Teleost fishes are characterized by a diversity of sexual patterns. Hermaphroditism, the expression of both male and female reproductive function in a single individual, generates the most curiosity and controversy. Yet diagnosis of this form of sexuality continues to challenge workers, in particular the distinction between functional and non-functional hermaphroditism. This distinction, reflected as it is in the relationships between gonad form and function, is important if we wish to improve our understanding of the origin of hermaphroditism in the teleosts and of its highly sporadic expression today. Although structure can indicate phylogenetic affinities, it does not always reflect reproductive function, and function is important for understanding adaptation. With resurgent interest in hermaphroditism comes the recognition that understanding sexual pattern is not only important for better knowledge of reproductive biology and ecology but may also elucidate phylogenetic relationships. On the basis of a conservative and clearly defined set of diagnostic criteria, which incorporate new accounts of hermaphroditic species, and by applying an improved understanding of gonadal ontogeny, a comprehensive review and careful re-examination of all primary literature was conducted. This overview documents the incidence of hermaphroditism in teleosts and explores its phylogenetic distribution, possible origin and range of expression. The review confirms functional hermaphroditism in 27 teleost families in seven orders, predominantly among tropical, marine perciforms in which its diversity of expression is greatest. In families with functional hermaphrodites, the sexual pattern is widespread and often highly variable in expression, even within a single genus or between populations. Based on our understanding of gonadal ontogeny in teleosts and on known phylogenetic interrelationships, the origin of functional hermaphroditism is most parsimoniously explained by a proto-hermaphroditic condition in teleosts and cyclostomes, constituting a hermaphroditic potential for these groups. Exploitation and expression of this potential appear to be a response to a suite of environmental and biological factors, opportunities and constraints that result in the independent appearance of the hermaphroditic option in many different fish lineages.

Functional hermaphroditism in teleosts

Coral reef ecosystems are remarkable for their high productivity in nutrient-poor waters. A high proportion of primary production is consumed by the dominant herbivore assemblage, teleost fishes, many of which are the product of recent and rapid diversification. Our review and synthesis of the trophodynamics of herbivorous reef fishes suggests that current models underestimate the level of resource partitioning, and thus trophic innovation, in this diverse assemblage. We examine several lines of evidence including feeding observations, trophic anatomy, and biochemical analyses of diet, tissue composition and digestive processes to show that the prevailing view (including explicit models) of parrotfishes as primary consumers of macroscopic algae is incompatible with available data. Instead, the data are consistent with the hypothesis that most parrotfishes are microphages that target cyanobacteria and other protein-rich autotrophic microorganisms that live on (epilithic) or within (endolithic) calcareous substrata, are epiphytic on algae or seagrasses, or endosymbiotic within sessile invertebrates. This novel view of parrotfish feeding biology provides a unified explanation for the apparently disparate range of feeding substrata used by parrotfishes, and integrates parrotfish nutrition with their ecological roles in reef bioerosion and sediment transport. Accelerated evolution in parrotfishes can now be explained as the result of (1) the ability to utilize a novel food resource for reef fishes, i.e. microscopic autotrophs; and (2) the partitioning of this resource by habitat and successional stage.

Integrating ecological roles and trophic diversification on coral reefs: multiple lines of evidence identify parrotfishes as microphages

Marine ecosystems throughout the Indo-Pacific region are highly threatened by anthropogenic stressors, yet the faunal interaction between different component habitats remains poorly understood. This information is vital as stress on one inter-connected habitat may have cascade effects on other habitats. The present study focused on the impact of inter-habitat connectivity on seagrass fish assemblages, specifically between seagrass, mangrove and reef habitats. Fish were sampled using a seine net within 3 seagrass habitats (seagrass near to reef, seagrass near to reef and mangrove, and seagrass near to mangrove) within eastern Indonesia. Visual surveys were also conducted within mangrove habitats. Fish abundance and species richness in seagrass beds in close proximity to mangroves was at least twice that found in seagrass beds that were distant from mangrove habitat. The trophic structures of seagrass fish assemblages change from being dominated by predators and omnivores close to the reef, to assemblages high in planktivores and herbivores close to mangroves. We found that mangroves enhance the fish assemblages of nearby seagrass beds probably by increasing the availability of shelter and food provision. This study indicates that Indo-Pacific seagrass beds play an important fish nursery role, which is influenced by the availability of nearby reef and mangrove habitats. Our research supports the need for ecosystem-level management of shallow water tropical habitats, but also suggests that successful management requires local-level knowledge of habitat interactions to successfully enhance or conserve fish assemblages. © Inter-Research 2008.

