Reproductive behavior of the halfmoon grouper, <Emphasis Type="Italic">Epinephelus rivulatus</Emphasis>, at Ningaloo Reef,Western Australia

Behaviors associated with spawning by the halfmoon grouper, Epinephelus rivulatus, at Ningaloo Reef, Western Australia, are described from in situ observations made each evening throughout most of a lunar cycle. Spawning occurred after sunset on six consecutive evenings during the full moon period. During this time males were particularly aggressive toward one another and maintained high levels of activity among the gravid females that rested within each of their territories. Spawning occurred when a male swam alongside a responsive female and the pair rose in a tight spiral 1–1.5 m into the water column before releasing gametes and returning to the seabed. Spawning activity was followed by a longer nonspawning period (ca. 20 days), when fewer intraspecific interactions were observed and gamete reserves were replenished. Histological and behavioral evidence suggests that this cycle of spawning and replenishment may occur on a monthly basis. Although individual fish, particularly females, moved into certain areas to spawn, E. rivulatus did not form spawning aggregations as do larger species of grouper.     

Male-biased sex ratios,female promiscuity,and copulatory mate guarding in an aggregating tropical bug,Dysdercus bimaculatus

The ecological and social bases of the mating system of the seed-feeding bug, Dysdercus bimaculatus(Hemiptera: Pyrrhocoridae), were studied in the lab and in aggregations at the host tree, Sterculia apetala(Malvales: Malvaceae), in Panama. On theoretical grounds, two factors are predicted to be of importance in determining the evolution of male mating tactics in Ms species: the operational sex ratio and the probability that undefended females will mate with other males, subjecting the gametes of deserters to sperm competition. Results of a study of a related species suggested that sperm displacement is probably substantial. Adult sex ratios at numerous sites were significantly male biased, and females whose mates were removed remated before oviposition (i. e., sperm utilization). These results predict that a mate defense tactic is likely to be superior to a nondefense tactic. The biological significance of the parameters is supported by observations that captive pairs often remained in copulafor several days, until just before oviposition. However, substantial variation in copulation duration was also observed, and possible causes of this variation are considered. Causes of male biased adult sex ratios were investigated by monitoring demographic changes within a single aggregation over 2 months. Both female juvenile and adult mortality rates were greater than male. In addition, dissections of reproductive adults showed that the flight muscles of females, but not males, had histolyzed, so that female reproduction is physiologically limited to a single site. Greater rates of immigration among both mature and young males suggests that an excess of males may also be found in the populations of bugs that subsequently colonize other host plants, so that female scarcity is typical of aggregations in all stages of development. The evolution of sex-limtied flight muscle histolysis may be explained by greater patchiness of females than males as mating resources, plus a lower energetic benefit/cost ratio of histolysis for males.     

The aggregating behaviour of <Emphasis Type="Italic">Argiope radon</Emphasis>, with special reference to web decorations

The existence of aggregations in taxa that are normally solitary poses questions regarding the costs and benefits of group living. Most orb-web spiders are solitary and are aggressive to conspecifics, but a few species aggregate in large numbers. These spiders benefit by enhancing the prey interception potential, but also suffer costs of increased predation and parasitism. In this study, we report on the natural history characteristics of the orb-web spider, Argiope radon, which not only lives in aggregations but also builds silk decorations. Our results show that A. radon aggregates facultatively and that the main benefit of aggregation that we could identify is enhanced mating potential. We also show that decorations built by A. radon are highly visible to both model prey and predator, and suggest that solitary individuals with longer and more frequent decorations may offset the foraging advantage of being in aggregations.     

Intentional multiple mating by females in a species where sneak fertilization circumvents female choice for parental males

This paper describes how individual female ocellated wrasse Symphodus ocellatus distribute their spawning among males and nests in space and time. It is based on previously collected genetic data of larvae from ten different nests (used to reconstruct half and full‐sibling groupings both within and among nests on multiple days) and behavioural data of marked females across the reproductive season. Both the genetic analyses and behavioural observations confirm that female S. ocellatus intentionally engage in multiple mating, by repeatedly spawning at the same nest on different days and at several different nests (up to 12 spawning events over 3 weeks), leading to mixed paternity among her young. The main benefit of such high and intentional multiple mating is probably insurance against brood failure due to nest predation, desertion or poor paternal care by the male. These findings reveal that even in systems where females attempt to avoid male‐controlled mixed paternity, they may still engage in intentional multiple mating due to these potential benefits.     

