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See detailPost-embryonic development of sheepshead minnow Cyprinodon variegatus: a staging tool based on externally visible anatomical traits
Schnitzler, Joseph ULg; Dussenne, Mélanie ULg; Frederich, Bruno ULg et al

in Ichthyological Research (in press)

The sheepshead minnow Cyprinodon variegatus has become a favoured model for laboratory studies because of their small size, rapid development, and tolerance of laboratory conditions. Here, we analyse ... [more ▼]

The sheepshead minnow Cyprinodon variegatus has become a favoured model for laboratory studies because of their small size, rapid development, and tolerance of laboratory conditions. Here, we analyse sheepshead minnow post-embryonic development with the goal of providing a generally useful method for staging fish after embryogenesis. Groups of three females and two males were placed in breeding chambers designed for this experiment. More than 100 eggs were collected and maintained in seawater. Embryos were selected under a dissection microscope and placed in incubation dishes (50 per dish) at 26 °C. On day six, embryos hatched and larvae were transferred to 1 L beakers. To define a simplified normalization table for sheepshead minnow development, we measured each fish for its standard length and examined the fish for four externally evident traits: pigmentation pattern, caudal fin morphology, anal fin morphology, and dorsal fin morphology. The four traits were chosen, because they are easily visualized with standard laboratory equipment such as the stereomicroscope and camera. We have provided criteria for staging sheepshead minnows in studies of post-embryonic development. Our data suggest that dorsal and anal fin morphology may serve as a useful phenotype for defining metamorphic climax stages throughout post-embryonic development in C. variegatus. The staging systems we propose should facilitate detailed anatomical and developmental analyses in relation to ecotoxicological studies on potential disruption of the thyroid axis by xenobiotics and endocrine-disrupting compounds. [less ▲]

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See detailEcomorphology and Iterative Ecological Radiation of Damselfishes
Frederich, Bruno ULg; Cooper, W. James; Aguilar-Medrano, Rosalia

in Frederich, Bruno; Parmentier, Eric (Eds.) Biology of Damselfishes (2016)

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See detailTrophic Ecology of Damselfishes
Frederich, Bruno ULg; Olivier, Damien ULg; Gajdzik, Laura ULg et al

in Frederich, Bruno; Parmentier, Eric (Eds.) Biology of Damselfishes (2016)

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See detailCerato-Mandibular Ligament: a Key Trait in Damselfishes?
Olivier, Damien ULg; Frederich, Bruno ULg; Parmentier, Eric ULg

in Frederich, Bruno; Parmentier, Eric (Eds.) Biology of Damselfishes (2016)

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See detailOntogeny and Early Life Stages of Damselfishes
Kavanagh, Kathryn; Frederich, Bruno ULg

in Frederich, Bruno; Parmentier, Eric (Eds.) Biology of Damselfishes (2016)

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See detailMeet the Damselfishes
Parmentier, Eric ULg; Frederich, Bruno ULg

in Frederich, Bruno; Parmentier, Eric (Eds.) Biology of Damselfishes (2016)

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See detailInsight into biting diversity to capture benthic prey in damselfishes (Pomacentridae)
Olivier, Damien ULg; Parmentier, Eric ULg; Frederich, Bruno ULg

in Zoologischer Anzeiger (2016), 264

The cerato-mandibular (c-md) ligament, joining the hyoid bar to the coronoid process of the angular, allows Pomacentridae to slam their mouth shut in a few milliseconds. Previous works have revealed that ... [more ▼]

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

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See detailBiology of Damselfishes
Frederich, Bruno ULg; Parmentier, Eric ULg

Book published by CRC-Press, Taylor & Francis (2016)

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See detailBrain lateralization involved in visual recognition of conspecifics in coral reef fish at recruitment
Roux, Natacha; Duran, Emilio; Lanyon, Rynae G. et al

in Animal Behaviour (2016), 117

In vertebrates, brain functional asymmetries are widespread and increase brain performance. Some species of fishes are known to have brain asymmetries; however, little information is available on brain ... [more ▼]

In vertebrates, brain functional asymmetries are widespread and increase brain performance. Some species of fishes are known to have brain asymmetries; however, little information is available on brain lateralization in coral reef fishes and the impact this could have during the recruitment phase. In this study, soldierfish, Myripristis pralinia, at the larval and juvenile stage recognized conspecifics through visual cues. Larvae with the ablation of either the right or left telencephalic hemisphere lost the attraction towards conspecific cues. In contrast, juveniles with the ablation of the right (but not left) telencephalic hemisphere still displayed a preference towards conspecific visual cues. These results suggest the left telencephalic hemisphere is responsible for the lateralization process used in the visual recognition of coral reef fish juveniles. The determinism of lateralized perception of conspecifics during fish ontogeny may be a consequence of genetic factors, linked with the metamorphosis processes and/or environmental factors such as predation at recruitment. [less ▲]

