Rhyparobia Maderae Research Articles

Role of myoinhibitory peptides in the light entrainment pathway to the circadian pacemaker of the Madeira cockroach (Rhyparobia maderae)

Event Abstract Back to Event Role of myoinhibitory peptides in the light entrainment pathway to the circadian pacemaker of the Madeira cockroach (Rhyparobia maderae) Julia Schulze1, Thomas Schendzielorz1 and Monika Stengl1* 1 University of Kassel, Department of Biology, Germany Myoinhibitory peptides (MIPs) are a family of insect W(X6)Wamide peptides with inhibitory effects on visceral muscles and juvenile hormone synthesis. Previously, it was concluded that MIPs might play a role in the light entrainment pathway to the circadian pacemaker center, the accessory medulla (AMe), in the optic lobes of the cockroach Rhyparobia (Leucophaea) maderae. It was suggested that γ-aminobutyric acid (GABA) containing distal tract neurons transmit photic information from the compound eye to the noduli of the AMe. Then, Mas-allatotropin-immunoreactive (-ir) local interneurons with processes in the noduli appear to integrate the visual information. Furthermore, orcokinin-ir AMe-neurons with nodular arborizations in the contralateral AMe provide photic input from the contralateral eye. The role of these three substances in photic entrainment was supported via injection experiments combined with locomotor activity assays, since all three resulted in light-like phase response curves (PRCs) in the Madeira cockroach. Here we focused on the further analysis of the light entrainment pathway in the Madeira cockroach searching for colocalizations between MIP and other neuropeptides or GABA. No colocalization between MIP- and GABA immunostaining was detected in the distal tract. However, in numerous transmedullary neurons colocalized staining of GABA and MIP was observed. Moreover, at least one ventromedian AMe neuron showed colocalized orcokinin- and MIP immunoreactivity. Colocalization of MIP- and Mas-allatotropin immunostaining was detected in somata and noduli of the AMe. Injections of synthetic Lem-MIP-1 peptide resulted in a dose-dependent monophasic PRC with the strongest delay at the beginning of the subjective night. Future studies will examine potential synergisms between MIP and different neuroactive substances in photic entrainment of the AMe. [Supported by DFG grant STE531/21-1 to MS] Keywords: Behavior, circadian rhythms, Cockroach, immunocytochemistry, myoinhibitory peptide Conference: Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012. Presentation Type: Poster (but consider for participant symposium and student poster award) Topic: Circadian Rhythms Citation: Schulze J, Schendzielorz T and Stengl M (2012). Role of myoinhibitory peptides in the light entrainment pathway to the circadian pacemaker of the Madeira cockroach (Rhyparobia maderae). Conference Abstract: Tenth International Congress of Neuroethology. doi: 10.3389/conf.fnbeh.2012.27.00123 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 26 Apr 2012; Published Online: 07 Jul 2012. * Correspondence: Prof. Monika Stengl, University of Kassel, Department of Biology, Kassel, Hessen, 34132, Germany, stengl@uni-kassel.de Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Julia Schulze Thomas Schendzielorz Monika Stengl Google Julia Schulze Thomas Schendzielorz Monika Stengl Google Scholar Julia Schulze Thomas Schendzielorz Monika Stengl PubMed Julia Schulze Thomas Schendzielorz Monika Stengl Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Dopamine as an anorectic neuromodulator in the cockroachRhyparobia maderae

Insects, including cockroaches, self-select a balanced diet when faced with different nutrient choices. For self-selection to be carried out effectively, insects possess neuroregulatory systems to control their food intake. In the present study, we examined the role of the neurotransmitter dopamine (DA) in the feeding regulation of the Madeira cockroach (Rhyparobia maderae). When R. maderae nymphs were injected with 20 μl of 100 mmol l(-1) DA, they showed an 83.3% reduction in sucrose intake and a 78.9% reduction in total intake compared with saline-injected controls. The DA agonist, 2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene (6,7-ADTN) (100 mmol l(-1) in 1 μl), caused a significant reduction in sucrose feeding, reducing feeding by 47.3% compared with saline-injected controls. Protein feeding was also significantly reduced by 6,7-ADTN to 62%. Rhyparobia maderae nymphs injected with the DA antagonist chlorpromazine (100 mmol l(-1) in 1 μl) did not differ significantly from control nymphs in their feeding behavior. Interestingly, R. maderae nymphs injected with 2 μl or 5 μl chlorpromazine (100 mmol l(-1)) showed significantly increased mortality rates of 47.5% or 66.7%, respectively. The DA antagonist, spiperone (100 mmol l(-1) in 1 μl), caused a significant feeding response, showing an increase in feeding in both sucrose (310.6%) and total intake (236.3%). Casein feeding in R. maderae nymphs was also elevated (70.8%) but this was not statistically significant. The experiments with DA, the DA agonist 6,7-ADTN and the DA antagonist spiperone strongly suggest that the neurotransmitter DA is involved in regulating feeding in the cockroach R. maderae.

