Distribution and Activity of CAPA-like Peptides in the Black-legged Tick, Ixodes scapularis

Ixodes scapularis is a chief vector for a range of diseases. Due to their obligate blood feeding strategy, it is crucial for I. scapularis to maintain ionic and osmotic homeostasis. In insects, CAPA peptides act as either diuretic or anti-diuretic hormones controlling the movement of excess ions, water, and metabolic wastes secreted in the primary urine. Immunohistochemical techniques were used to localize CAPA-like peptides to the synganglion, midgut, reproductive tissues, and hindgut. Given the presence of CAPA-like immunoreactivity in the hindgut, in vitro bioassays were conducted. A significant increase in the frequency of hindgut contractions were observed when exposed to 1 M IxoscCAPA-PVK. RT-PCR techniques, however, solely localized the CAPA transcript to the tick synganglion. The immunoreactivity observed in the peripheral tissues, including the midgut, are indicative of the RFamide-related peptide, sNPF, as the transcript coincides with the immunoreactivity, and ELISA results revealing affinity of the primary antibody (rabbit anti-RhoprCAPA-2).