A chromosomal analysis of eleven species of Gyrinidae (Coleoptera)

Abstract

Karyotypes are presented for 10 species of Gyrinus Geoffroy, 1762: G. minutus Fabricius, 1798, G. caspius Ménétriés, 1832, G. paykulli Ochs, 1927, G. distinctus Aubé, 1836 var. fairmairei Régimbart, 1883, G. marinus Gyllenhal, 1808, G. natator (Linnaeus, 1758), G. opacus Sahlberg, 1819, G. substriatus Stephens, 1869, G. suffriani Scriba, 1855, G. urinator Illiger, 1807 and for Orectochilus villosus (Müller, 1776) (Coleoptera: Gyrinidae). The 10 Gyrinus species have karyotypes comprising 13 pairs of autosomes plus sex chromosomes which are X0 (♂), XX (♀), with the X chromosomes the longest in the nucleus. O. villosus has 16 pairs of autosomes plus X0, XX sex chromosomes. The data obtained by Saxod and Tetart (1967) and Tetart and Saxod (1968) for five of the Gyrinus species are compared with our results. Saxod and Tetart considered the X chromosome to be the smallest in the nucleus in all cases, and this is considered to result from confusion arising from uneven condensation of some of the chromosomes. Small differences between the chromosomes of different Gyrinus species have been detected, but not between Greenland and Swedish populations of G. opacus, nor between typical G. distinctus from France and G. distinctus var. fairmairei from Kuwait.