Three neuropeptides Zopat-MS-2 (pEDVDHVFLRFa), Zopat-SK-1 (pETSDDYGHLRFa) and Zopat-NVPL-4trunc. (GRWGGFA), recently isolated from the neuroendocrine system of the Zophobas atratus beetle, were tested for their myotropic and hyperglycaemic activities in this species. These peptides exerted differentiated dose-dependent and tissue specific physiological effects. Zopat-MS-2 inhibited contractions of the isolated heart, ejaculatory duct, oviduct and hindgut of adult beetles and induced bimodal effects in the heart contractile activity of pupae in vivo. It also increased the haemolymph free sugar level in larvae of this species, apart from myotropic activity. Zopat-SK-1 showed myostimulatory action on the isolated hindgut of the adult beetles, but it decreased contractions of the heart, ejaculatory duct and oviduct. Injections of this peptide at a dose of 2 μg also caused delayed cardioinhibitory effects on the heartbeat of the pupae. Together with the ability to increase free sugar level in the haemolymph of larvae these were new physiological activities of sulfakinins in insects. Zopat-NVPL-4trunc. inhibited the muscle contractions of the two organs: hindgut and ejaculatory duct but it was inactive on the oviduct and the heart of the adult beetles. This peptide also increased free sugar level concentration in the haemolymph of Z. atratus larvae. These physiological actions are the first biological activities discovered for this group of the insect peptides. The present work showed pleiotropic activity of three neuropeptides and indicates that the visceral muscle contractions and the haemolymph sugar homeostasis in Z. atratus are regulated by complex mechanisms.

At birth, the newborn fat-tailed dunnart relies on cutaneous gas exchange to meet metabolic demands, with continuous lung ventilation emerging several days later. We hypothesised that the delayed expression of lung ventilation (V_E) in these animals is in part due to a low responsiveness of the respiratory control system to blood gas perturbations. To address this hypothesis, we assessed the ventilatory and metabolic response to hypoxia (10% O₂) and hypercapnia (5% CO₂) using closed-system respirometry from birth to 23 days postpartum (P). Neonatal fat-tailed dunnarts displayed no significant hypoxic or hypercapnic ventilatory responses at any age. Regardless, significant hyperventilation through a suppression of metabolic rate (VO₂) was observed at birth in response to hypercapnia and in response to hypoxia at all ages, except P12. Therefore, reliance on cutaneous gas exchange during early life may be partially attributed to reduced chemosensitivity or a lack of central integration of chemosensitive afferent information. This may be in part due to the relative immaturity of this species at birth, compared with other mammals.