A second gene encodes the anti-diuretic hormone in the insect, Rhodnius prolixus

In the haematophagous insect, Rhodnius prolixus, a rapid diuresis following engorgement of vertebrate blood is under the control of two main diuretic hormones: a corticotropin-releasing factor (CRF)-related peptide andserotonin (5HT). A CAP2b (CAPA)-related peptide is involved in the termination of this diuresis, and we have recently identified a gene, now referred to as RhoprCAPA-α, encoding CAPA peptides in R. prolixus. Here we identify a second gene, RhoprCAPA-β, which also encodes CAPA peptides and characterize its expression in fifth-instar and adults. The RhoprCAPA-β gene is more highly expressed in the CNS than the RhoprCAPA-α gene, but neither gene is expressed in other tested adult tissues. Both genes are expressed in a subset of immunoreactive neurons identified using an antisera which recognizes CAP2b-related peptides. The expression of each paralog is modified by feeding and we propose this to be a result of requirements of anti-diuretic regulation during salt and water homeostasis.