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See detailA morphospace for the marine angelfishes (Pomacanthidae): patterns of diversity
Frederich, Bruno ULg

Poster (2014, December 12)

The Pomacanthidae (marine angelfishes) is an iconic reef fish family of about 88 species. They have a circum-global distribution on tropical to warm-temperate reefs. Marine angelfishes occupy a diverse ... [more ▼]

The Pomacanthidae (marine angelfishes) is an iconic reef fish family of about 88 species. They have a circum-global distribution on tropical to warm-temperate reefs. Marine angelfishes occupy a diverse range of trophic niches, ranging from spongivory and algivory to zooplanktivory. Previous morpho-functional analysis of this family mainly focused on the head region and gut morphology in a limited number of species. However a morphological study including a large sample of angelfish representatives is currently lacking. Here, I explore the diversity of body morphology in this reef fish group. I collected x-ray images of 228 museum specimens from 71 species and I used landmark-based geometric morphometrics to quantify the overall body shape variation within this family. In a test for interspecific allometry, the linear regression of shape variables onto size (LogTL; TL = total length) was significant (P < 0.001). However, the percentage of explained variance in this model (23%) showed no strong relation between size and body shape. Main shape variation across species was explored using a principal component analysis on shape variables. The two main axes (PC1 and PC2) explained 74% of the total variance of the dataset. Pomacanthus spp., which mainly feed on fixed invertebrates (sponges and tunicates), have deep body with high and angular cephalic profile (lowest values along PC1). Conversely, the zooplanktivorous Genicanthus spp., those have a more pelagic lifestyle, show a slender body with shorter anal fin (highest values along PC1). The pigmy angelfishes from the genus Centropyge, which group different diets (omnivory or algivory), show a more robust and rectangular body shape (high scores along PC2). This work provides the row data for future studies dealing with the mode of phenotypic diversification of Pomacanthidae during evolution. [less ▲]

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See detailStable isotope ratios reveal trophic niche partitioning among hermit crabs from tropical polyspecific seagrass meadows
Michel, Loïc ULg; Frederich, Bruno ULg; Lavitra, Thierry et al

Poster (2014, December 12)

Polyspecific seagrass meadows are ubiquitous features of tropical coastal zones. These ecosystems are of critical ecological importance, and provide a wide range of socio-economical services to local ... [more ▼]

Polyspecific seagrass meadows are ubiquitous features of tropical coastal zones. These ecosystems are of critical ecological importance, and provide a wide range of socio-economical services to local populations. Meadows however undergo multiple threats linked to human activities (increased nutrient input, overfishing, invertebrate overharvesting, etc.). It is currently hard to assess how seagrass meadows could respond to anthropogenic impacts due to poor knowledge of their functional ecology. In an effort to unravel trophic interactions ruling the food webs associated to seagrass beds of the Toliara Great Reef (SW Madagascar), we studied resource segregation between two common Diogenidae hermit crabs (Dardanus scutellatus and Ciliopagurus tricolor) using stable isotope ratios. Interspecific differences were noted in isotopic composition of carbon (δ13C = -12.22 ± 1.73 ‰ for D. scutellatus, δ13C = -14.55 ± 0.73 ‰ for C. tricolor), nitrogen (δ15N = 4.73 ± 0.53 ‰ for D. scutellatus, δ15N = 5.20 ± 0.61 ‰ for C. tricolor) and sulfur (δ34S = 14.08 ± 2.32 ‰ for D. scutellatus, δ34S = 16.73 ± 1.49 ‰ for C. tricolor), suggesting that the two species do not feed on the same items. In addition, SIBER (Stable Isotope Bayesian Ellipses in R) modeling based on C and N data clearly showed that no overlap was present in the core isotopic niches of the two species. It also indicated that the isotopic niche of D. scutellatus was greater than the one of C. tricolor, implying that the former feeds on a greater number of items than the latter. While hermit crabs are generally considered as omnivorous species, this study highlighted differences in the foraging ecology of D. scutellatus and C. tricolor. These differences could help to limit competition for food between these two species, and facilitate their coexistence in Malagasy seagrass beds. [less ▲]

