References of "Vandewalle, Pierre"
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See detailEvidence of an atypical scale development during the settlement phase of a coral reef fish
Frederich, Bruno ULg; Lecchini, David; Vandewalle, Pierre ULg

Poster (2009, April)

As the majority of coral reef fishes, the Convict Surgeonfish Acanthurus triostegus (Acanthuridae) has a complex life cycle that involves an ontogenetic change in morphology, physiology and behaviour as ... [more ▼]

As the majority of coral reef fishes, the Convict Surgeonfish Acanthurus triostegus (Acanthuridae) has a complex life cycle that involves an ontogenetic change in morphology, physiology and behaviour as its pelagic larval stage colonizes the benthic habitat. Abrupt and spectacular changes in skeletal structures occurring when a fish takes on its juvenile form were highlighted in flatfish, bonefish, tarpon, eels, pearlfish and lampreys. However, few studies are devoted to the changes in skeleton during the settlement period of demersal coral reef fishes. In the present study conducted at Rangiroa Atoll (French Polynesia), we highlight an unexpected scales development in A. trisostegus during a fifteen days period just after the reef settlement. Fish was collected during the settlement and reared in aquaria. The osseous skeleton was displayed by a standard Alizarin red S staining technique. At settlement (t0) (SL = 22-25 mm), A. triostegus showed calcified and very long plates, lying in the dermis on the whole body. After three days, some small scales developed on the caudal peduncle. The plates seemed unchanged from the head to the pectoral girdle but were thinner on the trunk. The thin plates are pricked with whitish spots, which seem to indicate a poorer fixation of the alizarin corresponding to a decalcification process. Six days after the settlement, the squamation extended anteriorly to the pectoral girdle by the addition of new scales. Thin plates were always present on the head. Then the density of scales rapidly increased along the trunk during the following three days. The scales appeared on the head nine days after the settlement. Clearly, the plates do not transform into scales. The plates disappearance and the scales appearance appear as two parallel phenomena in the development. [less ▲]

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See detailBipartite life cycle of coral reef fishes promotes increasing shape disparity of the head skeleton during ontogeny.
Frederich, Bruno ULg; Vandewalle, Pierre ULg

Conference (2009, April)

Disparity is a major theme in the paleobiological literature. Most studies of disparity have focused on its temporal dynamics over a geological time scale and generally show that phenotypic disparity ... [more ▼]

Disparity is a major theme in the paleobiological literature. Most studies of disparity have focused on its temporal dynamics over a geological time scale and generally show that phenotypic disparity decreases or remains stable in numerous groups. Surprisingly, the relationship between ontogeny and disparity has received little attention. The ontogenetic dynamics of shape disparity are influenced by diverse interactions such as developmental constraints and/or environmental factors. Coral reefs have an extraordinary diversity of fishes. As the majority of demersal coral reef fishes, the damselfishes (Pomacentridae) have a bipartite life cycle. During the pelagic dispersion phase, all larvae feed on planktonic preys. On the other hand, juveniles and adults associated to the coral reef environment show a high diversity of diets. We test the hypothesis that this ontogenetic change in habitat and diet is related to an increase of shape disparity in head skeletal units (neurocranium, suspensorium, opercle, mandible and premaxilla). We also compare ontogenies of shape among eight species of damselfishes to identify the evolutionary changes in developmental processes modifying shape disparity. By comparing levels of disparity between the eight species at three developmental stages, at the end of the larval phase (reef settlement), at 60 mm SL, and at maximum adult body size, we found that disparity increases significantly during ontogeny. At the end of the larval stage, all skeletal units are already species-specific. The ontogenies of shape are highly divergent among species. At least, evolutionary changes affected three parameters of ontogenetic trajectories of shape in this group: (1) the allometric pattern (the direction in which the vector representing the ontogeny of shape point), (2) the amount of change undergone during the juvenile and adult phases and (3) the rate of shape changes. The interactions among environmental constraints and the three developmental parameters are responsible for increasing disparity. [less ▲]

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See detailTrophic niches of thirteen damselfishes (Pomacentridae) at the Grand Récif of Toliara, Madagascar
Frederich, Bruno ULg; Fabri, Grégory ULg; Lepoint, Gilles ULg et al

in Ichthyological Research (2009), 56

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 ... [more ▼]

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. [less ▲]

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See detailOntogenetic determinism of colour polymorphism in a coral reef fish, Chrysiptera brownriggii (Pomacentridae)
Frederich, Bruno ULg; Brié, Christophe; Santos, Raphael et al

