SUMMARYThe anal papillae of freshwater mosquito larvae are important sites of NaCl uptake, thereby acting to offset the dilution of the hemolymph by the dilute habitat. The ion-transport mechanisms in the anal papillae are not well understood. In this study, the scanning ion-selective electrode technique (SIET) was utilized to measure ion fluxes at the anal papillae, and pharmacological inhibitors of ion transport were utilized to identify ion-transport mechanisms. Na + uptake by the anal papillae was inhibited by bafilomycin and phenamil but not by HMA. Cl -uptake was inhibited by methazolamide, SITS and DIDS but not by bafilomycin. H

Evidence for the presence of allatostatin (AST) A-like neuropeptides in the larval midge Chironomus riparius is reported. Immunohistochemical studies on the nervous system and gut revealed the presence of AST A-like immunoreactive (AST-IR) cells and processes. The nerve cord contained AST-IR processes that originated from cells in the brain and travelled the length of nerve cord to the terminal ganglion. Within each ganglion, these processes gave rise to varicosities, suggesting that they formed synapses with neurons in the ganglia. Endocrine cells containing AST-IR were present in three regions of the midgut: near the attachment of the Malpighian tubules, between the anterior and posterior midgut, and in the vicinity of the gastric caecae. The terminal ganglion also contained four AST-IR cells that gave rise to axons that projected onto the hindgut and posterior midgut. Application of a cockroach AST to the semi-isolated hindgut of larval C. riparius led to dosedependent inhibition of muscle contractions with an EC 50 of 10 nmol l −1 and a decrease in rectal K + reabsorption resulting from reduced rectal Na + /K + -ATPase and vacuolar type H + -ATPase activities. The results suggest the presence of endogenous AST-like neuropeptides in larval C. riparius, where these factors play a role in the function of the gut. Furthermore, regulation of ion reabsorption by ASTs at the rectum could serve as an ideal mechanism of ion regulation in the face of abrupt and acute elevated salt levels. KEY WORDS: Na INTRODUCTIONJuvenile hormones are synthesized by the corpora allata and control the juvenile characteristics of insects during growth and development. In adult insect females, juvenile hormones can also regulate reproductive activities such as the maturation of oocytes. Synthesis of juvenile hormones is inhibited by allatostatins (ASTs), members of a large and diverse family of peptides that are structurally characterized into three distinct groups (Gäde and Goldsworthy, 2003).The C-type allatostatins with an N-terminal pGlu residue and a free C terminus have been discovered in the moth Manduca sexta, the fly Drosophila melanogaster and the mosquito Aedes aegypti (Kramer et al., 1991;Williamson et al., 2001;Li et al., 2006). The B-type allatostatins all have a common Trp-(X6)-Trp-amide C terminus and were first discovered in the cricket (Wang et al., 2004). The A-type allatostatins (ASTs) were the first to be discovered in the cockroach and share a Phe-Gly-Leu-amide C terminus (Donly et al., 1993;Siju et al., 2014). RESEARCH ARTICLEDepartmentAll allatostatins inhibit juvenile hormone synthesis in at least one group or species of insect; however, many do not in other insects, and instead have known inhibitory activity on contractile properties of muscle (Gäde and Goldsworthy, 2003). In particular, the ASTs have been shown to inhibit contractions of visceral muscle including the foregut and hindgut (Lange et al., 1993;Sarkar et al., 2003;Predel et al., 2001;Matthews et al., 2008), and have been localized to end...