Swarming, Delayed Sexual Maturation of Males, and Mating Behavior of Fopius arisanus (Sonan) (Hymenoptera: Braconidae)

Fopius arisanus is unusual among hymenopterous parasitoids in males having an obligatory premating period. We confirmed Hagen's (1953) view that sperm takes several days to migrate from the testes to the seminal vesicles. Males mated for the first time only 4 days after emergence, the time that sperm was first ever recorded in the seminal vesicles. In the field, we studied the sexual maturation of F. arisanus males in relation to their behavior. In general, sexually immature males were found in male-only swarms that persisted over several days in host tree canopies. Mature males were usually found in loose aggregations in the vegetation beneath host trees. Females entered these loose aggregations and were mated, whereas they were generally absent from swarms in the canopy. Swarming is therefore apparently not a primary component of the sexual communication system of the species. We describe, for the first time in F. arisanus, the behavioral sequence that accompanies the intersexual communication that leads to mating. Males probably release a volatile chemical that attracts females from a distance, but we have only circumstantial evidence for this. We also postulate that males may form aggregations to amplify the effects of this distance attractant. In the vicinity of males, females release a pheromone that attracts males, a process we demonstrated with female-baited sticky traps.     

Spawning behaviour of taimen (<Emphasis Type="Italic">Hucho taimen</Emphasis>) from the Uur River,Northern Mongolia

This study presents the first observations of Hucho taimen spawning in the wild based on underwater video recordings. One pair of taimen was monitored during a 19 h period, supplemented with visual observations from two other spawning pairs. We recorded two full spawning events performed in two different locations separated by approximately 30 m. The absence of an established male hierarchy along a nesting female was the most important difference between taimen and other salmonine breeding biology. Taimen spawning, based on our observations, is a single pair event. The male prevented the approach of other males by launching intense attacks that extended for several meters away from the redd. Our data suggests that taimen females, differently from other salmonines, do not cover their eggs immediately after having spawned but rest for a variable number of minutes before covering them.     

Contributions of female oviposition patterns and larval behavior to group defense in conifer sawflies (hymenoptera: diprionidae)

We studied the effects of adult oviposition and larval interactions on the defensive potential of gregarious behavior in conifer sawflies. Aggregation size and distribution initially reflected adult host plant selection and oviposition behavior. The contagious distribution of egg clusters resulted in part from the utilization of individual trees by multiple females, and of single host shoots by several females. Trees with the greates degree of prior defoliation received the most eggs, even though the potential for larval crowding made resource depletion possible. Foliar monoterpene and nitrogen contents explained only a small proportion of variability in female host utilization. Conifer needle architecture restricted the size of larval subgroups within aggregations, and limited the degree of defensive cohesiveness between subgroups. Subgroup turnover was frequent and independent of local food depletion. Risk of predation from wood ants varied with larval aggregation size and predator foraging level. When ant activity was high, large aggregations suffered greater numerical losses, but showed lower per capita predatory risk, than small groups. Results suggest that female oviposition patterns are influenced in part by the defensive benefits gained by offspring in large aggregations. Against ants, dilution effects and defensive synchrony due to gregariousness contribute to the overall antipredator strategy of sawfly larvae.     

Coexistence of congeneric spiny lobsters on coral reefs: differences in conspecific aggregation patterns and their potential antipredator benefits

Den sharing by conspecific spiny lobsters (aggregation) is modulated by chemical attraction but may confer several, not necessarily mutually exclusive, antipredator byproduct benefits: a “guide effect”, which only benefits the individual attracted to a sheltered conspecific; a “dilution effect”, which reduces per-capita risk of predation simply through aggregation; or active “group defense”. Each potential benefit has a different set of predictors (relationships between aggregation and conspecific or predator densities), but conflicting results could suggest the simultaneous operation of more than one benefit. These predictions were tested for coexisting Panulirus guttatus (a reef-obligate) and Panulirus argus (a temporary reef-dweller) using data collected during 11 surveys on fixed sites over a coral reef in Mexico. P. guttatus greatly outnumbered P. argus, but P. argus showed a greater tendency to aggregate. All three benefits of den sharing operated for the more social P. argus, with “group defense” being of the most benefit for larger individuals, and the “guide” and “dilution” effects for smaller individuals recently immigrating into the reef habitat and sharing dens with larger conspecifics. P. guttatus did not display “group defense” and its aggregations appeared to be modulated by the interplay between attraction and aggressive behaviors. This species relied more on solitary crypticity, especially at larger sizes, but appeared to benefit from a “guide effect” at high conspecific densities. In experimental tanks, each species tended to aggregate when tested separately, but when tested jointly, aggregation among P. guttatus was significantly reduced. The experimental results reflect the differential patterns of aggregation between the fore-reef, where P. guttatus dominated, and the back-reef, where coexistence of both species was greater.     

