The adipokinetic hormone family in Chrysomeloidea: structural and functional considerations

The presented work is a hybrid of an overview and an original research paper on peptides belonging to the adipokinetic hormone (AKH) family that are present in the corpora cardiaca of Chrysomeloidea. First, we introduce the AKH/red pigment-concentrating hormone (RPCH) peptide family. Second, we collate the available primary sequence data on AKH peptides in Cerambycidae and Chrysomelidae, and we present new sequencing data (from previously unstudied species) obtained by liquid-chromatography coupled with ion trap electrospray ionisation mass spectrometry. Our expanded data set encompasses the primary structure of AKHs from seven species of Cerambycidae and three species of Chrysomelidae. All of these species synthesise the octapeptide code-named Peram-CAH-I (pGlu-Val-Asn-Phe-Ser-Pro-Asn-Trp amide). Whereas this is the sole AKH peptide in Cerambycidae, Chrysomelidae demonstrate a probable event of AKH gene duplication, thereby giving rise to an additional AKH. This second AKH peptide may be either Emppe-AKH (pGlu-Val-Asn-Phe-Thr-Pro-Asn-Trp amide) or Peram-CAH-II (pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp amide). The peptide distribution and structural data suggest that both families are closely related and that Peram-CAH-I is the ancestral peptide. We hypothesise on the molecular evolution of Emppe-AKH and Peram-CAH-II from the ancestral peptide due to nonsynonymous missense single nucleotide polymorphism in the nucleotide coding sequence of prepro-AKH. Finally, we review the biological significance of the AKH peptides as hyperprolinaemic hormones in Chrysomeloidea, i.e. they cause an increase in the circulating concentration of proline. The mobilisation of proline has been demonstrated during flight in both cerambycid and chrysomelid beetles.     

The first decapeptide adipokinetic hormone (AKH) in Heteroptera: a novel AKH from a South African saucer bug, Laccocoris spurcus (Naucoridae, Laccocorinae)

A novel peptide of the adipokinetic hormone (AKH)/red pigment-concentrating hormone (RPCH) family has been elucidated by mass spectrometry from the corpora cardiaca of an African saucer bug species, Laccocoris spurcus. It is the first decapeptide member found in the species-rich taxon Heteroptera, has the primary sequence pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp-Gly-Gly amide and is denoted as Lacsp-AKH. The first eight amino acids are identical to the octapeptide Anaim-AKH of the European saucer bug, Ilyocoris cimicoides. The synthetic peptide Lacsp-AKH elevates lipids upon injection into the hemolymph of L. spurcus at a low dose of 3 pmol. Swimming activity in this saucer bug also causes a significant increase in the lipid concentration in the hemolymph. Thus, both results point to an apparent function of the endogenous new decapeptide Lacsp-AKH in L. spurcus, namely, to regulate lipid mobilization. Isolation of an AKH peptide from the corpora cardiaca of the water bug Aphelocheirus aestivalis (Aphelocheiridae) resulted in the assignment of the octapeptide Anaim-AKH, supporting current phylogenies on the infraorder Nepomorpha.     

Water scorpions (Heteroptera, Nepidae) and giant water bugs (Heteroptera, Belostomatidae): sources of new members of the adipokinetic hormone/red pigment-concentrating hormone family

Two novel octapeptide members of the AKH/RPCH family have been identified from the corpora cardiaca (CC) of two species of water bugs. The giant water bug Lethocerus indicus (family: Belostomatidae) contains a peptide code-named Letin-AKH with the sequence pGlu-Val-Asn-Phe-Ser-Pro-Tyr-Trp amide, and the water scorpion Nepa cinerea (family: Nepidae) has the peptide code-named Nepci-AKH with the sequence pGlu-Leu/Ile-Asn-Phe-Ser-Ser-Gly-Trp amide. The sequences were deduced from the multiple MS(N) electrospray mass data from crude CC extracts. Synthetic peptides were made and co-elution on reversed-phase high performance liquid chromatography (RP-HPLC) with the natural peptide from crude gland extract confirmed the accuracy of the deduced sequence for Letin-AKH and demonstrated that Nepci-AKH contains a Leu residue at position 2 and not an Ile residue. A previously characterized member of the AKH/RPCH family was identified in the stick water scorpion Ranatra linearis by mass spectrometry: Grybi-AKH (pGlu-Val-Asn-Phe-Ser-Thr-Gly-Trp amide) has the same mass (919 Da) as Nepci-AKH and differs in two positions from Nepci-AKH (residues 2 and 6). The apparent function of the peptides is to achieve lipid mobilization in the species under investigation; indications for this came from conspecific bioassays using the appropriate synthetic peptides for injecting into the insects. This function is very likely linked to dispersal flight metabolism of water bugs. Swimming activity in N. cinerea also results in an increase in lipid concentration in the hemolymph.     

