Insight into biting diversity to capture benthic prey in damselfishes (Pomacentridae)

peer reviewedThe cerato-mandibular (c-md) ligament, joining the hyoid bar to the coronoid process of the angular, allows Pomacentridae to slam their mouth shut in a few milliseconds. Previous works have revealed that such a mechanism is used to feed, but some variability in biting patterns has been observed between two damselfish species. The pelagic feeder Amphiprion clarkii performs two different kinematic patterns to bite fixed prey, one that does not depend on the c-md ligament (biting-1) and one that does (biting-2). The benthic feeder Stegastes rectifraenum only performs biting-2. The present study aims to shed light on the occurrence of biting-2 in the feeding behaviour of Pomacentridae. To test our hypothesis that biting-2 would be the only biting pattern for benthic feeders, we compared biting behaviours among four species: one pelagic feeder, A. clarkii, and three benthic feeders, Neoglyphidodon nigroris, Stegastes leucostictus and S. rectifraenum. Our results showed that the four species were able to perform biting-2, but they do not support that the use of this pattern is related to trophic habits. Contrary to S. rectifraenum, the two other benthic feeders randomly used biting-1 and biting-2 patterns, similar to A. clarkii. Two hypotheses are discussed for explaining this variability within Pomacentridae. Finally, it has been recently shown that some damselfishes do not possess the c-md ligament. We therefore included two species lacking the c-md ligament (Chromis chromis and Abudefduf troschelii) in our study and we demonstrate our expectation that they are unable to perform biting-2

A preliminary study of development of the buccal apparatus in Pomacentridae (Teleostei, Perciformes)

This study compares, in five species of Pomacentridae (Chromis viridis, Dascyllus flavicaudus, Chrysiptera glauca, Pomacentrus pavo, Plectroglyphidodon lacrymatus), the changes in cephalic skeletal structures between settling larvae and adults living on the reef. Variations were studied in the suspensorium, the opercle, the mandible, the premaxillary bone and the teeth. Comparisons of the feeding apparatus enabled two different types of feeding to be distinguished in adults: suction feeding and grazer sucking. Adult C. viridis and D. flavicaudus have a high suspensorium, a well-rounded mouth during jaw opening and caniniform teeth. These two species can be considered to be suction feeders. On the other hand, adult C glauca, P pavo and P lacrymatus have less developed suspensoria, opercles and ascending process of the premaxillar, and present incisiform teeth. These three species appear to be grazer suckers. However, the larvae of all five species present an unimodal way of feeding, defined as ram-suction. Differences between larvae and adults appear clearly to be related to their ecology. The increasing variation presented in feeding apparatus during the settlement phase could be linked to diversification leading to occupancy of different ecological niches.Peer reviewe

A Phylogenetic Context : The Diversification of Damselfishes (Pomacentridae)

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Trophic specializations of damselfishes are tightly associated with reef habitats and social behaviours

peer reviewedDespite the increasing need to understand factors shaping community assembly, few studies have simultaneously explored the influence of niche-based and phylogenetic processes. Here, we investigate the relationships between diet, habitat and social behaviour in damselfishes (Pomacentridae) collected in 2014 at Moorea Island (17°30′S, 149°50′W), French Polynesia. Isotope ratios of carbon and nitrogen, in association with stomach contents, delineate three trophic groups: pelagic feeders consuming zooplankton, benthic feeders mainly grazing on algae and an intermediate group feeding on prey from the whole bentho-pelagic compartment. Sulphur isotope ratios indicate segregation between species of the outer reef mostly depending on oceanic input of zooplankton and the lagoonal species relying on locally produced resources or even on terrestrial supply. We demonstrate a tight association between dietary specializations, habitat characteristics and social behaviours, and these correlations are further confirmed by integrating the phylogeny of Pomacentridae. We also provide evidence of phylogenetic conservatism for the stomach content and the habitat–behaviour characters. However, the isotopic trait is evolutionarily more labile probably because it thoroughly depicts the ecological niche of species. To summarize, pelagic feeders (mainly from the Chrominae) usually form shoals in areas close to the open ocean at a maximum depth of 20 m. Benthic feeders (well represented in the Stegastinae) are ubiquitous, solitary and mostly territorial species found at various depths. The intermediate group includes gregarious species from three subfamilies that forage in the lagoon usually above 12 m depth. Overall, we give insight into processes that have structured the damselfish community in Moorea

Morphological and genetic divergences in a coral reef damselfish, Pomacentrus coelestis

Population differentiation is one of the main topics in evolutionary biology. Except the exploration of color variation, few studies focused on morphological divergences among populations of coral reef fishes. In this work, we studied morphological and genetic differentiation among populations of the damselfish, Pomacentrus coelestis, in the northwestern Pacific Ocean. The shapes of the mandible and the premaxilla were explored using geometric morphometric methods and the genetic structure was investigated using microsattelites. Various tests revealed significant shape variation among most P. coelestis populations for both skeletal units. Morphological variation of the mandible accompanies a genetic break between populations of mainland Japan and Okinawa-Taiwan. However, Mantel and Procrustes tests revealed no congruence between morphological and genetic structures. We illustrate that phenotypic plasticity and adaptive divergence are potential evolutionary mechanisms underlying shape difference among P. coelestis populations. An ecomorphological approach suggests that various diet could be related to shape variation of oral jaws

