . ), but the pentaploids from Dongfanghong Saltern (China) had higher genetic variability in comparison with its sympatric diploid and other allopatric diploids and tetraploids (Zhang & King ).…”

“…Some studies have evidenced triploid and tetraploid parthenogenetic Artemia had lower genetic variation than diploids (Zhang & King ; Maniatsi et al . ), but the pentaploids from Dongfanghong Saltern (China) had higher genetic variability in comparison with its sympatric diploid and other allopatric diploids and tetraploids (Zhang & King ). Zhang & King () proposed that the genetic differences among allopatric di‐ and polyploidy populations could be attributed to the interaction among environmental parameters, ploidy levels and origins, while the dissimilarities between sympatric diploids and polyploids could result from the influence of ecological isolation.…”

Meiosis and Its Deviations in Polyploid Animals

“…There is no second polar body and the product of the first division divides endomitotically, generating nuclei with 2n = 42 chromosomes. The tetraploids probably arose automitotically [Zhang et al, 1991] via a process like this. As shown in figure 2 , this mode of meiosis produces homozygous offspring from a heterozygous female in a single generation.…”

“…Figure 2 shows the process of meiotic division as it occurs in a diploid animal such as the phyllopod crustacean Artemia parthenogenetica . The genus Artemia comprises 8 species that are often collectively called A. salina in the literature and which have diploid (2n = 42), triploid, tetraploid, pentaploid, octoploid, and decaploid races [Gross, 1932;Browne et al, 1984;Zhang et al, 1991]. Artom [1931] showed that the first meiotic division in diploid females at a population in Sète, southern France, proceeds in the normal fashion, eliminating 21 chromosomes.…”