Identification of the cockroach neuropeptide Pea-CAH-II as a second adipokinetic hormone in the firebug Pyrrhocoris apterus

A new member of the AKH/RPCH family was isolated from the corpora cardiaca of the firebug Pyrrhocoris apterus. It is the second adipokinetic peptide identified in this species. The peptide was characterized and its structure was deduced from the multiple MS(N) electrospray mass spectra as that of an octapeptide with the sequence pGlu-Leu-Thr-Phe-Thr-Pro-Asn-Trp-NH(2.) The peptide differs from the original P. apterus AKH (Pya-AKH) by one amino acid in position 3. Topical application and/or injection of the peptide induced lipid mobilization, but was inactive in mobilization of carbohydrates.     

The adipokinetic hormone of Mantodea in comparison to other Dictyoptera

Six species of the order Mantodea (praying mantises) are investigated for the presence and sequence of putative adipokinetic hormones (AKHs). The selected species span a wide evolutionary range of various families and subfamilies of the clade Mantodea. The corpora cardiaca of the different species are dissected, methanolic extracts prepared, peptides separated by liquid chromatography, and AKHs detected and sequenced by ion trap mass spectrometry. All six species investigated contain an octapeptide with the primary structure pGlu‐Val‐Asn‐Phe‐Thr‐Pro‐Asn‐Trp amide, which is code‐named Emppe‐AKH and had been found earlier in three other species of Mantodea. Conspecific bioassays with the species Creoboter sp. (family Hymenopodidae) reveal an adipokinetic but not a hypertrehalosemic function of Emppe‐AKH. Comparison with other members of the Dictyoptera (cockroaches, termites) show that Emppe‐AKH is only found in certain termites, which have been recently placed into the Blattaria (cockroaches) as sister group to the family Cryptocercidae. Termites and cockroaches both show biodiversity in the sequence of AKHs, and some cockroach species even contain two AKHs. In contrast, all praying mantises—irrespective of their phylogenetic position—synthesize uniformly only one and the same octapeptide Emppe‐AKH.     

Pyrgomorphid grasshoppers of the genus Phymateus contain species-specific decapeptides of the AKH/RPCH family regulating lipid-mobilization during flight

Abstract. Using heterologous and conspecific bioassays, two peptides have been isolated from methanolic extracts of corpora cardiaca from the pyrgomorphid grasshopper Phymateus morbillosus L.The structures of both peptides were elucidated by a combination of Edman degradation, after deblocking the N-terminal pyroglutamic acid residue, and mass spectrometric techniques.One peptide is an octapeptide (pGlu-Leu-Asn-Phe-Ser-Thr-Gly-TrpNH₂) which also occurs in other insects and is code-named Scg-AKH-II.The second peptide is a novel decapeptide member of the AKH/RPCH family (pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-SerNH₂ code-named here Phm-AKH.It is the first example of a different peptide in the same genus.The analysis of changes of metabolites in the haemolymph, fat body and flight muscles of male P.morbillosus during a 30 min flight and rest after flight reveal an overall picture of flight metabolism similar to that of Locusta migratoria. Carbohydrate-fuelled metabolism is pronounced during the first 15 min of flight, whereas lipid-based metabolism is mainly used thereafter.By analogy with work on L.migratoria , it is concluded that the endogenous peptides of P.morbillosus regulate these metabolic events.     

