Ontogenic apparition of luminous capabilities in the brittle star Amphiura filiformis

Bioluminescence is the capability to emit light thanks to a biochemical reaction. This reaction implies the oxidation of a substrate called luciferin catalyzed by an enzyme named luciferase. Today, the most widespread luciferin is the coelenterazine found in eight phyla. This broad phylogenetic distribution of this light-emitting molecule led to the hypothesis of its dietary acquisition so far demonstrated in one jellyfish (Haddock et al., 2001), one lophogastrid shrimp (Frank et al., 1984), and one brittle star species (Mallefet et al., 2020). The latter, Amphiura filiformis is a suspensive feeder known to use coelenterazine in a luciferin-luciferase reaction (Mallefet et al., 2013; Delroisse et al., 2017). A. filiformis is a brittle star model species with an established aquaculture protocol allowing obtention of fertilized eggs, pluteus larvae, and juveniles. As A. filiformis is a coelenterazine-dependent luminous organism needing exogenous supplies of this luciferin through its diet, this study aims to determine from which ontogenic larval stage the brittle star can produce luminescence. Our results showed (i) coelenterazine content and no luciferase activity from gametes to pluteus larvae (until day 13 post-fertilization) (ii) gametes and embryos are not able to produce light after potassium chloride depolarization. Work is still in progress to know when and how the juveniles of A. filiformis start to emit light. This work is supported by FRIA (FNRS) grant n°40004341