Post-copulatory Guarding Research Articles

Observations of the mating behavior of Portunus trituberculatus and the role of shelters in its mating process

In this study, the mating behavior of Portunus trituberculatus under indoor conditions and the role of shelters in its mating process were systematically studied by using behavioral observation methods. The results showed that the mating behavior of P. trituberculatus was divided into four stages: courtship and pre-copulatory guarding, reproductive moulting, copulation, and post-copulatory guarding. P. trituberculatus in the no shelter group (NSG) usually preferred to gather at the edges or corners of the cement tank, while P. trituberculatus in the shelter group (SG) preferred to hide in the shelters. During the whole experiment, the shelter occupancy rate of P. trituberculatus during the day (57.40%) was significantly higher than that at night (38.08%) (P < 0.05). In terms of hiding rate, the hiding rate was as high as 63.32% during the day, which was significantly higher than that at night (37.70%) (P < 0.05). The copulation time of the SG was similar to that of the NSG. However, the durations of the pre-copulatory guarding period and post-copulatory guarding period of the SG were shorter than those of the NSG, indicating that the presence of shelters could shorten the total mating duration of P. trituberculatus. P. trituberculatus provided with shelter did not hinder its mating behavior, and there was little difference in mating rate between NSG and SG, which were 100% and 97.22%, respectively. In addition, we found that there was certain cannibalism during the reproductive moulting of female crabs, which could lead to the death or injury of some individuals. However, the survival rate of the SG (89.58%) was significantly higher than that of the NSG (72.92%) (P < 0.05). Moreover, the injury rate in the SG was only 14.13%, which was significantly lower than that in the NSG (31.31%) (P < 0.05). In general, shelters have the capability of appealing to P. trituberculatus during mating and can effectively reduce the incidence of intraspecific cannibalism during mating and improve the survival rate of P. trituberculatus.

Is Potimirim potimirim (Crustacea, Decapoda, Atyidae) a protandric hermaphrodite species? Behavioral and morphological aspects of the reproductive system

We evaluated the mating behavior of Potimirim potimirim in the laboratory based on the assumption that this caridean might be hermaphroditic. We also performed histology and scanning electron microscopy analyses of the reproductive system of females, males, and differentiated individuals. The mating experiments produced three behavioral stages, namely, interaction, lateral positioning, and copulation (which did not necessarily occur in this sequence). The hypothesis of a random pure searching mating was corroborated by the lack of male courtship, postcopulatory guarding, and the high aggregation of individuals. Three macroscopic ovarian stages were recorded in adult females: rudimentary, developing and mature. Secondary vitellogenesis begins at the developing stage, producing mature yolk. The male reproductive system is formed by testes and the vasa deferentia (VD), that is divided into three regions: proximal, middle, and distal. The proximal VD has a typhlosole that produces a thin layer of type II secretion around the central spermatozoa mass immersed in a type I secretion. External and adherent type III secretion is produced from the MVD to DVD, and both compound the primordial spermatophore. Potimirim potimirim has a gonochoric reproductive system and mating behavior and its sexual system does not fit into any of the previously described protandric systems.

How Soon Hath Time… A History of Two "Seminal" Publications.

This review documents the history of the two papers written half a century ago that relate to this special issue of Cells. The first, “Sperm competition and its evolutionary consequences in the insects” (Biological Reviews, 1970), stressed that sexual selection continues after ejaculation, resulting in many adaptations (e.g., postcopulatory guarding phases, copulatory plugs, seminal fluid components that modify female reproduction, and optimal ejaculation strategies), an aspect not considered by Darwin in his classic treatise of 1871. Sperm competition has subsequently been studied in many taxa, and post-copulatory sexual selection is now considered an important sequel to Darwinian pre-copulatory sexual selection. The second, “The origin and evolution of gamete dimorphism and the male-female phenomenon” (Journal of Theoretical Biology, 1972) showed how selection, based on gamete competition between individuals, can give rise to anisogamy in an isogamous broadcast spawning ancestor. This theory, which has subsequently been developed in various ways, is argued to form the most powerful explanation of why there are two sexes in most multicellular organisms. Together, the two papers have influenced our general understanding of the evolutionary differentiation of the two forms of gametic cells, and the divergence of sexual strategies between males and females under sexual selection.