Isolation and amino acid composition of the adipokinetic neuropeptide from the corpus cardiacum of the cricket, Gryllus bimaculatus

ABSTRACT. The corpora cardiaca of the cricket, Gryllus bimaculatus De Geer, contain peptidic material which elicits hyperlipaemia in migratory locusts and in crickets. Appreciable amounts of this adipokinetic factor are found only in the corpora cardiaca of the cricket, and not in other parts of the nervous system. The factor is heat-stable and retains its activity after incubation with the exopeptidases leucine aminopeptidase and carboxypeptidase A. Fractionation of a methanolic extract of corpora cardiaca from Gryllus bimaculatus by RP-HPLC shows that the adipokinetic activity is confined to a single absorbance peak. The amino acid composition of the purified adipokinetic neuropeptide was determined after acid hydrolysis with HCI and with methanesulfonic acid. The factor is an octapeptide containing the following amino acid residues in equimolar amounts: Asx, Thr, Ser, Glx, Gly, Val, Phe and Trp. This composition closely resembles the AKHI II molecule from Schistocerca species , and the Gryllus peptide can be assigned to the AKH/RPCH family of neuropeptides.     

A novel adipokinetic peptide in a water boatman (Heteroptera, Corixidae) and its bioanalogue in a saucer bug (Heteroptera, Naucoridae)

The corpora cardiaca (CC) of two water bug species, the water boatman Corixa punctata and the saucer bug Ilyocoris cimicoides, contain a substance that cause hyperlipemia in the migratory locust. The primary sequence of one octapeptide belonging to the adipokinetic hormone (AKH)/red pigment-concentrating hormone (RPCH) family was deduced from the multiple MS(N) electrospray mass data of CC material from each species. Whereas the saucer bug contains the known octapeptide pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp amide, code-named Anaim-AKH, the water boatman has a novel peptide identified as pGlu-Leu/Ile-Asn-Phe-Ser-Pro-Ser-Trp amide, code-named Corpu-AKH. The ambiguity about the amino acid at position 2, i.e. Leu or Ile, in Corpu-AKH was solved by isolating the peptide in a single-step by reversed-phase HPLC and establishing co-elution with the synthetic peptide containing Leu at position 2. Functionally, the peptides regulate lipid mobilization, as evidenced by an adipokinetic effect after injecting synthetic Anaim-AKH and Corpu-AKH into the respective acceptor species. Swimming activity of I. cimicoides also causes hyperlipemia.     

Substrate usage and its regulation during flight and swimming in the backswimmer, Notonecta glauca

Abstract.  The metabolites that are generally used by insects during exercise are present in quite different concentrations in the haemolymph of the backswimmer Notonecta glauca L. Lipids are most abundant (between 10 and 20 mg/mL), whereas carbohydrates (2–3 mg/mL) and proline (approximately 1 mg/mL) are at very low concentrations. Injection of an extract of conspecific corpora cardiaca causes pronounced hyperlipaemia in the backswimmer. A neuropeptide with the same effect was isolated from the corpora cardiaca in a single high-performance liquid chromatography (HPLC) step; the primary sequence was deduced from mass spectrometric measurements (matrix-assisted laser desorption/ionization-time of flight and electrospray quadrupol time-of-flight mass spectrometry) of whole corpora cardiaca, and the mass was confirmed in the HPLC fraction that had adipokinetic activity. The biologically active octapeptide has the sequence pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp amide, which was characterized previously from the corpora cardiaca of the Emperor dragonfly, Anax imperator , and denoted Anaim-adipokinetic hormone (AKH). The synthetic Anaim-AKH peptide causes lipid mobilization when injected at a dose of 1 pmol into N. glauca . When other synthetic AKH members that occur in Hemiptera are injected into N. glauca at the same dose, the hyperlipaemic responses are significantly lower than after injection of Anaim-AKH. Because only lipids increase upon activity, such as continuous swimming for 1 h or during a 1-h rest period after a 3-min flight episode in the laboratory, it is assumed that Anaim-AKH serves as a true adipokinetic hormone in the backswimmer during bouts of natural swimming and flight.     

