When predator becomes prey: investigating the salivary transcriptome of the shark-feeding leechPontobdella macrothela(Hirudinea: Piscicolidae)

Abstract

Although several leech species have recently been screened for anticoagulation factors, piscicolids represent a major gap in our knowledge of the distribution of these proteins across the phylogeny of leeches. Piscicolidae is predominantly a marine family and its members feed on a variety of fish species. The pontobdelline species Pontobdella macrothela has evolved a preference for feeding on elasmobranch blood and, because of this, may have a divergent anticoagulant repertoire, compared to its mammal-, reptile- and amphibian-feeding counterparts. Representing the first piscicolid leech comprehensively investigated, here we convey results from a salivary transcriptome sequencing effort of P. macrothela collected from a blacktip shark (Carcharinus limbatus) in Veracruz, Mexico (Western Gulf of Mexico). Following orthology determination based on phylogenetic inference, amino acid conservation and a series of BLAST searches against the UniProtKB database, as well as searches of Pfam domains, we identified matches against ten known anticoagulants in the P. macrothela transcriptome. In addition, 13 hits were recovered against proteins that have previously been linked to anticoagulation but whose functions within leeches are not unequivocally understood. Finally, we discuss the largely untested hypothesis that prey choice in leeches impacts the diversity of anticoagulants.