Tetsuo Kuwamura

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.

New aspects of sex change among reef fishes: recent studies in Japan

New aspects of sex change in reef fishes are reviewed with special emphasis on recent studies in Japan. For protogyny, studies on both monandric and diandric species have been conducted, but the distinction of primary males from prematurational secondary males seems to need further examination. For protandry, detailed field studies on anemonefishes have revealed alternative life-history styles associated with movements between hosts before or after maturation. The most interesting new aspect has been the discovery of 2-way sex change within a species. Conditions for evolution of 2-way sex change are examined in relation to the size-advantage model and social control mechanisms. A fish may change sex when it becomes dominant in a mating group, but a dominant fish may also change sex in the reverse direction when its social status changes to subordinate through inter-group movement. Two-way sex change has hitherto been reported only from basically protogynous fishes (e.g., Gobiidae, Pomacanthidae, Cirrhitidae, Epinephelinae). Possibilities of the reverse sex change in the protandrous anemonefishes are discussed with data from some unpublished studies.

Both-ways sex change in monogamous coral gobies, Gobiodon spp

SynopsisWe confirmed both-ways sex change in the coral-dwelling gobies Gobiodon micropus, G. oculolineatus, G. quinquestrigatus and G. rivulatus rivulatus by mate-removal experiment in the field and by the aquarium experiment of keeping two consexual fish in a coral. Eight species of Gobiodon were found in Acropora corals on the reef flat of Sesoko Island, Okinawa, southern Japan. The 4 species mentioned above bred in monogamous pairs composed of a male and a female matched by size, and the male took care of eggs deposited on the coral branch. In G. quinquestrigatus and G. rivulatus rivulatus males were larger than females in newly formed pairs, and females grew faster than their mates until breeding. The growth-rate advantage in females seems to be the major factor in the evolution of female to male sex change. The gobies strongly depended on host corals, but they moved between the corals after mate loss or coral death to form new pairs. This provides opportunities for the evolution of male to female sex change; the ability to change sex in both directions reduces the frequency of risky movement between host corals to form new pairs. These conditions are very similar to those reported in the both-ways sex change of another coral-dwelling goby Paragobiodon echinocephalus.

Social and reproductive behavior of three mouthbrooding cardinalfishes, Apogon doederleini, A. niger and A. notatus

SynopsisSocial and reproductive behavior of three paternal mouthbrooding cardinalfishes (Apogonidae) were investigated in the shallow marine waters of Shirahama, Japan. The solitary species Apogon doederleini and A. niger bred in ‘transient pairs’, in which a male and female associated for only a few hours of each afternoon on less than 5 successive days. The prespawning behavior was the same as the courtship display on days prior to spawning. After spawning, egg-incubating males were usually left alone. The gregarious species Apogon notatus formed territorial ‘lasting pairs’, which resided at given sites from dawn to dusk on each day during a period of a month or more. After spawning, the egg-incubating male either continued to stay with his mate in the territory, or left it to enter into an aggregation. In the latter case, the female continued to reside in the territory, pairing with a new male whom she brought from an aggregation. It is suggested that in paternal apogonids the prolonged pair bond and territoriality should have developed only in gregarious species as secondary adaptation for reproductive success: to avoid conspecific interference during spawning.

Male morphological characteristics and mating success in a protogynous coral reef fish, Halichoeres melanurus

Abstract Morphological sexual differences and their effects on male mating success were investigated in the tailspot wrasse, Halichoeres melanurus, on a subtropical coral reef of Okinawa, southern Japan. Male mating territories were established along the reef edge from late April to early October, during which time pair-spawning occurred just before sunset in the male territories. Territorial males were larger and brighter than females in this protogynous fish. The males had longer, colorful ventral fins and colorful caudal fins, both of which were used during courtship. Multiple regression analysis of the effects of male characteristics on male mating success revealed that the yellow spot at the pectoral fin base was the most effective. It is suggested that large body size is favored in male–male competition for establishing mating territories and that conspicuous body color is favored in female mate choice.

