Clownfish Amphiprion Ocellaris Research Articles

Growth and Oxidative Stress of Clownfish Amphiprion ocellaris Reared at Different Salinities

Aquaculture of ornamental marine fish is often conducted in recirculating aquaculture systems (RAS) using artificial seawater. Considering the cost of salts to produce artificial seawater (salinity 35‰), we investigated the effect of different salinities (5, 15, 25, and 35‰) on survival, growth, and oxidative stress responses of juvenile clownfish Amphiprion ocellaris. All fish died when reared at salinity 5‰, but at all other salinities survival was ≥95% in the other treatment groups. There was no influence of salinity on growth and oxidative stress responses of clownfish reared at salinities 15, 25, and 35‰, except for the activity of glutathione S-transferase (GST) of fish reared at 25‰, which was significantly lower compared to those reared in salinity 35‰. The salinity of home aquariums is usually 35‰, so even though clownfish can be reared in brackish water, they need to be transferred to full strength seawater (35‰) in order to be commercialized. Therefore, we also evaluated the responses of acute transference of fish reared at 15 to salinity 35‰. There were no mortalities associated with acute salinity transference and no oxidative damage was observed either. The total capacity against peroxyl radicals (ACAP) was immediately increased after fish were placed in salinity 35‰, and remained high after 168 h (7 days), helping fish to deal with oxidative threats. In conclusion, it is possible to rear juvenile clownfish at 15‰ without harming growth or inducing oxidative stress, possibly reducing costs of water salinization. They can be transferred from brackish water to salinity 35‰ immediately before going to the retail market, with no mortality or oxidative damage.

Insulin-like growth factor II, a marker gene for determining the optimum dietary protein level in clownfish Amphiprion ocellaris.

In vivo study was conducted to determine the role of insulin-like growth factors (IGF-II) related to dietary protein utilization. For this early juvenile stage of marine false clownfish Amphiprion ocellaris, 300 numbers of 20-day-old larvae (initial body weight of 18.2±0.027 mg/fish) were used as an experimental animal. Animals were fed for 12 weeks with different dietary protein levels (35, 40, 45, 50, and 55%), using Spirulina maxima as a major protein source. Proximate compositions and amino acid profile of the formulated diet were analyzed by the standard methods. Eventually, significant (P<0.05) mean, body weight gain, absolute growth rate, specific growth rate, and feed conversion ratio were obtained in the fishes fed with 50% of dietary protein, whereas, poor growth performance was noticed in 35% of the dietary protein level fed juveniles. The growth-responsible gene IGF-II expression studies showed the significant upregulation in the growth of the juveniles at 2.05±0.11 for 40%, 3.13±0.20 for 45%, 4.97±0.13 for 50%, and 4.33± 0.24 for 55%, which were higher than the control group 35%. The study concluded that 50% of dietary protein level is optimal for better growth indices in clownfish; A. ocellaris juveniles and IGF-II can be used as a potential marker gene to assess the growth indices in A. ocellaris.

New cells added to the preoptic area during sex change in the common clownfish Amphiprion ocellaris

Sex differences in cell number in the preoptic area of the hypothalamus (POA) are documented across all major vertebrate lineages and contribute to differential regulation of the hypothalamic-pituitary-gonad axis and reproductive behavior between the sexes. Sex-changing fishes provide a unique opportunity to study mechanisms underlying sexual differentiation of the POA. In anemonefish (clownfish), which change sex from male to female, females have approximately twice the number of medium-sized cells in the anterior POA compared to males. This sex difference transitions from male-like to female-like during sex change. However, it is not known how this sex difference in POA cell number is established. This study tests the hypothesis that new cell addition plays a role. We initiated adult male-to-female sex change in 30 anemonefish (Amphiprion ocellaris) and administered BrdU to label new cells added to the POA at regular intervals throughout sex change. Sex-changing fish added more new cells to the anterior POA than non-changing fish, supporting the hypothesis. The observed effects could be accounted for by differences in POA volume, but they are also consistent with a steady trickle of new cells being gradually accumulated in the anterior POA before vitellogenic oocytes develop in the gonads. These results provide insight into the unique characteristics of protandrous sex change in anemonefish relative to other modes of sex change, and support the potential for future research in sex-changing fishes to provide a richer understanding of the mechanisms for sexual differentiation of the brain.

