Exploring the mimetic pigmentation of symbiotic shrimps associated with echinoderms

In marine ecosystems, organisms often form enduring associations with other species, creating rich symbiotic communities within benthic hosts. Among these associations, mimetic pigmentation where symbionts adopt colors resembling their hosts plays a key role in predator avoidance strategies. Despite its prevalence, this phenomenon remains poorly understood. This research aims to explore pigmentation dynamics in four symbiotic pairs: (i) Zenopontonia soror with Culcita novaeguineae, (ii) Synalpheus stimpsonii with Phanogenia distincta, and (iii) Tuleariocaris holthuisi, and (iv) Arete indicus with Echinometra mathaei. The study involves monitoring symbiont survivability, standardized photography to measure color variation, histological analysis to locate pigment-associated cells, and HPLC (High Performance Liquid Chromatography) to characterize pigment chemical composition. Results indicate a strong host dependency for all symbionts, with three species showing reliance on host metabolites. Host-symbiont separation affects symbiont pigmentation, leading to dynamic color changes. Histological analysis reveals chromatophores in all species, with A. indicus exhibiting two distinct layers of chromatophores containing different pigments. Chemical analysis shows differences in pigments between partners, with carotenoids detected in both Z. soror and C. novaeguineae, while S. stimpsonii and P. distincta show carotenoids predominantly
in the symbiont. These findings enhance our understanding of mimetic coloration mechanisms in symbiotic shrimps, advancing knowledge of symbiont ecology and host interactions.