Développement postembryonnaire du squelette céphalique en relation avec les changements morphologiques externes chez Labeo parvus (Ostariophysi, Cyprinidae)

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

Sound production in red-bellied piranhas (Pygocentrus nattereri, Kner): an acoustical, behavioural and morphofunctional study

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 ▲]

Comparative study on sound production in different Holocentridae species

in Frontiers in Zoology (2011), 8

Ontogeny of swimming movements in bronze corydoras (Corydoras aeneus)

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

Fish lateral system is required for accurate control of shoaling behaviour

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 ▲]

Sound production and associated behaviour in the Nile Tilapia, oerochromis niloticus (Cichlidae)

Conference (2010)

Evidence of an original scale development during the settlement phase of a coral reef fish (Acanthurus triostegus)

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 ▲]

Ontogeny of swimming movements in the catfish Clarias gariepinus

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 ▲]

Contribution à la connaissance de l’ichtyofaune de l’Inkisi au Bas-Congo (RD du Congo)

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 ▲]

The ontogenetic dynamic of skull shape disparity in damselfishes (Pomacentridae)

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 ▲]