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See detailCan we detect adaptive radiations in marine fishes?
Santini, Francesco; Carnevale, Giorgio; Marrama, Giuseppe et al

Conference (2016, January)

The concept of adaptive radiation, according to which a biological lineage undergoes elevated rates of species diversification while at the same time experiencing divergence along ecological axis, is ... [more ▼]

The concept of adaptive radiation, according to which a biological lineage undergoes elevated rates of species diversification while at the same time experiencing divergence along ecological axis, is often invoked in evolutionary studies to explain the astonishing diversity of groups such as the cichlids of the African rift lakes, silverswords plants and honeycreeper birds in Hawaii, and anole lizards in the Neotropics. Recent surveys of the scientific literature, however, revealed that most studies of adaptive radiation do not recover the expected signal of early burst of lineage diversification, and in several animal groups rates of cladogenesis and phenotypic evolution may often be unlinked, thus creating complex patterns in the tempo of lineage and trait diversification. Furthermore, in spite of the dramatic increase in number of studies of the tempo and mode of evolution in marine fishes during the past decade, very little evidence has been uncovered to support the idea that adaptive radiations played a role in generating their staggering diversity, and even when a signal of radiation is recovered this virtually never conforms to the “traditional” early burst scenario. Using examples from our research on diverse groups of marine teleost fishes such as jacks and allies (Carangoidei), pufferfish and allies (Tetraodontiformes) and snappers (Lutjanidae), we will discuss why it is so difficult to recover a signal of adaptive radiation in general, and early burst in particular, and offer some suggestions on how to test for these patterns. [less ▲]

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See detailModular Diversification of the Locomotor System in Damselfishes (Pomacentridae)
Aguilar-Medrano, Rosalia; Frederich, Bruno ULg; Barber, Paul H.

in Journal of Morphology (2016)

As fish move and interact with their aquatic environment by swimming, small morphological variations of the locomotor system can have profound implications on fitness. Damselfishes (Pomacentridae) have ... [more ▼]

As fish move and interact with their aquatic environment by swimming, small morphological variations of the locomotor system can have profound implications on fitness. Damselfishes (Pomacentridae) have inhabited coral reef ecosystems for more than 50 million years. As such, habitat preferences and behavior could significantly constrain the morphology and evolvability of the locomotor system. To test this hypothesis, we used phylogenetic comparative methods on morphometric, ecological and behavioral data. While body elongation represented the primary source of variation in the locomotor system of damselfishes, results also showed a diverse suite of morphological combinations between extreme morphologies. Results show clear associations between behavior, habitat preferences, and morphology, suggesting ecological constraints on shape diversification of the locomotor system. In addition, results indicate that the three modules of the locomotor system are weakly correlated, resulting in versatile and independent characters. These results suggest that Pomacentridae is shape may result from the interaction between (1) integrated parts of morphological variation that main- tain overall swimming ability and (2) relatively independent parts of the morphology that facilitate adaptation and diversification. [less ▲]

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See detailTrophic ecology of the seagrass-inhabiting footballer demoiselle Chrysiptera annulata (Peters, 1855); comparison with three other reef-associated damselfishes
Lepoint, Gilles ULg; Michel, Loïc ULg; Parmentier, Eric ULg et al

in Belgian Journal of Zoology (2016), 146(1), 21-32

Many damselfishes (Pomacentridae) are herbivorous or omnivorous with an important contribution of different kinds of algae in their diet. They display different levels of territoriality and farming ... [more ▼]

Many damselfishes (Pomacentridae) are herbivorous or omnivorous with an important contribution of different kinds of algae in their diet. They display different levels of territoriality and farming behavior, from almost non territorial to monoculture farmers. In addition, few species inhabit seagrass meadows but, presently, none can be considered as seagrass-eating specialists. The footballer demoiselle, Chrysiptera annulata, is found in the seagrass meadows on the reef flat of the Great Reef of Toliara (Madagascar, Mozambique Channel). Regarding this unusual habitat for pomacentrid, this study aimed to answer 3 questions: 1) What is the diet of C. annulata? 2) Do the resources supporting this diet include seagrass? 3) Does its trophic niche overlap those of other sympatric damselfishes (Pomacentrus trilineatus, Chrysiptera unimaculata and Plectroglyphidodon lacrymatus) living in close association with macrophytes or eating algae? Stomach content examination and stable isotope analysis showed that the footballer demoiselle is not a seagrass consumer but is an omnivorous/herbivorous species heavily relying on algal resources and small invertebrates. SIAR, a stable isotope mixing model, indicated it assimilated large amount of turf algae and various benthic or planktonic invertebrates in lower proportions. SIBER metrics pointed out that isotopic niche of the footballer demoiselle partly overlaps the one of its congeneric C. unimaculata, but not those of P. trilineatus and P. lacrymatus. Trophic strategies of C. annulata differed both from farming species such as P. lacrymatus or from less territorial herbivores such as P. trilineatus. Its seagrass meadow habitat on the Great Reef of Toliara allow the conquest of an unusual habitat for damselfishes and could limit competition with C. unimaculata, a species displaying the same territorial behavior and the same isotopic niche but living on the reef itself. [less ▲]

