Abstract
The chromosomes of triploid parthenogenetic Helophorus orientalis Motschulsky, 1860 are described from material from two localities in Heilongjiang, China. 3n = 33. All the chromosomes have clear centromeric C-bands, and in the longest chromosome one replicate appears to be consistently longer than the other two. The chromosomes of additional triploid parthenogenetic H. brevipalpis Bedel, 1881, from Spain and Italy, are described. In one Italian population one of the autosomes is represented by only two replicates and another appears more evenly metacentric than in material from Spain and the other Italian locality. Parthenogenetic and bisexual specimens of H. orientalis are illustrated, along with Pleistocene fossil material. Parthenogenetic H. brevipalpis is also illustrated. Parthenogenesis in Hydrophiloidea is discussed. It appears to be rare and, in all cases has been detected by chromosomal analysis of populations in which males are unexpectedly scarce. Parthenogenesis is suspected in Helophorus aquila Angus et al., 2014, from northern Qinghai (China), which should be verified in further studies.
Highlights
The family Helophoridae is one of the basal clades of the superfamily Hydrophiloidea (Fikáček et al 2012)
Parthenogenesis appears to be rare in the Hydrophiloidea and to date has been recorded only in H. orientalis Motschulsky, 1860 (Angus 1970) and H. brevipalpis Bedel, 1881 in the Helophoridae (Angus 1992), and Anacaena lutescens Stephens, 1829 in the Hydrophilidae
The aim of the present study was to study the karyotypes of two Helophorus species originating from China (H. orientalis) and Mediterranean region (H. brevipalpis) and to determine the mode of reproduction of the species, bisexual or parthenogenetic, in these unstudied populations
Summary
The family Helophoridae is one of the basal clades of the superfamily Hydrophiloidea (Fikáček et al 2012). The family comprises about 189 species classified in nine subgenera of which Rhopalohelophorus Kuwert, 1886, with about 146 species, is the largest and includes both Helophorus brevipalpis and H. orientalis (Angus 2015, Smetana 1985). The other diploid chromosome number occurring in Helophoridae is 2n = 18, found in the subgenera Helophorus s. Parthenogenesis appears to be rare in the Hydrophiloidea and to date has been recorded only in H. orientalis Motschulsky, 1860 (Angus 1970) and H. brevipalpis Bedel, 1881 in the Helophoridae (Angus 1992), and Anacaena lutescens Stephens, 1829 in the Hydrophilidae (van Berge Henegouwen 1986, Shaarawi and Angus 1991). Parthenogenesis appears to be rare in the Hydrophiloidea and to date has been recorded only in H. orientalis Motschulsky, 1860 (Angus 1970) and H. brevipalpis Bedel, 1881 in the Helophoridae (Angus 1992), and Anacaena lutescens Stephens, 1829 in the Hydrophilidae (van Berge Henegouwen 1986, Shaarawi and Angus 1991). Angus (1992) has shown that in H. brevipalpis Bedel, 1881 both diploid and triploid females may coexist in one population
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