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See detailEcological diversity of damselfishes (Pomacentridae) from Moorea
Gajdzik, Laura ULg; Parmentier, Eric ULg; Lepoint, Gilles ULg et al

Poster (2014, December)

The Pomacentridae (damselfishes) represents the 3rd most species-rich coral reef fish family, including 394 species spread worldwide. Recent studies suggested that damselfishes iteratively evolve along ... [more ▼]

The Pomacentridae (damselfishes) represents the 3rd most species-rich coral reef fish family, including 394 species spread worldwide. Recent studies suggested that damselfishes iteratively evolve along three main trophic guilds: “the pelagic feeders” feeding mainly on zooplankton, “the benthic feeders” grazing filamentous algae or biting coral polyps, and an “intermediate” group with species feeding on zooplankton, small benthic invertebrates and algae in variable proportions. Comparing the ecological diversity of damselfish communities among various geographical regions could assess such an iterative radiation. Within this context, the present study is a first attempt exploring the trophic diversity of damselfish community at Moorea Island (French Polynesia). The relationship between the trophic guilds, their habitat diversity and their behavior is evaluated. Habitat and behaviour of 16 damselfish species were described during transects along which different kinds of data were collected. For examples, the location within the reef (e.g. fringing or barrier reef), the depth, the substrate over which fishes are living or the solitary/gregarious habits were recorded. Diet of individuals was investigated by means of stomach content and stable isotopes analyses. Correlations between the dietary preferences and ecological data (habitat and behaviour) are given and the ecological diversity among trophic groups is compared. [less ▲]

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See detailEcomorfologia y evolucion del sistema locomotor de la familia Pomacentridae
Aguilar-Medrano, Rosalia; Frederich, Bruno ULg; Barber, Paul

Conference (2014, November)

Due their productivity, structural diversity, and potential to promote ecological, functional and morphological evolution, coral reefs have the highest species richness of fishes. As swimming is the ... [more ▼]

Due their productivity, structural diversity, and potential to promote ecological, functional and morphological evolution, coral reefs have the highest species richness of fishes. As swimming is the primary form of locomotion and interaction their aquatic environment, small morphological variations can have profound implications on the fitness of fishes. The damselfish family, Pomacentridae, has inhabited coral reef ecosystems for more than 50 million years. As such, habitat preferences and behavior could significantly contribute to the evolution of the morphology of damselfish through the impacts of shape on locomotion. To test this hypothesis, we employed comparative morphometric analyses of fish shape and ecology. While body elongation represented the primary source of variation in locomotor system shape, results also showed a diverse suit of morphological combinations in between the morphological extremes. Results showed strong associations between behavior and habitat preferences, suggesting that behavior may constrain the shape of the locomotor system in damselfishes. Position in the water column show relation with the cephalic region and truck, behavior is related to the cephalic angle and the angle of insertion of the pectoral fin, while maximum depth is related to the caudal peduncle. Was found little relation between the caudal peduncle, the angle of pectoral fin attachment and the rest modules, therefore, this two modules may be the main responsible of swimming fitness in damselfishes. Finally, cephalic region is highly related to most modules, especially to trunk. This strong integration may be responsible of the limit morphological variation of damselfishes. [less ▲]

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See detailThe cerato-mandibular ligament: a key functional trait for grazing in damselfishes (Pomacentridae)
Olivier, Damien ULg; Frederich, Bruno ULg; Spanopoulos-Zarco, Milton et al

in Frontiers in Zoology (2014), 11(63), 1-14

Introduction: The success of a taxonomic group can be promoted by a key character that allows the group to interact with its environment in a different way and to potentially occupy new niches. The ... [more ▼]

