The common morphospecies Cypridopsis vidua (O.F. MÜLLER, 1776) (Crustacea, Ostracoda) is not an obligate parthenogen

Abstract

The common non-marine ostracod Cypridopsis vidua (O.F. Müller, 1776) is used as a proxy in various biological disciplines, such as (palaeo-)ecology, evolutionary biology, ecotoxicology and parasitology. This morphospecies was considered to be an obligate parthenogen. We report on the discovery of the first population of C. vidua with males from Woods Hole (MA, USA) and determine that it is a population with mixed reproduction. We describe the morphology of the males and of the sexual and asexual females. We illustrate a copula of a male and a sexual female as well insemination in a sexual female, showing that males are functional. Therefore, Cypridopsis vidua is a morphospecies with mixed reproduction, not a full apomictic parthenogen. We use, for the first time, polychromatic polarization microscope technology to illustrate soft parts of ostracods. In addition, we compare the sexual species C. bisexualis, C. okeechobei, C. howei and C. schwartzi and conclude that these species, especially the latter three, are morphologically very close to C. vidua.

Two new species of Strandesia Stuhlmann, 1888 (Crustacea: Ostracoda) from Thailand, with first record of a male S. martensi Savatenalinton, 2015

“…This phenomenon resembles the case of Cypridopsis vidua (O.F. Müller, 1776) which was recently reported as a mixed reproduction species (see Martens et al 2023). Also, the morphology of asexual and sexual females of S. martensi corresponds to that of C. vidua in terms of sexual females being slightly smaller and more highly arched.…”

“…It is also known that copulation between males and asexual (parthenogenetic) females is possible as was demonstrated in E. virens, although the insemination could not be confirmed (see Horne et al 1998). Hence, the current investigation in S. martensi, together with the previous work for C. vidua (see Martens et al 2023), could be evidence for the insemination in both sexual and asexual females in species of Cyprididae.…”

“…Hence, the morphological difference of the females is more logically considered as different morphotypes which can presumably be interpreted in at least two traits: the intraspecific morphological variation and the different forms of reproductive (asexual / sexual) females. Given the fact that, in a species, the variation of the external morphology (if present) commonly happens between different populations (localities) caused by, e.g., an ecophenotypic effect (see, for example, Yin et al 1999;Martens et al 2023), but it usually does not occur in the same population as was observed at locality SK29. This weakens the possibility of the former trait.…”