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.     

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.     

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.     

Overlapping territories ofPseudosimochromis curvifrons males and other herbivorous cichlid fishes in Lake Tanganyika

Males of the herbivorous cichlid fishPseudosimochromis curvifrons established mating territories 3–10 m in diameter, which included both spawning and feeding sites. Territorial males attacked conspecific males and also other species. Only conspecific males were chased out of the territories. Territorial males attacked other species at the spawning sites while courting or waiting for females and at other sites in their territories while patrolling and foraging. Attacks against herbivorous species were more frequent than against non-herbivores since herbivores were much more abundant. Territories of four abundant herbivorous cichlids largely overlapped the territories ofP. curvifrons males. Symbiotic relationships were not detected between the species. Instead, they were aggressive towards each other but coexisted by segregating feeding sites in the overlapping areas. The aggressive coexistence ofP. curvifrons males with other herbivores may have resulted from the energetic costs of defending their relatively large territories against all food competitors. Interspecific food-resource partitioning may also have facilitated the coexistence.     

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.     

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.     

Monogamous Mating System and Spawning Cycle in the Gobiid Fish, Amblygobius phalaena (Gobiidae)

Reproductive ecology and mating system of the gobiid fish, Amblygobius phalaena, were studied on the coral reef at Sesoko Island, Okinawa, Japan. This goby usually lives in pairs, and maintains territories with several burrows for shelter and spawning. Although a few paired individuals changed partners, most pairs remained together over successive rounds of reproduction. Mate guarding by females appeared to prevent males from mating with other females. Spawnings were synchronous with semilunar periods. Several expected spawnings failed to occur (12%). These may have been caused by the delays in spawning preparation of the paired females or by the disturbance caused by a typhoon. A pair spawned in one of the several burrows within their home ranges. Eggs were deposited on the ceiling of the burrow, and were tended by the paired male for 3–4 days until embryos hatched. The males tended eggs at the expense of their feeding. Aggression toward fishes approaching their burrows were exhibited by the males as well as the females. Because of its low frequency in females, this behavior did not limit their ability to feed.     

Social factors of group spawning as an alternative mating tactic in the territorial males of the threespot wrasse <Emphasis Type="BoldItalic">Halichoeres trimaculatus</Emphasis>

In most labrid fishes, large males with bright terminal phase (TP) coloration normally defend mating territories and pair spawn after following (i.e., courting) solitary females. It has also been reported that the TP males may abandon their territories and participate in group spawning when mating groups of small non-territorial males with drab initial phase (IP) coloration frequently intrude into the territories of TP males. In the similar situation of the present study, however, the territorial TP males of the threespot wrasse, Halichoeres trimaculatus, did not always participate in group spawning but continued pair spawning. Only the TP males that had few opportunities to encounter solitary IP individuals participated in group spawning, frequently following the mating groups of IP individuals. It is therefore suggested that group spawning of the territorial TP males is regarded as a tactic of making the best of the bad situation by the TP males with few opportunities to pair spawn in an area where group spawning dominates.     

Reproductive success in male Japanese minnows,Pseudorasbora parva: observations under experimental conditions

To evaluate the spawning success of male Japanese minnows,Pseudorasbora parva, and female mate choice, spawning behaviour was observed under both artificial and experimental conditions. Larger males had larger territories and greater reproductive success. The body weight of territorial males decreased during the maintenance of territories, while that of non-territorial males increased significantly. When the weight of non-territorial males exceeded that of territorial males, the former began to establish new territories on the substrate, suggesting a conditional strategy by non-territorial males to trade off immediate reproductive success with growth and hence improve future reproductive success. Females chose males with larger body size, probably based on dominance rank rather than the quality (or size) of territory. It was concluded that females choose males of higher dominance rank and that males compete for large territories, both of which play an important part in male reproductive success.     