Competition-induced switch in young of the year perch,Perca fluviatilis: an experimental test of resource limitation

Synopis Reproductively developed male fathead minnows, Pimephales promelas, exhibited courtship behaviour in the presence of female conspecifies under laboratory conditions. Male courtship consisted of several distinctive and visually conspicuous behaviours directed toward females, including approach, display, and two contact behaviours, as well as leading behaviour from the female to a suitable spawning site. An ovulated condition in females was not necessary to generate male courtship behaviour; in fact, the amount of courtship exhibited by males may depend inversely on the readiness of females to spawn.     

The Role of Temperature and Embryo Development Time in the Diel Timing of Spawning in a Coral-reef Damselfish with High-frequency Spawning Synchrony

We studied the diel timing of spawning in the demersally spawning Hawaiian damselfish, Dascyllus albisella, from mid-June to late-September 1997 at two small patch reefs in Hawaii. Our objectives were to elucidate daily timing of spawning in relation to water temperature, diel timing of hatching, and short-period spawning synchrony. Spawning occurred every 5–7 days at both reefs, with all spawning on a reef concluded either within a single day (1-day spawning) or within two successive days (2-day spawning). Spawning began in early morning and continued for most of the day. There was a significant, positive linear relationship between mean daily average water temperature (= daily average temperature averaged over the period starting from the day following the last spawning day of the preceding nest cycle till the day before the first spawning day of the current cycle) and peak spawning hour of day, for 1-day spawning, and the first and second days of 2-day spawning at both reefs. The relationship between mean daily average water temperature and peak spawning hour of day was comparable among all spawning-day classes and reefs. Hatching occurred on the fourth day of development throughout the study despite the 26.5–29.1°C change in water temperature during the study period, and hatching was restricted to within two hours after sunset. We propose that D. albisella's peak spawning time is positively correlated with increased water temperature because it maintains the benefits of synchronous spawning within two constraints: the narrow daily period of hatching, and the inverse relationship between water temperature and embryo developmental time.     

Benefits and Costs of Dominance in the Angelfish Centropyge bicolor

Social groups are often structured by dominance hierarchies in which subordinates consistently defer to dominants. High‐ranking individuals benefit by gaining inequitable access to resources, and often achieve higher reproductive success; but may also suffer costs associated with maintaining dominance. We used a large‐scale field study to investigate the benefits and costs of dominance in the angelfish Centropyge bicolor, a sequential hermaphrodite. Each haremic group contains a single linear body size‐based hierarchy with the male being most dominant, followed by several females in descending size order. Compared to their subordinate females, dominant males clearly benefited from disproportionately high spawning frequencies, but bore costs in lower foraging rates and greater aggressive defence of their large territories. Within the female hierarchy, more dominant individuals benefited from higher spawning frequencies and larger home ranges, but displayed neither higher foraging rates nor spawn order priority. However, dominance in females was also linked to aggressiveness, particularly towards immediate subordinates, suggesting that females were using energetically costly aggression to maintain their high rank. We further showed by experimentally removing dominant females that the linear hierarchy was also a social queue, with subordinates growing to inherit higher rank with its attendant benefits and costs when dominants disappeared. We suggest that in C. bicolor, the primary benefit of high rank is increased reproductive success in terms of current spawning frequency and the prospect of inheriting the male position in the near future, which may be traded off against the cost of aggressively defending rank and territory.     

