Effects of mating, breeding system and parasites on reproduction in hermaphrodites: pulmonate gastropods (Mollusca)

Abstract

There are approximately 20 000 pulmonate gastropod species that are all hermaphroditic and (with a few exceptions) can act in both (i.e., male and female) sexual roles. Life history traits such as growth (rate), age at first reproduction, fecundity, fertility, future survival and offspring survival are highly variable within pulmonate species, even among individuals of the same population. Here, we review some aspects of reproduction (availability of partners, size-dependent sex allocation, courtship, (multiple) mating, sperm longevity/viability, social facilitation), breeding system (selffertilisation, outcrossing or mixed) and parasitism that may influence an individual's reproductive success and therefore account for part of the intraspecific variation in life history traits. A literature study showed that fecundity, fertility and/or growth are significantly affected by: i) the mating group size through changes in interference competition (e.g., crowding), breeding system and sex allocation; ii) individual body size with larger individuals producing more eggs than smaller individuals; iii) mating whereby female fitness may be positively or negatively affected; iv) social facilitation whereby female fitness is positively affected by the presence of conspecifics; v) the breeding system including the phenomena of inbreeding and outbreeding depression; and vi) parasites that may suppress or stimulate reproduction, especially egg-laying, in parasitised individuals. Moreover, multiple mating and multiple paternity seem very common in pulmonates. Interestingly, several of the above-mentioned aspects seem to interact or even act synergetically. Although many aspects of life history variation in pulmonate gastropods are still poorly understood which makes it difficult to draw general conclusions, pulmonates offer ample opportunities to study the evolution of major topics in evolution and life history strategies. Indeed, there is a growing number of basommatophoran and stylommatophoran model species, experimental setups and molecular, histological and histochemical techniques that are used to test current hypothesis on sex allocation, sexual selection (sexual conflict, sperm competition or cryptic female choice), the evolution of breeding systems and host-parasite interactions which will yield much information for the study of life history strategies as well.

Revaluation of the taxonomic characters and distribution of Omalonyx geayi (Gastropoda, Succineidae)

“…This pathology is well documented for many Gastropoda species (e.g. Wilson & Denilson 1980;Paschoal & Amato, 1996;Jordaens et al, 2007;Voutilainen et al, 2009;Averbuj & Cremonte, 2010).…”

Fitness Consequences of Reciprocally Asymmetric Hybridization between Simultaneous Hermaphrodites

“…However, the differences in fitness components demonstrated in the laboratory remain useful in estimating relative reproductive success, unless extrinsic factors affect it differentially through genotype-environment interactions. For example, fecundity of pulmonates often varies depending on the body size (Jordaens et al, 2007), although no effect of body weight at maturity on fecundity was detected over the 2-month duration of the experiment. Thus, relative intrinsic fitness, which incorporates the contribution of each trait as a component of lifetime fitness, is useful for examining relative differences in realized fitness under no genotype-environment interactions.…”

Evidence for age-dependent mating strategies in the simultaneous hermaphrodite snail,Lymnaea stagnalis(L.)

“…Thus, when mating with a larger animal, more resources should be diverted to sperm transfer than when mating with a small animal (Angeloni et al, 2002;Jordaens et al, 2007). Empirical studies provide ample evidence for the existence of size-dependent mating (DeWitt, 1996;Yusa, 1996;Angeloni et al, 2002;Ohbayashi-Hodoki et al, 2004;Chaine and Angeloni, 2005;Pal et al, 2006;Jordaens et al, 2007) but also non size-dependent mating strategies in hermaphrodite gastropods species (Switzer-Dunlap et al, 1984;Baur, 1992;. It is conceivable, however, that interpretation of some these studies is confounded by the fact that, for many of the species used, size is a covariant of age.…”

“…This theory builds on the presumption that larger individuals have more resources to invest in offspring and will therefore be better prepared to support the less economical female sex function. Various lines of evidence support this view (reviewed by Jordaens et al, 2007). For example, in many hermaphrodites, female fecundity, but not male fecundity, correlates significantly with body size (DeWitt,Age-dependent mating in Lymnaea Other studies provide evidence for the existence of size-assortative mating strategies in various simultaneous hermaphrodites (SwitzerDunlap et al, 1984;Baur, 1992;DeWitt, 1996;Yusa, 1996;Angeloni et al, 2002;Ohbayashi-Hodoki et al, 2004;Chaine and Angeloni, 2005).…”

“…Leonard, 2005;Leonard, 2006;Anthes et al, 2006). One theory often put forward and observed in several molluscan species is that simultaneous hermaphrodites deal with this issue by means of 'sperm trading' through either sequential or simultaneous reciprocal copulations (Leonard and Lukowiak, 1984;Leonard, 1990;Leonard, 1991;Leonard, 2005;Dall and Wedell, 2005;Koene and ter Maat, 2005;Jordaens et al, 2007). Another frequently proposed theory is that simultaneous hermaphrodites evolved size-assortative mating systems to abrogate mating conflicts (Angeloni et al, 2002;Angeloni, 2003).…”