The adipokinetic hormones of Odonata: a phylogenetic approach

Adipokinetic neuropeptides from the corpora cardiaca of the major families of all three suborders of the Odonata were identified by one or more of the following methods: (1) Isolation of the peptides from a methanolic extract of the corpora cardiaca by liquid chromatography, peak monitoring by fluorescence of the Trp residue and comparison of the retention time with those of known synthetic peptides of Odonata. (2) Hyperlipaemic bioassays of the HPLC-generated fractions either in Locusta migratoria or, in a few cases, in Anax imperator or Orthetrum julia. (3) Sequencing of the isolated, bioactive HPLAC fraction by Edman degradation. (4) Mass spectrometric measurement of the isolated, bioactive fraction. Sequence assignment revealed that the investigated Odonata species always contain only one adipokinetic peptide. This is always an octapeptide. The suborder Zygoptera contains the peptide code-named Psein-AKH, the Anisozygoptera and the families Aeshnidae, Cordulegastridae and Macromiidae of the Anisoptera contain Anaim-AKH, whereas Gomphidae, Corduliidae (with the exception of Syncordulia gracilis) and Libellulidae contain Libau-AKH; one species of Libellulidae has Erysi-AKH, a very conservative modification of Libau-AKH (one point mutation). When these structural data are interpreted in conjunction with existing phylogenies of Odonata, they support the following: (1) Zygoptera are monophyletic and not paraphyletic. (2) Anisozygoptera and Anisoptera are sister groups and contain the ancestral Anaim-AKH which is independently and convergently mutated to Libau-AKH in Gomphidae and Libellulidae. (3) The Corduliidae are of special interest. Only Corduliidae sensu stricto appear to contain Libau-AKH, other species placed into this family by most authorities contain the ancestral Anaim-AKH. Possibly, assignments of AKHs can untangle the paraphyly of this family.