Chorus organization and male mating behavior in the Japanese pond frog,Rana porosa brevipoda

Male mating behavior of a Japanese pond frog,Rana porosa brevipoda, was observed in an enclosed pond. Males organized chorus aggregation during the night. Within the chorus, most males defended “floating” territories. Territorial males exhibited 2 types of calls: advertisement and encounter. Mating occurred primarily in male territories with female initiation, while most spawning occurred outside of the territories. After spawning, males returned to their territories and resumed display behavior. The mating system of this frog is analogous to the typical lek system. Alternative male mating tactics, including satellite and ambush behavior, were also observed. Satellite and ambush males mated with females through forced clasping.     

Two spawning seasons and mating system of the bastard halibut, Tarphops oligolepis

We investigated the breeding habits of the bastard halibut, Tarphops oligolepis, in the southwest of Kyushu Island, Japan. This fish was found to have two spawning seasons in a year (around July and November); individual fish spawned over the two spawning seasons. During the spawning seasons, males established territories. Home ranges of females overlapped with those of other females and with territories of plural males. The courtship partner changed during a day, and multiple matings among both sexes were observed during a spawning season, suggesting that T. oligolepis bred promiscuously. This is the first report of the mating system among Paralichthyidae. Received: October 18, 2000 / Revised: May 7, 2001 / Accepted: July 9, 2001     

Male spawning success and female choice in the mottled triplefin,Forsterygion varium (Pisces: Tripterygiidae)

A detailed analysis was made of the variation in spawning success among male Forsterygion (э Tripterygion) varium. The aim was to assess whether females were mating selectively and, if so, to examine the basis of that choice. Eggs were laid on small rocks within the males' territories. Females did not distribute eggs randomly among males. Some males guarded as many as 23000 eggs in one breeding season, while others experienced little or no breeding success. Male spawning success was positively correlated with both their size and some characteristics of their territories, namely the amount of spawning substratum and the presence of a large boulder adjacent to the territory. Experimental manipulations indicated that female choice of males was based on these features. Addition of small rocks into the territories of previously unsuccessful males resulted in a significant increase in spawning success. Conversely, spawning success of the most successful males decreased when small rocks were removed from their territories. When successful males were removed, each territory was occupied by small males; however, there was no significant change in the spawning success of these males. This experiment suggested that, although territory quality was important, female mating decisions could also be influenced by male characteristics such as body size.     

The influence of age and experience with conspecifics on territorial behavior inDrosophila melanogaster

Drosophila melanogastermales initiated aggressive behavior toward other males and defended territories several hours after they were able to court and mate females. Males that were 3 days or more posteclosion were more successful at holding territories than younger males. Three-day-old males established territories more readily and escalated more often against territory residents than males that were 1 day old. Residents did not usually force young males from territories until they were a few hours posteclosion. The development of territorial behavior was not affected by familiarity or prior exposure to females. Males held in isolation established territories more quickly and behaved more aggressively than males held in groups. Males that previously held territories were more likely to reestablish them after a disturbance.     

Conflicting Territory Use in Males and Females of a Monogamous Ungulate,the Kirk's Dikdik

In monogamous mammals it is often unclear why males do not defend larger territories to attract more than one female. I investigated the territoriality of the monogamous Kirk's dikdik, Madoqua kirki, a dwarf antelope, in which food resources increase with territory size and some males defend enough resources for more than one female. Yet, all males are paired monogamously. When males were removed from small territories, their female partners spent more time outside of their territories than females in large ones. When females were removed, their male partners almost never left. Pairs in small territories spent more time together than pairs in large ones. Paired males left mostly together with their females, apparently not on their own initiative. Presumably because females in small territories left more often, their males spent more time outside in the female's company than males in large territories. I argue that males in smaller territories can keep better track of their females and that they can effectively reduce their females' time outside. Male intrusion pressure was unrelated to territory size, but it increased in the presence of unguarded females. If large territories decrease the ability to mate guard, and if unguarded females attract competing males, then defending large territories may be uneconomical, even it they could attract more than one female. On the other hand, territories must be large enough to satisfy the requirements of a single female.     

