Monogamous Fish Research Articles

Females increase reproductive investment when mated to less sexually attractive males in a serially monogamous fish

Reproductive investment decision is an integral part of life-history theory. Differential allocation hypothesis predicts that females should increase investment when mated to high-quality males, conversely, reproductive compensation hypothesis predicts that females should increase investment when mated to low-quality males. Empirical research dominantly focuses on polygamous species and rarely on serially monogamous species. So, the question remains: which hypothesis does serially monogamous species fit? And if it fits reproductive compensation hypothesis, do females only compensate once or continuously for multiple times when mating to low-quality males? Here, we used a serially monogamous fish, the lined seahorse (Hippocampus erectus), to investigate the reproductive investment pattern of females in relation to male quality (measured by sexual attractiveness). We found that females allocated more resources into eggs when they mated to less-sexually-attractive males, indicating the investment pattern of lined seahorse falls in with the prediction of reproductive compensation hypothesis. This finding may imply that the sex role of seahorses is reversed, and female is the side imposed on a greater sexual selection pressure. On this basis, we compared the investment difference of females in two consecutive breeding events when mated to less-sexually-attractive males. We found that females allocated less resources into eggs in the second breeding than in the first one. Females reduced their reproductive compensation in the second breeding, which may be attributed to the improvement in the quality (e.g., paternal care ability) of their mates after the first breeding, thus eliminating the need for them to invest more in the second breeding.

Prosocial and antisocial choices in a monogamous cichlid with biparental care

Human society is cooperative and characterized by spontaneous prosociality. Comparative studies on endotherm vertebrates suggest that social interdependence causes the evolution of proactive prosociality. To test the generality of this hypothesis, we modify a prosocial choice task for application to the convict cichlid, Amatitlania nigrofasciata, a monogamous fish with biparental care and a strong pair bond. We also affirm that male subjects learn to favor prosocial choices when their mates are the recipients in a neighboring tank. When the neighboring tank is empty, males choose randomly. Furthermore, in the absence of their mates, males behave prosocially toward a stranger female. However, if the mate of the subjects is also visible in the third tank, or if a male is a potential recipient, then subjects make antisocial choices. To conclude, fish may show both spontaneous prosocial and antisocial behaviors according to their social relationships with conspecifics and the overall social context.

Pair-bonding influences affective state in a monogamous fish species.

In humans, affective states are a key component in pair-bonding, particularly in the early stage of a relationship. Pairing with a high-quality partner elicits positive affective states which, in turn, validate and reinforce the mate choice. Affective states thus strongly affect pair stability and future reproductive success. We propose generalizing the link between affective states and pair-bonding to encompass other monogamous species exhibiting biparental care, chiefly where the reproductive success of the pair critically depends on the coordination between partners. The convict cichlid Amatitlania siquia is a monogamous fish species that forms long-lasting pairs with strong cooperation between parents for parental care. In this species, we showed that females paired with their non-preferred male had lower reproductive success than those paired with their preferred male. We then transposed the judgement bias paradigm, previously used in other animal species, to assess objectively affective states in fishes. Females that were assigned their non-preferred partner exhibited pessimistic bias, which indicates a negative affective state. By contrast, females that were assigned their preferred partner did not exhibit changes in their affective state. Our results highlight that the influence of pair-bonding on affective states is not human-specific and can also be observed in non-human species.

Effects of social experience on pair bonding in a monogamous fish (Amatitlania nigrofasciata)

For species in which individuals spend at least some time in groups, dominance relationships and various social cues are often important for mate assessment and choice. For pair bonding species, social experiences may affect reproductive decisions in both sexes. We tested whether prior experience in a mixed-sex group and having a higher dominance status coincides with faster pair formation or spawning in a monogamous fish. Individuals having prior experience in mixed-sex groups paired with a novel fish more frequently than fish from same-sex groups. Fish in mixed-sex groups performed more bites and lateral displays. Although spawning occurred infrequently across pairs, dominant fish from mixed-sex groups spawned more than dominant fish from same-sex groups. Otherwise, there were no clear behavioural relationships between treatment group and subsequent pair formation or spawning, nor were behaviours of the paired fishes related to their prior treatment group. We do not know how mixed-sex social experience may have affected the physiology of those individuals, although our results support a reproductive priming effect.