Mating and ejaculate allocation pattern in the kelp crab Taliepus dentatus (Decapoda: Epialtidae)

Ejaculate allocation patterns vary widely among species and often depend on characteristics of the individual. However, it is poorly known whether ejaculate allocation patterns change in response to distinct ontogenetic stages (i.e., adolescent vs. adult). The present study aims to describe the mating process and test variations in ejaculate allocation in response to the ontogenetic stage of the Chilean kelp crab Taliepus dentatus (H. Milne Edwards, 1834). Mating consists of the following sequence: (1) pre-copulatory guarding (i.e., male grasping female and/or caging female between legs), (2) copulation in sternum-to-sternum position, and (3) post-copulatory guarding (i.e., male grasping female or carrying her around by the chelae). The mating behavior and ejaculate allocation pattern differed between the two contrasting male ontogenetic stages. Adolescent males generally delivered less ejaculate in repeated short copulations and adult males transferred more ejaculate in a single extended copulation. Ejaculate allocation in adolescents was dependent on female size, but not so in adults. Variation in the ejaculate allocation pattern may be common in species with contrasting male ontogenetic stages, where less competitive males (i.e., adolescents) economize their limited seminal reserves. Conversely, adults which have a greater capacity to produce seminal material (fluids + spermatozoa) may invest greater quantities of seminal material.

Induced mating of newly molted females of orange mud crab, Scylla olivacea (Herbst, 1796), in captivity

Mud crab aquaculture is gaining attention in tropical and sub-tropical regions for its high commercial value. Mating is the fundamental requirement for the natural seed production of mud crabs. The aim of this study was to develop an induced mating technique of orange mud crab, Scylla olivacea in captivity to support sustainable mud crab farming through increasing the supply of hatchery-produced mud crab seeds. Induced mating technique involved the mating of a mature induced soft-shelled female (newly molted) with a mature intermolt male. The mating pairs were selected randomly. This study proved that S. olivacea can copulate without pre-copulation (pairing of male-female before copulation) and post-copulatory guarding by the male. Spermatophores were found in the seminal receptacles of all the copulated females. A mating success of 83.33 ± 5.77% was obtained in captivity using this technique, and can be applied in future breeding and hybridization trials of mud crabs.

Male reproductive strategies in two species of spider crabs, Leurocyclus tuberculosus and Libinia spinosa

Reproductive strategies vary according to season length, individual reproductive traits, and factors associated with the social context such as density and sex ratio of the individuals. The social context predicts the intensity of sexual selection due to its effect on mate choice and intra-sexual competition. Moreover, it exacerbates the costs derived from sexual conflict and allows for the existence of alternative reproductive tactics to counteract such costs. However, these mechanisms are still underexplored in many animal taxa. Majoidea “spider crabs” show a diversity of life history, and behavioral and morphological adaptations for reproduction, which have evolved as an outcome of competition to maximize reproductive success. We aimed to analyze in this study, male reproductive strategies through mating behavior under different social contexts, density of individuals, and males size differences in two species of “spider crabs”, Leurocyclus tuberculosus and Libinia spinosa. The experiments were as follows: one female and one male per aquarium (Experiment 1); a female and three males of similar sizes per aquarium (Experiment 2); and a female and three males of distinct sizes per aquarium (Experiment 3). The experiments showed that mating behavior and duration of mate guarding differ between species and among different social contexts. The presence of males with similar or different sizes showed a relevant different behavior, the female copulated with more than one male when males were similar in size (E2), and copulated only with the largest male when males were different in size (E3). In mate guarding, the shape and the use of the chelipeds had an important role: the male of Leurocyclus tuberculosus grasped the female with the chelipeds and did not fight with other males, but the male of Libinia spinosa surrounded the female with the chelipeds and fought with other males. The longest duration of mate guarding was during precopulatory guarding. Precopulatory guarding was present in all the experiments and its duration did not present significant differences among the experiments. However, in both species, the experiments differ in the duration of postcopulatory guarding until spawning. Gonopod morphology revealed important differences between species and are probably associated with sperm competition. The experiments under distinct social contexts linked to the use and shape of the chelipeds and the morphology of the gonopods, could allow to understand the functional significance of the different reproductive strategies.

