A sex-linked locus (Mpi) in the opossum shrimp Mysis relicta: implications for early postglacial colonization history

Abstract

Strong and persistent associations between sex and genotype frequencies at the Mpi allozyme locus (mannose-6-phosphate isomerase) were found in three lacustrine populations of Mysis relicta sp. I in eastern Finland. Almost all females were homozygotes 100/100, whereas most males were heterozygotes 107/100. This disequilibrium suggests a complete linkage between Mpi and a sex-determining factor in a male heterogametic system and provides the first evidence for a genetic sex-determining mechanism in the crustacean order Mysida. However, no disequilibria were found in other parts of the species range. Potential mechanisms involved in generating the disequilibria are considered (sex-specific selection, recombination modifiers, hitchhiking, population bottlenecks). The restricted geographical distribution of the sex-Mpi association can be related to the early postglacial geological evolution of the lakes studied. A detailed scenario for the colonization history and genetic changes in the populations is presented. This involves initial immigration using temporary connections among ice-marginal lakes in eastern Finland approximately 10 000 BP, associated population bottlenecks, and the origin and local selective spread of a nonrecombining Y-Mpi 107 chromosome in the Sotkamo area c. 9300 BP. Soon after the isolation of the three headwater lakes (c. 9100 BP), a new recombination modifier caused a breakdown of the association in populations downstream.

A first AFLP-Based Genetic Linkage Map for Brine Shrimp Artemia franciscana and Its Application in Mapping the Sex Locus

“…Sex-linked markers have been found in males of the isopod Mysis relicta [45] and of Triops cancriformis [46]. In female crustaceans, sex-linked markers have been found in the isopods Paracerceis sculpta [47] and Jaera ischiosetosa [48], in the crab Cancer setosus [49], in penaeid shrimps L. vannamei [41] and P. monodon [27] and in giant freshwater prawn M. rosenbergii [50].…”

Does the Ice Age legacy end in Central Europe? The shrinking distributions of glacial relict crustaceans in Lithuania

“…Several species of malacostracan crustaceans, and mysids and amphipods in particular, have colonized the Baltic Sea and inland waters of Northern and Central Europe and North America through waterways created by post‐glaciation events (Segerstråle, 1957; Holmquist, 1966; Väinölä, 1998; Audzijonyte, 2006). Their colonization history has been complex and most likely included several waves, facilitated by expanding and contracting ice sheets (Väinölä, 1990; Audzijonytė et al, 2005).…”

“…For example, European and North American lakes are colonized by four closely related species of glacial relict mysids, formerly known as a single species, Mysis relicta Lovén, 1862, but now separated into morphologically, physiologically, and ecologically distinct species with different phylogenetic and colonization histories (Väinölä, 1990; Audzijonytė et al, 2005; Audzijonytė & Väinölä, 2005; Audzijonyte, 2006; Audzijonyte & Väinölä, 2006). These species cannot actively swim upstream, they brood live young, are confined mainly to deeper waters, and generally cannot be dispersed by birds or other natural external agents (Segerstråle, 1957; Väinölä, 1990; Väinölä, 1998). Their dispersal and present occurrences, naturally confined to the formerly glaciated areas, have contributed to the original idea that past glaciation events might have shaped the present distribution of species and populations (Lovén, 1862; Högbom, 1916).…”