Abstract
Chromosome number, karyotype formula, C-banding pattern, genome size and DNA base composition were studied in three species of Hyalidae and seven species of Talitridae. A karyotype of 25 chromosome pairs, with median centromeres (FN = 100), was found in all the species of Talitridae analysed and Apohyale prevostii. Genome size (C-value) varies among Talitrida from 0.94 pg in Apohyale crassipes to 2.81 pg in Orchestia gammarellus, and the percentage of AT-DNA in the whole genome ranges from 56.12% in A. crassipes to 68.17% in Sardorchestia pelecaniformis. In comparison with Hyalidae, Talitridae show more uni- formity in chromosome number and karyotype formula, and have larger genomes. There is a direct correlation between total DNA content and the amount of C-heterochromatic DNA. The cytogenetical data on Talitrida were compared from a phylogenetic and an evolutional point of view. The increase in genome size during the evolution of the Talitrida possibly had a role in their adaptation to supralittoral life and extreme subaerial conditions.
Highlights
Systematics of talitroidean amphipods has been revised by many authors in recent years on the base of phylogenetic analyses of morphological and ecological characters
For Talidrida, haploid and/or diploid chromosome number is known for 8 species (4 of Hyalidae and 4 of Talitridae), karyotype for only 3 species, and there is no data on heterochromatin distribution and nuclear DNA content (Poisson & Le Calvez, 1948; Le Calvez & Certain, 1951; Bachmann & Rheinsmith, 1973; Coleman, 1994; Libertini & Krapp-Schickel, 2000)
The present study aims to improve our knowledge of the cytogenetics of both Hyalidae and Talitridae by providing original data on some karyological parameters
Summary
Systematics of talitroidean amphipods has been revised by many authors in recent years (see references in Serejo, 2004) on the base of phylogenetic analyses of morphological and ecological characters. For Talidrida, haploid and/or diploid chromosome number is known for 8 species (4 of Hyalidae and 4 of Talitridae), karyotype for only 3 species (all Hyalidae), and there is no data on heterochromatin distribution and nuclear DNA content (Poisson & Le Calvez, 1948; Le Calvez & Certain, 1951; Bachmann & Rheinsmith, 1973; Coleman, 1994; Libertini & Krapp-Schickel, 2000).
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