Bigamy or monogamy with maternal egg care in the triggerfish,Sufflamen chrysopterus

Reproductive behavior and mating systems of the triggerfish,Sufflamen chrysopterus (Balistidae), were studied on the fringing reef of Sesoko Island, Okinawa. Both males and females maintained territories against consexual adults, feeding on benthic animals within their own territories. Each male territory overlapped one or two female territories, with mating occurring between the cohabitants. The monogamous males were smaller and foraged more frequently than the bigamous ones, suggesting that the former allocated more energy to growth rather than to improving reproductive success. Pair spawning occurred around sunrise, females only taking care of the demersal eggs until hatching, which occurred around sunset of the same day. On spawning days females foraged less frequently than usual, but as frequently as males. Females spawned at intervals of 5–7 days, usually shifting sites within their territories. Thus both feeding and spawning sites were available for females within their territories, providing males with the opportunity to monopolize females by defending their territories.     

Spawning Behavior and Biparental Egg Care of the Crosshatch Triggerfish, Xanthichthys mento (Balistidae)

Reproductive ecology of the crosshatch triggerfish, Xanthichthys mento (Balistidae) was studied at Hachijojima, Izu Islands, Japan. Males established territories and repeatedly chased females passing nearby. There were 1–3 females in each male's territory before spawning and during egg care. This species spawned in pairs on the sandy bottom. Eggs were scattered and attached to sand particles. Females care for the eggs by blowing water on them and guarding them against intruders, while males helped in guarding. Thus, biparental egg care was observed for 2 days until hatching. Both the males and females disappeared from the territories after the egg care. The reproductive ecology of this species is compared with that of other balistids and the unique features of X. mento are described.     

Social organization and spawning in the Atlantic sharpnose puffer,Canthigaster rostrata (Tetraodontidae)

Synopsis Social organization and spawning in the sharpnose pufferCanthigaster rostrataere studied on a reef in the San Blas Islands, Panama. Sexes were dimorphic. In mixed coral and rubble habitat, females defended territories against other females and small males. From one to six female territories were included within the territories of certain large males. These haremic males visited their females and patrolled their territories throughout the day. Smaller, non-haremic males occupied territories or home ranges within or adjacent to those of haremic males or were wanderers. Spawning between a haremic male and a territorial female occurred within the female's territory. The female prepared an algal nest into which demersal eggs were deposited. There was no parental care. Eggs were spherical, translucent, and measured approximately 0.66 mm in diameter. Larvae were about 1.4 mm TL and closely resembled those of other species ofCanthigaster.     

Mating patterns of female Leon Springs pupfish Cyprinodon bovinus

In a field study of Leon Springs pupfish Cyprinodon bovinus, two questions about female promiscuity were investigated. First, were females selective in the males with whom they spawned or were they unselective, spawning randomly among males? Second, how promiscuous were the females, i.e. with how many males did they spawn? If simply spawning with many males maximized a female's reproductive success, then females might be expected to spawn randomly with as many males as possible. Alternatively, if females were selective but engaged in multiple mating, they would limit their spawning to preferred males. In the only wild population of this endangered fish, breeding males defend closely associated territories in the shallow margins of a single desert pool. No territories were observed elsewhere in the pool. Therefore, all territorial males were present simultaneously and females could survey all of them, depositing any number of eggs with one, a few or many males. Rather than spawning randomly, females surveyed many males first, visited relatively few males and ultimately spawned with a small fraction of those available males. With increasing numbers of spawns, however, females increased the number of different mates with whom they spawned. Thus, females showed a bet‐hedging tactic of having a narrow mate preference while also laying eggs in the territories of other males, possibly to reduce egg predation and to avoid inbreeding.     

Mating systems of two midwater-spawning cichlids,Cyprichromis microlepidotus andParacyprichromis brieni,in Lake Tanganyika

The breeding habits of 2 maternal mouthbrooding cichlids,Cyprichromis microlepidotus andParacyprichromis brieni, were investigated in Lake Tanganyika. Although spawning on the substrate in the male's mating territory is prevalent in maternal mouthbrooders, bothC. microlepidotus andP. brieni spawned in the water column. MaleC. microlepidotus established their mating territories in the open water column, while maleP. brieni did so around fixed spawning sites near a vertical rock surface. In both species, females visited male mating territories, departing soon after spawning and collecting the eggs. Sneaking, which was observed only inP. brieni, may be attributed to the presence of refuges for sneakers in this species. FemaleC. microlepidotus deposited their entire clutch of about 9 eggs in one male territory. In contrast, femaleP. brieni divided their clutch of about 11 eggs among several males. After the final egg-release, femaleC. microlepidotus repeatedly approached their mate, with the mouth near the abdomen of the latter (nuzzling), but femaleP. brieni often departed without nuzzling. Males may eject sperm during nuzzling to fertilize eggs inside the female's mouth. However, maleP. brieni is also known to eject sperm near spawning females when the females are not nuzzling. Such behavior seems to be a male countermeasure against female mate infidelity, because males could not ensure paternity of eggs by ejecting sperm only during female nuzzling.     