Mismatched partners that achieve postpairing behavioral similarity improve their reproductive success.

Behavioral similarity between partners is likely to promote within-pair compatibility and to result in better reproductive success. Therefore, individuals are expected to choose a partner that is alike in behavioral type. However, mate searching is very costly and does not guarantee finding a matching partner. If mismatched individuals pair, they may benefit from increasing their similarity after pairing. We show in a monogamous fish species-the convict cichlid-that the behavioral similarity between mismatched partners can increase after pairing. This increase resulted from asymmetrical adjustment because only the reactive individual became more alike its proactive partner, whereas the latter did not change its behavior. The mismatched pairs that increased their similarity not only improved their reproductive success but also raised it up to the level of matched pairs. While most studies assume that assortative mating results from mate choice, our study suggests that postpairing adjustment could be an alternative explanation for the high behavioral similarity between partners observed in the field. It also explains why interindividual behavioral differences can be maintained within a given population.

Evidence of multiple paternity and cooperative parental care in the so called monogamous silver arowana Osteoglossum bicirrhosum (Osteoglossiformes: Osteoglossidae)

Monogamy is rare in fishes and is usually associated with elaborate parental care. When parental care is present in fishes, it is usually the male that is responsible, and it is believed that there is a relationship between the high energetic investment and the certainty of paternity (except in the case of sneaker males). Osteoglossum bicirrhosum is considered a monogamous fish, and has particular behavioral traits that permit the study of mating systems and parental care, such as male mouthbrooding. We investigated the genetic relationships of males with the broods found in their oral cavities in Osteoglossum samples collected in a natural environment in the lower Purus river basin, Amazonas, Brazil. Fourteen broods were analyzed for parentage (268 young and 14 adult males) using eight microsatellite loci. The results indicate that eleven broods show a monogamous system. In one brood, however, approximately 50% of the young were genetically compatible with being offspring of another male, and in another two broods, none of the subsampled young were compatible with the genotypes of the brooding male. The result of this first brood may be explained by the extra-parental contribution of a sneaker male, whereas cooperative parental care may explain the result in the other two broods.

The role of sex ratios and resource availability on the pre-mating behavior of a monogamous fish

Convict cichlid fish (Archocentrus nigrofasciatus) are one of the few monogamous species where the female appears more colorful than the male. We examined whether this sexual dimorphism was reflected in a female-biased actual sex ratio (ASR) and whether convict cichlid females would exhibit behavioral traits typified in monogamous males when they possessed the extravagant colors and/or morphology. Our field observations revealed that females are marginally, but not significantly, more abundant than males but they did initiate more intersexual social interactions (i.e. approach behavior) than males. They also showed more intrasexual aggression. Furthermore, males more commonly chased females rather than vice versa. Our laboratory experiment also indicated that differences in intrasexual aggression were not related to differences in the ASR but did appear with the addition of a breeding site. Thus, while intrasexual competition was more frequently observed between females in the field it was probably related to the availability of breeding sites rather than our estimates of the ASR.

