Effects of 5-Hydroxytryptamine on the Formation of Peritrophic Membranes in Adult Blowflies, Calliphora erythrocephala (Diptera: Calliphoridae)
Finke, Rosemarie; Peters, Werner
In the cardia of the blowfly, Calliphora erythrocephala Meigen 1826, 3 tube-like, morphologically and biochemically different peritrophic membranes are synthesized continuously. 5-Hydroxytryptamine (5-HT) (= serotonin) was injected into adult flies to see whether it influences peritrophic membrane formation. Several parameters were compared to evaluate the quality of membranes formed in control flies and in flies injected with different concentrations of 5-HT: (a) length of membranes formed during a given period, (b) fine structure, (c) width of anisotropic bands, (d) protein and glycoprotein spectrum, and (e) protein and chitin content. - At a concentration of 7.5 x 10⁻⁵ M the rate of membrane formation increased by about 25 % compared with control flies. The rate of formation was only related to the length of membrane but not to its thickness. No differences in fine structure of membranes and cardia, protein and glycoprotein spectrum, and protein, glycoprotein and chitin content were observed compared with the controls. The anisotropic cross bands were wider than in controls, but in both cases considerable deviations occurred. At a concentration of 5 x 10⁻⁵ M the length of membrane formed during a certain period increased by about 14 %, but at a concentration of 1 x 10⁻⁶ M no effect was observed. - Concentrations >2.5 x 10⁻₂ M proved toxic. The flies were unable to move, and the rate of membrane formation under these conditions was reduced by about 18 % compared with controls. The thickness and fine structure of these membranes was altered. It is assumed that higher concentrations of 5-HT affect the mechanisms of formation of peritrophic membranes in the cardia.