Adipokinetic hormone controls lipid metabolism in adults and carbohydrate metabolism in larvae of Manduca sexta

The peptide hormone which controls activation of fat body glycogen phosphorylase in starving larvae of Manduca sexta was isolated from larval corpora cardiaca and sequenced by FAB tandem mass spectrometry. It was found to be identical with Manduca AKH. This, together with earlier observations, demonstrates that in M. sexta AKH controls glycogen phosphorylase activation in starving larvae while in adults it controls lipid mobilization during flight. Larval corpora cardiaca contain about 10 times less AKH than the corpora cardiaca of adults. The corpora cardiaca of M. sexta appear to contain only one AKH.     

The newly discovered insect order Mantophasmatodea contains a novel member of the adipokinetic hormone family of peptides

A novel member of the AKH/RPCH family of peptides has been identified from the corpus cardiacum of an, as yet, unidentified species of the newly discovered insect order Mantophasmatodea from Namibia. The primary sequence of the peptide, which is denoted Manto-CC, was deduced from multiple MS(N) electrospray mass data to be an octapeptide: pGlu-Val-Asn-Phe-Ser-Pro-Gly-Trp amide. Synthetic Manto-CC co-elutes on reversed-phase HPLC with the natural peptide from the gland of the insect. Interestingly, Manto-CC is structurally very closely related (only one point mutation) to the AKH/RPCH peptides previously identified in mostly more basal insect taxa (Odonata, Blattodea, and Ensifera) and in Crustacea, the sister group of insects, whereas larger structural differences occur with peptides from Mantodea and Phasmatodea, which are thought to be close relatives of Mantophasmatodea. Functionally, Manto-CC may be employed to activate glycogen phosphorylase to mobilize carbohydrates.     

An invertebrate [hydroxyproline]-modified neuropeptide: further evidence for a close evolutionary relationship between insect adipokinetic hormone and mammalian gonadotropin hormone family

An octapeptide of the adipokinetic hormone (AKH) peptide family is identified in the corpora cardiaca of the stink bug, Nezara viridula, by ESI-MS^N (electrospray ionization multistage MS). This is the second AKH in N. viridula and it has a hydroxyproline residue at position 6, whereas the major AKH (known as Panbo-RPCH) has Pro as the sixth amino acid residue. The correct sequence assignment of [Hyp⁶]-Panbo-RPCH is confirmed by retention time and MS spectra of the synthetic peptide. Various extraction procedures were followed to ascertain whether the hydroxylation is an artefact of extraction, or whether it is due to a true post-translational modification at the prohormone level. The proline hydroxylation is unique for invertebrate neuropeptides, while it has been described in the vertebrate gonadotropin-releasing hormone (GnRH). The current finding is another piece of evidence that AKH and GnRH form a peptide superfamily and are closely related evolutionarily. Biologically, [Hyp⁶]-Panbo-RPCH is active in vivo as an AKH, causing hyperlipaemia in the stink bug at low doses, indicating again that it is an endogenous, mature and functional hormone in this insect species.     

Adipokinetic hormones provide inference for the phylogeny of odonata

Adipokinetic neuropeptides from the corpora cardiaca of 17 species of Odonata encompassing mainly the families Corduliidae and Libellulidae were isolated and structurally elucidated using liquid chromatography coupled with ion trap electrospray ionization mass spectrometry. It became evident that all species of the family Corduliidae studied express the peptide code-named Libau-AKH (pGlu-Val-Asn-Phe-Thr-Pro-Ser-Trp amide), which is also present in all but one libellulid species, Erythemis simplicicollis which expresses Erysi-AKH (pGlu-Leu-Asn-Phe-Thr-Pro-Ser-Trp amide). This divergence from all other Libellulids is due to a nonsynonymous missense single nucleotide polymorphism (SNP) in the nucleotide coding sequence (CDS) of prepro-AKH CDS and supports the polyphyletic nature of Sympetrinae and other subfamilies of libellulids. Despite this exception, these findings then support the hypothesis that Corduliidae and Libellulidae are closely related as stated in most phylogenies. The presence of Anaim-AKH (pGlu-Val-Asn-Phe-Ser-Pro-Ser-Trp amide) in Macromiidae likely distinguishes species in this family from Corduliidae. Current molecular genetic phylogenies and our AKH findings suggest that Syncordulia gracilis, which expresses Anaim-AKH, does not belong in Corduliidae. Evolution of AKHs in anisopteran Odonata are likely due to nucleotide substitution involving nonsynonymous missense SNPs in the CDS of prepro-AKH.     

