FMRF‐NH 2 ‐related neuropeptides in Biomphalaria spp., intermediate hosts for schistosomiasis: Precursor organization and immunohistochemical localization

Freshwater snails of the genus Biomphalaria serve as intermediate hosts for the digenetic trematode Schistosoma mansoni , the etiological agent for the most widespread form of intestinal schistosomiasis. As neuropeptide signaling in host snails can be altered by trematode infection, a neural transcriptomics approach was undertaken to identify peptide precursors in Biomphalaria glabrata , the major intermediate host for S . mansoni in the Western Hemisphere. Three transcripts that encode peptides belonging to the FMRF‐NH 2 ‐related peptide (FaRP) family were identified in B . glabrata . One transcript encoded a precursor polypeptide ( Bgl‐FaRP1 ; 292 amino acids) that included eight copies of the tetrapeptide FMRF‐NH 2 and single copies of FIRF‐NH 2 , FLRF‐NH 2 , and pQFYRI‐NH 2 . The second transcript encoded a precursor ( Bgl‐FaRP2 ; 347 amino acids) that comprised 14 copies of the heptapeptide GDPFLRF‐NH 2 and 1 copy of SKPYMRF‐NH 2 . The precursor encoded by the third transcript ( Bgl‐FaRP3 ; 287 amino acids) recapitulated Bgl‐FaRP2 but lacked the full SKPYMRF‐NH 2 peptide. The three precursors shared a common signal peptide, suggesting a genomic organization described previously in gastropods. Immunohistochemical studies were performed on the nervous systems of B . glabrata and B . alexandrina , a major intermediate host for S . mansoni in Egypt. FMRF‐NH 2 ‐like immunoreactive (FMRF‐NH 2 ‐li) neurons were located in regions of the central nervous system associated with reproduction, feeding, and cardiorespiration. Antisera raised against non‐FMRF‐NH 2 peptides present in the tetrapeptide and heptapeptide precursors labeled independent subsets of the FMRF‐NH 2 ‐li neurons. This study supports the participation of FMRF‐NH 2 ‐related neuropeptides in the regulation of vital physiological and behavioral systems that are altered by parasitism in Biomphalaria .