References of "Vandewalle, Pierre"
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See detailFlore et faune de l'estran. Régions de Wimereux (Pas-de-Calais) et de Roscoff (Finistère)
Bussers, Jean-Claude ULg; Jeuniaux, Charles; Thomé, Jean-Pierre ULg et al

Learning material (2014)

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See detailFeeding ecology of the catfish Euchilichthys guentheri (Mochokidae, Siluriformes) of Pool Malebo, Congo River (Democratic Republic of Congo
Tembeni Makiadi, John; Mbomba Nseu, Bekeli; Micha, Jean-Claude et al

in Revue d'Ecologie (La Terre et la Vie) (2013), 68

Summary.— The feeding ecology of Euchilichthys guentheri (Schilthuis, 1891) of Malebo Pool (Congo River, Kinshasa, DRC) was studied between January 2008 and October 2010. The stomach contents of 243 ... [more ▼]

Summary.— The feeding ecology of Euchilichthys guentheri (Schilthuis, 1891) of Malebo Pool (Congo River, Kinshasa, DRC) was studied between January 2008 and October 2010. The stomach contents of 243 individuals were analysed and a diet was characterized by a feeding index computed by combining the occurrences, the numerical and volume percentages of the items identified in the stomach contents. The study showed that this species has an herbivorous diet mainly composed of periphyton. The study did not find any statistical differences in the diet related to the size of the specimens, the site and the hydrological season. The dietary strategies developed by this species likely contribute to its coexistence with the other Mochokidae species in Malebo Pool. The study thus provided relevant information regarding the feeding ecology of suckermouth catfishes intrinsically associated with the Congo River, one of the most threatened and biodiverse ecosystems of the Congo basin. [less ▲]

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See detailDéveloppement postembryonnaire du squelette céphalique en relation avec les changements morphologiques externes chez Labeo parvus (Ostariophysi, Cyprinidae)
Ledouroun, Djiman; Montchowui, Elie; Laleye, Philippe et al

in Cybium (2012), 36(2), 383-396

Postembryonic development of the external morphology and the cephalic skeleton in Labeo parvus has been studied from hatching up to 29 days post hatching. The specimens were obtained from a single ... [more ▼]

Postembryonic development of the external morphology and the cephalic skeleton in Labeo parvus has been studied from hatching up to 29 days post hatching. The specimens were obtained from a single artificial reproduction. After being trypsin-fixed, larvae and fry were cleared and stained with Alcian blue and alizarin Red S. The mouth opens at 18 h and the yolk sac is completely reduced at 36 h. The trabeculae, the parachardales plates, the wall of otic capsules, Meckel's catilages , the hyosymplectics are visible. At 24 h , the ceratobranchila are formed. At 36 h, the taeniae marginales, the ethmoid plate, the palatoquadrate, the hypohyals are already in place. Between 36 h and 4 days, the suspensorium is articulating with the neurocranium. At 10 days, all the important structures are formed and the chondrocranium regresses. The first bony structures, i.e. the operculars and the jaws appear at 4 days. The opercle is well developed at 6 days and functional. At 10 days, the parashenoid and teh basioccipital appear to form the floor of the braincase. From 14 to 29 days, new bony structures appear and rendre the braincase more efficient. [less ▲]

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See detailActual status of the ichthyofauna of the Mono river basin (Togo and Benin)
Lederound, Djiman; Vreven, Emmanuel; Lalèyé, Philippe et al

Conference (2012)

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See detailBipartite life cycle of coral reef fishes promotes increasing shape disparity of the head skeleton during ontogeny: an example from damselfishes (Pomacentridae)
Frederich, Bruno ULg; Vandewalle, Pierre ULg

in BMC Evolutionary Biology (2011), 11

Background: Quantitative studies of the variation of disparity during ontogeny exhibited by the radiation of coral reef fishes are lacking. Such studies dealing with the variation of disparity, i.e. the ... [more ▼]