Structure and function of adipokinetic hormones of the large white butterfly Pieris brassicae

The large white butterfly Pieris brassicae L. (also called cabbage white) is very common in Europe, Asia and the northern region of Africa, and has also been found in South Africa during approximately the last 20 years. The species is considered a pest insect, with larvae attacking brassicaceous crops. The adult is a strong migratory flyer and new territory can be infested this way. As a first step to investigate methods for combating this pest species, the present study aims to determine the complement of adipokinetic peptides, here generically referred to as adipokinetic hormones (AKHs), which are required to regulate the mobilization of fuels for insect flight. Biological assays, as well as mass spectrometry, reveal information about the presence, structure and function of AKHs in P. brassicae: a methanolic extract of the corpora cardiaca has hypertrehalosaemic activity in cockroaches, does not cause hyperlipaemia in locusts, and has adipokinetic activity in P. brassicae itself. Liquid‐chromatography electrospray ion trap mass spectrometry reveals three peptides that can be associated with the AKH family: the non‐amidated undecapeptide Vanca‐AKH (pELTFTSSWGGK‐OH), the nonapeptide Manse‐AKH (pELTFTSSWG amide) and the novel octapeptide Piebr‐AKH (pELTFSSGW amide). Sequence confirmation of all three assigned structures is obtained from matching mass spectrometry spectra from synthetic and native peptides. Moreover, the synthetic peptides Manse‐AKH and Piebr‐AKH have significant hyperlipaemic (=adipokinetic) activity when injected into newly‐emerged adult cabbage white butterflies. The non‐amidated Vanca‐AKH is, apparently, incompletely processed Manse‐AKH without hormonal activity. Simulated dispersal flight is able to release AKHs, as indicated by the higher concentration of lipids in the haemolymph of adult P. brassicae after activity and rest periods.     

A comparison of the neuropeptides from the retrocerebral complex of adult male and female Manduca sexta using MALDI-TOF mass spectrometry

The occurrence of neuropeptides in the retrocerebral complexes of adult male and females of the tobacco hawkmoth, Manduca sexta, was investigated using matrix-assisted laser desorption time of flight (MALDI-TOF) mass spectrometry (MS), post source decay (PSD) and collision-induced dissociation (CID) MS/MS. From fractions of methanol extracts of corpora cardiaca (CC)/corpora allata (CA), separated by reversed-phase high performance liquid chromatography (RP-HPLC), a total of 11 mass ions were assigned to known peptides from M. sexta. These peptides were adipokinetic hormone (AKH), FLRFamides I, II and III, crustacean cardioactive peptide (CCAP), cardioactive peptide 2b (CAP(2b)), three myoinhibitory peptides, corazonin, and M. sexta allatostatin (Manse-AS). A further six masses were in agreement with Y/FXFGLamide allatostatins identified from other Lepidoptera. The sequence identities of FLRFamide I and AKH were confirmed using post source decay analysis. Fragmentation by collision-induced dissociation MS/MS identified an extended AKH peptide. The apparent differences in the peptides present in male and female retrocerebral complexes are most likely quantitative rather than sex specific.     

A new member of the AKH/RPCH family that stimulates locomotory activity in the firebug, Pyrrhocoris apterus (Heteroptera)

A new member of the AKH/RPCH family was isolated and identified from the corpora cardiaca of the firebug Pyrrhocoris apterus. The peptide was isolated in a single step by reversed phase HPLC and the structure deduced from the multiple MS (MS(N)) electrospray mass spectra and amino acid analysis as that of an octapeptide with the sequence pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-NH(2): this sequence was confirmed by synthesis. The synthetic peptide induced lipid mobilisation and stimulated locomotory activity in macropterous females. This peptide, designated as Pyrrhocoris apterus adipokinetic hormone (Pya-AKH), is the first identified adipokinetic hormone described in a representative species of the suborder Heteroptera.     

