Repeatability of sperm number across multiple matings in three cricket species, Gryllodes sigillatus, Gryllus veletis, and Gryllus texensis (Orthoptera: Gryllidae)

Abstract

Although studies of various taxa have shown that males can alter the number of sperm in their ejaculates according to the risk of sperm competition, few studies have examined the extent to which the number of sperm transferred by males across multiple matings is repeatable. We assess the within-male and between-male components of variation in sperm number by counting the sperm in multiple ejaculates of males of three cricket species and determining the repeatability of sperm number. Sperm number was highly repeatable across multiple matings in all three species, leaving open the possibility that variation in sperm number is based, in part, on heritable genetic variation.

Ejaculate allocation under varying sperm competition risk in the house mouse, Mus musculus domesticus

“…Finally, as found by Pound and Gage (2004) in their study of sperm allocation in Rattus norvegicus, the numbers of sperm inseminated by individual males in the control and elevated sperm competition risk treatments were strongly correlated (see also Schaus and Sakaluk 2002;Gage and Morrow 2003 for evidence that this is a widespread phenomenon). Coupled with wide between male variation in sperm numbers, this suggests that some males may be at a consistent advantage in sperm competition.…”

Age-Related Sperm Production, Transfer, and Storage in the Sweet Potato Weevil, Cylas formicarius (Fabricius) (Coleoptera: Curculionidae)

“…Although insemination has been examined in various insects (Fowler 1973;Smith et al 1988;Ward 1993;Gack and Peschke 1994;Snook and Markow 1996;Otronen et al 1997;Snook 1998;Cook 1999;Reinhardt 2001;Schaus and Sakaluk 2002), these studies observed females only. To evaluate ejaculate size, both females and males need to be examined.…”

Song and Sperm in Crickets: A Trade-off between Pre- and Post-copulatory Traits or Phenotype-Linked Fertility?

“…We focused on crickets because (1) they are often used as model organisms to understand the mechanisms of sexual selection (Hedrick 1986, 1988; Wagner & Harper 2003; Wagner & Basolo 2007), (2) females usually choose high effort signalling males (Gray 1997; Rodríguez‐Muñoz et al. 2010), (3) females mate multiply, generating sperm competition, and (4) much is known about how ejaculate quality (i.e., sperm number and quality) influences fertilization success (Sakaluk & Eggert 1996; Schaus & Sakaluk 2001, 2002) and sperm competition success (Schaus & Sakaluk 2001; Garcia‐Gonzalez & Simmons 2005; Reinhardt & Siva‐Jothy 2005; Thomas & Simmons 2007). Cricket acoustic mate attraction signals thus represent a suite of pre‐copulatory sexually selected traits, while ejaculate quality represents a suite of post‐copulatory sexually selected traits.…”