Background: Quantitative studies of the variation of disparity during ontogeny exhibited by the radiation of coral reef fishes are lacking. Such studies dealing with the variation of disparity, i.e. the diversity of organic form, over ontogeny could be a first step in detecting evolutionary mechanisms in these fishes. The damselfishes (Pomacentridae) have a bipartite life-cycle, as do the majority of demersal coral reef fishes. During their pelagic dispersion phase, all larvae feed on planktonic prey. On the other hand, juveniles and adults associated with the coral reef environment show a higher diversity of diets. Using geometric morphometrics, we study the ontogenetic dynamic of shape disparity of different head skeletal units (neurocranium, suspensorium and opercle, mandible and premaxilla) in this fish family. We expected that larvae of different species might be relatively similar in shapes. Alternatively, specialization may become notable even in the juvenile and adult phase. Results: The disparity levels increase significantly throughout ontogeny for each skeletal unit. At settlement, all larval shapes are already species-specific. Damselfishes show high levels of ontogenetic allometry during their postsettlement growth. The divergence of allometric patterns largely explains the changes in patterns and levels of shape disparity over ontogeny. The rate of shape change and the length of ontogenetic trajectories seem to be less variable among species. We also show that the high levels of shape disparity at the adult stage are correlated to a higher level of ecological and functional diversity in this stage. Conclusion: Diversification throughout ontogeny of damselfishes results from the interaction among several developmental novelties enhancing disparity. The bipartite life-cycle of damselfishes exemplifies a case where the variation of environmental factors, i.e. the transition from the more homogeneous oceanic environment to the coral reef offering a wide range of feeding habits, promotes increasing shape disparity of the head skeleton over the ontogeny of fishes. [less ▲]

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See detailInterspecific variation of calls in clownfishes: degree of similarity in closely related species
Colleye, Orphal ULg; Vandewalle, Pierre ULg; Lanterbecq, Déborah et al

in BMC Evolutionary Biology (2011), 11

Clownfishes are colorful coral reef fishes living in groups in association with sea anemones throughout the Indo-Pacific Ocean. Within their small societies, size hierarchy determines which fish have ... [more ▼]

Clownfishes are colorful coral reef fishes living in groups in association with sea anemones throughout the Indo-Pacific Ocean. Within their small societies, size hierarchy determines which fish have access to reproduction. These fishes are also prolific callers whose aggressive sounds seem to play an important role in the social hierarchy. Agonistic interactions being involved in daily behaviour suggest how acoustic communication might play an important role in clownfish group. Sounds were recorded and compared in fourteen clownfish species (some of which have never been recorded before) to evaluate the potential role of acoustic communication as an evolutionary driving force. Surprisingly, the relationship between fish size and both dominant frequency and pulse duration is not only species-specific; all the specimens of the 14 species are situated on exactly the same slope, which means the size of any Amphiprion can be predicted by both acoustic features. The number of pulses broadly overlaps among species, whereas the pulse period displays the most variation even if it shows overlap among sympatric species. Sound comparisons between three species (A. akallopisos, A. ocellaris and A. frenatus) having different types of teeth and body shape do not show differences neither in the acoustic waveform nor in the power spectrum. Significant overlap in acoustic features demonstrates that the sound-producing mechanism is highly conservative among species. Differences in the calls of some species are due to size dimorphism and the sound variation might be in this case a by-product. This morphological constraint does not permit a consideration of acoustic communication as the main driving force in the diversification of clownfishes. Moreover, calls are not produced to find mate and consequently are less subject to variations due to partner preference, which restricts the constraints of diversification. Calls are produced to reach and defend the competition to mate access. However, differences in the pulse period between cohabiting species show that, in some case, sounds can help to differentiate the species, to prevent competition between cohabiting species and to promote the diversification of taxa. [less ▲]

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See detailSound production in red-bellied piranhas (Pygocentrus nattereri, Kner): an acoustical, behavioural and morphofunctional study
Millot, Sandie; Vandewalle, Pierre ULg; Parmentier, Eric ULg

in Journal of Experimental Biology (2011), 214

Piranhas are known to be sound-producing animals. Nevertheless, the biological significance of piranha calls remains unclear because sounds have been recorded only when specimens were held by hand or ... [more ▼]