Metabolic rates, feed intake, appetite control, and gut transit of clownfish Amphiprion ocellaris exposed to increased temperature and limited feed availability

Episodes of elevated temperature, combined with lower feed availability, are among the predicted scenarios of climate change representing a challenge for coral reef fish. We investigated the response of clownfish (Amphiprion ocellaris) to a scenario in which it received a single meal to satiety after 48 h fasting at 32 °C (climate change scenario) and 28 °C (control). We analysed the metabolic rate (MR), feed intake, gut transit, and expression of selected brain neuropeptides and one receptor believed to be involved in appetite control. Fish at 32 °C ingested 17.9% less feed and had a faster gut transit than did fish at 28 °C. MR in the unfed fish was 31% higher at 32 °C compared to 28 °C. In the fed fish, postprandial MR at 28 °C was 30% higher compared to that of unfed fish, while at 32 °C it was only 15% higher. The expression of agrp1 did not differ between unfed and refed fish. The levels of both pomca and mc4r increased immediately after the meal and subsequently declined, suggesting a possible anorexic role for these genes. Notably, this pattern was accelerated in fish kept at 32 °C compared with that in fish kept at 28 °C. The dynamics of these changes in expression correspond to a faster gut transition of ingested feed at elevated temperatures. For both agrp2 and pomcb there was an increase in expression following feeding in fish maintained at 32 °C, which was not observed in fish kept at 28 °C. These results suggest that low feed availability and elevated temperature stimulate anorexigenic pathways in clownfish, resulting in significantly lower feed intake despite the temperature-induced increase in metabolic rate. This may be a mechanism to ameliorate the decrease in aerobic scope that results from higher temperatures.

Stable and persistent male-like behavior during male-to-female sex change in the common clownfish Amphiprion ocellaris

Many fish species exhibit natural sex change as part of their life, providing unique opportunities to study sexually-differentiated social behaviors and their plasticity. Past research has shown that behavioral sex change in the female-to-male (protogynous) direction occurs rapidly and well before gonadal sex change. However, little is known about the timecourse of behavioral sex change in male-to-female (protandrous) sex-changing species, limiting our ability to compare patterns of behavioral sex change across species and identify conserved or divergent underlying mechanisms. Using the protandrous sex changing anemonefish Amphiprion ocellaris, we assessed behavior (aggression and parental care) and hormones (estradiol and 11-ketotestosterone) in fish over six months of sex change, and compared those fish against their non-changing partners as well as control males and females. Contrary to expectations, we found that sex-changing fish displayed behavior that was persistently male-like, and that their behavior did not become progressively female-like as sex change progressed. Hormones shifted to an intermediate profile between males and females and remained stable until gonads changed. These results support a new perspective that the timecourse for protandrous sex change in anemonefish is completely distinct from other well-established models, such that behavioral sex change does not occur until after gonadal sex change is complete, and that sex-changing fish have a stable and unique behavioral and hormonal phenotype that is distinct from a male-typical or female-typical phenotype. The results also identify aspects of sex change that may fundamentally differ between protandrous and protogynous modes, motivating further research into these remarkable examples of phenotypic plasticity.

A chromosome-scale genome assembly of the false clownfish, Amphiprion ocellaris.

The false clownfish Amphiprion ocellaris is a popular fish species and an emerging model organism for studying the ecology, evolution, adaptation, and developmental biology of reef fishes. Despite this, high-quality genomic resources for this species are scarce, hindering advanced genomic analyses. Leveraging the power of PacBio long-read sequencing and Hi-C chromosome conformation capture techniques, we constructed a high-quality chromosome-scale genome assembly for the clownfish A. ocellaris. The initial genome assembly comprised of 1,551 contigs of 861.42 Mb, with an N50 of 863.85 kb. Hi-C scaffolding of the genome resulted in 24 chromosomes containing 856.61 Mb. The genome was annotated with 26,797 protein-coding genes and had 96.62% completeness of conserved actinopterygian genes, making this genome the most complete and high quality among published anemonefish genomes. Transcriptomic analysis identified tissue-specific gene expression patterns, with the brain and optic lobe having the largest number of expressed genes. Further, comparative genomic analysis revealed 91 genome elements conserved only in A. ocellaris and its sister species Amphiprion percula, and not in other anemonefish species. These elements are close to genes that are involved in various nervous system functions and exhibited distinct expression patterns in brain tissue, potentially highlighting the genetic toolkits involved in lineage-specific divergence and behaviors of the clownfish branch. Overall, our study provides the highest quality A. ocellaris genome assembly and annotation to date, whilst also providing a valuable resource for understanding the ecology and evolution of reef fishes.

