The social and mating system of the maternal mouthbrooderTropheus moorii (Cichlidae) in Lake Tanganyika

Territorial behaviour, reproduction and migration of the epilithic algal eater,Tropheus moorii, were investigated in Lake Tanganyika, Africa. Adults of both sexes had individual feeding territories which adjointed each other. Males, who occupied higher rocks than females, usually stayed at the same sites for more than 5 months. Females left their territories to pair with males in the males’ territories. Paired females actively foraged under the protection of their mates for up to 3 weeks prior to spawning. After spawning, females usually settled in a site unoccupied by territory-holders to mouthbrood the offspring for a month. An examination of the ovaries and a removal experiment of dominant males suggest that females cannot attain fully mature ovaries in their own territories and choose males whose territories can provide enough food to satisfy their nutritive demand. The evolution of a number of local colour morphs in this fish is briefly discussed in relation to social selection.     

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.     

Evolution of Female Egg Care in Haremic Triggerfish,Rhinecanthus aculeatus

Paternal care is predominant among telcost fishes with external fertilization. This study describes maternal care in a haremic coral-reef fish and discusses the possible factors leading to its evolution. Both sexes of the triggerfish Rhinecanthus aculeatus (Balistidae) maintained territories; some individuals for more than 8 years. Each male's territory overlapped 2-3 female territories. Pair-spawning occurred around sunrise. Only females cared for the demersal eggs until hatching, which occurred just after sunset on the day of the spawning. No predation was observed on eggs under the maternal care, but experimental removal of parental females decreased the hatching rate to nearly zero. Egg-guarding females foraged as frequently as males, but less than half of non-spawning days. Spawning occurred only in the periods of about 1 wk around the new or full moon, and individual females spawned up to three times in each period. Thus, the maternal care did not significantly affect the duration of the females' spawning intervals, while males would suffer mate loss if they performed parental care. In this situation, maternal care should be the evolutionarily stable strategy. Evolutionary transition from no care to maternal care and then to biparental care is suggested in the Balistidae.     

Spawning behavior and haremic mating system in the corallivorous butterflyfish,Chaetodon trifascialis, at Kuroshima Island, Okinawa

Territorial and spawning behavior ofChaetodon trifascialis were investigated on a small patch of reef at Kuroshima Island, Okinawa, Japan. Three males and 8 females inhabited the reef, each individual defending a territory against conspecifics of the same sex. Each male territory included 2 or 3 female territories. In the daytime, each male frequently visited the females living in its territory. At dusk in the full or new moon periods, courtship began within the female territories, pair spawning subsequently occurring within or near those territories. When a male actively courted a female in the territory of a second male, the latter male immediately chased off the intruder. Thus, mating occurred only between a male and females living in former's territory. This is the first report of a haremic mating system among butterflyfishes (Chaetodontidae).     

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.     

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.     

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.     

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 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.     

Interspecific variation in spawning time and male mating tactics of the parrotfishes on a fringing coral reef at Iriomote Island,Okinawa

Spawning time and male mating tactics of parrotfishes (family Scaridae) were investigated on a fringing coral reef at Iriomote Island, Okinawa. Spawning was observed in 14 species, and more frequently in more abundant species such as Chlorurus sordidus, Scarus rivulatus and Chlorurus bowersi. At the reef-edge spawning site, C. bowersi spawned at high tide, C. sordidus spawned both at high tide and in the early morning, whereas Calotomus carolinus and most of the Scarus species such as S. rivulatus spawned only in the early morning, mostly 0630–0830 h. Spawning only in the early morning irrespective of tide phase and moon age has seldom been reported from the scarid species of other localities. It is suggested that spawning in the early morning would be adaptive in species such as S. rivulatus, which migrated considerable distances (ca. 500 m) to the inshore feeding sites, in order to minimize feeding losses due to migration. For male mating tactics, pair spawning by territorial TP (terminal phase) males occurred in all 14 species, and streaking and group spawning by nonterritorial small IP (initial phase) males were seen more frequently in more abundant species. Moreover, group spawning by nonterritorial TP males, which were larger than the IP males but smaller than the territorial TP males, frequently occurred in S. rivulatus. Such mating tactics of TP males have not been reported from Scaridae.     

Preliminary study on female choice of mates versus sites in a wrasse, Cirrhilabrus temminckii

Female choice of mates versus sites was studied in a wrasse, Cirrhilabrus temminckii. Males had territories within a restricted area on a rocky slope at which females visited and pair-spawned pelagic gametes. Females visited several males or territories before spawning, suggesting the opportunity of female choice. Of the four characteristics of territorial males examined—body size, ratio of pelvic fin length to body size, courtship, frequency and territory depth—only territory depth was significantly correlated with daily mating success of males. The former three male characters were not related to territory depth. These results suggest that female C. temminckii chooses deep sites rather than specific mates in mating.     

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.     

Female Mate Preference and Male Mating Success of Ayu Fish,Plecoglossus altivelis (Osmeridae) under a Promiscuous Mating System

The ayu, Plecoglossus altivelis, is known to show wide variation in adult body size. We examined the spawning behavior in experimental spawning groups of fish in which male body size varied. Males never competed with each other for females or spawning site, while females spawned repeatedly, 17–97 times depending on body size, with previous or novel males. Males exhausted their sperm after a single mating episode, on average, regardless of body size. Moreover, repeated sperm production apparently reduced the residual lifespan. Females preferred mating simultaneously with more than one male and allowed males of body size similar to their own to mate more frequently. Thus the largest male within a spawning group was not always the most successful at mating, but mating success of any given male appears to depend upon body size distribution of females within the population. Female mate preference has apparently evolved to ensure complete fertilization under circumstances where males have been selected to economize sperm output during any one mating episode.     