Piranhas are known to be sound-producing animals. Nevertheless, the biological significance of piranha calls remains unclear because sounds have been recorded only when specimens were held by hand or trapped in a gill net. These sounds are generated by rapid contractions of sonic muscles that insert on a broad tendon surrounding ventrally the cranial sac of the swimbladder. The piranha swimbladder is thought to play an important role in sound production as an impedance-matching device and as a resonator. However, the vibratory capacities of the cranial and caudal sacs and the exact role of both sacs in sound production remain poorly understood. In this study, three sounds were each associated to a specific behaviour. The first sound (type 1) was produced during frontal display; it had numerous pulses and lasted 140±17 ms, with a fundamental frequency of 120±4 Hz. It corresponded to the sound made by hand-held fishes. The second sound (type 2) was produced during circling and fighting behaviour; it was a single pulse lasting 36±8 ms, with a fundamental frequency of 43±10 Hz. The third sound (type 3) corresponded to chasing behaviour and comprised three to four pulses, each lasting 3±1 ms, with a fundamental frequency of 1739±18 Hz. Using a laser vibrometer to study the swimbladder displacement when stimulated at different frequencies, it was demonstrated that the first two sounds corresponded to the swimbladder mechanism. By contrast, the third sound was associated with the jaw mechanism. The vibrometer indicated that the swimbladder is a highly damping structure, simply copying the sonic muscle contraction rate. This study provides two interesting insights. First, it shows the relationships between three kinds of piranha sound and three specific behaviours. Second, using muscle stimulation at different rates, it shows which simultaneous conditions are required for production of sound in this species. Swimbladder calls were produced by a muscle contraction rate of approximately 100 Hz because this periodicity allowed the swimbladder to vibrate. At this frequency range, the contraction–relaxation cycles of the swimbladder muscles engendered wall displacements that had short amplitudes and with only a small variability between them. [less ▲]

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See detailComparative study on sound production in different Holocentridae species
Parmentier, Eric ULg; Vandewalle, Pierre ULg; Brié, Christophe et al

in Frontiers in Zoology (2011), 8

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See detailTrophic niche width, shift, and specialization of Dascyllus aruanus in Toliara lagoon, Madagascar
Frederich, Bruno ULg; Lehanse, Olivier; Vandewalle, Pierre ULg et al

in Copeia (2010), 2010(2), 218-226

Intrapopulation diet specializations may result from the use of different dietary items or foraging tactics by individuals within a single population. The damselfish, Dascyllus aruanus, is a highly site ... [more ▼]

Intrapopulation diet specializations may result from the use of different dietary items or foraging tactics by individuals within a single population. The damselfish, Dascyllus aruanus, is a highly site-attached coral reef fish living in size hierarchies among branched corals. The trophic niche width and feeding specialization of this species were explored using stable isotopes and stomach content analyses. Intra-group niche variation was mainly related to fish size. Within social groups, D. aruanus gradually shifted its foraging tactics according to size; smaller fish fed on benthic prey such as isopods and copepods, and the larger fish foraged in the water column on planktonic copepods and larger-sized prey. Group density was found to explain some variation in trophic niche characteristics; greater specialization on prey size was observed in the colony having the highest density. All members of the largest colony foraged more frequently in the water column. Knowing that planktonic copepods are more energy-rich than benthic ones, a positive group-size effect facilitating access to preferred prey is suggested. Group size and group density effects on trophic specialization did not have any impact on body condition, suggesting that the behavioral plasticity of D. aruanus in its foraging strategies permits compensation for the maintenance of body conditions. [less ▲]

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See detailEvidence of an original scale development during the settlement phase of a coral reef fish (Acanthurus triostegus)
Frederich, Bruno ULg; Lecchini, David; Vandewalle, Pierre ULg

in Journal of Applied Ichthyology (2010), 26

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. Few studies are devoted to the changes in skeleton during the settlement phase of coral reef fishes. In the present study, we highlighted an unexpected scales development in A. trisostegus just after the reef settlement. At settlement (t0), A. triostegus showed calcified and very thin vertical plates, lying in the dermis on the whole body. During the first 9 days after settlement, thin vertical plates regressed and adult scales began to appear simultaneously. At 12 days post-settlement, the whole body was covered with small scales. Overall, such a rapid skeletal transformation is an example of morphological changes dealing with metamorphosis of coral reef fishes. [less ▲]

