Pyrosequencing the salivary transcriptome of Haemadipsa interrupta (Annelida: Clitellata: Haemadipsidae): anticoagulant diversity and insight into the evolution of anticoagulation capabilities in leeches

Freshwater, marine, and terrestrial leeches that depend on a diet of fresh blood have evolved salivary peptide components that inhibit normal thrombus formation by prey. Although bloodfeeding in leeches has long been of interest to biologists and medical practitioners alike, only a few studies have comprehensively examined the anticoagulant repertoires of hematophagous leeches, and these have largely been confined to representatives of Glossiphoniidae, Hirudinidae, and Macrobdellidae. Here, we present 454 pyrosequencing data from the salivary transcriptome of the hematophagous terrestrial leech Haemadipsa interrupta (Haemadipsidae). Assembled transcripts were annotated using both similarity scores (BLAST) and gene ontology (Blast2GO). Subsequently, transcripts were examined within alignments containing well-characterized anticoagulants and other select bioactive (i.e., affecting the living cells of the prey) salivary proteins and phylogenies were reconstructed for each protein data set to verify orthology predictions. In total, transcripts significantly matching 20 salivary proteins of interest were found in the transcriptome, representing several different antagonistic pathways. After reviewing gene ontologies, alignments, and phylogenetic trees, sequences for 15 out of the 20 hits were deemed correctly annotated. Additionally, we recovered matches against several proteins that have previously been linked to anticoagulation (e.g., cathepsin and disintegrins), but the specific function of which in leeches needs further investigation. Finally, in light of these data as well as those previously published, we discuss our current understanding of the distribution and evolution of anticoagulants in leeches.