Biochemically identified neuropeptides in a caddisfly (Trichoptera) and a pygmy mole cricket (Orthoptera: Caelifera: Tridactyloidea)

Abstract

One representative of the order Trichoptera, namely the caddisfly Chaetopteryx villosa, was investigated along with the pygmy mole cricket Xya capensis which is a representative of the most basal superfamily of the caeliferan Orthoptera, that is, the Tridactyloidea. From both clades neuropeptides have not been biochemically characterized before this study. Here, members of the adipokinetic hormone family (AKHs) are sequenced via liquid chromatography (LC)‐ion trap mass spectrometry from methanolic extracts from the corpora cardiaca of respective species. The corpora cardiaca were dissected, methanolic extracts prepared, peptides separated by liquid chromatography (LC), and AKHs detected and sequenced by ion trap mass spectrometry. Both species investigated contain an octapeptide AKH: the trichopteran species has the peptide with the sequence pGlu‐Leu‐Thr‐Phe‐Thr‐Pro‐Ser‐Trp amide; the ambiguity of the isobaric amino acids Leu and Ile at position two was solved by comparing retention times on LC and by co‐elution with the synthetic Leu2‐form. This peptide is known as Aedae‐AKH and found in certain dipteran species and in an alderfly (Megaloptera). The tridactyloid species contains the peptide with the sequence pGlu‐Val‐Asn‐Phe‐Ser‐Pro‐Gly‐Trp amide which had first been identified in a member of the order Mantophasmatodea and is called Manto‐CC. Comparisons are made between the AKH complements of the sister groups Trichoptera and Lepidoptera and their possible relatedness and, on the other hand, between the AKH of X. capensis with those of closely related caeliferan superfamilies. The biology of the two studied species is used to speculate about a possible function of the elucidated hormones. Lastly, the use of a larval stage as starting material for structural neuropeptide information is discussed.