Prothoracicostatic Activity of the Ecdysis-Regulating Neuropeptide Crustacean Cardioactive Peptide (CCAP) in the Desert Locust

Accurate control of innate behaviors associated with developmental transitions requires functional integration of hormonal and neural signals. Insect molting is regulated by a set of neuropeptides, which trigger periodic pulses in ecdysteroid hormone titers and coordinate shedding of the old cuticle during ecdysis. In the current study, we demonstrate that crustacean cardioactive peptide (CCAP), a structurally conserved neuropeptide described to induce the ecdysis motor program, also exhibits a previously unknown prothoracicostatic activity to regulate ecdysteroid production in the desert locust, Schistocerca gregaria. We identified the locust genes encoding the CCAP precursor and three G protein-coupled receptors that are activated by CCAP with EC50 values in the (sub)nanomolar range. Spatiotemporal expression profiles of the receptors revealed expression in the prothoracic glands, the endocrine organs where ecdysteroidogenesis occurs. RNAi-mediated knockdown of CCAP precursor or receptors resulted in significantly elevated transcript levels of several Halloween genes, which encode ecdysteroid biosynthesis enzymes, and in elevated ecdysteroid levels one day prior to ecdysis. Moreover, prothoracic gland explants exhibited decreased secretion of ecdysteroids in the presence of CCAP. Our results unequivocally identify CCAP as the first prothoracicostatic peptide discovered in a hemimetabolan species and reveal the existence of an intricate interplay between CCAP signaling and ecdysteroidogenesis.

Physiological changes throughout the ear due to age and noise - a longitudinal study

Biological and mechanical systems, whether by their overuse or their aging, will inevitably fail. Hearing provides a poignant example of this with noise-induced and age-related hearing loss. Hearing loss is not unique to humans, however, and is experienced by all animals in the face of wild and eclectic differences in ear morphology and operation. Here we exploited the high throughput and accessible tympanal ear of the desert locust, Schistocerca gregaria (mixed sex) to rigorously quantify changes in the auditory system due to noise exposure (3 kHz pure tone at 126 dB SPL) and age. We analysed tympanal dispalcements, morphology of the auditory Mullers organ and measured activity of the auditory nerve, the transduction current and electrophysiological properties of individual auditory receptors. We found that noise mildly and transiently changes tympanal displacements, decreases both the width of the auditory nerve and the transduction current recorded from individual auditory neurons. Whereas age, but not noise, decreases the number of auditory neurons and increases their resting potential. Multiple other properties of Mullers organ were unaffected by either age or noise including: the number of supporting cells in Mullers organ or the nerve, membrane resistance and capacitance of the auditory neurons. The sound-evoked activity of the auditory nerve decreased as a function of age and this decrease was exacerbated by noise, with the largest difference during the middle of their life span. This middle-aged deafness pattern of hearing loss mirrors that found for humans exposed to noise early in their life.

The Effects of Structural Alterations in the Polyamine and Amino Acid Moieties of Philanthotoxins on Nicotinic Acetylcholine Receptor Inhibition in the Locust, Schistocerca gregaria

Alterations in the polyamine and amino acid (tyrosine) moieties of philanthotoxin-343 (PhTX-343) were investigated for their effects on the antagonism of nicotinic acetylcholine receptors (nAChRs) isolated from the locust (Schistocerca gregaria) mushroom body. Through whole-cell patch-clamp recordings, the philanthotoxin analogues in this study were shown to cause inhibition of the inward current when co-applied with acetylcholine (ACh). PhTX-343 (IC50 = 0.80 μM at −75 mV) antagonised locust nAChRs in a use-dependent manner, suggesting that it acts as an open-channel blocker. The analogue in which both the secondary amine functionalities were replaced with methylene groups (i.e., PhTX-12) was ~6-fold more potent (IC50 (half-maximal inhibitory concentration) = 0.13 μM at −75 mV) than PhTX-343. The analogue containing cyclohexylalanine as a substitute for the tyrosine moiety of PhTX-343 (i.e., Cha-PhTX-343) was also more potent (IC50 = 0.44 μM at −75 mV). A combination of both alterations to PhTX-343 generated the most potent analogue, i.e., Cha-PhTX-12 (IC50 = 1.71 nM at −75 mV). Modulation by PhTX-343 and Cha-PhTX-343 fell into two distinct groups, indicating the presence of two pharmacologically distinct nAChR groups in the locust mushroom body. In the first group, all concentrations of PhTX-343 and Cha-PhTX-343 inhibited responses to ACh. In the second group, application of PhTX-343 or Cha-PhTX-343 at concentrations ≤100 nM caused potentiation, while concentrations ≥1 μM inhibited responses to ACh. Cha-PhTX-12 may have potential to be developed into insecticidal compounds with a novel mode of action.

