Evidence of chitin in the ampullae of Lorenzini of chondrichthyan fishes

• Published in: Current biology Vol. 30; no. 20; pp. R1254 - R1255
• Main Authors: Phillips, Molly, Tang, W. Joyce, Robinson, Matthew, Daza, Daniel Ocampo, Hassan, Khan, Leppert, Valerie, Hirst, Linda S., Amemiya, Chris T.
• Format: Journal Article
• Language: English
• Published: England Elsevier Inc 19.10.2020
• ISSN: 0960-9822; 1879-0445; 1879-0445
• DOI: 10.1016/j.cub.2020.08.014

We previously reported that the polysaccharide chitin, a key component of arthropod exoskeletons and fungal cell walls, is endogenously produced by fishes and amphibians in spite of the widely held view that it was not synthesized by vertebrates [1]. Genes encoding chitin synthase enzymes were found in the genomes of a number of fishes and amphibians and shown to be correspondingly expressed at the sites where chitin was localized [1,2]. In this report, we present evidence suggesting that chitin is prevalent within the specialized electrosensory organs of cartilaginous fishes (Chondrichthyes). These organs, the Ampullae of Lorenzini (AoL), are widely distributed and comprise a series of gel-filled canals emanating from pores in the skin (Figure 1A). The canals extend into bulbous structures called alveoli that contain sensory cells capable of detecting subtle changes in electric fields (Figure 1B) [3,4]. The findings described here extend the number of vertebrate taxa where endogenous chitin production has been detected and raise questions regarding chitin’s potential function in chondrichthyan fishes and other aquatic vertebrates. Phillips et al. provide data suggesting that chitin is synthesized within the electrosensory organs of diverse chondrichthyan fishes. Using biological and physicochemical evidence, the authors propose that chitin is a component of the gel inside the organs. These results suggest that chitin exists in yet another vertebrate anatomic system.