Two alternative female tactics in the polygynous mating system of the threadsail filefish,Stephanolepis cirrhifer (Monacanthidae)

Reproductive behavior of the threadsail filefishStephanolepis cirrhifer was studied at Kashiwajima, southern Shikoku, Japan. This species spawned in pairs on the sandy bottom, the eggs being scattered over an area of about 15 cm in diameter and attached to sand particles. After spawning, males departed immediately, while the females remained at the site to guard the eggs for a few minutes. Thereafter the eggs were left unguarded for three days until hatching. Females spawned only once daily, whereas males mated with multiple females in succession. The reproductive males established territories, in which 1–4 resident females defended smaller territories from each other. The harem size changed according to some ecological conditions, such as population density. Moreover, the males also mated with visiting non-resident females. Thus, the two alternative tactics of females resulted in two mating patterns, haremic polygyny and female visiting of male territories, in a single population ofS. cirrhifer.     

Reproductive biology and female parental care in the cockscomb prickleback,Anoplarchus purpurescens (Pisces: Stichaeidae)

Synopsis Reproduction and parental care in the cockscomb prickleback, a Pacific coast intertidal fish, were examined using a combination of field and laboratory observations. The sexes were dimorphic, particularly during the breeding season, and males competed with other males for access to females. Males performed lateral and spasm displays. In the wild, the breeding season extended from January to March on cobblestone beaches. Assortative mating was positive with respect to body size. Females exhibited solitary parental care of the eggs. Each female coiled around, guarded and fanned a single egg mass that likely represented her total reproductive effort for the year. The number of eggs in the mass increased linearly with female size (weight or length). Males did not remain after spawning. Aquarium observations revealed that males spawn with more than one female given the opportunity. It is not known whether this occurs in the wild. Incubation to hatching took 29 days. Upon hatching, the young swam towards the surface. Parental care did not extend beyond hatching.     

Why egg-caring males of Isaza (<Emphasis Type="Italic">Gymnogobius isaza</Emphasis>, Gobiidae) refuse additional females: preliminary field observations

Like many other gobies, males of the Isaza goby, Gymnogobius isaza endemic to Lake Biwa, Japan, conduct parental care of eggs at nests, and females are likely to choose mates while visiting nests. The reproductive strategy should induce polygyny, but Isaza males never accept additional females in one breeding cycle. Sampling data of broods indicated that the egg mass areas were much smaller than the nest sizes, suggesting that nest size is not the limiting factor in obtaining further eggs from additional females. The brood size greatly decreased as the duration of care progressed. Few individuals including caring males ate eggs, and heterospecific egg predators were rarely observed. Sixty percent of egg masses at the middle stages of egg development were infected with aquatic fungi, some being covered with a fungus mat that drastically reduced survivorship. Infected egg masses contained more eggs than non-infected ones at the same stage, indicating that large egg masses are prone to be frequently destroyed by fungi. It is likely that the activity of parental males is lowered during the long care periods at low water temperature in early spring. Such lowered activity of caring males might be responsible for infections in large broods that would have needed more care. We propose the hypothesis that male rejection of additional females may be related to optimal brood size, which will be less susceptible to fungus infection and produce more hatching young than otherwise. This hypothesis will explain not only male avoidance of additional females but also some unique reproductive behaviors of this fish such as some females spawning of a portion of of the mature eggs in one nest.     

Reproductive behavior of the territorial herbivoreStegastes nigricans (Pisces: Pomacentridae) in relation to colony formation

Reproductive behavior of the herbivorous damselfishStegastes nigricans was studied. Both males and females held individual feeding territories, which were distributed contiguously and formed colonies. Spawning season was from June to September. Females visited males' territories and spawned eggs on the algal nest. Males tended eggs until hatching but exhibited less care taking behavior than other damselfishes. The mating system was promiscuous in that both males and females spawn with several mates, even within a single day. However, only 1 female was accepted in the nest at a time. The restriction of the number of mates in the nest may be an adptation to prevent the sneaking which was often conducted by other males of the same colony, and may also be avoidance of disturbing the spawning female. Most spawnings were done among members of the same colony and inter-colonial spawnings were rare (27 cases of 333 spawnings observed). The results of this study suggest that colonial distribution ofS. nigricans may bring several benefits in reproduction to the colony members (e.g. easy mate findings within fellow colony members), but also seems to bring costs (e.g. restriction of number of mates).     