/pdf/high-connectivity-of-indo-pacific-seagrass-fish-assemblages-9fvtc4wreb.pdf

High connectivity of Indo-Pacific seagrass fish assemblages with mangrove and coral reef habitats

https://horizon.documentation.ird.fr/exl-doc/pleins_textes/divers16-09/010067959.pdf

Diet composition of carnivorous fishes from coral reef lagoons of New Caledonia

The faunal communities of seagrass beds throughout SE Asia are highly threatened by continued overexploitation, yet their ecology is poorly understood. Developing a greater understanding of the faunal linkages between seagrass beds and associated coastal habitats can facilitate more informed ecosystem level management. The present study used beach seine netting to sample seagrass bed fish assemblages in the Wakatobi Marine National Park, Indonesia, to investigate diel migrations of fish into and out of seagrass beds. These fish assemblages were found to be diverse relative to other studies within the region, with many species being economically important to local subsistence fisheries. The abundance, species richness and trophic structure of these fish assemblages changed with time of day indicating that fish populations are in a dynamic state. Mean fish abundance increased by ?45% from day to night (Day: 8.61 ± 0.13 fish 100 m?2; Night: 15.6 ± 1.4 fish 100 m?2) while mean species richness increased from 6.6 ± 1.9 per seine haul to 11.4 ± 0.2. Increasing abundance and diversity of fish at night suggests migration onto these habitats from nearby habitats such as reefs, mangroves or deep water; and/or increased activity of those fish resident within seagrass habitats. Division of species into trophic categories enabled the trophic structure of changing fish assemblages to be examined. Assemblages were dominated during both the day and night by invertebrate and fish feeders; however, a major diel change in trophic structure occurred in the abundance of omnivores. During the day omnivores were abundant, but they were replaced at night by exclusive invertebrate feeders. We therefore propose that diel changes in seagrass fish assemblages are predominantly structured by food availability, although other factors such as increased night-time shelter provision were also found to be important albeit to a much lesser extent.

Diel trophic structuring of seagrass bed fish assemblages in the Wakatobi Marine National Park, Indonesia

To clarify the feeding habits of fishes in tropical seagrass beds on coral reefs, the gut contents of 53 fish species, collected in an Enhauls acoroides-dominated bed at Iriomote Island, southern Japan, were examined. Ontogenetic changes in food preference were recognized in 9 species, including lethrinids, mullids, pomacentrids, labrids, and scarids. Cluster analysis based on dietary overlaps showed that the seagrass fish assemblage comprised seven feeding guilds (small-crustacean, large-crustacean, plant, detritus, hard-shelled mollusc, fish, and planktonic-animal feeders). Of these, small-crustacean feeders were the most abundantly represented. On the other hand, planktonic-animal and hard-shelled mollusc feeders were each represented by only two species. Compared with previous studies on the feeding habits of temperate seagrass fishes, the present fish assemblage was characterized by larger species numbers of detritivores, herbivores, and piscivores and fewer planktonic-animal feeders.

Food habits of fishes in a seagrass bed on a fringing coral reef at Iriomote Island, southern Japan

The feeding habits of the serranid fish Cephalopholis urodeta were examined on the basis of 204 adult specimens collected from coral reef areas at Iriomote Island, Ryukyu Islands, Japan. Sampling was conducted in November 1997 and February, May, and August 1998. Among the specimens, 95 (46.6%) had empty stomachs, the mean Stomach Fullness Index of the specimens overall being extremely low (0.6). Over a 1-year period, the most important prey of this species were small fishes and decapod crustaceans, the two categories together constituting 73.4% of stomach contents by weight. However, seasonal differences in basic dietary composition were apparent. Fishes were abundant in the diet in May and November, whereas the proportion of hermit crabs in the diet was higher in February compared to other months.

Feeding habits of the darkfin hind Cephalopholis urodeta (Serranidae) at Iriomote Island, southern Japan

Evidence of protogynous hermaphroditism in the darkfin hind Cephalopholis urodeta (Serranidae) at Iriomote Island, southern Japan

Management of fishery resources for groupers (Serranidae) in Okinawa, southern Japan

The feeding habits of juvenile serranids, Cephalopholis urodeta, were examined on the basis of 104 specimens (≤100mm in total length, TL) collected from coral reef areas at Iriomote Island, Ryukyu Islands, Japan, from May to September between 1998 and 2001. Thirtyone (29.8%) of the specimens collected had empty stomachs, the overall mean stomach fullness index being low (0.94). The most important prey comprised small fishes and shrimps, food preferences not differing among three juvenile size classes (≤60, 61-80 and 81-100mm TL).

Tadaomi Nakai

Papers

Food habits of fishes in a seagrass bed on a fringing coral reef at Iriomote Island, southern Japan

Feeding habits of the darkfin hind Cephalopholis urodeta (Serranidae) at Iriomote Island, southern Japan

Evidence of protogynous hermaphroditism in the darkfin hind Cephalopholis urodeta (Serranidae) at Iriomote Island, southern Japan

Management of fishery resources for groupers (Serranidae) in Okinawa, southern Japan

Feeding habits of juvenile darkfin hind Cephalopholis urodeta (Serranidae) at Iriomote Island, southern Japan