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See detailEffect of evolutionary miniaturization on the tempo and mode of diversification - An example from marine angelfishes
Frederich, Bruno ULg; Santini, Francesco; Konow, Nicolai et al

Conference (2015, October 09)

Evolutionary change in body size is a widespread phenomenon in animals. Numerous studies have highlighted evolutionary miniaturization, referring to the evolution of small body size, in various taxa. As ... [more ▼]

Evolutionary change in body size is a widespread phenomenon in animals. Numerous studies have highlighted evolutionary miniaturization, referring to the evolution of small body size, in various taxa. As other traits shift, decrease in size can be viewed as a morphological novelty that enables colonization of new “adaptive zones” and subsequent diversification (i.e. a “key innovation”). Thus, evolution to small body size is hypothesized to influence lineage, morphological and ecological diversification. Until now, few studies have tested this hypothesis and current supports are mixed. Here, we present a quantitative analysis of the radiation of Pomacanthidae (angelfishes), an iconic coral reef fish family where small taxa, the so called “pygmy angelfishes” of the genus Centropyge, appear to have evolved three-times. If an evolutionary decrease in size has acted as a key innovation during the evolutionary history of Pomacanthidae, we predict that diversification rates would be the highest in clades of pygmy angelfishes. We produced a time-calibrated phylogeny including 67 species, collected ecological data and quantified the body shape of 80 species using geometric morphometrics. Then, we tested the prediction by modelling macroevolutionary dynamics of diversification using the Bayesian Analysis of Macroevolutionary Mixture (BAMM) framework. BAMM results do not support a common macroevolutionary regime for every pigmy angelfish clades. Only the clade Centropyge Xiphypops shows higher rates of lineage and morphological diversification than the other clades of angelfishes. We show that miniaturization has few effects on the rate of diversification. The shifts in the tempo of diversification observed in C. Xiphypops might instead be related to a functional innovation of the feeding apparatus. Using the Pomacanthidae, we illustrate that miniaturization may not be a main factor in triggering increased of diversification rates at the family level. [less ▲]

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See detailStable isotope ratios suggest limited trophic importance of seagrasses for invertebrate consumers from Malagasy tropical polyspecific seagrass meadows
Michel, Loïc ULg; Wang, Haolin; Frederich, Bruno ULg et al

Conference (2015, October 09)

Polyspecific seagrass meadows are of critical ecological importance in tropical coastal zones. These ecosystems provide a wide range of socio-economical services to local populations. Meadows however ... [more ▼]

Polyspecific seagrass meadows are of critical ecological importance in tropical coastal zones. These ecosystems 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 difficult to assess how seagrass meadows could respond to anthropogenic impacts due to poor knowledge of their functional ecology. Here, stable isotope ratios of carbon, nitrogen and sulfur were used to unravel trophic interactions ruling the food webs associated to seagrass beds of the Toliara Great Reef (SW Madagascar). The contributions of various potential food items (sediment-associated and suspended particulate organic matter, plankton, leaves, roots and epiphytes of 7 seagrasses and thalli of 7 dominant macroalgae) to the diet of 20 invertebrate taxa (one sea urchin, 2 sea stars, 2 sea cucumbers, 5 gastropods including one sea hare, one bivalve, 2 amphipods, one leptostracan, one cumacean 2 hermit crabs and 3 shrimps) were assessed using a Bayesian stable isotope mixing model. Model outputs revealed that important trophic diversity existed among the invertebrate assemblage. In some groups (e.g. hermit crabs and amphipods), resource use by morphologically and taxonomically close taxa was markedly different. Many of the dominant taxa heavily relied on macroalgae for their nutrition. On the other hand, few species apparently consumed seagrass tissues. Moreover, when they did, seagrass generally accounted for a minor portion of the diet only. Overall, our results suggest that seagrass grazing in meadows of the Toliara Great Reef could be lower than in other tropical areas. These discrepancies could be linked with seasonal variation in resource availability or with eutrophication. Higher nutrient load is indeed known to cause ecosystem phase shifts and it may induce diet shift to algivory in some invertebrate consumers. [less ▲]

