The following hypotheses were tested for groups of simultaneous hermaphrodites Biomphalaria tenagophila: (a) snails that have low reproductive success during the process of self-fertilization do not increase their reproductive success after the end of grouping; (b) the copulation behaviour and the presence of one snail whose eggs have a low viability rate influence the partner's reproductive su...

Mating elicits profound behavioral and physiological changes in many species that are crucial for reproductive success. After copulation, Drosophila melanogaster females reduce their sexual receptivity and increase egg laying [1, 2]. Transfer of male sex peptide (SP) during copulation mediates these postmating responses [1, 3-6] via SP sensory neurons in the uterus defined by coexpression of th...

Background: In this study, we report the first case of a male reef manta ray, Mobula alfredi, becoming sexually mature in captivity and present its reproductive characteristics. Methods: We investigated changes in external morphology, behavior, and levels of steroid hormones in a male M. alfredi during its sexual maturation process. Results: At 2 years and 6 months of age, the male exceeded 300...

Postcopulatory sexual selection may favour mechanisms to reduce sperm competition, like physical sperm removal by males. To investigate the origin of sperm removal, I studied the reproductive behaviour and mechanisms of sperm competition in the only living member of the oldest damselfly family, Hemiphlebia mirabilis, one species that was considered extinct in the 1980s. This species displays sc...

In many taxa, females signal during courtship when they are receptive. However, just because a female signals does not mean that the male responds to the signal. This study examines female signaling of receptivity (readiness to copulate) and male response in the parasitoid wasp Spalangia endius Walker. Females folded their antennae against their heads when they were receptive, and antennal fold...

Transitions from sexual to asexual reproduction provide a useful context for investigating the evolutionary loss of nonfunctional traits. It is often assumed that useless behaviors or structures will degrade, but this process is poorly understood. Potamopyrgus antipodarum is an ancestrally sexual New Zealand freshwater snail characterized by numerous independent transitions to asexual all-femal...

The oral administration of the amino acid, tyrosine, has been for years recommended in order to improve fertility, especially to improve copulation behaviour in female dogs. However, evidence is comparatively poor. The objective of our study was to determine whether oral administration of tyrosine has an effect on oestradiol-17β concentrations and the oestrous behaviour in the bitch. Fifty bitc...

Despite the fact that insect learning capacity has been broadly demonstrated, the role that this process plays during mate searching has been scarcely explored. We studied whether the sexual behaviour of a male parasitic wasp can be conditioned to the odours from two alternative host plant complexes (HPCs) present during its first copulation. The experimental subjects were newly emerged males o...

The objective of this study was to determine size of testes, sexual behaviour, semen quality and testosterone concentration on 40 Ossimi rams in relation to scrotal circumference and age. Rams were divided into two groups similar in age and body weight. Group A with age of 1-1.5 years old and group B with 2-2.5 years old. Each group was divided into subgroups according to the scrotal circumfere...