Juvenile hormone and methyl farnesoate production in cockroach embryos in relation to dorsal closure and the reproductive modes of different species of cockroaches

Juvenile hormone (JH), produced by the corpora allata (CA), is first detectable after dorsal closure, a conspicuous event in embryogenesis. The present research found that the timing of dorsal closure was consistently at about 45% of the total embryonic development time across most of the oviparous and ovoviviparous cockroach species examined. These included the ovoviviparous cockroaches Blaberus discoidalis, Byrsotria fumigata, Rhyparobia maderae, Nauphoeta cinerea, Phoetalia pallida, Schultesia lampyridiformis, and Panchlora nivea, as well as the oviparous cockroaches Blatta orientalis, Periplaneta americana, Eurycotis floridana, and Supella longipalpa. However, the only known viviparous cockroach Diploptera punctata completed dorsal closure at 20.8% of embryo development time. Methyl farnesoate (MF), the immediate precursor of JH III, is considered a functional molecule in crustaceans; however, in insects its function is still unclear. To understand the role of JH and MF in cockroach embryos, I compared JH and MF biosynthesis and release in several cockroach species of known phylogenetic relationships. Using a radiochemical assay, the present research showed that cockroach embryos representing all three reproductive modes produced and released both JH and MF, as previously shown for B. germanica, N. cinerea, and D. punctata. Members of a pair of embryonic CA from B. discoidalis, B. fumigata, R. maderae, and D. punctata were incubated with and without farnesol. MF accumulated in large amounts only in CA of R. maderae in the presence of farnesol, which indicates that control of the last step of biosynthesis of JH, conversion of MF into JH by MF epoxidase, is probably a rate-limiting step in this species.

Methyl-branched hydrocarbons, major components of the waxy material coating the embryos of the viviparous cockroach Diploptera punctata

The viviparous cockroach Diploptera punctata carries a wax-coated batch of embryos in a brood sac. When the embryos are expelled into saline, flakes of wax from the surface of the embryos float to the surface. In contrast, embryos of the ovoviviparous species such as Rhyparobia maderae are not nourished by the mother during embryogenesis and do not have a copious waxy coating. As a first step in determining the function of this copious wax layer on the batch of embryos of D. punctata, its composition was compared to that of the waxy material on the outer cuticular surface of the mother (female cuticle) by thin-layer chromatography (TLC) and gas chromatography–mass spectrometry. The major lipid class on the embryos was hydrocarbons with lesser amounts of wax esters and long-chain alcohols. Hydrocarbons from both sources had similar elution times and chemical composition, but were markedly different in the amounts of the major methyl-branched hydrocarbon components. A mixture of 3, X-dimethyl alkanes were 44% of the hydrocarbons on the embryos and were only 29% on the female cuticle. However, trimethylalkanes were only 22% of the hydrocarbons on the embryos and were 34% of the hydrocarbons on the female cuticle. The major hydrocarbons from both sources were mixtures of methyl-branched alkanes with backbones of 33 and 35 carbon atoms. Methyl-branched tritriacontanes were 59% of embryo and 35% of female cuticular hydrocarbons; methyl-branched pentatriacontanes were 19% of embryo and 42% of female hydrocarbons. The difference in proportions of the similar hydrocarbons on the outer cuticular surface of the female and those covering the embryos may suggest that the evolution of copious nutrient secretion for the embryos was accompanied by selection for a mixture of hydrocarbons that prevents water loss by the embryos and protects them against invasion by microorganisms without preventing the movement of nutrient fluid into the embryos.

Cockroaches of the Galápagos Islands, Ecuador, with descriptions of three new species (Insecta: Blattodea)

Eighteen species of cockroaches are reported to occur on the Galápagos Islands. Five species are endemic and in this paper three of these are described as new species: Chorisoneura cristobalensis Roth, C. carpenteri Roth, and Ischnoptera santacruzensis Roth. Endemic Ischnoptera snodgrasii (McNeill) COMB.NOV. is transferred from Anisopygia, and redescribed. Previous reports of the introduced species Periplaneta brunnea, Nauphoeta cinerea, and Phoetalia pallida could not be confirmed. These species may not have become established or may have become extinct. New records of native or introduced species are given for Holocompsa nitidula, Holocompsa sp., Anaplecta lateralis, Blaberus parabolicus, and Rhyparobia maderae. Of the introduced species, only Periplaneta australasiae, Symploce pallens, and Pycnoscelus surinamensis seem to have invaded native (undisturbed) habitats. The endemic species are partially or wholly flightless. This may not be a result of island life per se, but may be a specialization for life in more homogeneous litter or cave habitats at higher elevations on the islands.