Introduction: The success of a taxonomic group can be promoted by a key character that allows the group to interact with its environment in a different way and to potentially occupy new niches. The Pomacentridae possess a synapomorphic trait, the cerato-mandibular (c-md) ligament, which joins the hyoid bar to the inner part of the lower jaw. It has previously been shown that this ligament is a key trait in communication in damselfishes because it enables them to slam the oral jaws shut causing teeth collision and sound production. This specific behavior of mouth closing could, however, also be used for other tasks, such as feeding. Many territorial damselfishes are referred to as farmers, due to their ability to manage algal crops on which they feed. This study hypothesizes that the c-md ligament provides an advantage for grazing filamentous algae, and should thus be considered a key trait for farming behavior. Results: The kinematic patterns associated with sound production and biting filamentous algae or attached animal prey are all based on the same mechanism and are associated with a slam of the oral jaws. We observed that transection of the c-md ligaments makes the fish unable to perform such actions. We also counted biting rates on filamentous algae in fish with and without the c-md ligament and observed a drop of more than 80% in the latter. Conclusion: This study shows that the c-md ligament is a key trait both for sound production and for grazing activities in damselfishes. The buccal jaw slam enables the fish to perform accurate strikes on small filamentous algae. This kind of bite probably plays a major role in farming activity and allows grazing damselfishes to occupy distinct niches, possibly increasing their competitive evolutionary success. [less ▲]

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See detailTrait decoupling promotes evolutionary diversification of the trophic and acoustic system of damselfishes
Frederich, Bruno ULg; Olivier, Damien ULg; Litsios, Glenn et al

in Proceedings of the Royal Society B : Biological Sciences (2014)

Trait decoupling, wherein evolutionary release of constraints permits specialization of formerly integrated structures, represents a major conceptual framework for interpreting patterns of organismal ... [more ▼]

Trait decoupling, wherein evolutionary release of constraints permits specialization of formerly integrated structures, represents a major conceptual framework for interpreting patterns of organismal diversity. However, few empirical tests of this hypothesis exist. A central prediction, that the tempo of morphological evolution and ecological diversification should increase following decoupling events, remains inadequately tested. In damselfishes (Pomacentridae), a ceratomandibular ligament links the hyoid bar and lower jaws, coupling two main morphofunctional units directly involved in both feeding and sound production. Here, we test the decoupling hypothesis by examining the evolutionary consequences of the loss of the ceratomandibular ligament in multiple damselfish lineages. As predicted, we find that rates of morphological evolution of trophic structures increased following the loss of the ligament. However, this increase in evolutionary rate is not associated with an increase in trophic breadth, but rather with morphofunctional specialization for the capture of zooplanktonic prey. Lineages lacking the ceratomandibular ligament also shows different acoustic signals (i.e. higher variation of pulse periods) from others, resulting in an increase of the acoustic diversity across the family. Our results support the idea that trait decoupling can increase morphological and behavioral diversity through increased specialization rather than the generation of novel ecotypes. [less ▲]

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See detailPattern of morpho-functional diversifcation of damselfishes (Pomacentridae)
Frederich, Bruno ULg

Conference (2013, December 18)

Coral reef fishes represent one of the most outstandingly diverse assemblages of vertebrates on the planet but our understanding of their mode of diversification remains limited. Currently, some ... [more ▼]

Coral reef fishes represent one of the most outstandingly diverse assemblages of vertebrates on the planet but our understanding of their mode of diversification remains limited. Currently, some biologists are testing various hypotheses about the evolutionary history of coral reef fishes and are exploring the factors driving their diversification. During my post-doctoral research, I explored the pattern of morphological diversification of damselfishes (Pomacentridae, 386 species). I produced a time-calibrated phylogeny based on 8 loci including 208 species and collected eco-morphological data (trophic data, body shape and oral jaws shape) in more than 120 species. Using various phylogenetic comparative methods, I have illusrated that the Pomacentridae observed repeated ecological radiation and morphological convergence during their evolutionary history. I have also highlighted the primary role of a ligament joining the mandible and the hyoid in the evolution and the morpho-functional diversification of pomacentrids. [less ▲]