Female Mate Preference for Males Having Long and Symmetric Fins in the Bower-holding Cichlid Cyathopharynx furcifer

Female mate preference in a bower-holding cichlid, Cyathopharynx furcifer, was studied in Lake Tanganyika. Most males held territories with crater-shaped bowers in sand, but some males held territories without bowers. Territories were distributed adjacently and females visited them to spawn. After engaging in circling behaviour with the male, a female deposited eggs in the bower. Soon after spawning, the female picked the eggs up into her mouth and brooded them in places away from male territories. Female mate choice appeared to follow three steps: 1) females visited only bower-holding male territories, and more frequently visited territories of males that performed courtship displays at a higher frequency and had longer pelvic fins; 2) females preferred to start circling with males having longer and more symmetrical pelvic fins; 3) females chose males with more symmetrical pelvic fins as their mates. Less than 7% of females that visited male territories spawned eggs in the bowers. In contrast to other bower-holding species, bower size did not correlate with male reproductive success in C. furcifer. Bowers may therefore be essential as spawning sites or may function as a species recognition character for females. Female choice may be dependent instead on males having long and symmetrical pelvic fins apparent during the circling behaviour carried out in the bowers.     

Components of care: are they honest signals of parental care quality?

It has been argued that male parental care provides direct benefits to females and therefore should be under sexual selection. Given this, we expect signals that honestly indicate the quality of care to be favoured by selection. One such potential signal is care itself. Fish have several features that make them excellent model systems for studying the evolution and dynamics of parental care. We use the flagfish, Jordanella floridae , as a model to evaluate these general ideas. Males of this species guard, clean and fan empty nests and then eggs. Females prefer males that fan more (1) before spawning and (2) when eggs are newly received. When single males and females were paired, males that fanned and visited their nests more prior to spawning were more likely to be mated. Furthermore, among successful males, rates of fanning in the first day after spawning were correlated with the number of eggs received in the future (but not current egg numbers). We then considered whether these two putative signals were correlated and whether males that fan more in these contexts actually have higher egg survivorship. We found no correlation between nest fanning rates before and after spawning and neither 'signal' was predictive of variation in egg survivorship among mated males. We further considered whether pre‐spawning fanning rates were predictive of hatching success in an experiment in which single males were allowed to establish nests and provided eggs. We found little evidence that fanning is an honest signal of care quality and discuss alternative explanations. In particular, we discuss patterns of care elaboration in light of our results.     

Unravelling the evolution of complex reproductive traits with phenotypic engineering

The social dynamics surrounding courtship, mating and parental care are complex enough when just a single male and female are involved, but for species that employ multiple strategies for achieving fertilization success, the network of interactions among rivals, allies and suitors can be utterly complicated. Such is the case in the ocellated wrasse, Symphodus ocellatus, in which males adopt one of three mating strategies. The large, colourful “nesting males” court females, defend territories and care for fertilized eggs until they hatch. The smaller “satellite males” help the nesting males court females and guard against the third morph, the “sneaker males”, which sneak in when a nesting male is spawning with a female and surreptitiously release sperm. Sneaker males perform no courtship displays nor defend territories, so their reproductive investment is devoted entirely to sperm production. And these alternative male strategies work: 100% of nests contain some eggs fertilized by sneaker and satellite males, despite the fact that parental care is solely the responsibility of nesting males In this issue of Molecular Ecology, work to untangle the proximate mechanisms regulating the reproductive physiology of nesting males and their behaviour towards other males, which impacts the entire social network. Moreover, they describe how variation in neuroendocrine regulation can give rise to variation in reproductive traits, upon which sexual selection can act.     

Parental care and mating systems of cichlid fishes in Lake Tanganyika: a preliminary field survey

Reproductive ecology and ethology of 52 cichlid fishes were studied along the shore of Myako, east-middle coast of Lake Tanganyika. Seventeen species were substrate-brooders (guarders), 31 were mouthbrooders, and the remaining 4 were intermediate, performing prolonged biparental guarding of fry after mouthbrooding. Among the substrate-brooders maternal care (and polygyny) was seen about as frequently as biparental care. In most of the mouthbrooders only females took care of the brood, but in 3 species eggs and small larvae were mouthbrooded by females and larger fry by males. In most of the maternal mouthbrooders males defended mating territories which females visited to spawn. The mating system differed from lekking in that there was no concentration of territories and males fed within them. In the remaining maternal mouthbrooders males and overlapping home ranges and only temporarily defended courtship sites in each bout of spawning. Brood size, egg size, breeding site, and sexual differences in body size and color are described. The relationship between parentalcare patterns and mating systems within the family Cichlidae are discussed.     