Establishment of culture and microinjection methods for false clownfish embryos without parental care.

Anemonefish, including the false clownfish Amphiprion ocellaris, are attractive model organisms because of their unique features, such as sex change and brilliant color patterns in mutants. However, anemonefish are not widely used to study gene function using reverse genetic approaches owing to microinjection difficulties and subsequent rearing and hatching of embryos without parental care. A. ocellaris embryos are spawned on a hard substrate and cared for by their parents until hatching. However, the eggs need to be detached from the substrate and raised without their parents to perform successful microinjection. We established a method to culture and hatch A. ocellaris embryos without spawning substrates or parental care. We found that changing water and generating water flow are critical for culturing the embryos, and that water flow (as physical stimulation) and complete darkness in the dark period are necessary for successful hatching. We further investigated the effectiveness of microinjection into the yolk sac of fertilized eggs rather than into the cytoplasm, which makes microinjection easier. A reporter RNA injected into the yolk sac was transferred to the cytoplasm and translated, indicating that yolk sac microinjection is an efficient alternative as has been used for zebrafish. These findings highlight the potential of A. ocellaris as an experimental model organism for reverse genetics, and our methods could be applied to other anemonefish species.

Conserved fatty acid profiles and lipid metabolic pathways in a tropical reef fish exposed to ocean warming – An adaptation mechanism of tolerant species?

Climate warming is causing rapid spatial expansion of ocean warm pools from equatorial latitudes towards the subtropics. Sedentary coral reef inhabitants in affected areas will thus be trapped in high temperature regimes, which may become the “new normal”. In this study, we used clownfish Amphiprion ocellaris as model organism to study reef fish mechanisms of thermal adaptation and determine how high temperature affects multiple lipid aspects that influence physiology and thermal tolerance. We exposed juvenile fish to two different experimental conditions, implemented over 28 days: average tropical water temperatures (26 °C, control) or average warm pool temperatures (30 °C). We then performed several analyses on fish muscle and liver tissues: i) total lipid content (%), ii) lipid peroxides, iii) fatty acid profiles, iv) lipid metabolic pathways, and v) weight as body condition metric. Results showed that lipid storage capacity in A. ocellaris was not affected by elevated temperature, even in the presence of lipid peroxides in both tissues assessed. Additionally, fatty acid profiles were unresponsive to elevated temperature, and lipid metabolic networks were consequently well conserved. Consistent with these results, we did not observe changes in fish weight at elevated temperature. There were, however, differences in fatty acid profiles between tissue types and over time. Liver showed enhanced α-linolenic and linoleic acid metabolism, which is an important pathway in stress response signaling and modulation on environmental changes. Temporal oscillations in fatty acid profiles are most likely related to intrinsic factors such as growth, which leads to the mobilization of energetic reserves between different tissues throughout time according to organism needs. Based on these results, we propose that the stability of fatty acid profiles and lipid metabolic pathways may be an important thermal adaptation feature of fish exposed to warming environments.

A star is born again: Methods for larval rearing of an emerging model organism, the False clownfish Amphiprion ocellaris.

As interest increases in ecological, evolutionary, and developmental biology (Eco‐Evo‐Devo), wild species are increasingly used as experimental models. However, we are still lacking a suitable model for marine fish species, as well as coral reef fishes that can be reared at laboratory scales. Extensive knowledge of the life cycle of anemonefishes, and the peculiarities of their biology, make them relevant marine fish models for developmental biology, ecology, and evolutionary sciences. Here, we present standard methods to maintain breeding pairs of the anemonefish Amphiprion ocellaris in captivity, obtain regular good quality spawning, and protocols to ensure larval survival throughout rearing. We provide a detailed description of the anemonefish husbandry system and life prey culturing protocols. Finally, a “low‐volume” rearing protocol useful for the pharmacological treatment of larvae is presented. Such methods are important as strict requirements for large volumes in rearing tanks often inhibit continuous treatments with expensive or rare compounds.

Trophic contamination by octocrylene does not affect aerobic metabolic scope in juveniles clownfish

The effect of trophic exposure to Octocrylene (OC) on aerobic metabolism of clownfish Amphiprion ocellaris was investigated. There were no significant differences in Standard Metabolic Rate (SMR), Active Metabolic Rate (AMR) or aerobic metabolic scope (AS) at the concentration of 10 µg/g of octocrylene in diet of juvenile’s clownfish whatever the time of exposure. This suggests that under these experimental conditions, exposure to OC in food at a concentration of 10 µg/g did not influence aerobic metabolism of this species.