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See detailDiversification of the pectoral fin shape in damselfishes (Perciformes, Pomacentridae) of the Eastern Pacific
Aguilar-Medrano, Rosalia; Frederich, Bruno ULg; Balart, Eduardo F. et al

in Zoomorphology (2013)

Fin shape strongly influences performance of locomotion across all swimming styles. In this study, we focused on the diversity of the pectoral fin morphology in damselfishes of the Eastern Pacific ... [more ▼]

Fin shape strongly influences performance of locomotion across all swimming styles. In this study, we focused on the diversity of the pectoral fin morphology in damselfishes of the Eastern Pacific. Underwater observations and a review of literature allowed the characterization of ten behavioral groups. Territorial and non-territorial species were discriminated easily with traditional morphometrics. Five ecomorphological groups were recognized by geometric morphometric analyses. Geometric data segregated the outgroup from the damselfishes and allowed the distinction of mean morphologies from extreme ones within territorial and non-territorial species. Additionally, geometric morphometric data split Abudefduf into two groups: (1) A. troschelii is similar to C. atrilobata and (2) A. concolor and A. declivifrons are close to Stegastes. Solitary territorial species (e.g., Stegastes) show rounded and high fins whereas non-territorial species living in groups (e.g., Chromis) present long and curved pectoral fins. In the range of morphological variation, the morphologies of Microspathodon (elongate with highly curved hydrodynamic trailing edge) and Azurina (long, slender and angular) represent the extreme morphologies within territorial and non-territorial species, respectively. Our study revealed a strong relationship between the pectoral fin shape and the behavioral diversification in damselfishes. [less ▲]

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See detailA ligament influences the diversification of damselfishes (Pomacentridae)
Frederich, Bruno ULg; Olivier, Damien ULg; Litsios, Glenn et al

Conference (2013, June)

The Pomacentridae (damselfishes) is one of the most successful families of reef-associated fishes (386 species). In 1981, Stiassny described a synapomorphic trait of the Pomacentridae: the cerato ... [more ▼]

The Pomacentridae (damselfishes) is one of the most successful families of reef-associated fishes (386 species). In 1981, Stiassny described a synapomorphic trait of the Pomacentridae: the cerato-mandibular ligament (CML) joining the hyoid bar (ceratohyal) to the internal part of the mandible (coronoid process of the articulo-angular). Here, we highlight that this ligament is lacking in at least 18 damselfish species from different subclades (i.e. Chrominae, Abudefdufinae and Pomacentrinae) and we explore the impact of its disappearance on lineage, morphological and ecological diversification through their evolutionary history. Using a time-calibrated phylogeny including 208 species, we found no support for different rates of lineage diversification between species that lack the CML and the others. Yet, the CML clearly governs a part of the morphological diversity in damselfishes. Indeed, the body and mandible shapes differ significantly between species without CML and the others. Evolutionary modeling of some phenotypic traits (i.e. body and mandible shape) mainly supports models with two rates of morphological diversification across the time-tree with the species without CML having a higher rate of morphological diversification than the others. Mapping the diet of all studied species illustrates that damselfishes lacking CML are highly zooplanktivorous species. Their shapes suggest they feed on planktonic copepods with a higher contribution of ram-feeding (i.e. predator movement towards prey) in comparison with the other planktivorous damselfishes. Finally, the CML could have promoted easy shifts among the three main trophic guilds in damselfishes (i.e. grazers, zooplanktivorous and omnivorous) during evolution but the disappearance of the CML allowed a functional specialization linked to prey-capture strategies. These results support the primary role of the CML in the evolution and diversification of pomacentrids. [less ▲]