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See detailOntogeny of swimming movement in bronze corydoras (Corydoras aeneus)
Mauguit, Quentin; Olivier, Damien ULg; Vandewalle, Nicolas ULg et al

in Canadian Journal of Zoology (2010), 88(4), 378-389

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See detailContribution à la connaissance de l’ichtyofaune de l’Inkisi au Bas-Congo (RD du Congo)
Wamuini Lunkayilakio, Soleil; Vreven, Emmanuel; Vandewalle, Pierre ULg et al

in Cybium (2010), 34(1), 83-91

L’étude de la composition et de la distribution de la faune ichtyologique de la partie congolaise de la rivière Inkisi a permis d’inventorier 61 espèces réparties en 37 genres appartenant à 15 familles ... [more ▼]

L’étude de la composition et de la distribution de la faune ichtyologique de la partie congolaise de la rivière Inkisi a permis d’inventorier 61 espèces réparties en 37 genres appartenant à 15 familles. Les Cyprinidae sont les mieux représentés avec 15 espèces. Les Mormyridae, Cichlidae et Clariidae viennent ensuite avec respectivement 11, 9 et 7 espèces. La composition spécifique des communautés des poissons est différente, du cours supérieur vers l’aval. Le profil longitudinal de cette partie de l’Inkisi est caractérisé par la présence de trois chutes qui sont, de l’aval vers l’amont : la chute de Mantumpu (8 m de hauteur) à l’entrée de l’Inkisi dans le fleuve Congo, la chute de Zongo (58 m) à 6 km du confluent et la chute de Sanga (24 m) à 10 km de la chute de Zongo. La présence de ces chutes sur le cours de la rivière semble avoir influencé l’ichtyofaune et pourrait même être à l’origine du nombre important d’espèces endémiques en amont. Si l’on s’en tient au cours principal, la différence entre la richesse spécifique en amont et celle en aval n’est pas significative, probablement à cause de la morphologie du bassin. La richesse et la composition spécifique de la partie comprise entre les deux chutes (Zongo et Sanga) ne diffèrent pas de celles de l’amont de la chute de Sanga. Toutefois, cette composition est fort différente de celle de la zone tout en aval. [less ▲]

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See detailFunctional study of the pectoral spine stridulation mechanism in different mochokid catfishes
Parmentier, Eric ULg; Fabri, Grégory ULg; Kaatz, Ingrid et al

in Journal of Experimental Biology (2010), 213

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See detailFish lateral system is required for accurate control of shoaling behaviour
Faucher, Karine ULg; Parmentier, Eric ULg; Becco, Christophe ULg et al

Conference (2010)

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do ... [more ▼]

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do not stop schooling unless they are also blinded. This conclusion, however, was based on experiments where only the trunk lateral line was inactivated, leaving the head lateral system intact. Here the aim was to test how inactivation of the whole lateral system affects the fish shoaling behaviour. Groups of firehead tetras, Hemigrammus bleheri, were video-recorded before and after inactivation of their whole lateral system with aminoglycoside antibiotics (and also in sham-treated specimens). Shoaling behaviour was characterized by: nearest distance to the first, second, and third neighbour, shoal radius, shoal order parameter, and the number of collisions between individuals. SEM observations showed damage to most superficial neuromasts as a result of antibiotic treatment. Importantly, the antibiotic-treated fish proved unable to maintain a shoal. After the end of the treatment, however, they recovered both a normal tissue morphology and normal shoaling behaviour within about a month. The lateral system is thus more crucial to shoaling behaviour than previously believed. [less ▲]

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See detailFish lateral system is required for accurate control of shoaling behaviour
Faucher, Karine ULg; Parmentier, Eric ULg; Becco, Christophe ULg et al

in Animal Behaviour (2010), 79

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do ... [more ▼]