Poster (2008, October)

The determinism of ontogenetic colour changes induced by environmental factors is poorly understood in marine fishes, especially in coral ecosystems. The present study, conducted at the Rangiroa Atoll ... [more ▼]

The determinism of ontogenetic colour changes induced by environmental factors is poorly understood in marine fishes, especially in coral ecosystems. The present study, conducted at the Rangiroa Atoll (French Polynesia) explored the effects of fish density and brightness/darkness condition (type of background) on colour determination during the ontogeny of a territorial damselfish Chrysiptera brownriggii (Bennett 1828). In this species, larvae always colonize the reef (settlement) in a yellow morph, while juveniles and adults can display two distinct colour-patterns: yellow and dark brown. Our experiments in aquaria showed that a significant higher proportion of C. brownriggii larvae turned into the brown morph in a dark condition during a period of 5 and 15 days (70-100% of brown morph induction) just after reef settlement. A significant positive effect of fish density inducing a brown colour morph was also highlighted. After a first colour induction, reversibility experiments illustrated that juveniles can change their colour morph anew after a 5-day period. Although a shift from brown to yellow morph seemed to be more limited. In the dark condition, yellow adults did not change their colour after a 5-day period. Our results showed that the colour dimorphism in C. brownriggii should be density-dependent. The period of sensitivity seems to last throughout the post-settlement period. We suggest that the yellow morph in C. brownriggii can be viewed as a paedomorphic trait. Overall, our results reveal that a darkness/lightness environment and fish density are environmental cues related to colour determinism in the polyphenetic C. brownriggii. [less ▲]

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See detailComparative Trophic Morphology in Eight Species of Damselfishes (Pomacentridae)
Frederich, Bruno ULg; Pilet, A.; Parmentier, Eric ULg et al

in Journal of Morphology (2008), 269(2), 175-88

Damselfishes show significant biodiversity in the coral reefs. To better understand such diversity, an ecomorphological approach was investigated in the trophic morphology of eight species of ... [more ▼]

Damselfishes show significant biodiversity in the coral reefs. To better understand such diversity, an ecomorphological approach was investigated in the trophic morphology of eight species of Pomacentridae (Chromis acares, C. margaritifer, Dascyllus aruanus, D. flavicaudus, Pomacentrus pavo, Plectroglyphidodon johnstonianus, Pl. lacrymatus and Stegastes nigricans) belonging to different trophic guilds (zooplankton, algal, coral polyp feeders and omnivores). Geometric morphometrics were used to quantify size and shape variations in four skeletal units: (1) neurocranium, (2) suspensorium and opercle, (3) mandible and (4) premaxilla. This method allowed us to reveal shape and size differences correlated to functional diversity both within and between trophic guilds. Among zooplanktivores, C. margaritifer, D. aruanus and D. flavicaudus have a high and long supraoccipital crest, short mandibles forming a small mouth and high suspensoria and opercles. These three species can be considered to be suction feeders. In the same guild, C. acares shows opposite characteristics (long and thin mandibles, lengthened neurocranium and suspensorium) and can be considered as a ram feeder. Among herbivores and corallivores, the two species of Plectroglyphidodon and S. nigricans can be considered as grazers. Differences in skeletal shape are mainly related to improving the robustness of some skeletal parts (broad hyomandibular, short and high mandibles). The shapes of P. pavo, which feeds largely on algae, strongly differ from that of the other three grazers exhibiting similar morphological characteristics to C. acares (e.g., long and shallow suspensorium, lengthened neurocranium). This highlights likely differences concerning cutting or scraping method. Finally, no strong correlations exist between size and shapes in the eight studied species. Size difference among species having a very similar shape could be viewed as a factor optimizing resource partitioning. [less ▲]

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See detailAgonistic sounds in the skunk clownfish (Amphiprion akallopisos) : spectral and temporal basis for fish size assessment and individual recognition
Colleye, Orphal ULg; Frederich, Bruno ULg; Vandewalle, Pierre ULg et al

Poster (2008)

Clownfishes (i.e. Amphiprion akallopisos) are territorial fishes that use sound production to defend their anemone territory. They live in social groups within which there is a size-based dominance ... [more ▼]