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See detailIterative ecological radiation and convergence during the evolutionary history of damselfishes (Pomacentridae)
Frederich, Bruno ULg; Sorenson, Laurie; Santini, Francesco et al

in American naturalist (2013), 181(1), 94-113

Coral reef fishes represent one of the most spectacularly diverse assemblages of vertebrates on the planet, but our understand- ing of their mode of diversification remains limited. Here we test whether ... [more ▼]

Coral reef fishes represent one of the most spectacularly diverse assemblages of vertebrates on the planet, but our understand- ing of their mode of diversification remains limited. Here we test whether the diversity of the damselfishes (Pomacentridae), one of the most species-rich families of reef-associated fishes, was produced by a single or multiple adaptive radiation(s) during their evolutionary history. Tests of the tempo of lineage diversification using a time-calibrated phylogeny including 208 species revealed that crown pomacentrid diversification has not slowed through time as expected under a scenario of a single adaptive radiation resulting from an early burst of diversification. Evolutionary modeling of trophic traits similarly rejected the hypothesis of early among-lineage partitioning of ecologically important phenotypic diversity. Instead, damselfishes are shown to have experienced iterative convergent radiations wherein subclades radiate across similar trophic strategies (i.e., pelagic feeders, benthic feeders, intermediate) and morphologies. Regionalization of coral reefs, competition, and functional constraints may have fueled iterative ecological radiation and convergent evolution of damselfishes. Through the Pomacentridae, we illustrate that radiations may be strongly structured by the nature of the constraints on diversification. [less ▲]

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See detailMorphological and genetic divergences in a coral reef damselfish, Pomacentrus coelestis
Frederich, Bruno ULg; Liu, S.-Y. Vanson; Dai, C.-F.

in Evolutionary Biology (2012), 39(3), 359-370

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 ... [more ▼]

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. [less ▲]

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See detailTempo and mode of eco-morphological evolution in damselfishes (Pomacentridae)
Frederich, Bruno ULg; Sorenson, Laurie; Santini, Francesco et al

Conference (2012, July)

Coral reef fishes represent one of the most outstandingly diverse assemblages of vertebrates on the planet but our understanding of their mode of diversification remains limited. Here we test whether the ... [more ▼]

Coral reef fishes represent one of the most outstandingly diverse assemblages of vertebrates on the planet but our understanding of their mode of diversification remains limited. Here we test whether the damselfishes (Pomacentridae), one of the most species-rich families of reef-associated fishes, adaptively radiated during their evolutionary history. Tests of the tempo of lineage diversification using a time-calibrated phylogeny including 208 species did not support the expected pattern of rapid inital diversification that slowed through time as predicted by macroevolutionary theory. Evolutionary modeling of trophic traits similarly rejected the hypothesis of early among-lineage partitioning of ecologically relevant phenotypic diversity. Instead, damselfishes are shown to have experienced iterative convergent radiations wherein subclades converge on similar trophic strategies (i.e. pelagic feeders, benthic feeders, intermediate) and morphologies. We discuss that regionalization of coral reefs, bipartite life cycle of reef fishes, competition and functional constraints are good candidate of causal factors underlying the iterative ecological radiation and convergent evolution of damselfishes. [less ▲]

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See detailEffects of alternate reef states on coral reef fish habitat associations
Lecchini, David; Carassou, Laure; Frederich, Bruno ULg et al

in Environmental Biology of Fishes (2012), 94(2), 421-429

The present study describes ontogenetic shifts in habitat use for 15 species of coral reef fish at Rangiroa Atoll, French Polynesia. The distribution of fish in different habitats at three ontogenetic ... [more ▼]

