Identification and localisation of selected myotropic neuropeptides in the ventral nerve cord of tenebrionid beetles

MALDI-TOF MS and MS/MS techniques were used for the isolation and identification of neuropeptides from the ventral nerve cord (VNC) of two beetle species Tenebrio molitor and Zophobas atratus. Two peptides, proctolin and myosuppressin (Zopat-MS), with well-established myotropic properties were identified as well as Trica-NVPL-4trunc. The presence of proctolin and myosuppressin was confirmed by immunocytochemical studies in adults and larvae of both beetles. In addition, the myosuppressin gene in Z. atratus was sequenced and expression analyses showed that it is present in all parts of the beetle central nervous system. Results suggest that the identified peptides act as neurotransmitters/neuromodulators in beetles, regulate visceral muscle contractions and indirectly influence important physiological processes such as feeding and reproduction.