High mobility of the protandrous anemonefish Amphiprion frenatus: nonrandom pair formation in limited shelter space

Protandry in anemonefishes has been attributed to random pair formation, which results from their limited mobility after random recruitment to isolated host anemones. The recruitment and movement of the anemonefish Amphiprion frenatus were investigated in relation to its group structure and the spatial distribution of its host anemone on a coral reef, where it inhabits isolated single hosts and interhost movement is rare. A juvenile tended to be recruited to a host from which a former resident(s) had disappeared, indicating that larval recruitment is not random. After mass bleaching of corals during which many hosts died, a quarter of adults moved between hosts on average 42 m in 3 weeks, indicating that their mobility is potentially high. The few migrations under normal conditions were probably due to the low benefit of movements. Even after the movements, a female was much larger than her mate in a host, and a large female tended to pair with a large male. Although body size of females was positively correlated with their host size, that of males was not. It is suggested that the size of a single host does not allow the coexistence of two or more large fish, and the size composition of each pair is affected by the host size. Protandry in the monogamous fish may be attributed to the nonrandom pair formation in the limited space of a host.

How does a parent respond when its mate emphasizes the wrong role? A test using a monogamous fish

The convict cichlid fish, Archocentrus nigrofasciatus, is biparental: the male spends the majority of his time defending the territory and the female spends much of her time close to the offspring. Under natural conditions, this separation into sex-typical roles is somewhat blurred as males do spend some time with the offspring and females do attack intruders. Here we tested whether an individual selects a parental role based on the location (i.e. parental role) of its mate. For example, do females emphasize offspring care because the male is away from the offspring? Will males be more likely to care for the offspring when the female is away from the offspring? We manipulated the location of one parent by placing it in a transparent plastic box, either near the offspring or at the far end of the tank near a clear plastic compartment that held a conspecific male intruder. We tested both male and female parent under the following four conditions: boxed mate near offspring with no intruder present, boxed mate near offspring with intruder present, boxed mate near intruder compartment with no intruder present, and boxed mate near intruder compartment with intruder present. We found that both parents spent more time with the offspring and less time attacking the intruder when the mate was positioned near the offspring and more time away from the offspring and more time attacking the intruder when the mate was near the intruder. Males were more affected by the location of their mates than were females and we concluded that males were attracted both to their mates' location and their offspring while females were mostly attracted to their offspring. Overall, the location of the mate had little effect on the types of aggressive activities used against the intruder. We did find that males increased their aggression towards boxed females when they were positioned far from the offspring, whereas the aggressive behaviour of females towards boxed males when they were positioned near the offspring was ambiguous. We suggest that males in particular enforce the separation of sex-specific parental roles via this aggression.

How Similar is the Coordination of Parental Roles Among Different Pairs? An Examination of a Monogamous Fish

AbstractAlthough most studies on biparental care assume that parents cooperate in raising offspring, few studies have documented how parents coordinate their activities. Using the biparental convict cichlid (Archocentrus nigrofasciatum) we compared the parental behavior of both single (‘widowed’) parents and individuals within pairs during the 5 d when the offspring were in the relatively uniform and stationary wriggler stage. In particular, we were interested in the consistency of day‐to‐day parental activities among single individuals and among individuals within pairs. Single parents showed differences in most parental activities that were consistent from one day to the next. This day‐to‐day consistency remained after an intruder was added and / or the mate was present. Thus, although the social context changed (i.e., presence or absence of mate, presence or absence of an intruder), an individual's consistency remained. The male and female within pairs were significantly correlated in the time spent on most parental activities across experimental pairs. Thus, while individuals within pairs were unique in their performance of a parental activity, paired males and females managed a high degree of correlation (i.e., coordination). In general, pairs were homogeneous in the degree to which males and females were correlated across different parental activities.

Division of labor in the monogamous goby,Valenciennea longipinnis, in relation to burrowing behavior

Feeding and burrowing behavior of the monogamous gobiid fish,Valenciennea longipinnis, were studied on the coral reef at Sesoko Island, Okinawa, Japan. These fish usually live in pairs, the male and female feeding in close proximity to one another upon benthic animals and constructing several burrows cooperatively for purposes of shelter or spawning. Paired females fed more and burrowed less frequently than their mates. Because burrow maintenance was mostly conducted by the latter, the paired females performed work much less frequently than solitary females. Thus, the paired females may be able to allocate more energy toward egg production. The division of labor related to burrowing behavior in this species may be an effective way to increase reproductive success for both sexes. Moreover, the fameles burrowed even less frequently when paired with larger males, probably because burrowing ability may be correlated with mouth size in males. This is a likely reason for the preference of females to mate with larger males.