Isolation and identification of AKH/RPCH family peptides in blister beetles (Meloidae)

Abstract. Two peptides were isolated from methanolic extracts of corpora cardiaca of the blister beetle, Decupotoma lunata , by a single-step purification procedure, utilizing C-18 reversed-phase high-performance liquid chromatography (RP-HPLC) for separation, and the increase of haemolymph lipids in Locusta migratoria for bioassay. The native peptides were analysed by matrix-assisted laser-desorption ionization mass spectrometry revealing main ions at m/z 1180 and 1009 respectively which were attributed to the [M + Na]⁺ form of the respective peptides. After deblocking of the N-terminal pyroglutamate residue of each peptide, the structures of the deblocked peptides were determined by pulsed-liquid phase sequencing employing Edman chemistry. The sequences of the two peptides, (1) pGlu-Leu-Asn-Phe-Ser-Pro-Am-Trp-Gly-AsnNH₂ and (2) pGlu-Leu-Asn-Phe-Ser-Pro-Asn-TrpNH₂, characterize them as deca- and octapeptide members of the AKH/RPCH family. Whereas the decapeptide is a novel member of this family and is given the acronym Del-CC ( Decupotoma lunata corpus cardiacum peptide), the octapeptide has previously been found in tenebrionid beetles and has the acronym Tem-HrTH. The corpora cardiaca of two other species of blister beetles ( Cyaneolytta pectoralis and Mylabris coeca ) contain the same two peptides as D. lunata , as judged by RP-HPLC and biological activity. Neither a corpus cardiacum extract of Decupotoma lunata nor the synthetic peptides Del-CC and Tem-HrTH were active in mobilizing carbohydrates or lipids in the blister beetle.     

Structural data on hypertrehalosaemic neuropeptides from Cryptocercus punctulatus and Therea petiveriana: how do they fit into the phylogeny of cockroaches?

Hypertrehalosaemic neuropeptides from the corpora cardiaca of the cockroaches Cryptocercus punctulatus and Therea petiveriana were structurally analysed to gather phylogenetic information independent from that provided by morphoanatomical data. Isolation of the peptides by liquid chromatography and structural elucidation by Edman degradation and mass spectrometry revealed an identical octapeptide for both species: pGlu-Leu-Asn-Phe-Ser-Pro-Asn-Trp-NH₂. This peptide, denoted Tem-HrTH, was previously found in tenebrionid beetles and in the cockroach Polyphaga aegyptiaca. Using this information for phylogenetic analysis yielded a peptide tree that supports the previous morphoanatomical data and thus places the woodroach Cryptocercus inside the cockroach subfamily Polyphaginae.     

Dragonfly Erythemis simplicicollis contains a novel adipokinetic neuropeptide

We have isolated a novel member of the adipokinetic hormone family of peptides from a methanolic extract of corpora cardiaca of the libellulid dragonfly Erythemis simplicicollis by using a single‐step reversed‐phase high performance liquid chromatography method and monitoring biological activity in various heterologous bioassays and a homologous one. The sequence, as determined by Edman degradation and mass spectrometry, was of an uncharged blocked octapeptide: pGlu‐Leu‐Asn‐Phe‐Thr‐Pro‐Ser‐Trp amide. The structure was confirmed by chemical synthesis. The synthetic peptide increased hemolymph lipids in the dragonfly and was active in another libellulid (Orthetrum julia‐falsum) as well, but to a lesser extent than the conspecific peptide Lia‐AKH, which is an isoform of the novel peptide differing by a Val (instead of Leu) at position 2. Since lipids are apparently used as substrate for muscle contraction during flight of Erythemis simplicicollis and the native peptide induces lipid mobilization, this novel peptide is denoted Ers‐AKH. Arch. Insect Biochem. Physiol. 40:99–106, 1999. © 1999 Wiley‐Liss, Inc.     

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.