PROTEÍNAS DE INSETOS: FONTE DE PEPTÍDEOS BIOATIVOS

Introdução: A entomofagia, isto é, a prática de comer insetos, vem crescendo ao longo dos últimos anos devido ao baixo impacto ambiental, elevado valor nutricional e potenciais benefícios à saúde. A composição nutricional destes animais varia de acordo com a espécie, estágio de desenvolvimento, origem, alimentação, entre outros fatores. Estes alimentos apresentam elevado teor proteico (atingido valores de até 61%) de alta qualidade nutricional com um adequado perfil de aminoácidos essenciais. Em paralelo, a hidrólise enzimática de proteínas vem sendo aplicada visando a geração de peptídeos com relevantes propriedades biológicas, como exemplo, atividade antioxidante, antidiabética, anti-hipertensiva, antimicrobiana e outras. Objetivo: Neste contexto, essa revisão apresenta o potencial de insetos comestíveis, como substrato proteico para a produção de peptídeos bioativos. Materiais e Métodos: O processo metodológico adotado foi a pesquisa bibliográfica em bases acadêmicas virtuais (Scoups, Scielo e Google acadêmico) utilizando as palavras chaves: “insetos comestíveis”, “peptídeos bioativos”, “hidrólise enzimática de insetos comestíveis” para obtenção de artigos científicos publicados nos últimos 5 anos. As proteínas de insetos comestíveis são fontes de peptídeos bioativos. Resultados: Geralmente, esses pequenos fragmentos são formados por menos de 20 resíduos de aminoácidos com massa molecular <6 kDa. Pesquisadores sugerem que os peptídeos com massa molecular menor que 1kDa são melhores para incorporação em alimentos, devido à melhor absorção na forma intacta pelo sistema circulatório. Dentre os principais insetos com potencial de geração de peptídeos bioativos, destacam-se os peptídeos obtidos do Grilo (Amphiacusta annulipes) e do tenébrio gigante (Zophobasmorio) com capacidade antioxidante, os peptídeos do gafanhoto-do-deserto (Schistocerca gregária) e da larva-da-farinha (Tenebrio molitor) com bioatividade anti-hipertensiva e os peptídeos do grilo-doméstico tropical (Gryllodes sigillatus) desempenhando atividade antioxidante, antidiabética e anti-hipertensiva. Conclusão: Desta forma, a hidrólise enzimática das proteínas de insetos possibilita a obtenção de peptídeos bioativos, podendo estes serem utilizados em formulações alimentícias ou em nutracêuticos. Neste sentido, outros estudos vem sendo conduzidos para o desenvolvimento de técnicas de incorporação desses peptídeos em diferentes matrizes alimentícias.

Desert Locust Schistocerca gregaria Forskål (Acrididae): Biology, Management and Strategies: A Review

Early 2020 witnessed the emergence of global agrarian crisis with the widespread burgeoning of destructive migratory pest, Desert Locust (Schistocerca gregaria) in East Africa, Southwest Asia, Pakistan and India. Characterised by the ability to eat ravenously, breed exponentially and migrate rapidly; locust swarms has led to substantial agrarian disaster. The current official strategy is to control the upsurges to evade plague. Though it may seem attractive and efficient, it is sensible only if the numbers are relatively low. The socio-economic and environmental challenges posed by the unprecedented locust outbreak has prompt the scientists worldwide to emanate an effective preventive management strategies that rely on updated knowledge of pest biology, ecology and behaviour along with efficient monitoring, data management, analysis, forecasting, resource deployment and control techniques. In addition, the integrated network of field teams, decision makers, analysts, rural governing bodies and farmers potentially offers better compliance of pest management strategies.

The 2019–2020 upsurge of the desert locust and its impact in Pakistan

The recent upsurge of the desert locust Schistocerca gregaria (Forskål, 1775) has had an impact on East Africa and the Middle East as far as India. It has affected and slowed down many aspects of the Pakistani economy. Swarms of locusts have infested many areas and caused immense damage to all types of crops. Both farmers and economists are concerned and are trying to get the most up-to-date information on the best strategy to manage this pest. This paper is an attempt to (i) provide insight into the dynamics of this upsurge internationally as well as in the various regions of Pakistan, (ii) briefly assess its local impact and locust control measures, and (iii) clarify the role of the various stakeholders in the management, both nationally and internationally, suggesting various improvements for the future.