Delayed copulation as a means of female choice by the hermit crab Pagurus filholi

Male hermit crabs perform precopulatory mate-guarding behavior during their reproductive season. As females generally cannot reject guarding attempts by males, male guarding prevents females from inspecting and choosing other male mates. However, as guarding males are often replaced by other males through competition for females during the guarding phase, females may be able to select males by delaying their copulation. To examine the possibility of female choice by hermit crabs, we investigated whether female Pagurus filholi that were being guarded in the field were ready to copulate and spawn. We found that about 30% of females guarded in the field were ready to spawn, indicating that guarded females delayed copulation with their current male. Our results suggest that by delaying copulation females may exploit male–male competition to choose dominant males. However, delaying copulation reduced the spawning potential of females. Hence, there is a trade-off between waiting for the opportunity to mate with a dominant male and decreased spawning success if females exploit male–male competition.     

Variation in polyandry and its fitness consequences among populations of the red flour beetle, <Emphasis Type="Italic">Tribolium castaneum</Emphasis>

Female mating with multiple males in a single reproductive period, or polyandry, is a common phenomenon in animals. In this study we investigated variation in female mating behavior and its fitness consequences among three genetic strains of the red flour beetle, Tribolium castaneum. We found that the extent of polyandry and its fitness consequences varied significantly among the strains. In the first strain PRUZ, females mated multiply but incurred costs of polyandry in the form of reduced offspring production. Females of the second strain, NDG11, mated readily with multiple partners and benefited because polyandry led to higher offspring quality. Finally, TIW1 females were resistant to multiple mating and polyandry resulted in lower offspring production but improved offspring quality. Thus, in the first population we observed only costs of polyandry, in the second strain only benefits of polyandry whereas in the third we detected both costs and benefits of polyandry. Possible explanations for such a pattern are discussed.     

The Reproductive Behavior of Acanthurus nigrofuscus (Forskal) and other Surgeonfishes (Fam. Acanthuridae) off Eilat,Israel (Gulf of Aqaba,Red Sea)

The reproductive behavior of Acanthurus nigrofuscus, a common surgeonfish of the Red Sea, is described for two overlapping populations inhabiting the coral reefs off Eilat, Israel (Gulf of Aqaba). The spectacular daily spawning activities, often involving aggregations of thousands of individuals, as well as the often long distance migrations to and from the spawning grounds by groups in highly organized formations are characterized in detail. Evidence is provided that the precise timing of these various phenomena is controlled by ambient light levels during the late afternoon. Less detailed information is also provided on comparable activities of two other surgeonfishes from the same reefs: Ctenochaetus striatus and Zebrasoma xanthurum. Finally, comparisons are made of reproduction and its associated environmental controls among populations of the same and related species of surgeonfishes at widely distributed locations in the Indo-Pacific.     

Mate choice by males of the hermit crab Pagurus filholi: Do males assess ripeness and/or fecundity of females?

Males of the hermit crab, Pagurusfilholi, often grasp the edges of shells occupied by females and drag them during the mating season. This behavior was experimentally confirmed to be a precopulatory guarding behavior displayed by males for ripe females, and males were found to recognize females which were within about 5 days of spawning. Most theoretical models for mating preference assume the choosing sex (the male in the present case) has complete reproductive information about potential mates, and predict that males will preferably choose more fecund females and/or females that will require less guarding time (i.e. that will spawn sooner) as partners. Several male-choice experiments between two ripe females, both previously guarded by other males, were carried out to examine the above predictions. Males did not prefer females of larger size, higher fecundity or with less time remaining until spawning. These results suggest that males may not have complete information about potential partners, rather that male hermit crabs may adopt a mating strategy of pairing with the first ripe female they encounter. Even with such incomplete mate assessment, males may enhance their reproductive success by recognizing ripe females that will spawn within a given time (about 5 days in the present case).     

Seasonal occurrence and feeding habits of black marlin, <Emphasis Type="Italic">Istiompax indica</Emphasis>, around Yonaguni Island,southwestern Japan

The seasonal occurrence of black marlin, Istiompax indica, around Yonaguni Island, southwestern Japan, was analyzed. Black marlin was abundant from April to July, and the majority of landed fish were female (97%). None of these females was reproductively mature. The condition factor of females increased from April to July. Of 56 black marlin examined, 21 individuals contained 12 prey species; the most important prey species was skipjack tuna, Katsuwonus pelamis, and one neonatal silky shark, Carcharhinus falciformis, was also found. These results indicate that the occurrence of black marlin off Yonaguni Island was associated with feeding and not with spawning.     

