Radomír Socha

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.

Adipokinetic Hormone Stimulates Insect Locomotor Activity

85 Pierce HD, de Groot P, Borden JH, Ramaswamy S, Oehlschager AC (1995) Pheromones in the red pine cone beetle, Conophthorus resinosae Hopkins, and its synonym, C. banksianae McPherson (Coleoptera: Scolytidae). J Chem Ecol 21 :169–185 Turgeon JJ, Roques A, de Groot P (1994) Insect fauna of coniferous seed cones: diversity, host plant interactions, and management. Ann Rev Entomol 39 :179–212 Wilson IM, Borden JH, Gries R, Gries G (1996) Green leaf volatiles as antiaggregants for the mountain pine beetle, Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae). J Chem Ecol 22 :1861–1875

Developmental and diel changes of adipokinetic hormone in CNS and haemolymph of the flightless wing-polymorphic bug, Pyrrhocoris apterus (L.).

We have used an enzyme-linked immunoassay (ELISA) for determination of the AKH content in CNS (brain + corpora cardiaca + corpora allata) and haemolymph of adult macropterous and brachypterous females of the bug Pyrrhocoris apterus. The tests revealed that the AKH content fluctuates between 1 and almost 4 pmol/CNS during the first 14 days of adult life and significantly increased in order diapausing brachypters<reproductive brachypters<macropters. The titre of AKH in haemolymph is detectable mostly only in macropterous females during that period; in reproductive or diapausing brachypterous females keeps mostly below the detectable limit--1 fmol/microl. There are significant changes of AKH content in CNS and haemolymph of 10-day-old macropterous females during a 24 h period, with the highest values at about 10 h after the onset of light and at second half of the light period, respectively. The diel changes of AKH content in CNS are positively correlated with diel changes of adipokinetic response to AKH. Immunohistochemistry revealed that almost all reactive material is localized in the posterior part of the corpora cardiaca, and just a small amount in a few cell groups and axons distributed over the whole brain.

Feeding, drinking and digestive enzyme activities in long- and short-day females of Pyrrhocoris apterus (Heteroptera)

Abstract. .Reproducing females of the firebug, Pyrrhocoris apterus (Linnaeus) (Heteroptera: Pyrrhocoridae), reared under long‐day (LD 18:6h) photocycle (long‐day females), and diapausing females reared under short‐day (LD 12:12h) conditions (short‐day females) were analysed for temporal patterns of feeding, drinking and gut digestive enzyme activities. In long‐day females the highest activities of feeding and drinking were found at the beginning of each reproductive cycle. Significant correlation between feeding and drinking activities in both reproducing long‐day females and short‐day females during pre‐diapause state was found. In pre‐diapausing short‐day females the cyclical pattern of feeding and drinking was maintained despite the inhibition of reproduction. After entering the diapause their feeding activity became very low. Analysis of five gut enzymes revealed that short‐day females differ significantly from long‐day females in higher protease, amylase and esterase activities, in case of lipase only at certain times of their adult life; no significant difference was found in the aminopeptidase activity. Positive correlations between intensity of feeding and gut enzyme activities were observed in short‐day females. Using several protease inhibitors most protease activity in the gut of P.apterus was identified as cysteine and aspartyl proteases, and only a small part of the activity could be caused by some serine proteases.

Topical application of Pya‐AKH stimulates lipid mobilization and locomotion in the flightless bug, Pyrrhocoris apterus (L.) (Heteroptera)

Abstract Two different methods of applying Pya‐AKH to long‐winged (macropterous) females of the firebug, Pyrrhocoris apterus (Linnaeus) (Heteroptera) were compared: both injection and topical application increased the levels of lipids in the haemolymph and stimulated locomotor activity. Lipid mobilization was maximal when 10 pmol was applied by injection or 40–100 pmol by topical application, with the first significant responses occurring 1.5 h after injection and 2 h after topical application. The highest elevations of lipid concentration in the haemolymph were comparable between the treatments, i.e. 14.36 ± 3.59 mg/mL for injection and 14.43 ± 4.07 mg/mL for topical application. However, these maximal elevations were achieved at different times: 3 h after the injection and 7 h after the topical application.

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.