Mating behaviour of the leucosiid crabPyrhila pisum(De Haan, 1841)

AbstractMating behaviour of the leucosiid crabPyrhila pisumwas studied in the laboratory and tidal flats in Japan. Most males actively approached females. Males started guarding females without any courtship behaviour (pre-copulatory guarding). Males began copulation within several minutes. The copulation continued for about 1–2 h, following which males began post-copulatory guarding. This guarding lasted from almost 0 to over 3 days, but its duration was generally much longer than that prior to copulation. Release of guarding was not linked to ovulation by females. Long-term rearing experiments revealed that both sexes ofP. pisumcould copulate multiple times with various mates. Developmental stages of the embryos recorded from copulating ovigerous females widely varied; their timing of copulation may not be fixed. In the tidal flat, wandering males frequently contacted with other individuals, but without distinguishing single males, single females and pairs ofP. pisum, orHemigrapsus takanoi. MaleP. pisumcannot recognize female conspecifics, and they approach their mates relying only on vision, without using any attractive cues from females. In cases in which males encountered pairing crabs, they successfully stole the females when the guardians were smaller than the challengers, suggesting that effectiveness of guarding depends on male size. Among the mating pairs, males tended to be larger than females, and the tendency of size-assortative mating was weak or absent. Therefore, the mating behaviour ofP. pisumis not elaborate, although their guarding behaviour may contribute to improve success to some degree.

Mating behaviour of the orange mud crab, Scylla olivacea: The effect of sex ratio and stocking density on mating success

Mud crabs from the genus Scylla have high commercial value and are considered as one of the highly sought luxury seafood items. Thorough understanding about their biology and mating behaviour is vital in providing important information for a sustainable exploitation and future incorporation into the aquaculture industry. The mating process of S. olivacea lasted 82.0±10.8h was divided into four phases: precopulation, molting, copulation, and postcopulation. Courtship displays and fighting were shown by mature males while they were courting females. Precopulatory position lasted for 55.2±10.8h before the pairs disengaged for the female to molt. The molting process was 4.6±0.3h. Copulation (mean duration was 6.6±0.5h) occurred while the female’s exoskeleton was still soft. Postcopulatory guarding lasted for 13.6±0.6h. Separation of the mating pairs indicates the end of postcopulation phase. Mating success percentage was unaffected by sex ratio, but inversely affected by stocking density. Cumulative mortality increased with increasing stocking density and unequal sex ratios. Postcopulatory guarding duration was significantly shorter in treatment with 1 male:2 females ratio and treatment with the lowest stocking density (2 crabs m−2). We proposed rearing of mud crab broodstocks for mating purpose using sex ratio of 1 male:2 females and stocking density of 6 crabs m−2 to maximize output (successful mating pairs) while maintaining low mortality percentage and shorter postcopulatory guarding duration.

Do Males Bite Females' Antennae to Coerce Copulation or to Continue Mate Guarding in Oiceoptoma subrufum (Coleoptera: Silphinae)?

In several species, males frequently immobilize females during copulation. In some species, female immobilization enables males to copulate with unwilling females, while in others, female immobilization prolongs postcopulatory guarding. Male carrion beetles often bite and pull hard on one of the female's antennae during copulatory mounting. Previous descriptive studies have hypothesized that antenna biting is important for postcopulatory guarding in Silphinae. Here, we observed the mating behavior of Oiceoptoma subrufum, to understand the roles of antenna-biting in the initiation and termination of copulation. We compared the success and duration of intromission and pre- and postcopulatory mounting duration between males that did and did not bite female antennae during copulatory mounting. The success and duration of intromission and precopulatory mounting duration were unaffected by antenna biting. However, antenna-biting males mounted females for longer after intromission compared to non-biting males. These results indicate that antenna biting contributes to postcopulatory guarding behavior, not coercive copulation, in O. subrufum.

Sexual Recognition and Mating Behavior of the Populus Longhorned Beetle, Batocera lineolata (Coleoptera: Cerambycidae)

We studied the sexual recognition and mating behavior of B. lineolata by video tracking capture system (EthoVision 3.1) and field observation, in order to get some fundamental information for the effective control of Batocera lineolata Chevrolat (Coleoptera: Cerambycidae) and enrich the reproductive behavior of the insect. Result showed that, during the encountering, the intersection time of two tracks and net relative movements for the female-male group were longer than for the female-female group or the male-male group; while the reaction time was shorter than the latters. A complete mating of B. lineolata included three stages, i.e. (ⅰ) pair-bonding (ⅱ) mating attempt and ejaculation (ⅲ) post-copulatory guarding. The average time of pair-bonding is 2.16 min, and 10.28 min, 5.37 min for mating and post-copulatory guarding, respectively. In mating experiments with different sex ratios, the mating number fluctuated regularly, and it was greatly different in mating number for male or female individuals. The virgin female or male, spent more total ejaculation time than mated ones. Higher mating rates were observed on the host plant than on the open ground. The mating behavior in the field test was similar to results from the laboratory experiment.