Male and Female Parental Roles in the Monogamous Cichlid, Tilapia mariae, Introduced in Florida

We documented male and female parental roles of a monogamous fish, the spotted tilapia, Tilapia mariae, in channelized rivers in southern Florida, where this species dominated the fish fauna within 10 years of their introduction. Clearly differentiated parental roles existed between males and females, with females performing nearly all tending of embryos and most tending of free embryos. After young became free-swimming and left the nest, however, males took over primary tending of the school of young while the female patrolled the perimeter of the school and performed nearly all chases directed at predators. Male and female T. mariae also traded off vigilance and feeding, and showed a high degree of intrapair coordination. Experimental removal of one or both parents had major effects on parental behavior and brood survival and integrity. Solitary females took on a parental role intermediate between that of the male and female of a pair. Untended broods were attacked by predators and scattered into aquatic vegetation, and were not observed to reform. Under dense nesting conditions we observed adoption of broods, group rearing of free-swimming young and the presence of non-breeder ‘satellites’ sharing and defending a territory with breeders. This highly complex parental care may have allowed T. mariae to invade fish communities dominated by uniparental centrarchids, as well as allowing them to use disturbed habitats such as channelized rivers that are of poor quality for nesting and rearing offspring.

Female sand gobies prefer good fathers over dominant males

Female preference for males successful in male–male competition is generally assumed to result in mating with high quality males. Here I report results from an experiment disentangling the effects of intra– and intersexual selection in the sand goby, Pomatoschistus minutus , a marine fish that exhibits paternal care. I show that large males are successful in male–male competition, but contrary to what one would expect, dominants are not preferred by females and are not better at taking care of the eggs. Female preference, however, correlated with the subsequent hatching success of the eggs. Thus, female choice selects for good parenting. Hence, direct benefits in the form of superior paternal care can explain female choice in this species, supporting a good parent process of sexual selection. However, choosing on the outcome of male–male competition does not enable females to mate with the ‘best’ males.

The natural history of a monogamous coral-reef fish, Valenciennea strigata (Gobiidae): 1. abundance, growth, survival and predation

The population dynamics of a monogamous coral-reef fish were examined to test hypotheses of recruitment limitation, predation, and postrecruitment processes, and to determine their affects on the mating system. Valenciennea strigata are monogamous gobies that live in sand and rubble zones throughout the Indo-Pacific. Seasonal abundance was recorded in the summer and winter over 2.5 years. A subset of this population was tagged (n = 256) and followed to determine mortality and mobility. Valenciennea strigata were more abundant in summer than in winter, suggesting that a pulse of recruitment in the spring set the maximum population density. Growth rates derived from tagged fish support the hypothesis that recruitment peaked in the spring. Tagged fish experienced 88% mortality within six months; the annual mortality rate approached 100%. Evidence of predation, antipredatory behavior and strong site fidelity implicate predation as the primary source of mortality. Competition for space was not observed between adults, but may affect settlement and recruitment. Despite the lack of adult competition for space, both sexes guarded their mates and courted individuals of the opposite sex. Thus, although population size appears to be determined by nonequilibrium processes, the mating system is affected by competition for mates. Successful mate guarding by both sexes enforced monogamy.

