Biology subjects

Besseau, L.

Publications and source records attributed to Besseau, L..

6 recordsLinked to original sources

bioRxiv2026

Time in shells: Complex interaction between biological clock and biomineralisation in Mytilus galloprovincialis

The growth of bivalve shells is neither homogeneous nor continuous in time, resulting in the formation of growth patterns that correspond to the alternation of growth lines and increments deposited at regular intervals of time. The control of periodic increment formation is poorly understood and several hypotheses have been proposed. It has been proposed that environmental factors directly impact shell growth patterns, although it occasionally fails to adequately explain the observed shell growth patterns. The present study investigates the alternative hypothesis that the process of shell biomineralisation is controlled by biological clocks. This study demonstrates the existence of a functional circadian clock in M. galloprovincialis, as evidenced by molecular and behavioural results. Core circadian clock genes and biomineralisation genes have been observed to be expressed in the same cells of the mantle as revealed by in situ hybridisation experiments. However, the expression of core circadian clock genes and biomineralisation genes tested in situ and in aquaria exhibited different rhythmic profiles. This finding suggests that the clock does not directly activate the expression of the targeted biomineralisation genes in the mantle. Nevertheless, a significant rhythm of expression of biomineralisation-related genes was observed in mussels reared under free-running conditions, revealing the endogenous nature of the rhythm. The present study suggests that biological clocks play a role in controlling shell biomineralisation in M. galloprovincialis, although the precise underlying mechanism remains to be elucidated.

physiology↗

bioRxiv2025

Cell-cell communication as underlying principle governing color pattern formation in fishes

The diverse pigmentation patterns of animals are crucial for predation avoidance and behavioral display, yet mechanisms underlying this diversity remain poorly understood. In zebrafish, Turing models have been proposed to explain stripe patterns, but it is unclear if they apply to other fishes. In anemonefish (Amphiprion ocellaris), we identified gja5b, a gene orthologous to zebrafish leopard and encoding a connexin involved in pigment cell communication, as responsible for the Snowflake phenotype. Using CRISPR/Cas9 and transgenesis, we recapitulate the Snowflake phenotype and show expression of gja5b in iridophores. A matching allele was recovered in zebrafish, revealing complementary requirements in both species. Our findings highlight conserved roles of gap junction mediated communication in pigment patterning across divergent teleosts.

developmental biology↗

bioRxiv2024

From Genes to Pathways: A Curated Gene Approach to Accurate Pathway Reconstruction in Teleost Fish Transcriptomics

Interpreting the vast amounts of data generated by high-throughput sequencing technologies can often present a significant challenge, particularly for non-model organism. While automated approaches like GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) enrichment analyses are widely used, they often lack specificity for non-model organisms. To bridge this gap, we present a manually curated gene list tailored for teleost fish transcriptomics. This resource focuses on key biological processes crucial for understanding teleost fish physiology, development, and adaptation, including hormone signaling, various metabolic pathways, appetite regulation, digestion, gastrointestinal function, vision, ossification, osmoregulation, and pigmentation. Developed through collaborative efforts of specialists in diverse fields, the list prioritizes genes with established roles in teleost physiology, experimental evidence, and conservation across species. This curated list aims to provide researchers with a reliable starting point for transcriptomic analyses, offering a carefully evaluated set of genes relevant to current research priorities. By streamlining the process of gene selection and interpretation, this resource supports the broader teleost fish research community in designing and analyzing studies that investigate molecular responses to developmental and environmental changes. We encourage the scientific community to collaboratively expand and refine this list, ensuring its continued relevance and utility for teleost fish research.