Synergistic Effects of Ocean Warming and Cyanide Poisoning in an Ornamental Tropical Reef Fish

An array of anthropogenic pressures is affecting tropical ecosystems, posing major conservation challenges for scientists, stakeholders and populations. Illegal cyanide fishing is one of the major threats to Indo-Pacific coral reefs, targeting a multitude of colorful species for the marine aquarium trade as well as large-sized groupers and wrasses for the food fish trade. Ultimately, the continued use of this destructive practice as oceans warm may overload tropical ecosystems and result in irreversible ecological damage. Here we show that the impact of cyanide poisoning in ornamental tropical marine fish is magnified under increased temperatures. A sole pulse exposure of 60 seconds to 50 mg L-1 of cyanide under current temperature (26 oC) caused substantial mortality (50-100 %) in eight species of Pomacentridae. The clownfish Amphiprion ocellaris was the most resilient, especially medium-sized fish (average total length and weight of 38 mm and 1.12 g; LC50 (95% CI) = 50.00 (46.76 – 53.24) mg L-1) that showed shorter recovery times and higher survival rates (%) when compared to small-sized ones (average total length and weight of 25 mm and 0.30 g; LC50 (95% CI) = 28.45 (20.17 – 36.72) mg L-1). However, when the most resistant size-class was concomitantly exposed to a sub-lethal dosage of cyanide (25 mg L-1 instead of 50 mg L-1) and ocean warming scenarios for 2100 (+3 oC and heat wave +6 oC), survival rates (%) decreased to 60 % and 20 %, respectively and recovery times increased in the worst case scenario. Mortality outbreaks, as well as vulnerability to predation, will likely expand in fish inhabiting coral reefs exposed to cyanide fishing unless stronger conservation measures are taken in tropical reefs to limit this destructive practice now and in the oceans of tomorrow.

Autochthonous bacterium Lactobacillus plantarum as probiotic supplementation for productive performance and sanitary improvements on clownfish Amphiprion ocellaris

This current study evaluated the probiotic dietary supplementation with autochthonous bacterium Lactobacillus plantarum for Amphiprion ocellaris. Therefore, it was performed an experiment in complete randomized design with four treatments (T1: Control without probiotic; T2: 104; T3: 106 and T4: 108 CFU/g of ration) and three replicates. Juvenile fish (n = 120; 0.46 ± 0.01 g and 0.26 ± 0.06 cm) were distributed in twelve aquarium (80 L) and it received trial meal three times a day at fed rate of 4% live weight during 90 days. The fish were monthly measured and determined the total length, standard length, height, weight gain, biomass gain, specific growth rate, apparently feed conversion, relative condition factor, uniformity and survival. At the end of experiment (90 days) fish were submitted to hematological (n = 9/ treatment; Erythrogram, Leukogram and Thrombogram) and histological analysis (n = 6/ treatment; Intestinal tract). Also, after the supplementation period, the fish were challenged with pathogenic bacteria and the survival and blood analyzed. Results showed the fish fed T3 and T4 had improvement on weight gain, feed conversion, specific growth rate, height and total height from the intestinal villi. Increases of red blood cell (Erythrocyte, hematocrit and hemoglobin) and white blood cell (Lymphocyte and monocyte) also observed to both treatments (T3 and T4), However the T4 promoted the greater fish resistance to pathogenic bacteria. As conclusion, probiotic supplementation with the autochthonous bacterium Lactobacillus plantarum 106 CFU/g provides zootechnical improvement for clownfish rearing, but to improve the pathogenic infection resistance, the 108 CFU/g presented more adequate.

The effect of spatial position and age within an egg-clutch on embryonic development and key metabolic enzymes in two clownfish species, Amphiprion ocellaris and Amphiprion frenatus.

