Biology subjects

Flammang, P.

Publications and source records attributed to Flammang, P..

5 recordsLinked to original sources

bioRxiv2025

Tube feet dynamics drive adaptation in sea star locomotion

Sea stars use hundreds of tube feet on their oral surface to crawl, climb, and navigate complex environments--all without the coordination of a central brain. While the morphology of tube feet and their role as muscular hydrostats are well described, the dynamics underlying their locomotion remain poorly understood. To investigate these dynamics, we employed an optical imaging method based on frustrated total internal reflection to visualize and quantify tube foot adhesion in real time across individuals of Asterias rubens spanning a wide size range. Our results reveal an inverse relationship between crawling speed and the duration of tube foot contact with the substrate. This suggests that sea stars regulate locomotion by modulating foot-substrate interaction time in response to body load. To test this, we conducted perturbation experiments using 3D-printed backpacks that increased body mass by 25% and 50%, along with numerical simulations based on a mechanistic model incorporating decentralized feedback control of the tube feet. The added load significantly increased adhesion time, supporting the role of a load-dependent mechanical adaptation. We further investigated inverted locomotion, both experimentally and through simulation, and found that tube feet adjust their contact behavior when the animal is oriented upside down relative to gravity. Together, our findings demonstrate that sea stars adapt their locomotion to changing mechanical demands by modulating tube foot-substrate interactions, revealing a robust, decentralized strategy for navigating diverse and challenging terrains.

biophysics↗

bioRxiv2024

Opsin-based photoreception in Crinoids

Opsins are essential photoreceptor proteins that enable both visual and nonvisual light perception in metazoans. Although extensively studied in eyed invertebrates, their role in eyeless organisms such as echinoderms remains underexplored. Within the echinoderm phylum, studies have primarily focused on sea stars, sea urchins, and brittle stars, leaving crinoids, the most basal echinoderm lineage, entirely unexplored. Currently, only a limited number of behavioural observations have suggested that crinoids may possess light sensitivity. This study investigated the behavioural, morphofunctional, and molecular foundations of opsin-based photoreception in Antedon bifida, a European crinoid species from the comatulid order. In this context, the behavioural response to different light wavelengths, characterisation of opsin genes in the recent chromosome-scale genome of this species, opsin immunolocalisation within the crinoid tissues, and in vitro functional characterisation of opsins have been investigated. In vivo tests indicated significant negative phototactic behaviour induced by a wide range of light wavelengths (463-630 nm) with maximum sensitivity to blue light ({lambda}max = 463 nm). In silico genome analyses revealed the presence of only three rhabdomeric opsin genes, located on chromosomes 4 (Abif-opsin 4.1) and 6 (Abif-opsin 4.2 and 4.3). All crinoid opsins were phylogenetically clustered as a sister group to all other echinoderm rhabdomeric opsins, supporting their evolution via duplication of an ancestral gene in the crinoid lineage. The low opsin diversity contrasts with that of other echinoderms, which are generally characterised by up to eight bilaterian opsin types. Interestingly, A. bifida opsin sequences present typical amino acid residues of rhabdomeric opsins of other bilaterians, including two conserved cysteines (C110 and C187), the probable ancestral E181 counterion, the typical G-protein signalling NPxxY(x)6F pattern, a highly conserved lysine potentially covalently bound to a chromophore, and the (D)RY motif, all of which support a photoreceptive function. Heterologous in vitro expression in HEK293T cell cultures subsequently confirmed the photoreceptive function of all three A. bifida opsins. Indeed, these three crinoid opsins formed active complexes with 11, cis-retinal association, and once purified, showed different absorbance peaks in the short wavelengths of the visible light spectrum ranging from 425 to 520 nm. Finally, immunoreactivity to newly generated antibodies against sea star opsins highlighted two potential crinoid opsins in several tissues associated with the ambulacral grooves of the calyx and pinnules. Within these tissues, one Abif-opsin is potentially expressed both in the ectoneural basiepithelial nerve plexus and in the hyponeural nerve plexus. However, a different opsin is also expressed in the sensory papillae of tube feet. Localisation of at least two opsins in different sensory structures suggests the presence of a complex extraocular photoreception system based exclusively on rhabdomeric opsins in this crinoid species.