Clownfishes (i.e. Amphiprion akallopisos) are territorial fishes that use sound production to defend their anemone territory. They live in social groups within which there is a size-based dominance hierarchy. In such a system, agonistic interactions are usual and play an important role in social organization by maintaining size differences between individuals adjacent in rank. Sounds are known to be used in agonistic interactions; they could therefore be associated with aggressive display within the group hierarchy. In the present study, we compared the sonic characteristics between individuals of different sizes and of different sexual status (non-breeder, male and female). Sound analysis revealed that dominant frequency and pulse length are highly correlated with fish size, and are not related to sex. No information related to size can be extracted from the pulse period, interpulse duration and number of pulses per train. Evidence is provided that dominant frequency and pulse length are morphologically determined signals related to fish size. In that case, smaller individuals produce shorter duration and higher frequency sounds than larger individuals. Both sonic features are signals conveying information related to the size of the emitter. This finding could be of significant importance, and might help to understand one of the mechanisms that carry the clue for individual recognition within the group hierarchy. [less ▲]

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See detailMechanism of sound production in Oreochromis niloticus
longrie, Nicolas; van Wassemberg, Sam; Mauguit, Quentin et al

Poster (2008)

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See detailHistology and ultrastructure of the elastic spring apparatus in Synodontis eupterus
Fabri, Grégory; Montchowui, E; Vandewalle, Pierre ULg et al

Poster (2008)

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See detailEtude de l'âge et de la croissance chez Clarias gariépinus (Pisces, Clariidae) dans le delta de l'Ouémé au Bénin (Afrique de l'Ouest)
Lalèyè, Philippe; Raemakers, Valérie; Vandewalle, Pierre ULg et al

in International Journal of Biological and Chemical Sciences (2008), 2(2), 157-167

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See detailMorphological alterations of zooxanthellae in bleached cnidarian hosts
Ladrière, Ophélie ULg; Compère, Philippe ULg; Decloux, Nicole ULg et al

in Cahiers de Biologie Marine (2008), 49(3), 215-227

Studying the morphological changes of zooxanthellae in the host gastroderm is essential to understand the mechanisms of bleaching. Transmission electron microscopy was used to observe samples from four ... [more ▼]

Studying the morphological changes of zooxanthellae in the host gastroderm is essential to understand the mechanisms of bleaching. Transmission electron microscopy was used to observe samples from four coral species-three collected from a barrier reef in Madagascar (Acropora digitifera (Dana, 1846), Echinopora hirsutissima Milne-Edwards & Haime, 1849 and Porites (Synaraea) rus Forskal, 1775)) and one cut from an aquarium-grown coral (Pocillopora damicornis (Linnaeus, 1758)-and from the hermatypic (zooxanthellae-containing) sea anemone Aiptasia pulchella (Carlgren, 1943). Zooxanthellae from bleached animals showed different stages of degradation or disorganization. Some were free, detached from the host gastroderm, associated or not with host-cell remains. Others were vacuolated, with abundant reserve material globules and angular holes probably created by the loss of crystalline material during cutting. Experimentally heat-shocked P. damicornis harboured, moreover, a greater number of dividing algae. Bleached individuals were found to vary as regards their response to stress, and zooxanthellae expelled from heat-shocked anemones showed a greater mitotic index and a higher survival rate than algae extracted or naturally externalized from healthy individuals. We propose a combination of morphological criteria for use in diagnosing the health state of algae-cnidarian symbiosis, so vulnerable in the case of bleaching. [less ▲]

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See detailEffects of fish size on agonistic sounds in the clownfish Amphiprion akallopisos : implications for the role of the swimbladder in the sound production mechanism?
Colleye, Orphal ULg; Vandewalle, Pierre ULg; Frederich, Bruno ULg et al

Conference (2008)

Clownfishes (i.e. Amphiprion akallopisos) are territorial fishes that use sound production to defend their anemone territory. They live in social groups which display a size-based dominance hierarchy. In ... [more ▼]

Clownfishes (i.e. Amphiprion akallopisos) are territorial fishes that use sound production to defend their anemone territory. They live in social groups which display a size-based dominance hierarchy. In such a system, agonistic interactions are frequent and play an important role in the social organization. In addition, these interactions are often associated with sounds. In this study, we compared the sonic features between individuals of different sizes and in different sexual status (juvenile, male and female). The existent relationship between fish size and swimbladder size also implied to seek the swimbladder role in the sound production. Sound analyses showed that juveniles, males and females had distinct sounds in the dominant frequency and pulse duration. These differences were however not in relation to the sexual state; influence of sex on sonic features being mainly the result of a size dimorphism between sexes. Differences in calls were therefore due to the respective size of the emitter. This observation highlighted the role of the swimbladder as a resonance chamber. This role was also reinforced because the experimental filling of the swimbladder with physiological liquid significantly modified the acoustic features. In A. akallopisos, frequency and pulse duration are directly related to swimbladder size, and thus to fish size. This relationship provides strong evidence that the emitter could be identified by its calls. [less ▲]

