The omnivorous triggerfish Melichthys niger is a functional herbivore on an isolated Atlantic oceanic island

This study evaluated the functional role of the highly generalist omnivore Melichthys niger in the remote St. Peter and St Paul's Archipelago (SPSPA), Brazil, where grazing herbivorous fishes are very scarce. We analysed patterns of distribution from zero to 30 m deep during three time intervals during the day and sampled different aspects of their feeding behaviour, including diel feeding rate, feeding substrate and diet. The density of M. niger increased with depth (26–30 m) and decreased by the end of the day. Although M. niger did not present a typical herbivore diel feeding pattern, they targeted the epilithic algal matrix as their primary feeding substrate, ingesting predominantly algae and detritus. The characteristic Caulerpa racemosa var. peltata from SPSPA was ingested only as detached fronds. We suggest that in the isolated SPSPA, the single species M. niger may perform a unique role as a link between benthic primary production and higher levels. Further studies on the trophic ecology of omnivorous species are necessary to better understand their roles in a reef system, especially in impoverished areas where they are likely to play a crucial role.     

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.     

Female defense polygyny in the territorial triggerfish <Emphasis Type="Italic">Sufflamen chrysopterum</Emphasis>

The occurrence of polygyny requires specific environmental conditions such as female aggregation or patchy resource distribution. However, it is difficult to determine the factors responsible for polygyny in species in which the territories of both sexes overlap. To overcome this, we performed female removal experiments in the polygynous triggerfish Sufflamen chrysopterum (Balistidae) in the Okinawa coral reef. Both sexes defended their territories exclusively against consexuals of the same species, and female aggregation was absent. Each male territory included 1–3 female territories, and nonterritorial males were significantly smaller than territorial males. Further, the body size of territorial males was positively correlated with that of the largest female in their territories, and larger males tended to mate with more females. The results of the female removal experiments (n = 10 females) indicated that females competed for better territories rather than larger mates. In contrast, males abandoned the territories once the females emigrated. These results strongly suggest that males defend females rather than sites and compete for larger and a greater numbers of females. Thus, in S. chrysopterum, female defense polygyny occurs in the absence of female aggregation.     

Feeding and territorial behaviour in juveniles of three co-existing triggerfishes

Of three coexisting triggerfishes, in the intertidal and immediate subtidal zones of a coral reef within the Kenting National Park, southern Taiwan, Balistoides viridescens was observed only in the subtidal zone and foraged preferentially by nipping directly at small invertebrates among algal covered substrata. They fed also, although at a lower frequency, by using a water-jet technique to uncover prey on sandy substrata. Territory size ranged from 61·05 to 161·57 m² but was not related to rates of feeding or defence. Feeding frequency was, however, positively related to the area of algae present in the territory, and inversely related to the frequency of defence. In contrast to B. viridescens, Rhinecanthus verrucosus and R. aculeatus foraged mainly in the intertidal zone when the tide was high. They fed preferentially off rocky substrata and used only nipping (not water-jetting) to secure prey.     

Cableia balistidicola n. sp. (Digenea, Monorchiidae) from Pacific Ocean balistids (Tetraodontiformes) and new reports of Cableia pudica Bray, Cribb and Barker, 1996 in temperate Australian monacanthids

Cableia balistidicola n. sp. is described from Abalistes stellatus (type-host) off New Caledonia (type-locality) and the Great Barrier Reef and Pseudobalistes fuscus off New Caledonia and Rhinecanthus aculeatus off Moorea, French Polynesia. It is distinguishable by its large ventral sucker with a highly developed sphincter around the aperture. Cableia pudica is reported from Meuschenia freycineti off northern Tasmania, M. hippocrepis off south-western Western Australia and northern Tasmania and Acanthaluteres spilomelanurus off Kangaroo Island, South Australia. Measurements of C. pudica are given and the distinguishing features of the three known species of Cableia are discussed and summarised in a key. C. balistidicola is reported only in balistid fishes in the tropical Pacific Ocean and C. pudica is reported only in monacanthid fishes in Australian coastal waters.

Résumé

Cableia balistidicola n. sp. est décrit de Abalistes stellatus (hôte type) de Nouvelle-Calédonie (localité type) et de la Grande Barrière de Corail, de Pseudobalistes fuscus en Nouvelle-Calédonie et de Rhinecanthus aculeatus à Moorea, Polynésie Française. L'espèce se distingue par une grande ventouse ventrale avec un sphincter très développé autour de l'ouverture. Cableia pudica est signalé de Meuschenia freycineti du nord de la Tasmanie, M. hippocrepis de l'Australie du sud-ouest et du nord de la Tasmanie et de Acanthaluteres spilomelanurus de Kangaroo Island, au sud de l'Australie. Des mesures de C. pudica sont données et les caractères distinctifs des trois espèces connues de Cableia sont discutés et résumés dans une clé. C. balistidicola est signalé seulement de poissons Balistidae dans l'Océan Pacifique tropical et C. pudica est signalé seulement de poissons Monacanthidae des eaux côtières de l'Australie.     

Protogynous sex change in the haremic triggerfish Sufflamen chrysopterus (Tetraodontiformes)

The size-advantage model predicts that protogyny is likely to evolve in polygynous species. Polygynous mating systems have been reported from several species of triggerfishes (Balistidae), but sex change has never been confirmed among them. We performed male-removal experiments in the haremic triggerfish Sufflamen chrysopterus on the coral reefs of Sesoko Island, Okinawa. After removal and movement of territorial males, some females became single and later changed body color and sex. This is the first report of sequential hermaphroditism from Tetraodontiformes.     

A new genus and species of triggerfish from the Middle Eocene of the Northern Caucasus,the earliest member of the Balistidae (Tetraodontiformes)

Until now, the earliest known members of the triggerfish family Balistidae have been two genera from the Oligocene. Herein is described the new balistid Gornylistes prodigiosus gen. et sp. nov. from the uppermost Middle Eocene (Kuma Horizon) of the Northern Caucasus (Gorny Luch locality); it is as thoroughly modern in its bauplan as the taxa of balistids from the Oligocene and more recent periods, and far more advanced morphologically than the several stem taxa of the balistoid + ostracioid clade known from earlier in the Middle and Lower Eocene and from the Upper Paleocene.     

Arterioles in the swimming muscles of the leatherjacket Parika scaber (Pisces: Balistidae)

Summary The leatherjacket (Parika scaber) is a balistiform fish which swims using its dorsal and anal median fins. The muscles controlling these fins are well vascularised, with control of blood flow effected by arterioles. These arterioles are long with a single layer of smooth muscle surrounding the endothelium, although the amount of contractile material is sparse, probably a consequence of the low blood pressure. The endothelial cells contain microfilaments, probably contractile, running along the length of the arteriole. The function of this material is unknown.