The effect of parental quality and malaria infection on nestling performance in the Collared Flycatcher (Ficedula albicollis)

Plumage ornamentation often signals the quality of males and, therefore, female birds may choose elaborately ornamented mates to increase their fitness. Such mate choice may confer both direct and indirect benefits to the offspring. Males with elaborate ornaments may provide good genes, which can result in better nestling growth, survival or resistance against parasitic infections. However, these males may also provision their offspring with more food or food of better quality, resulting in nestlings growing at a higher rate or fledging in better condition. In this study, we examined if there was an association between male ornamentation and malaria infection in Collared Flycatchers (Ficedula albicollis). We also investigated offspring performance in relation to malaria infection in the parents and the quality of the genetic and rearing fathers (assessed by the size of two secondary sexual characters) under simulated good and bad conditions (using brood size manipulation). We found that secondary sexual characters did not signal the ability of males to avoid parasitic infections, and malaria infection in the genetic and the rearing parents had no effect on nestling growth and fledging size. Our results do show, however, that it may be beneficial for the females to mate with males with a large forehead patch because wing feathers of nestlings reared by large-patched males grew at a higher rate. Fast feather growth can result in earlier fledging which, in turn, could improve nestling survival in highly variable environments or under strong nest predation.     

Female choice for heterozygous mates changes along successive matings in a lizard

Female mate choice and female multiple mating are major focuses of studies on sexual selection. In a multiple mating context, the benefits of mate choice can change along successive matings, and female choice would be expected to change accordingly. We investigated sequential female mate choice in the moderately polyandrous common lizard (Zootoca vivipara, synonym Lacerta vivipara). Along successive mating opportunities, we found that females were relatively unselective for the first mate, but accepted males of higher heterozygosity for subsequent mating, consistent with the trade-up choice hypothesis. We discuss the evidence of trade-up mate choice in squamates and generally trade-up for mate heterozygosity in order to motivate new studies to fill gaps on these questions.     

Fitness effects of Wolbachia and Spiroplasma in Drosophila melanogaster

Maternally inherited endosymbionts that manipulate the reproduction of their insect host are very common. Aside from the reproductive manipulation they produce, the fitness of these symbionts depends in part on the direct impact they have on the female host. Although this parameter has commonly been investigated for single infections, it has much more rarely been established in dual infections. We here establish the direct effect of infection with two different symbionts exhibiting different reproductive manipulation phenotypes, both alone and in combination, in the fruit fly Drosophila melanogaster. This species carries a cytoplasmic incompatibility inducing Wolbachia and a male-killing Spiroplasma, occurring as single or double (co-) infections in natural populations. We assessed direct fitness effects of these bacteria on their host, by comparing larval competitiveness and adult fecundity of uninfected, Wolbachia, Spiroplasma and Wolbachia–Spiroplasma co-infected females. We found no effect of infection status on the fitness of females for both estimates, that is, no evidence of any benefits or costs to either single or co-infection. This leads to the conclusion that both bacteria probably have other sources of benefits to persist in D. melanogaster populations, either by means of their reproductive manipulations (fitness compensation from male death in Spiroplasma infection and cytoplasmic incompatibility in Wolbachia infection) or by positive fitness interactions on other fitness components.     

The influence of visibility and escape ability on sex-specific susceptibility to fish predation in Eudiaptomus gracilis (Copepoda,Crustacea)

The susceptibility to fish predation in males, ovigerous, and non-ovigerous females of the freshwater copepod Eudiaptomus gracilis is investigated in the laboratory by direct observation of the predation sequence of zebrafish, and by studying mortality when confronted with zebrafish or roach. Ovigerous females had the highest encounter rate indicating that the highly visible egg-clutch is a major determinant of their susceptibility. Males were least successful in escaping, the main reason being their inability or disinclination to react fast enough when attacked. This difference in escape reaction may have evolved because of sex-specific requirements in mate encounter and mate location. Ovigerous females and males had higher mortality than non-ovigerous females in all experiments while ovigerous mortality was higher than male mortality only in the zebrafish experiments. Neither experiment showed any difference in male and overall female mortality but as a consequence of the abrupt change in susceptibility between the ovigerous and non-ovigerous condition, it follows that sex-specific mortality rates may be dependent on the reproductive condition within diaptomid populations. A consequence of the sex-specific difference in escape ability is that the sex-specific mortality may be influenced by variation in the attack efficiency within and among predator populations.