Reproductive Isolation and Distinct Population Structures in Two Types of the Freshwater Shrimp Palaemon paucidens

Abstract

Twenty local populations of the Japanese freshwater shrimp Palaemon paucidens were electrophoretically and morphologically surveyed. Based on the diagnostic distributions of some alleles at Gpi, Mpi, Mdh-1, and Mdh-2, these populations were largely classified into two types (A and B). The A type occurred in lakes, ponds, and rivers, while the B type was observed only in rivers. Average Nei's genetic distance (D) between the two types fell into the subspecies range (D¯=0.1186). The coefficient of gene differentiation, G , varied considerably between the two types. In 12 populations of the A type, with a G value of 0.281, nine pond and lake populations showed a higher G (0.246) than the three river populations (0.151). On the other hand, G was 0.036 for the eight local populations of the B type. The lower rostrum tooth number had a mode of two in type A and three in type B. Type-A populations largely varied in the upper rostrum tooth number and egg size but type B did not. Under laboratory conditions, mating frequently occurred within each type, but not between types. Furthermore, no embryonic development was observed in the few cases of intertype mating. These results indicate that the A and B types had experienced cladogenic separation with pre- or postmating isolation, whereafter the A type, under geographic isolation, underwent genetic and phenotypic differentiation, while the B type, under extensive gene flow, did not undergo differentiation.

Estructura genética de la cigala <i>Nephrops norvegicus</i> (L., 1758) (Crustacea: Nephropidae), en el Mediterráneo

“…Our estimates of mean heterozygosity for Nephrops norvegicus from Adriatic Sea and Alboran Sea are slightly higher than those reported in previous studies on other decapod species (De Matthaeis et al, 1983;Nelson and Hedgecock, 1980;Chow et al, 1988;Sardà et al, 1995), whereas mean heterozygosities of the other populations are consistent with those of the above mentioned studies. Mantovani and Scali (1992) analysed by allozyme electrophoresis two samples of N. norvegicus from the Adriatic Sea and found mean heterozygosity per locus values of 0.033 and 0.036.…”

Reproductive aspects of the caridean shrimp Atya scabra (Leach, 1815) (Decapoda: Atyidae) in Sao Sebastiao Island, southwestern Atlantic, Brazil

“…However, eggs of A. scabra seems to be substantially smaller than those of A. margaritacea (Table 2). Inter-and intraspecific differences in egg size are a common phenomenon in decapods (for caridean shrimps see: Chow et al, 1988;Anger & Moreira, 1998;Wehrtmann & Kattner, 1998;Lardies & Wehrtmann, 2001;Terossi et al, 2010). Nevertheless, egg size is an indicator of energy allocation for reproduction (see Ramírez-Llodra, 2002), and it is especially important for the understanding of life history traits in amphidromous species, such as Atyidae (see Bauer, 2011aBauer, , 2011bBauer, 2013).…”

Biochemical and Morphological Evidence of Two Sympatric Forms, Interpreted as Sibling Species, in the Estuarine Grapsid Crab Hemigrapsus penicillatus (De Haan)

“…In the electrophoretic analysis, the discovery of a locus, 6Pgd, with fixed differences between the two forms indicates a high possibility of reproductive isolation Benthos Research December, (Chow & Fujio 1985;Chow et al 1988;Fidhiany et al 1988).…”

“…Recently, electrophoretic analyses have helped to reveal sibling species complexes in decapod crustaceans and other marine invertebrates (Chow & Fujio 1985;Chow et al 1988;Fidhiany et al 1988;Knowlton 1986Knowlton ,1993.…”