An experimental test of the role of male mating history on paternal effects in the livebearer fish Gambusia holbrooki

Studies often show that paternal age affects offspring fitness. However, such effects could be due either to age, or to a male's previous mating effort (which is necessarily confounded with age). We experimentally tested whether differences in the mating history of old males affect offspring performance in the mosquitofish Gambusia holbrooki. Upon maturation, males were housed for a duration of the natural field-breeding season (23 weeks) either with mating access to females (lifetime-mating), or with visual but no physical access to females (no-mating). We then paired these males with a female to test whether male mating history had a significant effect on their mate's breeding success or offspring performance. The daughters, but not the sons, of ‘no-mating’ treatment males matured significantly sooner, and at a significantly smaller size, than those of ‘lifetime-mating’ treatment males. There was, however, no effect of male mating history on their daughters' initial fecundity, or on proxy measures of their sons’ reproductive success. These results, when combined with earlier studies showing effects of male mating history on sperm quality, growth and immunity, suggest that variation in paternal effects currently attributed to male age could partly arise because older males have usually mated more often than younger males.

Self-referent phenotype matching and its role in female mate choice in arthropods

A growing body of empirical evidence shows that females of many animal species gain benefits by mating polyandrously, and often prefer to mate with novel males over previous mates. Although a female preference for novel males has been demonstrated for multiple animal taxa, the mechanisms used by females to discriminate between novel and previous mates remain largely unknown. However, recent studies suggest that in decorated crickets Gryllodes sigillatus, females actually imbue males with their own chemical cues, known as cuticular hydrocarbons (CHCs) during mating, and utilize chemosensory self-referencing to recognize recent mates. Here we review evidence that self-referent phenotype matching is a widespread mechanism of recognition in arthropods, and explore how CHCs are used to facilitate mate-choice decisions. There is substantial evidence that CHCs are used as recognition cues to discriminate between species, kin, sexes, mates, individuals, and self and non-self, and are used to facilitate mate-choice decisions in a wide range of arthropod taxa. There is also evidence that CHCs are often transferred between individuals during direct physical contact, including copulation. Chemosensory self-referencing via cuticular hydrocarbons could provide a simple, but reliable mechanism for identifying individuals from previous mating encounters. This mechanism does not require any specialized cognitive abilities because an individual’s phenotype is always available for reference. Given the ubiquitous use of CHCs among arthropods, chemosensory self-referencing may be a widespread mechanism used by female arthropods to facilitate female mate-choice decisions and to enhance opportunities for polyandry.

Sperm utilization in subadult and adult simultaneous hermaphrodite snails mating in the wild

In species with multiple mating and long-term sperm storage, males are expected to show a preference for mating with virgin and young females to reduce the risk of sperm competition. In various simultaneous hermaphrodite land snail species, sperm production precedes egg production by 2–4 weeks, resulting in a short period of protandric hermaphroditism before shell growth is completed. In a natural population, we collected copulating pairs of the simultaneous hermaphrodite land snail Arianta arbustorum (L., 1758) consisting either of two adults, of two subadults, or of one adult and one subadult snail, and determined the paternity of their hatchlings that emerged from subsequently deposited eggs. Adult snails used sperm received from subadult mating partners for egg fertilization in the same frequency as sperm from adults, indicating that subadult and adult snails do not differ in male function. Furthermore, an unfinished shell is not a reliable indicator for virginity, because 35% of the subadult individuals had already sperm stored from previous mating(s). Compared with adults, young individuals exhibited a lower risk of sperm competition, indicated by a higher last mate sperm precedence. However, subadult snails produced fewer eggs than adult snails, counteracting the evolutionary advantage of preferring a young partner with low sperm competition risk.

When Love Comes Calling: Measuring Sexual Selection on Sagebrush Crickets

Male sagebrush crickets exhibit differential mating success based on their previous mating experience: virgin males have a higher probability of obtaining a mating than do non-virgin males. Measures of lifetime mating success in male sagebrush crickets have revealed that the median mating frequency is one, with many males failing to secure a mate at all and a small minority obtaining two to four mates. The purpose of this study was to investigate the acoustic and morphological characteristics that make male sagebrush crickets attractive to females. Male crickets were captured from Deadman’s Bar in Grand Teton National Park and their songs were recorded on subsequent evenings. Five song characteristics were measured including pulse duration, interpulse duration, dominant frequency, train duration, and intertrain duration. Multivariate selection analysis revealed significant linear and nonlinear selection on male song, with each of the five measured song characters contributing to male attractiveness. There was significant directional selection favoring longer pulse durations and shorter interpulse durations, which could be an honest indicator of male quality because these song characters likely impose high energetic costs. Significant stabilizing selection favored males with ~ 13.2 kHz calls and intermediate intertrain durations, which may be imposed by the auditory sensitivity of females.

Some factors affecting responses of four stored product beetles (Coleoptera: Tenebrionidae & Bostrichidae) to pheromones

Males of Tribolium castaneum (Herbst), T. confusum (Duval) (Tenebrionidae), Rhyzopertha dominica (Fabricius) and Prostephanus truncatus (Horn) (Bostrichidae) secrete aggregation pheromones attractive to both sexes. Responses of the four species to synthetic aggregation pheromones were investigated in relation to age, habituation, time of day, sex and previous mating experience in an olfactometer in which odour gradients were set up in moving air. Habituation reduced pheromone response in all the species tested but all recovered to pre-habituation levels after 48 h except Tribolium spp. males. Both sexes of T. castaneum and T. confusum were responsive to pheromone immediately upon eclosion, males reaching maximum response after 19 and 21 days and females after 21 and 16 days, respectively. Pheromone response was linearly related to age of the Tribolium spp. and T. castaneum males showed a greater response than the females. Sex or having mated did not affect the responses of T. confusum, P. truncatus and R. dominica. All the pheromones evoked periodicity of response, peaking between 10.00 and 18.00 h.

SEXUAL BEHAVIOR IN THE BLISTER BEETLE GENUS CYSTEODEMUS (COLEOPTERA: MELOIDAE)

Sexual behavior in the two species of Cysteodemus LeConte consists of: (1) a simple form of courtship that lacks an elaborate tactual display, (2) a prolonged mating period during which the male remains mounted on the female, (3) high levels of female receptivity regardless of previous mating, and (4) postcopulatory behavior. This behavior represents a condition intermediate between that found in the Meloinae and Nemognathinae, the two major subfamilies of blister beetles.