Female-female Spawning and Sex Change in a Haremic Coral-reef Fish, Labroides dimidiatus

Abstract In the polygynous coral-reef fish, Labroides dimidiatus, the largest female may complete sex change within a few weeks if the male disappears. We conducted male removal experiments just prior to spawning time. The largest female possessing ovulated eggs spawned in the male role with smaller females, 1–2 hr after the male removal, suggesting that ovulation could not prevent male sexual behavior. During the female-female spawning eggs were actually released, but of course unfertilized. The largest female subsequently spawned in the female role when the male was immediately returned. If the male was never returned, such spawning behavior was repeated almost every day until the largest fish was able to release sperm. Smaller females will participate in such fruitless spawning according to their preference for larger mates. The largest females should perform male sexual behavior to secure future mates, even before completion of gonadal sex change.

Male mating territory and sneaking in a maternal mouthbrooder,Pseudosimochromis curvifrons (Pisces; Cichlidae)

Sneaking, a male mating behavior alternative to defending a territory, is known in various kinds of fishes (Gross 1984; Magurran 1986). Although male mating territories are common in maternal mouthbrooding cichlids (Fryer & Iles 1972; McKaye 1984; Kuwamura 1986), sneaking has been observed only in Cyrtocara eucinostomus (McKaye 1983) and Simochromis diagramma in aquarium situations (T. Sato personal communication). I report here sneaking behavior of a mouthbrooding cichlid Pseudosimochrornis curvifrons (Poll) observed in Lake Tanganyika, East Africa. Males of this species establish mating territories; females visit them to spawn and mouthbrood about 10 eggs of 4.5 mm diameter (Kuwamura 1986). However, its spawning behavior and the structure of the male territory have not been reported in detail Mating and related behaviors of P. curvifrons were investigated in the coastal water of Uvira (3~ 29~ Zaire, during August and September, 1986. Observations by snorkeling were made in a boulder area, composed of rocks up to 1 m in diameter, at depths of about 1 m. Most observations were conducted in the morning (0900-1200) , since in the afternoon the wind and waves usually became strong and the fish were less active. Courting pairs were continuously observed for 15-38 min (N -8, for 6 males) until the female went out of the males territory and was lost from sight. Frequencies of courtship, spawning, attacks and sneaking were recorded. Behaviors of .territorial males while they were not visited by females were also recorded for 5 1 0 rain (N = 8, for 6 males). Their ranges of feeding sites and frequencies and locations of attcks were noted. Total lengh (TL) of the observed fish was estimated underwater to the nearest 1 cm with help of a ruler, and their body color was also recorded.

Female-to-male shift of mouthbrooding in a cichlid fish, Tanganicodus irsacae, with notes on breeding habits of two related species in Lake Tanganyika

SynopsisParental-care patterns and mating systems of three goby-like cichlids in Lake Tanganyika were investigated. In Tanganicodus irsacae females mouthbrooded eggs and small young for about two weeks and then males took over the role for about one week. Field observations of tagged fish suggest that this species is monogamous: a males home range largely overlapped with that of its mate, while their home ranges were segregated from those of similar-sized consexual adults. Eretmodus cyanostictus also performed female-to-male shift of mouthbrooding and appeared to be monogamous. The third species, Spathodus marlieri, however, exhibited exclusively maternal mouthbrooding. The differences in parental care and mating system among the three species are discussed in relation to their feeding habits, and the pattern of monogamy in the goby-like cichlids is compared with those of other fishes.

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.

Reexamination on the aggressive mimicry of the cleaner wrasseLabroides dimidiatus by the blennyAspidontus taeniatus (Pisces; Perciformes)

Field observations on feeding and related behavior of the mimic blennyAspidontus taeniatus and 3 species closely related to it, and the cleaner fish (model)Labroides dimidiatus were made at the coral reef of Sesoko Island, Okinawa, Japan, along with analysis of gut contents. The mimic blenny fed mostly on demersal eggs of fishes and tentacles of polychaetes, but it rarely tore pieces from the fins of host fishes even when they were posing for cleaning. The feeding habits of the mimic blenny are compared with those in other localities and with those of related species. It is concluded that the mimicry can hardly be regarded as an aggressive one: posing by host fishes seems to be a secondary result of the resemblance which may have developed because of the benefit for immunity from predation, and the resemblance itself prevents the blenny from becoming a specialized fin-eater because it can be easily recognized by host fishes.