Lipid mobilization and locomotor stimulation in Gryllus bimaculatus by topically applied adipokinetic hormone

Abstract.  Walking activity of 3‐day‐old adult female Gryllus bimaculatus (de Geer) (Ensifera, Gryllidae) was measured over 24 h. A high level of locomotor activity during the scotophase was found, which was two‐ to three‐fold higher than that during the photophase. The titre of lipid in the haemolymph was relatively low 2 h after lights on, increased significantly 2 h after lights off, although, 2 h after lights on in the next photophase, the lipid titre had decreased to the basal level. Topical application of homologous Grybi‐adipokinetic hormone (AKH) (100 pmol in 20% 2‐propanol) led to a significant increase in haemolymph lipids, comparable with the maximal increase caused by injection of AKH (3 pmol in water). Topical application of AKH also stimulated locomotor activity in crickets (maximal stimulation 1.8‐fold with 100 pmol Grybi‐AKH). The results suggest that AKH penetrates the cuticle quickly. It is assumed that AKH stimulates locomotory activity at least in part via the increase of haemolymph lipid titres; however, the stimulation of locomotor activity via a direct neuromodulatory effect of AKH cannot be excluded.

The adipokinetic hormones of Heteroptera: a comparative study.

The adipokinetic hormones (AKHs) from 15 species of heteropteran Hemiptera (encompassing eight families, six superfamilies and three infraorders) have been isolated and structurally identified using liquid chromatography coupled with mass spectrometry. None of the structures are novel and all are octapeptides. These peptide sequence data are used, together with the previously available AKH sequence data on Heteroptera, to create a larger dataset for comparative analyses. This results, in total, in AKH sequences from 30 species (spanning 13 families), which are used in a matrix confronted with the current hypotheses on the phylogeny of Heteroptera. The expanded dataset shows that all heteropterans have octapeptide AKHs; three species have two AKHs, whereas the overwhelming majority have only one AKH. From a total of 11 different AKH peptides known from Heteroptera to date, three AKHs occur frequently: Panbo‐red pigment‐concentrating hormone (RPCH) (×10), Schgr‐AKH‐II (×6) and Anaim‐AKH (×4). The heteropteran database also suggests that particular AKH variants are family‐specific. The AKHs of Heteroptera: Pentatomomorpha (all terrestrial) are not present in Nepomorpha (aquatic) and Gerromorpha: Gerridae (semiaquatic); AKHs with a Val in position 2 are absent in the Pentatomomorpha (only AKHs with Leu2 are present), whereas Val2 predominates in the nonterrestrial species. An unexpected diversity of AKH sequences is found in Nepomorpha, Nepoidea, Nepidae and Nepinae, whereas Panbo‐RPCH (which has been identified in all infraorders of decapod crustaceans) is present in all analysed species of Pentatomidae and also in the only species of Tessaratomidae investigated. The molecular evolution of Heteroptera with respect to other insect groups and to crustaceans is discussed

Oxidative stress elicited by insecticides: A role for the adipokinetic hormone

Adipokinetic hormones (AKHs) are insect neuropeptides responding to stress situations including oxidative stress. Two insecticides - endosulfan and malathion - were used to elicit oxidative stress conditions in the firebug Pyrrhocoris apterus, and the physiological functions of AKHs and their ability to activate protective antioxidative reactions were studied. The insecticide treatments elicited only a slight increase of the AKH level in CNS, but more intensive increase in haemolymph, which indicates an immediate involvement of AKH in the stress response. The treatment also resulted in a significant increase of catalase activity in the bugs body and depletion of the reduced glutathione pool in the haemolymph, however, co-application of the insecticides with the AKH (80 pmol) reduced the effect. It has also been found that co-application of the insecticides with AKH increased significantly the bug mortality compared to that induced by the insecticides alone. This enhanced effect of the insecticides probably resulted from the stimulatory role of AKH on bug metabolism: the carbon dioxide production was increased significantly after the co-treatment by AKH with insecticides compared to insecticide treatment alone. It was hypothesized that the increased metabolic rate could intensify the insecticide action by an accelerated rate of exchange of metabolites accompanied by faster penetration of insecticides into tissues.

The effect of constant darkness on the content of adipokinetic hormone, adipokinetic response and walking activity in macropterous females of Pyrrhocoris apterus (L.)

Abstract.  Changes in the content of adipokinetic hormone (AKH), the adipokinetic response and the walking activity of 10‐day‐old adult macropterous females of the firebug, Pyrrhocoris apterus (L.), reared under long‐day (LD) photoperiod (LD 18 : 6 h) are compared with those exposed for 3 days to constant darkness (DD). Diel changes of all the parameters studied in LD females persist in females kept in constant dark. A positive correlation exists between diel changes of AKH content in the central nervous system (CNS) in the LD and DD females, and a negative correlation in the AKH level in haemolymph and walking activity. In addition, there is a positive correlation between diel changes of AKH level in haemolymph and walking activity in macropterous females reared under LD conditions, as well as in those transferred to constant darkness. The data suggest that there is some feedback between the release of AKH from CNS into the haemolymph and walking activity in macropterous females. Preliminary studies on the simultaneous expression of mRNA for the period gene and a positive reaction to an antibody against AKH in the same corpus cardiacum cells suggest that the period gene may be involved in regulating the AKH content in this gland.