Karyotypes of some medium-sized Dytiscidae (Agabinae and Colymbetinae) (Coleoptera)

Abstract

An account is given of the karyotypes of 29 species of medium sizedDytiscidae (Coleoptera). Of the 20 species of Agabus Leach, 1817, 18have karyotypes comprising 21 pairs of autosomes and sex chromosomeswhich are either X0(male) or XX (female). These species are A.serricornis (Paykull, 1799), A. Labiatus (Brahm, 1791), A. congener(Thunberg, 1794), A. lapponicus (Thomson, 1867), A. thomsoni (J.Sahlberg, 1871), A. confinis (Gyllenhal, 1808), A. sturmfi (Gyllenhal,1808), A. bipustulatzts (Linnaeus, 1767), A. nevadensis Hakan Lindberg,1939, A. wollastoni Sharp, 1882, A. melanarius Aube, 1837, A. biguttatus(Olivier, 1795), A. binotatus Aube, 1837, A. affinis (Paykull, 1798), A.unguicularis (Thomson, 1867), A. ramblae Milian & Ribera, 2001, A.conspersus (Marsham, 1802) and A. nebulosus (Forster, 1771). However twospecies, A. infuscatus Aube, 1838 and A. adpressus Aube, 1837, havedeveloped a neo-XY system, with karyotypes comprising 21 pairs ofautosomes and XY sex chromosomes male. No chromosomal differences havebeen detected between typical A. bipustulatus and A. bipustulatus var.solieri Aube, 1837, nor have any been found between the three species ofthe A. bipustulatus complex (A. bipustulatus, A. nevadensis and A.wollastoni). The four species of Colymbetes Clairville, 1806, C. fuscus(Linnaeus, 1758), C. paykulli Erichson, 1837, C. piceus Klug, 1834 andC. striatus (Linnaeus, 1758) have karyotypes comprising 20 pairs ofautosomes and sex chromosomes which are X0 (male),) XX (female). Two ofthe species of Rhantus Dejean, 1833, R. exsoletus (Forster, 1771) and R.suturellus (Harris, 1828) have karyotypes comprising 20 pairs ofautosomes and X0/XX sex chromosomes, but the other three species, Rgrapfi (Gyllenhal, 1808), R. fivntalis (Marsham, 1802) and R. suturalis(Macleay, 1825) have 22 pairs of autosomes and X0/ XX sex chromosomes.Agabus congener and Rhantus suturellus may have one B-chromosome. Nineof the species have previously published karyotype data but for seven ofthese the data are wrong and are here corrected.