The present study describes ontogenetic shifts in habitat use for 15 species of coral reef fish at Rangiroa Atoll, French Polynesia. The distribution of fish in different habitats at three ontogenetic stages (new settler, juvenile, and adult) was investigated in coral- dominated and algal-dominated sites at two reefs (fringing reef and inner reef of motu). Three main ontogenetic patterns in habitat use were identified: (1) species that did not change habitats between new settler and juvenile life stages (60% of species) or between juvenile and adult stages (55% of species—no ontoge- netic shift); (2) species that changed habitats at different ontogenetic stages (for the transition “new settler to juvenile stage”: 15% of species; for the transition “juvenile to adult stage”: 20% of species); and (3) species that increased the number of habitats they used over ontogeny (for the transition “new settler to juvenile stage”: 25% of species; for the transition “juvenile to adult stage”: 25% of species). Moreover, the majority of studied species (53%) showed a spatial variability in their ontogenetic pattern of habitat use according to alternate reef states (coral reef vs algal reef), suggesting that reef state can influence the dynamics of habitat associations in coral reef fish. [less ▲]

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See detailMismatch between shape changes and ecological shifts during the post-settlement growth of the surgeonfish, Acanthurus triostegus
Frederich, Bruno ULg; Colleye, Orphal ULg; Lepoint, Gilles ULg et al

in Frontiers in Zoology (2012), 9

Background: Many coral reef fishes undergo habitat and diet shifts during ontogeny. However, studies focusing on the physiological and morphological adaptations that may prepare them for these transitions ... [more ▼]

Background: Many coral reef fishes undergo habitat and diet shifts during ontogeny. However, studies focusing on the physiological and morphological adaptations that may prepare them for these transitions are relatively scarce. Here, we explored the body shape variation related to ontogenetic shifts in the ecology of the surgeonfish Acanthurus triostegus (Acanthuridae) from new settler to adult stages at Moorea Island (French Polynesia). Specifically, we tested the relationship between diet and habitat shifts and changes in overall body shape during the ontogeny of A. triostegus using a combination of geometric morphometric methods, stomach contents and stable isotope analysis. Results: After reef settlement, stable isotope composition of carbon and nitrogen revealed a change from a zooplanktivorous to a benthic algae diet. The large amount of algae (> 75% of stomach contents) found in the digestive tract of small juveniles (25–30 mm SL) suggested the diet shift is rapid. The post-settlement growth of A. triostegus is highly allometric. The allometric shape changes mainly concern cephalic and pectoral regions. The head becomes shorter and more ventrally oriented during growth. Morphological changes are directly related to the diet shift given that a small mouth ventrally oriented is particularly suited for grazing activities at the adult stage. The pectoral fin is more anteriorely and vertically positioned and its basis is larger in adults than in juveniles. This shape variation had implications for swimming performance, manoeuvrability, turning ability and is related to habitat shift. Acanthurus triostegus achieves its main transformation of body shape to an adult-like form at size of 35–40 mm SL. Conclusion: Most of the shape changes occurred after the reef colonization but before the transition between juvenile habitat (fringing reef) and adult habitat (barrier reef). A large amount of allometric variation was observed after diet shift from zooplankton to benthic algae. Diet shift could act as an environmental factor favouring or inducing morphological changes. On the other hand, the main shape changes have to be achieved before the recruitment to adult populations and start negotiating the biophysical challenges of locomotion and feeding in wave- and current-swept outer reef habitat. [less ▲]

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See detailDivergences morphologiques et génétiques chez une espèce de demoiselle (Pomacentridae): Pomacentrus coelestis
Frederich, Bruno ULg; Liu, Shang-Yin

Conference (2012, March 30)

La différentiation des populations est l’un des principaux thèmes de la biologie de l’évolution. Mise à part l’étude des variations des patrons de coloration, très peu d’études concernent les divergences ... [more ▼]