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See detailOntogenetic shape changes in Pomacentridae (Teleostei, Perciformes) and their relationships with feeding strategies: a geometric morphometric approach
Frederich, Bruno ULg; Adriaens, Dominique; Vandewalle, Pierre ULg

in Biological Journal of the Linnean Society (2008), 95

The present study explores the shape changes of cranial structures directly involved in food capturing during growth after reef settlement in two species of Pomacentridae (Dascyllus aruanus and ... [more ▼]

The present study explores the shape changes of cranial structures directly involved in food capturing during growth after reef settlement in two species of Pomacentridae (Dascyllus aruanus and Pomacentrus pavo). Landmark-based geometric morphometrics were used to study allometric patterns and related shape changes in four skeletal units: neurocranium, suspensorium and opercle, mandible and premaxilla. At settlement, the larvae of both species have a relatively similar morphology, especially with respect to the mandible. Their shapes suggest a feeding mode defined as ram/suction-feeding. Ontogenetic shape changes show a shift to a suction feeding mode of prey capture. The main transformations involved are an increase in height of the suspensorium and the opercle, an elevation of the supraoccipital crest, a relative shortening of the mandible, and a lengthening of the ascending process of the premaxilla. Shape changes of the mandible in the two studied species also reflect an increase of biting capacities. The high disparity between adult shape results from differences in the rate and in the length of ontogenetic trajectories, from divergence of the ontogenetic trajectories (neurocranium, mandible, and premaxilla) and parallel shifts of the trajectories in the size-shape space (suspensorium and opercle). In an evolutionary context, allometric heterochronies during ontogeny of different skeletal unit of the head may be considered as a basis for the explanation of the diversity of damselfishes. [less ▲]

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See detailMorphological recognition of artificial F1 hybrids between three common European cyprinid species: Rutilus rutilus, Blicca bjoerkna and Abramis brama.
Matondo, B. N.; Ovidio, Michaël ULg; Poncin, Pascal ULg et al

in Dong Wu Xue Bao = Acta Zoologica Sinica (2008), 54(1),

The F1 hybrids of roach Rutilus rutilus, silver bream Blicca bjoerkna, and common bream Abramis brama from experimental reciprocal cross-breedings were identified at 18 months of age in relation to the ... [more ▼]

The F1 hybrids of roach Rutilus rutilus, silver bream Blicca bjoerkna, and common bream Abramis brama from experimental reciprocal cross-breedings were identified at 18 months of age in relation to the parental species. The morphological analysis, including quantitative (plastic and meristic) and nonmetric features differing in the roach, the silver bream and the common bream, revealed that roach * common bream and roach * silver bream hybrids were easier to distinguish from their parents than silver bream * common bream hybrids. These roach hybrids had many morphological similarities such as the upper iris coloured in red as in the roach, and they were morphologically intermediate to the two parents. This contrasted with the silver bream * common bream hybrids, in which intermediate characteristics were also observed, but with some parental variants. Roach * silver bream hybrids were distinguishable from roach * common bream hybrids by its large eye, its lower scale numbers along the lateral line and its two rows of pharyngeal teeth. Silver bream * common bream hybrids, compared to the two other types of hybrids studied, had higher anal fin soft ray numbers and a clear eye iris with a median black line. In all interspecific crosses of these three cyprinid species fish, the reciprocal hybrids were generally indistinguishable. [less ▲]

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See detailTeleostean Phylogeny based onn osteological and myological characters
Diogo, Rui; Doadrio, Ignacio; Vandewalle, Pierre ULg

in International Journal of Morphology (2008), 26(3), 463-522

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See detailSound production in the clownfish Amphiprion clarkii
Parmentier, Eric ULg; Colleye, Orphal ULg; Fine, M. L. et al

in Science (2007), 316(5827), 1006-1006

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 ... [more ▼]

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. [less ▲]

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See detailSound production by pectoral spines in Six Synodontis species (Mochokidae)
Fabri, Grégory; Mauguit, Quentin; Vandewalle, Pierre ULg et al

Poster (2007)

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See detailMechanism of sound production in Oreochromis niloticus
Longrie, Nicolas; Herrel, Anthony; Mauguit, Quentin et al

Poster (2007)

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