In teleost fishes, the lateral system is assumed to contribute, among other roles, to maintaining schooling behaviour. Sight is also assumed to play a role in schooling, as fish with a cut lateral line do not stop schooling unless they are also blinded. This conclusion, however, is based on experiments where only the trunk lateral line was inactivated, leaving the head lateral system intact. We investigated how inactivation of the whole lateral system affects fish shoaling behaviour. Groups of firehead tetras, Hemigrammus bleheri, were videorecorded before and after inactivation of their whole lateral system with aminoglycoside antibiotics (and also in sham-treated specimens). Shoaling behaviour was characterized by nearest distance to the first, second and third neighbours, shoal radius, shoal order parameter and the number of collisions between individuals. Scanning electron microscope observations showed damage to most superficial neuromasts as a result of antibiotic treatment. Importantly, the antibiotic-treated fish proved unable to maintain a shoal. After the end of the treatment, however, they recovered both a normal tissue morphology and normal shoaling behaviour within about a month. The lateral system is thus more crucial to shoaling behaviour than previously believed. [less ▲]

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See detailOntogeny of swimming movements in the catfish Clarias gariepinus
Mauguit, Quentin ULg; Gennotte, Vincent ULg; Becco, Christophe ULg et al

in The Open Fish Science Journal (2010), 3

The swimming movements of C. gariepinus larvae were recorded with a high-speed camera (400, 500 and 800 fps) from 0 to 336 hours post-hatching. Movements of adult fish were also recorded to provide ... [more ▼]

The swimming movements of C. gariepinus larvae were recorded with a high-speed camera (400, 500 and 800 fps) from 0 to 336 hours post-hatching. Movements of adult fish were also recorded to provide information on the last developmental stage. Seven landmarks positioned on the fish midline were used during tail beating to determine various parameters during ontogeny and, on the basis of these parameters, to describe the first appearance of swimming movements and their development and efficiency during growth. Larvae were unable to swim at hatching (4 mm total length). Swimming movements were established at 48 hours posthatching when the fish measured between 7 and 8 mm total length and the yolk sac was more than 95% absorbed. At this stage, lateral excursion of the head appeared strongly reduced (from 13% to 6% of the total length). The efficiency of swimming movements increased throughout ontogeny, as did the homogeneity of the speed of the propulsive wave. Spontaneous swimming speed of 1 to 10 TLs-1 were observed in early stage (8-12 hPH). The various speed induced significant variations in parameters such as the amplitude of lateral head movements, swimming efficiency, and body rigidity. No major change was observed at the theoretical flow-regime transition. [less ▲]

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See detailThe ontogenetic dynamic of skull shape disparity in damselfishes (Pomacentridae)
Frederich, Bruno ULg; Vandewalle, Pierre ULg

Conference (2009, May)

Damselfishes (Pomacentridae) are among the most speciose of coral-reef fishes, with > 350 species world-wide, most of which live on coral reefs. They have a life history with two distinct phases: a ... [more ▼]

Damselfishes (Pomacentridae) are among the most speciose of coral-reef fishes, with > 350 species world-wide, most of which live on coral reefs. They have a life history with two distinct phases: a dispersive pelagic larval phase and a sedentary benthic adult phase. The larval stage ends at coral reef settlement. All larvae feed on planktonic preys whereas juveniles and adults associated to the coral reef show a higher diversity of diets: zooplanktivorous, herbivorous, coral polyp feeders and omnivorous species. Morphological disparity is a major theme in paleobiology. Most studies of disparity have focused on its temporal dynamics over a geological time scale. Surprisingly, the relationship between ontogeny and disparity has received little attention. Using landmark-based geometric morphometrics, this study aims to test the hypothesis that the ontogenetic change in diet is related to an increase of shape disparity in head skeletal units (neurocranium, suspensorium + opercle, mandible and premaxilla) during the post-settlement growth in eight species of damselfishes. At the end of the larval stage (coral reef settlement), all skeletal units are already species-specific. By comparing levels of shape disparity between species at three developmental stages (at settlement, at 60 mm SL and at maximum adult body size), we found that disparity increases significantly during ontogeny. The ontogenies of shape were also compared to identify evolutionary changes in developmental processes modifying shape disparity. The ontogenetic patterns are highly divergent among species. At least, evolutionary changes affected three parameters of ontogenetic trajectories of shape in this group: (1) the allometric patterns (the direction in which the vector representing the ontogeny of shape point), (2) the amount of change undergone during the post-settlement phase and (3) the rate of shape changes. From a functional point of view, the ontogenetic transformations enhance suction-feeding and/or algae scraping (e.g. heightening of the suspensorium and opercle, shortening of the mandible). [less ▲]

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