La différentiation des populations est l’un des principaux thèmes de la biologie de l’évolution. Mise à part l’étude des variations des patrons de coloration, très peu d’études concernent les divergences morphologiques entre les populations de poissons des récifs coralliens. Dans ce travail, nous avons étudié la différentiation morphologique et génétique entre plusieurs populations de l’espèce de demoiselle, Pomacentrus coelestis Jordan & Starks, 1901, dans le Nord-Ouest de l’océan Pacifique. Cette espèce, inféodée aux récifs coralliens, se nourrit principalement de zooplancton. Elle est particulièrement abondante dans cette région du monde. Les formes des mâchoires buccales (c’est-à-dire la mandibule et le prémaxillaire) ont été étudiées au moyen des méthodes de morphométrie géométrique et la structure génétique des populations a été caractérisée au moyen de cinq microsattelites (POM3, POM2, AC1578, Pom2269 et Pom2416). Différents tests statistiques ont révélé une variation significative de forme entre les populations de P. coelestis pour chacune des deux pièces squelettiques. Les variations de forme de la mandibule et du prémaxillaire apparaissent non-corrélées. Les variations morphologiques de la mandibule accompagne une rupture génétique entre des populations de l’île principale du Japon et les îles d’Okinawa et Taiwan. Cependant, les tests de Mantel et Procrustes n’ont révélé aucune congruence entre les structures génétiques et morphologiques. Des variables géographiques telles que la latitude, la longitude et les distances kilométriques expliquent peu ou pas les variances morphologiques observées. Dans notre discussion, nous illustrons que la plasticité phénotypique serait un mécanisme évolutif potentiel sous-jacent à la différence de formes entre les populations de P. coelestis. Cependant l’hypothèse d’une divergence adaptative ne pourrait cependant pas être exclue vu que nous avons uniquement étudié des marqueurs génétiques neutres (microsattelites). Une approche écomorphologique suggère que des régimes alimentaires différents pourraient être liés aux variations de forme des mâchoires buccales. A titre d’exemple, les individus des populations de l’île principale du Japon ont des mandibules plus massives suggérant des activités de broutage et/ou de morsure plus fréquentes. Inversément, les individus de Taiwan et d’Okinawa arborent un processus ascendant du prémaxillaire proportionellement plus long que les poissons des autres populations. Cette caractéristique, directement liée à l’efficacité de protrusion des mâchoires supérieures, confirmerait un degré de zooplanctonophagie plus élevé chez ces deux populations. [less ▲]

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See detailFurther insight into the sound-producing mechanism of clownfishes: what structure is involved in sound radiation?
Colleye, Orphal ULg; Nakamura, Masaru; Frederich, Bruno ULg et al

in Journal of Experimental Biology (2012), 215

It was recently demonstrated that clownfishes produce aggressive sounds by snapping their jaw teeth. To date, only the onset of the sound has been studied, which raises the question, what structure is ... [more ▼]

It was recently demonstrated that clownfishes produce aggressive sounds by snapping their jaw teeth. To date, only the onset of the sound has been studied, which raises the question, what structure is involved in sound radiation? Here, a combination of different approaches has been used to determine the anatomical structure(s) responsible for the size-related variations observed in sound duration and frequency. Filling the swimbladder with physiological liquid specifically modified size-related acoustic features by inducing a significant decrease in pulse duration of approximately 3 ms and a significant increase in dominant frequency of approximately 105 Hz. However, testing the acoustics of the swimbladder by striking it with a piezoelectric impact hammer showed that this structure is a highly damped sound source prevented from prolonged vibrations. In contrast, the resonant properties of the rib cage seems to account for the size-related variations observed in acoustic features. For an equivalent strike on the rib cage, the duration and dominant frequency of induced sounds changed with fish size: sound duration and dominant frequency were positively and negatively correlated with fish size, respectively. Such relationships between sonic features and fish size are consistent with those observed in natural sounds emitted by fish. Therefore, the swimbladder itself does not act as a resonator; its wall just seems to be driven by the oscillations of the rib cage. This set of observations suggests the need for reassessment of the acoustic role of swimbladders in various fish species. [less ▲]

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See detailPatterns of morphological evolution of the cephalic region in damselfishes (Perciformes: Pomacentridae) of the Eastern Pacific
Aguilar-Medrano, Rosalia; Frederich, Bruno ULg; De Luna, Efrain et al

in Biological Journal of the Linnean Society (2011), 102

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 ... [more ▼]

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. [less ▲]

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