Mating Behaviour of Flower Crab, Charybdis Feriata (Linnaeus)

The production of berried females in controlled condition is essential for that knowledge on mating behaviour is very much needed. Hence in the present study mating behaviour of C. feriata was studied. For convenient, the mating behaviour of C. feriata is divided into five phases viz., Pre-moult Guarding (PMG), Moulting (M), Precopulatory guarding (PCG), Mating or Copulation (C) and Post-copulatory Guarding (POCG). Premoult guarding is last for 92.0 hrs. Moulting last for 4.0 hrs. The Pre-copulatory guarding lasted 3.6 hrs. The copulation lasted 7.28 hrs and Post-copulatory guarding lasted 12.12 hrs. The total mating sequence lasts for 119.00 hrs.The spawning of the female took 17.62 days after copulation.

Mating system of the burrowing crab Neohelice granulata (Brachyura: Varunidae) in two contrasting environments: effect of burrow architecture

Few studies conducted in crustaceans have demonstrated how habitat features could shape the mating systems. Here, the burrow of Neohelice granulata was considered as a resource used for mating, and its architecture was characterized in two contrasting study sites: Mar Chiquita Lagoon (MCL), an estuary composed of muddy sediments, and San Antonio Oeste (SAO), a marine bay composed of gravel sediment. Burrow features differed between study sites and occupant gender. Large males constructed burrows with a chamber in MCL and with a widened entrance in SAO, while small males constructed the same narrow burrows as females at both study sites. Field experiments demonstrated that burrows with chambers or widened entries are places used for copulation, although successful post-copulatory guarding was displayed only in those with chambers. The intensity of the agonistic encounters and the success of males in winning resources (burrows/females) also depend on the habitat characteristics. N. granulata shows a resource defense mating system where males employ different mating strategies according to the burrow architecture to ensure mating success.

Comparison of Mating Behavior and Copulation in Male Morphotypes of the Spider Crab Libinia spinosa (Brachyura: Majoidea: Epialtidae)

The mating behavior of the spider crab Libinia spinosa Milne Edwards 1834 was studied in the laboratory. Two male morphotypes as morphometrically immature (MI) with small chelae and morphometrically mature (MM) with large chelae were used in non competitive and competitive mating trials. The liberation of putative hormones by receptive females to attract males was studied. We examined whether male body or cheliped size influence mate acquisition and copulation. The liberation of putative hormones by receptive females could not be demonstrated because males did not behave differently among four treatments exposed to water from 1) ovigerous females, 2) non ovigerous females, 3) males, and 4) a control of water unexposed to crabs. Under non competitive and competitive scenarios, copulation occurred immediately after physical contact between partners, thus a contact pheromone could be involved. The copulatory behavior and the time of copulation were similar between both male morphotypes. In non-competitive mating trials, MI males copulated successfully with females, and immediately after the mating pairs decoupled. By contrast, MM males displayed a post-copulatory guarding behavior that consisted of holding the female with the major cheliped and carrying her around the aquarium. In a competitive scenario, MM males guarded females for several hours by either caging them within the legs, or holding them out of the water when MI males approached. MI males of larger sizes than MM males did not gain mates and avoided agonistic interactions with MM males; thus, large chelae size is a more decisive trait than large body size for mate acquisition.

Behavioral ecology of Heteragrion consors Hagen (Odonata, Megapodagrionidae): a shade-seek Atlantic forest damselfly

Behavioral ecology of Heteragrion consors Hagen (Odonata: Megapodagrionidae): a shade-seek Atlantic forest damselfly. The intensity of the inter and intra-sexual selection can affect male behavioral traits as territorial fidelity and aggressiveness allowing the existence of different strategies. However, its differential success could be affected by environmental - as the diel variation in temperature - and physiological constrains - as the variation in thermoregulatory abilities. In this context, we present a behavioral analysis of Heteragrion consors (Zygoptera, Megapodagrionidae) trying to characterize its mating system, diel activity pattern, temporal budget, territoriality and reproductive biology. These data were obtained based on field observations using the focal individual method and mark-recapture techniques in 120 m of a shaded Atlantic Forest stream in Brazil. The males of this species were territorial, varying in its local fidelity, while the females appear sporadically. Males were perched in the majority of the time, but were also observed in cleaning movements, longitudinal abdominal flexion, wing flexion and sperm transfer during perch. The males presented a perched thermoregulatory behavior related to an exothermic regulation. Foraging and agonistic interactions were rare, but dominate the other behavioral activities. Abdominal movements associated to long lasting copula pointed to the existence of sperm competition in this species. Males performed contact post-copulatory guarding of the females. These observations pointed to a non-resource mating system for this species.