Effect of clutch size on male egg-fanning behavior and hatching success in the goby, Eviota prasina (Klunzinger)

In fish that exhibit paternal care, the females often choose their mates on the basis of male traits that are indicative of the parental ability of the males. In a marine goby, Eviota prasina, males tend their eggs within their nests until hatching, and females prefer males that have longer dorsal fins and exhibit courtship behavior with a higher frequency as their mates. In order to clarify the relationship between these sexually selected traits and the parental ability of males of E. prasina, the factors affecting the hatching success of eggs within male nests and the male parental care behavior were examined in an aquarium experiment. Females spawned their eggs in male nests and the clutch size of females showed a high individual variation (range = 88-833 eggs). The hatching success of eggs within male nests showed a positive correlation with the time spent by males in fanning eggs and the clutch size. In contrast to the prediction, however, the hatching success did not show a significant correlation with the sexually selected traits, i.e., the male dorsal fin length and the frequency of courtship displays. Moreover, multiple regression analysis indicated that the time spent by the males in fanning was the most important factor affecting the survival rate of the eggs. The time spent by males in fanning behavior was influenced by the clutch size within their nests; the fanning behavior of males occurred with a higher frequency when they tended larger clutches. Males are required to invest a greater effort in egg-tending behavior to achieve a higher hatching success when they receive larger clutches, probably due to the greater reward for their parental behavior. Based on their mate choice, females may obtain other benefits such as high quality offspring.     

Spawning and biparental egg-care in a temperate filefish,Paramonacanthus japonicus (Monacanthidae)

Synopsis Reproductive habits of a temperate filefish, Paramonacanthus japonicus, were studied on a rocky reef at Tsuyazaki, Fukuoka, Japan, from 1989 through 1990. Males had territories of 30–70m² and defended them from conspecific males and potential egg predators such as another filefish, Stephanolepis cirrhifer. Egg masses were found on the sandy bottom in male territories. Individual discrimination of males and females occurring in three male territories revealed that males and females stayed in stable pairs during one month of observation in 1989. In these stable pairs, males fed only within their territories, but females occasionally foraged outside. The occurrence of egg masses within male territories and biparental egg care showed that fish were reproducing as monogamous pairs. Contrary to this, males tagged in 1990 changed their territories after the disappearance of females, and males and females mated polygamously. Spawning was observed only four times during the study period, between 1633 and 1754h. Prior to spawning, the female prepared a spawning bed on the sandy bottom. The male nuzzled the female and the pair spawned, touching their gonopores on the spawning bed. Spawning was very quick and took only 1–3 seconds. The adhesive eggs were spherical with a diameter of 0.56 mm. They were mixed with sand particles and formed a doughnut-shaped mass of about 4 cm in diameter. One egg mass contained 3300–3800 embryos of similar developmental stage, which hatched 2–3 days later. P. japonicus appears to be monogamous but may also practice polygamy when pair-bonds are unstable.     

Reproductive behavior and mate fidelity in the monogamous goby,Valenciennea longipinnis

Reproductive behavior and mate fidelity of the gobiid fish,Valenciennea longipinnis, were studied on the coral reef at Sesoko Island, Okinawa, Japan. These fish usually live in pairs, not only foraging together for benthic animals in sandy areas, but also constructing several burrows within their home range. Before spawning, both fish, although mainly the male, constructed a mound, piling up dead-coral fragments, pebbles, shells, sand and algae onto one of the burrows. After spawning an egg mass on the ceiling of the burrow, the female stayed outside and continued the construction and maintenance of the mound for 3–5 days until hatching, while the male tended the eggs inside. Mate guarding of females seemed to prevent males from monopolizing several females. Although some pairs showed mate fidelity through several spawnings, more than half of the pairs broke up after only one spawning. The pair bond was broken by mate desertion and the disappearance of each sex. Both sexes preferred larger spawning partners; larger females spawned more eggs and larger males provided better egg care. Mate desertion occurred when larger potential mates, relative to the current partner, became available. The frequency of solitary individuals was higher in males than in females, resulting in females deserting their mates more often than males. Two factors seem to have facilitated mate desertion: (1) occurrence of size mis-matched pairing and (2) overlapping home ranges.     

