Advisor: Tim Wollesen
Master's Defensio - Wednesday, May 20th 2026, 15:00
SR 1.4, UBB, Djerassiplatz 1, 1030 Vienna
Abstract
Adhesion to the substrate is a critical function trait for marine invertebrates, particularly for members of the molluscan class Polyplacophora (chitons) that inhabit high-energy, rocky intertidal environments. Despite its ecological importance for positional maintenance, locomotion and defense, the molecular and biochemical mechanisms underlying the polyplacophoran adhesives system remain poorly understood compared to other molluscan groups like bivalves or gastropods. This study addresses this knowledge gap by investigating the spatial distribution of adhesion related genes expression and glycan moieties during the larval and early post-metamorphic stages of the chiton Acanthochitona fascicularis. Candidate adhesion related orthologous genes – including tyrosinase B, settlement inducing protein complex, pedal mucus protein 4 and chain – alpha proximal thread matrix protein, were identified through bioinformatic screening and localized using in situ hybridization in 48-hour post- fertilization trochophore larvae and 11-day post-fertilization settled juveniles. Concurrently, a panel of 13 lectins was employed in a binding assay to map the distribution of specific glycoproteins and associated glycans in the specimen. Results from the in-situ hybridization revealed distinct developmental expression patterns. In trochophore larvae, tyrosinase B showed dispersed epidermal expression, while the settlement inducing protein complex exhibits strong inner expression on the dorsal side near the shell fields. The pedal mucus protein is expressed in epidermal glandular cells in the larval episphere and posterior hyposphere with fewer cells being present in the anterior mouth region in the settled juveniles. Chain – alpha proximal thread matrix protein is expressed in the larval perinotum and prototroch, while settled juveniles express this gene in the inner dorsal region close to the shell plates. The lectin assay identified diverse glycan distribution patterns. Notably, ConA and WGA label the glycans in the epidermis and highlight specialized secretory structures in both stages. Secretory cells glycoconjugates bind to ConA, sWGA, WGA and the cells also showed expression with the PMP4 gene. WGA, SBA, UEA and PHA-E label the circumference of secretory cell pores, while the juvenile’s foot is best visualized with WGA, SBA, RCA120, ConA, UEA, PNA and PHA-L. The mantle’s glycans bind to WGA, SBA, ConA and UEA, while the hyponotum glycans bind to WGA, sWGA, ConA and LCA. Lastly, the mantle cavity and surrounding area bind PHA-E and PHA-L lectins. These findings provide molecular insights into the dual genetic and biochemical factors contributing to adhesion in Polyplacophora. The shift in molecular patterns between free-swimming larvae and settled juveniles suggests specialized attachment mechanisms for different life stages, offering a foundation for further research into marine invertebrate bio-adhesives and their potential applications in biotechnology and medicine.