systems biology↗

bioRxiv2024

The multi-level effect of chlorpyrifos during clownfish metamorphosis

Chemical pollution in coastal waters, particularly from agricultural runoff organophosphates, poses a significant threat to marine ecosystems, including coral reefs. Pollutants such as chlorpyrifos (CPF) are widely used in agriculture and have adverse effects on marine life and humans. In this paper, we investigate the impact of CPF on the metamorphosis of a coral reef fish model, the clownfish Amphiprion ocellaris, focusing on the disruption of thyroid hormone (TH) signalling pathways. Our findings reveal that by reducing TH levels, CPF exposure impairs the formation of characteristic white bands in clownfish larvae, indicative of metamorphosis progression. Interestingly, TH treatment can rescue these effects, establishing a direct causal link between CPF effect and TH disruption. The body shape changes occurring during metamorphosis are also impacted by CPF exposure, shape changes are less advanced in CPF-treated larvae than in control conditions. Moreover, transcriptomic analysis elucidates CPFs effects on all components of the TH signalling pathway. Additionally, CPF induces systemic effects on cholesterol and vitamin D metabolism, DNA repair, and immunity, highlighting its broader TH-independent impacts. Pollutants are often overlooked in marine ecosystems, particularly in coral reefs. Developing and enhancing coral reef fish models, such as Amphiprion ocellaris, offers a more comprehensive understanding of how chemical pollution affects these ecosystems. This approach provides new insights into the complex mechanisms underlying CPF toxicity during fish metamorphosis, shedding light on the broader impact of environmental pollutants on marine organisms. HighlightsO_LIChlorpyrifos (CPF) is an insecticide widely used in agriculture for the past five decades and has adverse effects on marine life and humans C_LIO_LICPF exposure impairs the formation of characteristic white bands in clownfish larvae, indicative of metamorphosis progression C_LIO_LIDuring metamorphosis, clownfish larvae lose their elongated body shape and transform into miniature ovoid-shaped adults, these shape changes are less advanced in CPF-treated larvae C_LIO_LICPF induces systemic effects on cholesterol and vitamin D metabolism, DNA repair, and immunity, highlighting its broader TH-independent impacts C_LI

developmental biology↗

bioRxiv2024

Anemonefish use sialic acid metabolism as Trojan horse to avoid giant sea anemone stinging

Anemonefish association with giant sea anemone is an iconic example of mutualistic symbiosis. Living inside the sea anemone without triggering the firing of highly toxic nematocysts present at the surface of sea anemone tentacles provides a unique shelter to the fish, which in return, by its territorial aggressiveness, protects the sea anemone from predators. The mechanisms by which the fish avoids triggering nematocysts discharge remain elusive. One hypothesis proposes that absence of sialic acids might disable nematocysts discharge. Here, we verified four predictions about the role of sialic acids in anemonefish protection: (i) sialic acid levels are lower in anemonefish mucus than in non-symbiotic and sensitive damselfish mucus; (ii) this decrease is specific to mucus and not observed in other organs; (iii) during post-embryonic development the levels of sialic acids are inversely correlated with the level of protection; (iv) the levels of sialic acids are minimal in sea anemone mucus. Taken together, our results allow us to propose a general model, in which anemonefish specifically regulates the level of sialic acids in their mucus to avoid nematocysts discharge. Our analysis also highlights several genes implicated in sialic acid removal as potential targets for allowing protection. Interestingly, our results also suggest that unrelated juveniles of damselfish (Dascyllus trimaculatus) capable to live in proximity with giant sea anemone may use the same mechanisms. Altogether, our data suggest that clownfish use sialic acids as a Trojan horse system to downplay the defenses of the sea anemones and illustrate the convergent tinkering used by fish to allow a mutualistic association with their hosts. Significance statementThe mutualistic relationship between anemonefish and giant sea anemones, where the fish shelter among the anemones tentacles while defending it from predators, is a classic example of symbiosis. However, how the fish avoids triggering the anemones venomous nematocysts has remained a mystery. This study reveals that the fish decrease the levels of sialic acids in their mucus, potentially preventing nematocyst discharge. This finding shed light on the mechanisms underlying this symbiotic relationship. Moreover, the discovery that unrelated damselfish may employ similar strategies underscores the broader significance of convergent adaptations in facilitating similar mutualistic associations in marine fishes.

zoology↗

bioRxiv2022

The multi-level regulation of clownfish metamorphosis by thyroid hormones

Most marine organisms have a biphasic life cycle during which a pelagic larva is transformed into a radically different juvenile. In vertebrates the role of thyroid hormones (TH) in triggering this transition is well known, but how the morphological and physiological changes are integrated in a coherent way with the ecological transition remains poorly explored. To gain insight into this question, we performed an integrative analysis of metamorphosis of a marine teleost, the clownfish Amphiprion ocellaris. We reveal how TH coordinate a change in color vision as well as a major metabolic shift in energy production, hence highlighting its central integrative role in regulating this transformation. By manipulating the activity of LXR, a major regulator of metabolism, we also reveal a tight link between metabolic changes and metamorphosis progression. Strikingly, we observed that these regulations are at play in the wild revealing how hormones coordinate energy needs with available resources during life cycle.

developmental biology↗