Characteristic Features of Insect Peptide Hormones and Endocrine Systems: Comparison with Vertebrate Hormones and Endocrine Systems

Although the insect endocrine system shares many features with those of vertebrates, some features are unique to insects. This chapter summarizes characteristics of insect peptide hormones (PHs) and endocrine systems compared to those of vertebrates. Whereas vertebrates have many endocrine glands that produce and release PHs, most of the insect PHs are produced by neurosecretory cells in the central nervous system and released from neurohemal organs or areas. The circulatory systems also differ: insects have an open circulatory system, while vertebrates have closed one. This difference may be related to the differences in the structure and function of endocrine systems. In insects and some other invertebrates, precursor proteins sometimes generate multiple copies of small PHs or neuropeptides with similar sequences, a feature not seen in vertebrates.