Rygmodus, WHITE, 1846

Angus, Robert B, Sadílek, David, Shaarawi, Fatma, Dollimore, Hayley, Liu, Hsing-Che, Seidel, Matthias, Sýkora, Vít & Fikáček, Martin, 2021, Karyotypes of water scavenger beetles (Coleoptera: Hydrophilidae): new data and review of published records, Zoological Journal of the Linnean Society 192 (3), pp. 958-958 : 958-

GENUS RYGMODUS WHITE, 1846

( FIG. 13F–H, J )

Material examined: Rygmodus modestus White, 1846: 1 male (NMPC): New Zealand: Rangitikei (RI), Ruahine Forest Park, Kashmir Road, sweeping of flowering Gaultheria L. and Brachyglottis repanda J.R.Forster & G.Forster , 39.94°S 176.16859°E, 655 m, 25.xi.2016, M. Fikáček & M. Seidel lgt. (MM25). 1 female (NMPC): New Zealand: Taranaki, 0.2 km S of Pukeiti Garden, 9 km E of Okato, lowland Nothofagus forest, flight interception trap, 370 m, 173.98°S 39.20°E, 10.xii.2016, lgt. M. Fikáček & M. Seidel (MM09).

Karyotype: 2 n = 13 + Xy p (♂). There is a gradual decrease in length along the karyotype, with pair 13 about a quarter of the length of pair 1. Most of the chromosomes, including the X, are acrocentric or subacrocentric. The Y chromosome is small, though not dot like, and first metaphase of meiosis shows the typical parachute association, Xy

p

.

Figures

Figure 13. Karyotypes of the Cylominae, without treatment. A, D, Exydrus gibbosus, mitosis, midgut. B–C, E, Tormissus magnulus, mitosis, midgut. F–H, Rygmodus modestus (F–G, meiotic metaphase I, testes; H, mitotic karyotype, midgut). Habitus figures: (I) Exydrus gibbosus; (J) Rygmodus modestus, from Minoshima et al. (2018).