Vigorously courting male sticklebacks are poor fathers

Male threespine sticklebacks (Gasterosteus aculeatus) that are unsuccessful at hatching eggs may provide insufficient parental care or have unhealthy or unfertilized eggs. In this study, most males that were unsuccessful at hatching eggs appeared to be poor fathers because they depleted their energy reserves by vigorously courting females and by maintaining intense nuptial coloration during courtship and parental care, leading to reduced fanning of the eggs. Unsuccessful males differed from successful males by investing more in obtaining a clutch of eggs and less in the eggs once they had them, suggesting a trade-off between investing in courtship and investing in paternal care. Received: 14 August 1998 / Received in revised form: 26 August 1999 / Accepted: 6 September 1999     

Parental investment of male two-spotted goby, Gobiusculus flavescens (Fabricius)

The trade-off between parental care and feeding was studied in the male two-spotted goby (Gobiusculus flavescens F.). Two temperatures, 8.5 degrees C and 13.0 degrees C, were used, with five replicates at each temperature, in order to determine whether temperature influenced parental behaviour. In each replicate, two males and four females were introduced to an aquarium, where the males chose between two nests and courted the females. In each replicate, one male spawned. After spawning, the males guarded the eggs until hatching. The guarding males' behaviour was recorded with a video camera twice a day (15 min each time), once before and once after they were fed. The male's condition (c-factor) was calculated at the start of the experiment and after egg hatching. The eggs were spawned in an artificial nest (half of a PVC tube), and attached to the nest in a single layer. The areas with eggs (representing brood size) were marked after spawning and the fry counted after hatching (which was used to calculate area hatched). Numbers of prey eaten (plankton) and number of aggressive encounters between the guarding male and the other fishes were recorded. Time spent in the nest and time used on fertilisation, fanning and cleaning were estimated and related to egg age, brood size, hatching success, temperature and food availability (no food or food).The results showed that feeding (expected to influence future reproduction) decreased and parental expenditure (current reproduction) increased, as the eggs developed (became closer to independence). Parental expenditure was significantly higher at 13.0 degrees C than at 8.5 degrees C, presumably due to higher oxygen demands by the eggs, and a greater risk of egg-infections. The c-factor of the males guarding eggs decreased over time, in contrast to the non-guarding males' c-factor. Guarding males' aggressiveness decreased as the eggs got older, but increased just before hatching. A possible explanation for this could be the decreasing intrusion by the non-guarding male and females caused by high aggressive behaviour by the guarding male early in the brood cycle. The exploitation of the nest (percentage of total nest area covered by eggs) seemed to determine the amount of parental expenditure and loss of condition, while brood size (area of eggs) had no effect.     

Parental care in a monogamous mouthbrooding cichlidXenotilapia flavipinnis in Lake Tanganyika

Breeding pairs ofXenotilapia flavipinnis held their territories on the sandy bottom and repeated several breeding cycles. Females mouthbrooded the eggs and early larvae but afterward males took over the mouthbrooding role. When the young became free swimming, they were guarded by both parents and remained in the spawning territory. Males played a leading role in the guarding, while females were more active in foraging during the guarding period. It was concluded that males’ active participation in the parental care could accelerate the gonadal recovery of females and consequently could maximize the fecundity of serially monogamous pairs.     

Body mass dynamics during incubation and duration of parental care in Pacific Dunlins Calidris alpina pacifica: a test of the differential parental capacity hypothesis

Breeding is energetically expensive and individuals face a trade‐off between current and future breeding investment. Due to their production of large eggs, female birds are thought to have substantially higher initial energetic investments than males, which decrease the female's offspring rearing capacity. The differential parental capacity hypothesis argues that this large initial investment limits the ability of female shorebirds to provide extended parental care, which can ultimately lead to offspring desertion. This hypothesis predicts that (1) during early incubation females will be in poorer condition than males, (2) both sexes will lose condition during incubation, but the decline in females will be slower than the decline in males and (3) there will be a positive relationship between female condition and the duration of maternal brood care. These predictions were tested using data on body mass adjusted for body size (as a proxy for condition) and parental care from Pacific Dunlins Calidris alpina pacifica nesting on the Yukon Kuskokwim Delta, Alaska. None of the predictions received support: females were heavier than males in early incubation, the overall pattern during incubation was that males gained mass while female mass remained relatively constant, and there was no relationship between female mass and maternal brood care duration. These results suggest that the factors influencing parental care decisions are more complex than a parent simply caring until it is physiologically unable to do so.