Parasitic mites influence intra- and interpopulational variation in sperm length in a simultaneous hermaphrodite land snail (Gastropoda: Helicidae)

Abstract

Sperm morphology can be highly variable among species, but less is known about patterns of population differentiation within species. Sperm morphology is under strong sexual selection, may evolve rapidly, and often co-varies with other reproductive traits that differ between populations. We investigated variation in sperm morphology in the simultaneous hermaphrodite land snail Arianta arbustorum in relation to parasitic mite infection. Variation in total sperm length and sperm head length was assessed in 23 populations sampled across the distributional range of the species in Central and Northern Europe. We found a pronounced variation in total sperm length among the populations studied, with a difference of 11.0% of total sperm length between the shortest and longest population means. Differences among populations explained 62.9% of the variance in total sperm length, differences among individual snails within population 23.4% and differences within individual snail 13.7%. Mantel tests showed that interpopulation differences in total sperm length increased significantly with geographical distance between populations. A minimal adequate model revealed that parasitic infection had a positive effect and longitude a negative effect on total sperm length. Thus, independent of the population examined, mite-infected individuals of A. arbustorum produced larger sperm than uninfected snails and total sperm length decreased from west to east. Sperm head length also varied among populations, but it was not influenced by any of the factors examined. In a subsample of 12 populations restricted to the mountains of Switzerland (elevational range 440-2485 m a.s.l.), total sperm length decreased with increasing elevation. Our results suggest that selection pressures acting among populations may differ from those acting within. Stabilizing selection might be a possible mechanism for producing the reduced variation observed in sperm length within a population.

The effects of parasitism on sex allocation of a hermaphroditic acorn barnacle

“…Few studies have examined the effect of parasite infestation on male investment in simultaneous hermaphrodites, and the few studies that have done so reported inconsistent trends. For example, land snails infested by parasitic mites produced larger sperm than uninfested ones (Haeussler et al 2014). However, infestation status by a parasitic isopod did not affect male reproductive success in a protandric simultaneous hermaphrodite, the caridean shrimp (Calado et al 2005).…”

Breeding system, shell size and age at sexual maturity affect sperm length in stylommatophoran gastropods

“…In this context the intraspecific variation of sperm length is of interest. In stylommatophoran gastropods, data on intraspecific variation of sperm length are available for only a single species [ 8 , 64 ]. In 23 populations of Arianta arbustorum sampled across the distributional range of the species, a difference of 11 % in total sperm length between the lowest and highest population means was found [ 64 ].…”

“…In stylommatophoran gastropods, data on intraspecific variation of sperm length are available for only a single species [ 8 , 64 ]. In 23 populations of Arianta arbustorum sampled across the distributional range of the species, a difference of 11 % in total sperm length between the lowest and highest population means was found [ 64 ]. Differences among A. arbustorum populations explained 62.9 % of the variance in total sperm length, differences among individual snails within population 23.4 % and differences within individual snail 13.7 %.…”

Male Gammarus roeseli provide smaller ejaculates to females infected with vertically transmitted microsporidian parasites

“…Most of them have investigated the direct effect of the parasitic status of the male on its sperm production, with evidence of either negative effects (e.g. Yan & Stevens 1995;Galipaud, Dechaume-Moncharmont, Oughadou & Bollache, 2011) or positive effects (reflecting an increased investment to compensate negative effects of parasitism on other life-history traits) (Figenschou et al 2013;Haeussler, Schmera & Baur, 2014). Only a few studies have investigated the effect of female parasitic status on sperm allocation in the male (Edward & Chapman 2011).…”