Female spawning migrations of the protogynous wrasse,Halichoeres marginatus

Spawning sites and spawning migration paths of tagged females of the protogynous wrasse,Halichoeres marginatus, were studied on the shallow reefs at Kuchierabu-jima Island, Japan. Males set up mating territories above prominent rocks on the offshore reef slope in the late afternoon, and pair-spawned with females, which had migrated there from their home ranges located in inshore areas. Small females migrated to the spawning sites near their home ranges, whereas large females migrated to various spawning sites located within a wide area, including downcurrent sites. Spawning at the downcurrent sites favors transport of eggs offshore, thereby increasing the female’s fitness. The spawning sites where an individual had spawned as a female were subsequently used for mating after it had changed sex. It is suggested that the wide migration of females to various spawning sites, enables the storing up of information on those sites, which later helps in the acquisition of mating territories after changing sex.     

Uncertainty in territory quality affects the benefits of usurpation in a Mediterranean wrasse

Individuals should defend sites when the expected benefits ofthe territory exceed the cost of defense. However, if territoryqulaity is unpredictable or difficult to assess, the expectedpattern of territorial behavior is less clear. In a Mediterraneanwrasse, Symphodus ocellatus, mating success is skewed with 2%of nesting males getting more than 20% of the spawning success.Yet, variation in mating success is not explained by any knownphysical characteristic of males or their territories. Instead,females prefer nests with a recent history of mating successbecause males are less likely to desert the offspring she leavesbehind. Thus, territory quality is transient and determinedby interactions between the sexes. I measured the frequencyof territorial takeovers and the uncertainty in mating successamong days at a nest. Observations indicated that S. ocellatusmales usurped their neighbor's successful nests when males wereunsuccessful and larger than their successful neighbor. Sitesthat achieved mating success had a significantly higher probability(0.84) of remaining sucessful between consecutive days thanunsuccessful territories had of becoming successful (0.30).Unsuccessful males obtained higher and more certain fitnessreturns if they usurped a successful neighbor's territory. Interactionswithin and between the sexes drive uncertainty in success, whichinfluences territorial behavior in this species.     

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.     

Pre-oviposition Ejaculation in Externally Fertilizing Fish: How Sneaker Male Rose Bitterlings Contrive to Mate

Pre-oviposition ejaculation as a mating tactic of sneaker males in the rose bitterling, Rhodeus ocellatus, was studied under natural and artificial conditions. In a small pond in Yao city, Osaka, Japan, the operational sex ratio of males and females was found to be approximately 3.5:1 and the proportion of males to the mussels, which serve as spawning beds for the rose bitterling, was approximately 2:1. Competitively subordinate rose bitterling males which spawned into the mussels participated in mating by sneaking, because not all males could occupy territories around the mussels. The sneaker males often released sperm not only after but also before egg-laying (this ejaculation movement by the male before egg-laying is termed ‘pre-oviposition ejaculation’). In pair spawning with sneaker, the sneakers frequently performed pre-oviposition ejaculations, which territorial males never performed. In the field, pre-oviposition ejaculations by sneakers coincided with the leading of females by territorial males. Under artificial conditions, I demonstrated by using electrophoretic paternal analyses that the pre-oviposition ejaculations by the sneakers were more effective than the post-oviposition ejaculations by the territorial males. In addition, there were negative size-dependences in ejaculation achievement rate and fertilization success of the sneaker males.     

Mating behavior and male mating success in wildAnastrepha Ludens (Diptera: Tephritidae) on a field-caged host tree

Mating behavior and factors affecting mating success of males were studied using wild Anastrepha ludens on a fieldcaged host tree. The most common courtship sequence had five components: (1) male calls from the underside of a leaf, (2) female arrives to the maleoccupied leaf, (3) male orients to female and stops calling, (4) one or both approach to a face-to-face position 1–3 cm apart, and (5) male mounts female after 1–2 s. Courtship behavior was almost identical to that of laboratoryculture flies observed previously under laboratory conditions. Most malefemale encounters occurred at a height of 1–2m, well inside the outer canopy of the tree. Differential mating success by males occurred. No male mated more than once per day, owing possibly to a very short sexual activity period. Factors favoring mating success of males were survival ability and tendency to join male aggregations and to fight other males. Thorax length and age (9–11 days difference) had no effects on male copulatory success. Overall win/loss percentage was not related to mating success because the males that were most successful at mating fought mostly among themselves, driving their win/loss percentage down. However, these successful males (at mating) won most of their fights against less successful males. Results confirmed a lek mating system: males aggregated, called, and defended territories; territories did not contain femalerequired resources; and females exercised mate choice, apparently through selection of sites within leks.     

Spawning migrations in the monogamous butterflyfish,Chaetodon trifasciatus

Spawning and related behavior of a monogamous butterflyfish,Chaetodon trifasciatus, were observed at Kuroshima Island, Okinawa, Japan. Each heterosexual pair defended a feeding territory in the daytime. Spawning occurred at dusk on the days around full or new moon in the daytime. Spawning occurred at dusk on the days around full or new moon in the vicinity of offshore tidal currents. Spawning migration to such sites occurred in pairs, the feeding territories of which were located in areas of inshore currents. In the evening each pair established a small temporary territory, which they spawned adjacent to and slept within until the next morning. The distribution of sleeping sites as well as tidal current directions may determine the spawning sites of this butterflyfish.     

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