Identification of a female sex pheromone in Carcinus maenas

Despite major progress in our understanding of animal signaling systems, the identification of chemical signals in aquatic organisms is still in its infancy. Exemplary for this is the lack of structural knowledge of crustacean sex pheromones despite their initial description in crabs almost 40 yr ago. We hypothesized that species in which the reproductive event is linked to a short window of mating opportunities centered around the time of ecdysis would be ideal to purify and identify such a cue. Here we present the first identification of a crustacean sex pheromone, the female signal produced by the green crab Carcinus maenas from both conditioned seawater and female urine. We used a bioassay-driven purification scheme combined with a candidate approach focusing on excreted compounds that changed through the course of the female molt cycle. Uridine diphosphate (UDP), a nucleotide accumulated from UDP-N-acetylglucosamine during chitin biosynthesis, is the major component of the female crab pheromone and induced all key characteristics of male sexual behavior in bioassays (i.e. pre- and post-copulatory guarding of the female and initiation of mating) at a threshold of 10–5 M UDP in seawater. The identification of a nucleotide pheromone in crustaceans will enable future studies on signal specificity, biological function, biosynthesis, reception, and evolution as well as focus its potential use in pest control and aquaculture, thus allowing for a major expansion of crustacean chemical and behavioral ecology research that was hindered by the lack of structural knowledge.

The Effect of Inbreeding on Mating Behaviour of West Indian Sweet Potato Weevil Euscepes postfasciatus

When there is an inbreeding depression, mating with a kin individual is generally considered maladaptive behaviour. However, in some conditions, the inclusive fitness benefits from inbreeding may outweigh the costs of inbreeding depression, and thus, inbreeding tolerance is often adaptive. Inbreeding depression and the effect of relatedness on mating behaviour in the West Indian sweet potato weevil Euscepes postfasciatus were examined. No significant inbreeding depression was detected as indicated by body weight and number of progeny emerging from sweet potato roots. Male mating performance (i.e. number of mating occurrences per night) was adversely affected by inbreeding depression, but the effect was low (fitness loss was 6.3%). Although there were no significant differences in latency to mounting, pre-copulatory guarding, copulation and post-copulatory guarding duration between full-sib and non-kin pairs, the copulation rate of full-sib pairs was significantly higher than that of non-kin pairs. These results support the theoretical prediction that when inbreeding depression is weak, copulation with close relative individuals is favoured.

Copulatory pattern and behavior in a semi-captive population of Eld’s deer

Abstract Male copulatory patterns, female multiple copulation and male post-copulatory guarding were studied in Eld’s deer Cervus eldi in Datian National Nature Reserve, China. Mating behavior in 18 females and 11 males from a group of 61 semi-captive Eld’s deer were observed. The majority (55.8%) of copulations occurred between 15:00–19:00 h. The ejaculatory mount was preceded by an average of 5.1 prior mounts. Successful copulation consisted of a single thrust with ejaculation during one intromission, with no lock. This copulatory pattern is classified as pattern No. 15 (no lock, no intravaginal thrusting, single intromission, and multiple ejaculation) and No. 16 (no lock, no intravaginal thrusting, single intromission, and single ejaculation) under Dewsbury’s scheme (1972) and as No. 16 (no lock, no thrusting, single and brief intromission) under Dixson’s classification (1998). Copulation frequency was 1.5 ± 0.9 times for males/ females with the same female/male per day. The duration of the final mount, which included ejaculation, was brief (3.4 ± 1.3 s), and ejaculation usually terminated copulation. Eleven females copulated more than once in this study: three of them copulated with several males (multi-male copulations) and the remainder copulated with a single male (repeated copulations). Our results indicate that some female Eld’s deer may seek multiple copulations to be a strategy to improve the genetic quality of their offspring or to avoid harassment. Post-copulatory guarding of females by males followed all copulations, with dominant males guarding for significantly longer than subordinate males. Dominant males appear to be more effective at post-copulatory guarding than subordinate males. Subordinate males engaged in a quicker pre-copulatory phase to improve their chances of finishing copulation before being forced to accede to dominant males.

