Few parasites, and no evidence for Wolbachia infections, in a freshwater ostracod inhabiting temporary ponds

Abstract

Biological systems with asexual reproduction have often attracted research on parasites and host immune defence, because parasites are expected to be better able to exploit genetically less diverse populations. In addition, maternally inherited parasitic microorganisms such as Wolbachia can directly alter the reproductive systems of their hosts and induce parthenogenesis. In the freshwater ostracod Eucypris virens, both sexual and asexual reproduction is known, and we speculated that parasite pressures might help to explain their co-existence. This species complex inhabits shallow, often eutrophic temporary water bodies, conditions that should provide ample opportunities for parasite infections. We surveyed natural populations of E. virens throughout its Europe-wide range for natural parasites, and particularly tested for the presence of intracellular Wolbachia bacteria. Surprisingly, the results indicate that very few E. virens populations support parasite infections. We also found no evidence for the presence of Wolbachia in the populations screened. The results therefore show that parasitic infections do not play a role in the maintenance of sex in this system.

Role of parasite load and differential habitat preferences in maintaining the coexistence of sexual and asexual competitors in fish of theCobitis taeniahybrid complex

“…Bruvo et al . , ). Therefore, a robust test of the RQH should be based on its three explicit predictions.…”

“…() and Weeks () did not support prediction 2 in bryozoans and in Poecilopsis fish; and prediction 3 was not confirmed in Melanoides tuberculata , the bark beetle Ips acuminatus , Daphnia complex, or Eucypris virens (Ben‐Ami & Heller, ; Meirmans et al ., ; Killick et al ., ; Bruvo et al . , ). Although we may not rule out the decisive role of other microscopic pathogens and diseases, the present analysis of the whole macroparasite community adds to studies failing to confirm parasite‐mediated coexistence of sexual and asexual biotypes.…”

“…However, in spite of clearly positive cases (see Neiman & Koskella, 2009 for a review), a number of negative tests have also been recorded. , Tobler, Wahli & Schlupp (2005), Brown, Kwan & Shero (1995), and Hanley et al (1995) failed to confirm prediction 1 in Poecilia fishes and Lepidodactylus and Hemidactylus geckos; Vernon et al (1996) andWeeks (1996) did not support prediction 2 in bryozoans and in Poecilopsis fish; and prediction 3 was not confirmed in Melanoides tuberculata, the bark beetle Ips acuminatus, Daphnia complex, or Eucypris virens (Ben-Ami & Heller, 2005;Meirmans et al, 2006;Killick et al, 2008;Bruvo et al, 2011). Although we may not rule out the decisive role of other microscopic pathogens and diseases, the present analysis of the whole macroparasite community adds to studies failing to confirm parasitemediated coexistence of sexual and asexual biotypes.…”

“…The insignificant effect of the most abundant parasites on the host's condition factor may also rather imply that the RQ mechanism does not play a significant role in the maintenance of sex in a given system (e.g. Bruvo et al, 2011). Therefore, a robust test of the RQH should be based on its three explicit predictions.…”

General environmental heterogeneity as the explanation of sexuality? Comparative study shows that ancient asexual taxa are associated with both biotically and abiotically homogeneous environments

“…No Difference Tend to be associated with marginal habitats, springs and interstitial (Pieri, Martens, Stoch, & Rossetti, 2009;Pinto, Rocha, & Martens, 2005;Schön, et al 1998;Schön, et al 2009) + torpor (Carbonel, et al 1988;Delorme & Donald, 1969;Retrum, Hasiotis, & Kaesler, 2011), but the same applies to some degree also to the sexual control; Darwinuloidea does not dominate in hot springs over its sexual control (Brues, 1932;Jana & Sarkar, 1971;Klie, 1939;Külköylüoğlu, Meisch, & Rust, 2003;Moniez, 1893;Wickstrom & Castenholz, 1985) Yes Tend to be associated with marginal habitats, springs and interstitial, but the same applies to some degree also to the sexual control (Pieri et al, 2009;Pinto et al, 2005;Schön et al, 1998Schön et al, , 2009; no typical predators and parasites (filtration) in comparison with the sexual control (Dole-Olivier, et al 2000); able to escape from competitors, predators and parasites because of torpor, but the same applies also to the sexual control (Carbonel et al, 1988;Delorme & Donald, 1969;Retrum et al, 2011); little parasitized, but the same applies to some degree also to the sexual control (Bruvo et al, 2011;Schön et al, 2009); aquatic representatives are exclusively benthic and sedentary in contrast to sexual control (Dole-Olivier et al, 2000;Pokorný, 1965;Rossetti, Pinto, & Martens, 2011;Schön et al, 2009); riverine and lacustrine representatives predominantly inhabit hypoxic depths with few competitors, predators and parasites (Rossi, Todeschi, Gandolfi, Invidia, & Menozzi, 2002;Schön et al, 2009;Smith, Kamiya, & Horne, 2006); litt...…”