Plasticity in size and age at maturity in a monogamous fish: effect of host coral size and frequency dependence

The number and maximum body size of the gobioid fish, Paragobiodon echinocephalus, increase with the size of its obligate host coral, Stylophora. Only the largest two individuals breed monogamously in each coral head, and the reproductive success of each spawning is positively correlated with body size. In this study, the plasticity in size and age at maturity in P. echinocephalus was examined. We analyzed life history data from gobies 15–20 mm TL (total length) at their initial marking. Gobies found in larger corals were of lower rank in size order and began to breed later at a larger size, usually upon moving to other corals. The size at maturity ranged widely from 17.2 to 36.0 mm TL. After maturation, growth rates decreased. Mortality, however, was not affected by the timing of maturation. The host coral size did not affect the growth and mortality of marked fish, but the mortality rate of juveniles prior to marking appeared to be higher in smaller corals. The estimated lifetime reproductive success did not differ between the gobies inhabiting corals of different size. Thus the plasticity in size and age at maturity in this species may be maintained by frequency-dependent selection in choosing a host coral size that affects an individual’s social status.

Conspecific intruders influence pair formation in a monogamous fish

In aquaria, monogamous Texas cichlid fish ( Cichlasoma cyanoguttatum) formed reproductive pairs significantly more often when another conspecific male (termed ‘intruder’) was visible behind a plexiglass partition. Without an intruder present, males often violently attacked and injured the female. Larger females, although attacked more frequently, were less prone to severe injuries. Pairs did not form when females were larger than males, irrespective of the presence of an intruder.

Parental Investment and Division of Labor in the Midas Cichlid (Cichlasoma citrinellum)

AbstractThe Midas cichlid (Cichlasoma citrinellum) is an aggressive, monogamous fish living in the Great Lakes of Nicaragua. Its breeding success rates are low due to intense competition for breeding sites and high levels of predation on the young.Male Midas cichlids devote a small portion of body weight to gonads and gametes compared with females. Males produce relatively small amounts of sperm perhaps because cichlid fertilization is very efficient and the male has a high certainty of paternity.While pair members invest equal amounts of time in parental care over the course of the breeding cycle, there is a clear division of labor. Males invest more in territorial protection than do females, whereas females provide more nurturance. Both parents are active over the course of the cycle but the male invests more intensely in the early stages of the cycle. About the time the eggs hatch, the burden of care shifts to the female and she continues to invest significantly more than the male over the remainder of the cycle.Females invest much more than do males when tissue investment and parental behavior are combined. Females also assume more of the burden of care as the brood matures. The male is not free to take advantage of this and leave his mate to initiate other broods because two parents are needed to defend the breeding site and brood. Monogamy with biparental care results.

Sex ratio, monogamy and breeding success in the Midas cichlid (Cichlasoma citrinellum)

The Midas cichlid (Cichlasoma citrinellum) is a large, aggressive monogamous fish from the Great Lakes of Nicaragua. It lives in an ecosystem where breeding sites are at a premium and where breeding success can be low. I tested the strength of the pair bond by manipulating the sex ratios in captive groups, using ratios of 1:1, 2:1, 4:1, 1:2 and 1:4 (♂♂:♀♀). No polygamy was seen at any of the ratios. Departure from a ratio of 1:1 decreased breeding success for those pairs that formed. Both sexes appeared to enforce the pair bond but did so in different ways: females attacked males and females equally but males attacked other males significantly more than they did females. These results, coupled with field observations, indicate the Midas cichlid is obligated to monogamy by the demands of competition for breeding sites, the need for two parents to protect the fry and by energetic constraints.

Parental Division of Labor in a Monogamous Fish

Both parents of the monogamous Texas cichlid (Cichlasoma cyanoguttatum) participate in offspring care and territorial defense. These activities are typically synchronized, with and without intruders being present, such that only one parent is away from the offspring. During the egg and wriggler stage, the male spends more time patrolling the territory while the female devotes more time to offspring care. During the fry stage, both parents tend to remain with the offspring. Either sex can rear the offspring in the absence of the mate. With the removal of the mate, the female's activities remain largely unchanged while the male (in the absence of the female) becomes female-like. It appears as if the male adjusts his responses according to the activity of the female.