zoology↗

bioRxiv2024

Abundance, diversity and evolution of tyrosinase enzymes involved in the adhesive systems of mussels and tubeworms

The blue mussel (Mytilus edulis) and the honeycomb tubeworm (Sabellaria alveolata) have evolved similar adhesive systems to cope with the hydrodynamic conditions of the intertidal environment where they live. Both organisms can establish a permanent adhesion through the secretion of adhesive proteins rich in DOPA (3,4-dihydroxyphenylalanine), a post-translationally modified amino acid playing essential roles in interfacial adhesion and bulk cohesion. DOPA is produced by the hydroxylation of tyrosine residues by tyrosinase enzymes, which can also in some cases oxidise it further into dopaquinone Compared to the detailed knowledge available on mussel and tubeworm adhesive proteins, little information exists about the tyrosinases involved in their adhesive systems. By combining different molecular analyses, a catalogue of tyrosinase candidates potentially involved in the adhesive systems of M. edulis and S. alveolata was identified. Some of these candidates were shown to be expressed in the adhesive glands by in situ hybridization, with a high gland-specificity in mussels but not in tubeworms. The diversity of tyrosinases highlighted in the two species suggests the coexistence of different functions (monophenol monooxygenase or catechol oxidase activity) or different substrate specificities. However, the exact role of the different enzymes needs to be further investigated. Phylogenetic analyses support the hypothesis of independent expansions and parallel evolution of tyrosinases involved in adhesive protein maturation in both lineages, supporting the convergent evolution of their DOPA-based adhesion.

evolutionary biology↗

bioRxiv2021

Integument transcriptome profile of the European sea cucumber Holothuria forskali (Holothuroidea, Echinodermata)

In non-model organisms, Next Generation Sequencing (NGS) technology improve our ability to analyze gene expression and identify new genes or transcripts of interest. In this research, paired-end Illumina HiSeq sequencing has been used to describe a composite transcriptome based on two libraries generated from dorsal and ventral integuments of the European sea cucumber Holothuria forskali (Holothuroidea, Echinodermata). A total of 43,044,977 million HQ reads were initially generated. After de novo assembly, a total of 111,194 unigenes were predicted. On all predicted unigenes, 32,569 show significant matches with genes/proteins present in the reference databases. Around 50% of annotated unigenes were significantly similar to sequences from the purple sea urchin Strongylocentrotus purpuratus genome. Annotation analyses were performed on predicted unigenes using public reference databases. These RNA-seq data provide an interesting resource for researchers with a broad interest in sea cucumber biology.

zoology↗

bioRxiv2018

De novo Transcriptome Analyses Provide Insights into Opsin-based Photoreception in the Lantern shark Etmopterus spinax

The velvet belly lantern shark (Etmopterus spinax) is a small deep-sea shark commonly found in the Easter Atlantic and the Mediterranean Sea. In this study, paired-end illumina HiSeqTM technology has been employed to analyse transcriptome data from eye and ventral skin tissues of the lantershark species. About 64 and 49 million Illumina reads were generated from skin and eyetissues respectively. The assembly allowed us to predict 119,749 total unigenes including 94,569 for the skin transcriptome and 94,365 for the eye transcriptome while 74,753 were commonly found in both transcriptomes. Among unigenes, 60,322 sequences were annotated using classical public databases. The assembled and annotated transcriptomes provide a valuable resource for further understanding of the shark biology. We identified potential \"light-interacting toolkit\" genes including multiple genes related to ocular and extraocular light perception processes such as opsins. In particular, a single rhodopsin gene mRNA and its potentially associated peropsin were only detected in the eye transcriptome confirming a monochromatic vision of the lantern-shark. Conversely, an encephalopsin mRNA was mainly detected in the skin transcriptome. The encephalopsin was immunolocalized in various shark tissues confirming its wide expression in the shark skin and pinpointing a possible functional relation with the photophore, i.e. epidermal light organs. We hypothesize that extraocular photoreception might be involved in the bioluminescence control possibly acting on the shutter opening and/or the photocyte activity itself.

evolutionary biology↗