Anacaena, THOMSON, 1859

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 ANACAENA THOMSON, 1859

( FIG. 7A–D )

Material examined: Anacaena gaetanae Bameul, 2001: 1 female (BMNH): France, Corsica, Corse du Sud, R. Stabiacciu, Porto Veccio, 12.vii.2009, R . B. & E.M. Angus lgt. ( BMNH) .

Anacaena lutescens (Stephens, 1829) : 3 female specs. ( BMNH): Germany, Hamburg district, 16.iv.1988, R. Angus lgt .; 1 spec. ( BMNH): United Kingdom, Norfolk, R. Angus lgt .

Karyotype: The karyotype of A. gaetanae ( Fig. 7A ) is similar to that of bisexual A. lutescens (2 n = 16 + Xy p (♂ )) but the chromosome taken to be the X is noticeably larger.

Comments on karyotypes: The karyotypes are discussed in detail by Shaarawi & Angus (1991a). Parthenogenetic A. lutescens is heterozygous for loss of a small apical section of chromosome 8, distal to a secondary constriction ( Fig. 7C ). Anacaena globulus (Paykull, 1798) has a fusion of two chromosomes (autosomes) to give a reduction from eight to seven pairs (2 n = 14 + Xy p). Anacaena rufipes (Guillebeau, 1896) has two further fusions, one involving the X chromosome, to give five pairs of autosomes and neo-XY sex chromosomes (2 n = 10 + neo-XY). Shaarawi & Angus (1991a) suggested that the original small Y chromosome had also fused with the neo-Y chromosome, but it is also possible that it has simply been lost. Triploidy (3 n = 27) was found in two widely separated populations of A. lutescens , from the United Kingdom (Armathwaite, Cumbria) and the Netherlands (Doetinchem, Gelderland). In both cases diploid females were also present. In the triploids there was one pair of intact chromosome 8 and one extra chromosome 8 with the deletion. In the Armathwaite population, one of three replicates of chromosome 8 has a pericentric inversion and is acrocentric.

Figures

Figure 7. Mitotic karyotypes of Chaetarthriinae from the midgut.A–C: Anacaena: (A) Anacaena gaetanae; (B–C) Anacaena lutescens (B, sexually reproducing specimen; C, parthenogenetic female). E–J, Horelophus walkeri. L, Chaetarthria simillima. A, C-banded; B, C, E–J, L, without treatment. Habitus figures: (D) karyotyped voucher of Anacaena gaetanae; (K) Horelophus walkeri, from Fikáček et al. (2012a); (M) Chaetarthria seminulum, from Fikáček & Liu (2019).