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See detailTriclosan retardes development of Sheepshead minnow (Cyprinodon variegatus)
Dussenne, Mélanie ULg; Frederich, Bruno ULg; Das, Krishna ULg et al

Conference (2015, October)

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS), with his chemical structure similar to thyroid hormones (THs), may have ... [more ▼]

The aquatic environment represents the final sink for many chemicals, including bactericidal agents. Among them Triclosan (TCS), with his chemical structure similar to thyroid hormones (THs), may have adverse effects on the thyroid system. The study we carried out aims to evaluate the effects of TCS exposure on development of Cyprinodon variegatus, a fish model used in ecotoxicological studies. We investigated the potential effects of TCS on C. variegatus during two key periods; embryonic development and metamorphosis. We exposed eggs and larvae to environmental relevant concentrations. We showed that TCS had no effect on reproduction parameters, such as egg fertility or survival rate of larvae. However, we highlighted the fact that hatching of exposed larvae was delayed of around 6 to 13 hours compared to control embryos. During the larval phase, measurements of THs levels were performed. We showed that TCS affected the typical ontogenic variations of the whole body thyroid hormones concentrations during metamorphosis. As THs are known to control somatic growth and development, we tested the effects of TCS exposure on morphological development. We observed no deformity or malformation, but we revealed a developmental retardation in larvae exposed to TCS, of around 18 to 32 hours. Such a developmental delay had never been highlighted in previous studies on TCS exposed fish. We hypothesize that the disruption of THs homeostasis affects the timing of the start of metamorphosis. As a consequence, exposed larvae showed an extended larval phase compared to the control group. The harmful effects of TCS on physiology and development are a major concern, as marine organisms are constantly exposed to it. Furthermore, strong connections exist between thyroid and reproductive system, which might have deleterious effects on population dynamics. [less ▲]

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See detailImpact of the trophic strategy on the eco-functional diversification of a coral reef fish family
Gajdzik, Laura ULg; Aguilar-Medrano, Rosalia; Parmentier, Eric ULg et al

Conference (2015, September)

The analyses of the role of trophic strategies as promoter or constraint on processes of diversification remain understudied, especially in fish. The Pomacentridae (damselfishes), a species-rich (394 ... [more ▼]

The analyses of the role of trophic strategies as promoter or constraint on processes of diversification remain understudied, especially in fish. The Pomacentridae (damselfishes), a species-rich (394 species) and worldwide distributed reef fish family, include three main trophic guilds: (1) pelagic zooplankton feeders, (2) benthic feeders grazing on turf algae or biting polyps and (3) an intermediate group feeding on zooplankton, small benthic invertebrates and algae. Our study aims to analyze the role of the trophic strategies in the eco-functional diversity of Pomacentridae. Due to its feeding versatility, we hypothesize that the intermediate trophic group is the most successful group in terms of eco-functional diversity through evolutionary time. To target our aim, we compiled detailed dietary, environmental and behavioral data for 201 pomacentrid species, and compared the eco-functional diversity among trophic guilds. Various metrics, such as functional entity (i.e. unique combinations of functional traits) and functional richness revealed that the intermediate trophic group exhibited the lowest diversity. Then, we used time-calibrated phylogenies and comparative methods to evaluate the impact of trophic strategies on the tempo of ecological diversification. Results were consistent and the lowest rate of diversification was found for the intermediate trophic group. Our study shows that a generalist trophic strategy does not promote ecological diversification but being specialized may increase the ability to evolve greater diversity. [less ▲]

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See detailComparison of isotopic turnover dynamics in two different muscles of a coral reef fish during the settlement phase
Gajdzik, Laura ULg; Lepoint, Gilles ULg; Lecchini, David et al

in Scientia Marina (2015), 79(3), 325-333

The temporal variation in carbon and nitrogen isotopic compositions (noted as δ13C and δ15N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period ... [more ▼]

The temporal variation in carbon and nitrogen isotopic compositions (noted as δ13C and δ15N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period of 24 days, juveniles were reared in aquaria and subjected to two different feeding treatments: granules or algae. The dynamics of δ13C and δ15N in two muscles (the adductor mandibulae complex and the epaxial musculature) having different functions were compared. At the end of experiments, a steady-state isotopic system in each muscle tissue was not reached. Especially for the algal treatment, we found different patterns of variation in isotopic compositions over time between the two muscles. The turnovers of δ13C showed opposite trends for each muscle but differences are mitigated by starvation and by the metamorphosis. Our study highlighted that the metabolism of coral reef fish may be subjected to catabolism or anabolism of non-protein precursors at settlement, inducing variation in isotopic compositions that are not linked to diet change. [less ▲]

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