BREEDING COMPETITION IN A PACIFIC SALMON (COHO: ONCORHYNCHUS KISUTCH): MEASURES OF NATURAL AND SEXUAL SELECTION

In the breeding system of Pacific salmon, females compete for oviposition territories, and males compete to fertilize eggs. The natural selection in females and sexual selection in males likely has been responsible for their elaborate breeding morphologies and the dimorphism between the sexes. We quantified direct-selection intensities during breeding on mature coho salmon (Oncorhynchus kisutch), measured for seven phenotypic characters, including three secondary sexual characters. Wild and sea-ranched hatchery coho were used to enhance the range of phenotypes over which selection could be examined. The fish were allowed to breed in experimental arenas where we could quantify components of breeding success as well as estimate overall breeding success. We found that without competition, natural selection acts only on female body size for increased egg production; there is no detectable selection on males for the phenotypic distribution we used. Under competition, the opportunity for selection increased sixfold among females. Natural selection favored female body size and caudal-peduncle (tail) depth. Increased body size meant increased egg production and access to nesting territories. The caudal peduncle, used in burst swimming and nest digging, influenced both successful egg deposition and nest survival. Increasing density increased competition among females, though it did not significantly intensify natural selection on their characters. In males, competition increased the opportunity for selection 52-fold, which was nine times greater than for females. Sexual selection favored male body size and hooked snout length, both characters directly influencing male access to spawning opportunities. Selection on male body size was also affected significantly by breeding density. The ability of large males to control access to spawning females decreased at higher densities reflecting an increase in the operational sex ratio. Further, the relative success of small males, which could sneak access to spawning females, appeared to increase as that of intermediate-sized males decreased. Such disruptive selection may be responsible for the evolution of alternative reproductive tactics in salmon.     

Mating system of the lefteye flounder,Engyprosopon grandisquama

Underwater observations were conducted on the reproductive behavior and mating system of the lefteye flounder,Engyprosopon grandisquama, off Nagashima, southwest of Kyushu Island, Japan. Two types of males were found: large males, which defended territories against other large males, and small males, which did likewise but only against smaller males. Large males established territories which encompassed or ovelapped the home ranges of 1 or 2 cohabitant females. Territories of the small males, in which a smaller female often maintained a home range, overlapped those of large males. Pair spawning occurred around sunset. Mating of large males with cohabitant females was observed 36 times and that of a small male with a smaller female once. Pair formation was assorted by body size, paired males being larger than females in most cases. Thus, inE. grandisquama, gigamous large males were common, small males occurring within the former's erritorial boundaries mating with smaller females.     

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.     

Disruption of Dear Enemy Recognition Among Neighboring Males by Female Leon Springs pupfish, Cyprinodon bovinus

Males defending territories often settle into adjacent areas, sharing a common border that is maintained by a reduced level of aggression known as dear enemy recognition. While social conditions may affect the dear enemy relationship among males, what role females play, if any, is unclear. In a field study of the highly promiscuous Leon Springs pupfish, Cyprinodon bovinus, we asked whether females influenced this relationship of neighbors to their advantage. We observed 16 territorial residents, mapping the precise location of each male's behaviors within its territory. Resident males engaged in less aggression against neighbors compared with intruders, and neighbors intruded less deeply into the residents’ territories than intruders. Despite this locality restriction, neighbors were responsible for as many spawning interruptions as intruders. Females did not spawn randomly in the males’ territories, nor did they spawn near territory centers where aggression was low. Rather, females were more likely to settle and spawn in the outer half of the territories where competition among males was highest. When a neighbor entered a resident's territory to interrupt a spawn, the female was more likely to leave the resident's territory for the neighbor's than to remain. These observations suggest that the female used the intrusion by the neighbor to engage the resident and interrupt the spawn as a measure of this male's quality and that, while neighboring males benefit from the presence of dear enemy recognition, females benefit from its disruption.     

Alternative male mating tactics of the endemic Red Sea parrotfish Scarus ferrugineus

The present study shows that small non‐territorial terminal‐phase males of the rusty parrotfish Scarus ferrugineus are reproductively active and are comparable with initial‐phase males in behaviour, rates of participation during group‐spawning and success in streaking into pair spawning. Large territorial terminal‐phase males defend contiguous territories for several hours during the morning where they pair spawn with initial‐phase females.