Since the size of newly hatched larval fish is directly related to egg size, small differences in initial egg size can be critical to survival and further development of offspring. Underlying processes causing size variation in fish offspring are still not entirely understood. In this study we investigated whether the spatial position of an individual egg within a clutch affects size variation in two benthic spawning coral reef fishes, the clownfishes Amphiprion ocellaris and A. frenatus. To evaluate the effects of within-clutch position on embryonic development, egg growth metrics and protein content were analysed on day 2, 5 and 8 after deposition (adp). Additionally the activities of the key metabolic enzymes citrate synthase (CS) and lactate dehydrogenase (LDH) were investigated to evaluate the physiological status of the embryos. Central eggs of A. frenatus were significantly longer and heavier than peripheral eggs only on day 2 and 5 adp (2.07 mg, 2.59 mm vs. 1.84 mg, 2.49 mm). No significant differences were observed in A. ocellaris between eggs originating from a central or peripheral (5 mm from edge) position (1.33 mg, 2.26 mm vs. 1.15 mg, 2,18 mm). Diameter of the eyes did not differ between the two fish species nor between different positions, for any age group. The protein content of eggs (7.5% of wet weight) was independent of age, position and species. Enzymatic activity increased from 2 adp until peak activity was observed for both enzymes on day 8 adp, independent from position. The range of CS- and LDH-activity was 0.3–13.0 and 0.2–71.7 U g-1 wet weight, respectively. Significant differences in enzymatic activity were observed between age groups in both species, which in connection with significantly larger eggs of A. frenatus at day 2 and 5 adp could hint at a better O2 supply of central eggs. Potential implications for captive breeding are given.

Sea anemone and clownfish microbiota diversity and variation during the initial steps of symbiosis

Clownfishes and sea anemones form an intriguing long-term association, but the mechanism underlying this symbiosis is not well understood. Since clownfishes seem to cover themselves with sea anemone mucus, we investigated the microbiomes of the two partners to search for possible shifts in their compositions. We used a 16S rRNA gene sequencing strategy to study the dynamics of the microbiota during the association between the clownfish Amphiprion ocellaris and its host Heteractis magnifica under laboratory conditions. The experiment conducted in aquaria revealed that both clownfish and sea anemone mucus had specific signatures compared to artificial sea water. The microbiomes of both species were highly dynamic during the initiation of the symbiosis and for up to seven days after contact. Three families of bacteria (Haliangiaceae, Pseudoalteromonadacae, Saprospiracae) were shared between the two organisms after symbiosis. Once the symbiosis had been formed, the clownfishes and sea anemone then shared some communities of their mucus microbiota. This study paves the way for further investigations to determine if similar microbial signatures exist in natural environments, whether such microbial sharing can be beneficial for both organisms, and whether the microbiota is implicated in the mechanisms that protect the clownfish from sea anemone stinging.

Glycolytic capacities depend on developmental stage in the clownfish Amphiprion ocellaris

Glycolytic capacities depend on developmental stage in the clownfish Amphiprion ocellaris

In vitro selection of autochthonous lactic acid bacterium from clownfish Amphiprion ocellaris

In vitro selection of autochthonous lactic acid bacterium from clownfish <i>Amphiprion ocellaris</i>

Thermal preference, tolerance, and thermal aerobic scope in clownfish Amphiprion ocellaris (Cuvier, 1830) predict its aquaculture potential across tropical regions

The clownfish Amphiprion ocellaris is widely distributed in the coral reef ecosystems of tropical and subtropical regions of the West Indo Pacific, an area that hosts economically valuable species, and, thus, a suitable candidate for warm water aquaculture. This study determined the preferred temperature, critical threshold limits, represented by critical thermal maximum and critical thermal minimum, thermal window width, and aerobic metabolic scope of A. ocellaris clownfish acclimated to 20, 23, 26, 29, 32, and 35 °C. A positive response (P < 0.05) occurred when the preferred temperature significantly increased with increasing acclimation temperature. The preferred temperature obtained graphically was 30.0 °C. Acclimation temperature significantly affected the thermal tolerance which increased with acclimation temperature. The thermal window calculated for A. ocellaris was 301.5 °C2. The thermal metabolic scope obtained in animals acclimated at the interval from 23 to 32 °C (P > 0.05) had a mean value of 4240.8 mg O2 h−1 kg−1 w.w., revealing that A. ocellaris is a eurythermal species with a range of optimal physiological performance that closely matches the environmental conditions where it can be farmed. Therefore, the highest value of the thermal aerobic scopes corresponded to the intervals of the preferred temperature obtained for A. ocellaris. These results may partially explain their worldwide distribution pattern, as well as their aquaculture potential in tropical regions.

Staging and normal table of postembryonic development of the clownfish (Amphiprion ocellaris).