Competing for last place: Mating behaviour in a pill-box crab, Halicarcinus cookii (Brachyura: Hymenosomatidae)

The mating strategy of Halicarcinus cookii was investigated to ascertain how males maximised their fitness through mate choice. An intertidal population at Kaikoura, New Zealand, was dominated by mature crabs of both sexes in summer and by immature crabs in the colder months. More than 95% of mature females were ovigerous with early stage and late stage broods found in almost every month, indicating that egg production and larval release is continuous. The operational sex ratio was less than 1 male/female in summer, but often more than 1.0 in the colder months. The gonosomatic index increased along with brood development so that as soon as zoeae were released, the next clutch of eggs was ready to be fertilised. Males searched for receptive females and began pre-copulatory mate guarding without any courtship display. They mated preferentially with late stage or non-ovigerous females: copulation duration was longest for stage 5 females as was post-copulatory guarding (mean 18.3 h). Late stage females were up to 14% of the female population. Mate attraction seems to be the result of an ovarian signal rather than from the developing brood. Manipulation of the sex ratio had effects upon copulation duration and post-copulatory guarding: presence of a rival male increased duration of guarding. Females showed precocious mating in the penultimate instar and were able to lay fertilised eggs after their pubertal moult in the absence of males. H. cookii females have many mates, but males attempt to ensure paternity by preferentially pursuing mature females close to egg laying and by guarding these females after copulation. These behaviours are all elements of a competitive strategy to ensure that a male loses (not wins) the race to copulate because females have a ventral seminal receptacle, giving sperm precedence to the last male to mate. Male mating behaviour is a consequence and evolutionary response to female morphology.

Divergence of courtship and mating behaviors among endemic Hawaiian swordtail crickets

Crickets in the family Gryllidae are well known for their elaborate mating behaviors; however, behavior of the subfamily Trigonidiinae is poorly understood. A large portion of this clade is endemic to Hawaii, including three genera: Trigonidium , Laupala and Prolaupala . The only Hawaiian genus that has been studied is Laupala , which exhibits unusual nuptial feeding in the form of spermless 'micro' spermatophores. Microspermatophore donation has been suggested to increase sperm transfer, constituting a novel mechanism of mating effort in crickets. We observed mating from representatives of each genus to investigate behavioral diversity and reconstruct character state evolution. We found that Prolaupala species produce microspermatophores during a behavioral sequence very similar to Laupala . Trigonidium do not produce microspermatophores, but exhibit other behavioral strategies that likely function to improve insemination, such as prolonged copulation and post-copulatory guarding. We also observed spermatophore and copulation characteristics that were previously considered unique to other gryllids. Behavioral diversity among the Hawaiian fauna reflects the evolutionarily labile nature of gryllid mating behavior and convergence of behavioral strategies in response to sexual selection. Furthermore, our results suggest that microspermatophore donation may be a common mating effort strategy within Trigonidiinae.

Differences in sperm competition and sperm competition avoidance in Drosophila melanogaster

When females mate multiply (polyandry), they create opportunities for competition among males for the fertilization of their eggs. Selection is expected to favour males capable of fathering more progeny under competition or males that can somehow induce females to refrain from multiply mating. Studies in Drosophila show that there is extensive variation in sperm competitive ability within populations and in adaptations to sperm competition between closely related species. Here we test differences in reproductive success when first or last to mate among Drosophila melanogaster males from strains of different geographical origin. Males from a Congo strain were weak sperm competitors when they were first or second to mate with females from an ebony strain. The weak sperm competitive ability of Congo males appears to be related to the quality of their sperm in female storage, but the effect was independent of female genotype. When Congo males mate first, they are capable of inducing higher female fidelity and egg laying than other males. However, egg-laying advantages are female dependant. These results suggest that males can evolve alternative adaptations to maximize their reproductive fitness, such as avoiding sperm competition through postcopulatory guarding (i.e. female fidelity) and inducing higher female reproductive investment (i.e. egg laying). Such adaptations are not necessarily transitive across competing males and females, which highlights the complexity of postmating reproductive adaptations in Drosophila.