Patterns of morphological evolution of the cephalic region in damselfishes (Perciformes: Pomacentridae) of the Eastern Pacific

Pomacentridae are one of the most abundant fish families inhabiting reefs of tropical and temperate regions. This family, comprising 29 genera, shows a remarkable diversity of habitat preferences, feeding, and behaviours. Twenty-four species belonging to seven genera have been reported in the Eastern Pacific region. The present study focuses on the relationship between the diet and the cephalic profile in the 24 endemic damselfishes of this region. Feeding habits were determined by means of underwater observations and the gathering of bibliographic data. Variations in cephalic profile were analyzed by means of geometric morphometrics and phylogenetic methods. The present study shows that the 24 species can be grouped into three main trophic guilds: zooplanktivores, algivores, and an intermediate group feeding on small pelagic and benthic preys. Shape variations were low within each genus except for Abudefduf. Phylogenetically adjusted regression reveals that head shape can be explained by differences in feeding habits. The morphometric phylogeny recovered the subfamily Stegastinae and the relationship between Abudefduf troschelii and Chromis species. The cephalic profile of damselfishes contains a clear and strong phylogenetic signal

Trophic niches of thirteen damselfishes (Pomacentridae) at the Grand Récif of Toliara, Madagascar

The damselfishes, with more than 340 species, constitute one of the most important families that live in the coral reef environment. Most of our knowledge of reef-fish ecology is based on this family, but their trophic ecology is poorly understood. The aim of the present study was to determine the trophic niches of 13 sympatric species of damselfishes by combining stable isotope (d15N and d13C) and stomach content analyses. Isotopic signatures reveal three main groups according to their foraging strategies: pelagic feeders (Abudefduf sexfasciatus, A. sparoides, A. vaigiensis, Chromis ternatensis, C. dimidiata, Dascyllus trimaculatus and Pomacentrus caeruleus), benthic feeders (Chrysiptera unimaculata, Plectroglyphidodon lacrymatus and Amphiprion akallopisos) and an intermediate group (D. aruanus, P. baenschi and P. trilineatus). Stomach contents reveal that planktonic copepods and filamentous algae mainly represent the diets of pelagic feeders and benthic feeders, respectively. The intermediate position of the third group resulted from a partitioning of small planktonic prey, small vagile invertebrates and filamentous algae. In this last feeding group, the presence of a wide range of d13C values in P. trilineatus suggests a larger trophic niche width, related to diet-switching over time. Some general considerations about the feeding habits of damselfishes reveal that their choice of habitat on the reef and their behavior appear to be good predictors of diet in this group. Benthic (algae and/or small invertebrates) feeders appear to be solitary and defend a small territory on the bottom; zooplankton feeders remain in groups just above the reef, in the water column.Peer reviewe

Sound production in the clownfish Amphiprion clarkii

Although clownfish sounds were recorded as early as 1930, the mechanism of sound production has remained obscure. Yet, clownfish are prolific "singers" that produce a wide variety of sounds, described as "chirps" and "pops" in both reproductive and agonistic behavioral contexts. Here, we describe the sonic mechanism of the clownfish Amphiprion clarkii

Unprecedented biting performance in herbivorous fish: How the complex biting system of Pomacentridae circumvents performance trade-offs

peer reviewedIt is well accepted that the complexity of functional systems may mitigate performance trade-offs. However, data supporting this theory are hard to find because they need to be based on a functional system with different complexity levels in closely related species. The Pomacentridae (damselfishes) provide an excellent opportunity to test this hypothesis because most of the species have two mouth-closing systems: the first using the adductor mandibulae, as in all teleost fishes, and the second relying on the ceratomandibular (cmd) ligament, a synapomorphic trait of the family. Interestingly, some pomacentrids have secondarily lost the cmd ligament during evolution and therefore have a less complex mouth-closing system. Using dissection, kinematic analysis, and mathematical modeling, we demonstrated that the possession of two mouth-closing systems enabled grazing damselfishes to have a forceful and extremely fast bite. This combination challenges a major functional trade-off in fish jaw dynamics, as systems better suited for force transmission are usually less suited for speed transmission, and vice versa. The combination of grazing behavior, small and robust lower jaws (conferring high biting force), and an ultrafast bite is unusual within actinopterygians. These attributes and their associated performance seem to be required conditions to colonize the ecological niche of farming, that is, the maintenance of small filamentous algae crops serving as both food and storage

Sound production in four damselfish (Dascyllus) species: phyletic relationships?

peer reviewedMost studies of fish sounds show that the sounds are species-specific, with unique spectral and timing characteristics. This raises the question as to whether these sounds can be used to understand phyletic relationships between species and which acoustic parameters are subject to variation between species. In the present study, 597 sounds (and 2540 pulses) related to signal jumps of four Dascyllus species (Dascyllus aruanus, Dascyllus trimaculatus, Dascyllus albisella, and Dascyllus flavicaudus) from different geographic regions (Madagascar, Moorea, Rangiroa, and Hawaii) were analysed. It was possible to discern species-specific sounds, but also variation in sounds between populations. Large variations in sound length were found between Dascyllus species, whereas differences in interpulse duration were found to be variable between populations. In the regions where species live in sympatry, it appears that they restrict the variability in their sounds. This could comprise evidence of adaptation with character displacement of sonic characteristics where different species co-occur. However, sonic characteristics still overlapped substantially between species, suggesting that females would need to sample more than one sound and potentially use other cues to discriminate between species