Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records Author Angus, Robert B Author Sadílek, David Author Shaarawi, Fatma Author Dollimore, Hayley Author Liu, Hsing-Che Author Seidel, Matthias Author Sýkora, Vít Author Fikáček, Martin text Zoological Journal of the Linnean Society 2021 2021-07-01 192 3 958 958 https://academic.oup.com/zoolinnean/article/192/3/958/5930869 journal article 10.1093/zoolinnean/zlaa105 0024-4082 5301134 GENUS EXYDRUS BROUN, 1886 ( FIG. 13A, D, I ) Material examined: Exydrus gibbosus Broun, 1886: 1 female (NMPC): New Zealand : Wellington ( WL ) , Tararua Range , 1 km W of Titurea Dam , start of Greens Rd. , 40.4295°S 175.66064°E , 145 m , 26.xi.2016 , fragment of broadleaf forest with sparse understory with ferns and Pandanus Parkinson : sifting, M. Fikáček & M. Seidel lgt. ( MM31 ) . Karyotype: 2 n = 30 ( ♀ ). The only nucleus obtained has 29 chromosomes and the karyogram shows a serious size mismatch in pair 3 so there should be at least 30 chromosomes in the karyotype, presumably 14 pairs of autosomes plus the sex chromosomes. The smallest chromosome appears heavy and almost single-stranded; however, this is almost certainly because the two chromatids of a metacentric are lying on top of each other. This is frequent with small chromosomes. There is gradual decrease in length along the karyotype, with no pair strikingly longer than the others. The smallest pair is about a third of the length of the longest pair. Most of the chromosomes are metacentric or submetacentric; however, pairs 6–9 are subacrocentric.