BackgroundThe clownfish Amphiprion ocellaris is one of the rare coral reef fish species that can be reared in aquaria. With relatively short embryonic and larval development, it could be used as a model species to study the impact of global changes such as temperature rise or anthropogenic threats (eg, pollution) on the postembryonic development at molecular and endocrinological levels. Establishing a developmental table allows us to standardize sampling for the scientific community willing to conduct experiments on this species on different areas: ecology, evolution, and developmental biology.ResultsHere, we describe the postembryonic developmental stages for the clownfish A. ocellaris from hatching to juvenile stages (30 days posthatching). We quantitatively followed the postembryonic growth and described qualitative traits: head, paired and unpaired fins, notochord flexion, and pigmentation changes. The occurrence of these changes over time allowed us to define seven stages, for which we provide precise descriptions.ConclusionsOur work gives an easy system to determine A. ocellaris postembryonic stages allowing, thus, to develop this species as a model species for coral reef fishes. In light of global warming, the access to the full postembryonic development stages of coral reef fish is important to determine stressors that can affect such processes.

Developmental and comparative transcriptomic identification of iridophore contribution to white barring in clownfish.

Actinopterygian fishes harbor at least eight distinct pigment cell types, leading to a fascinating diversity of colors. Among this diversity, the cellular origin of the white color appears to be linked to several pigment cell types such as iridophores or leucophores. We used the clownfish Amphiprion ocellaris, which has a color pattern consisting of white bars over a darker body, to characterize the pigment cells that underlie the white hue. We observe by electron microscopy that cells in white bars are similar to iridophores. In addition, the transcriptomic signature of clownfish white bars exhibits similarities with that of zebrafish iridophores. We further show by pharmacological treatments that these cells are necessary for the white color. Among the top differentially expressed genes in white skin, we identified several genes (fhl2a, fhl2b, saiyan, gpnmb, and apoD1a) and show that three of them are expressed in iridophores. Finally, we show by CRISPR/Cas9 mutagenesis that these genes are critical for iridophore development in zebrafish. Our analyses provide clues to the genomic underpinning of color diversity and allow identification of new iridophore genes in fish.

Metamorphosis of marine fish larvae and thyroid hormones

Life history transitions are critical for many animal species and often correspond to concomitant developmental and ecological shifts. However, to date, little is known on how internal and external cues act together during these events. The life cycle of most teleostean reef fish includes a major developmental and ecological transition. Adults reproduce in the vicinity of the reef, emitting eggs that disperse and hatch in the ocean, where the larvae grow. Thereafter, larvae migrate back towards reefs where they settle and persist, at a step called larval recruitment. Larval recruitment involves the perception of environmental cues for larvae to localize and select their new benthic habitat, and is accompanied by major morphological changes. This ecological and developmental transition of pelagic larvae into reef-associated juveniles, often referred to as metamorphosis, are under the control of Thyroid Hormones (TH: T4, T3) and their receptors (TRαa, TRαb and TRβ). This step is critical for the maintenance of reef fish populations, but its molecular control remains largely unknown. Recent results have brought new insights on coral reef fish metamorphosis. We have shown that TH and TR coordinate the metamorphosis that occurs during the entry in the reef of two coral reef fishes, the surgeon fish Acanthurus triostegus, and the clown fish Amphiprion ocellaris. We demonstrated an increase of TH-levels and TR-expression in the larvae, followed by a decrease in deriving juvenile. We observed similar trends (although with different dynamics and/or magnitude) in other coral reef fish species, therefore allowing us to generalize these observations. Interestingly, functional experiments such as treatments with pharmacological compounds exhibiting antagonist activity interfere with the surgeonfish and the clown fish larval transformation demonstrating a direct role of these hormones in controlling metamorphosis. All these results and in particular the dependency on thyroid hormones of the larval to juvenile transformation suggest that this step can be sensitive to disruption by environmental pollutants, such as endocrine disruptors. Using as model compound, chlorpyrifos, a pesticide often encountered in coral reefs, we showed that it impairs surgeonfish as well as clown fish transformation, hence diminishing the quality of the juvenile emerging from this transition. Larval recruitment in coral reef fish therefore corresponds to a TH-controlled metamorphosis, sensitive to endocrine disruption. Since metamorphosis and larval recruitment are essential for the maintenance of fish populations and subsequent coral reef resilience, it is important to better understand, at the molecular, anatomical and behavioral levels, how global changes and water pollution can threaten reef ecosystems.