No abstract

For insects, chilling injuries that occur in the absence of freezing are often related to a systemic loss of ion and water balance that leads to extracellular hyperkalemia, cell depolarization and the triggering of apoptotic signalling cascades. The ability of insect ionoregulatory organs (e.g. the Malpighian tubules) to maintain ion balance in the cold has been linked to improved chill tolerance, and many neuroendocrine factors are known to influence ion transport rates of these organs. Injection of micromolar doses of CAPA (an insect neuropeptide) have been previously demonstrated to improve cold tolerance, but the mechanisms through which it impacts chill tolerance are unclear, and low doses of CAPA have been previously demonstrated to cause anti-diuresis in insects, including dipterans. Here, we provide evidence that low (femtomolar) and high (micromolar) doses of CAPA impair and improve chill tolerance, respectively, via two different effects on Malpighian tubule ion and water transport. While low doses of CAPA are anti-diuretic, reduce tubule K clearance rates and reduce chill tolerance, high doses facilitate K clearance from the haemolymph and increase chill tolerance. By quantifying CAPA peptide levels in the central nervous system, we estimated the maximum achievable hormonal titres of CAPA and found further evidence that CAPA may function as an anti-diuretic hormone in We provide the first evidence of a neuropeptide that can negatively affect cold tolerance in an insect and further evidence of CAPA functioning as an anti-diuretic peptide in this ubiquitous insect model.

Statement: Many insects ion balance in the cold. We show how one 26 neuropeptide can slow ion transport and reduce the cold tolerance of a fly. 27 28 29 30 Abstract 31For insects, chilling injuries that occur in the absence of freezing are often related to a 32 systemic loss of ion and water balance that leads to extracellular hyperkalemia, cell 33 depolarization, and the triggering of apoptotic signalling cascades. The ability of insect 34 ionoregulatory organs (e.g. the Malpighian tubules) to maintain ion balance in the cold has been 35 linked to improved chill tolerance, and many neuroendocrine factors are known to influence ion 36 transport rates of these organs. Injection of micromolar doses of CAPA (an insect neuropeptide) 37 have been previously demonstrated to improve Drosophila cold tolerance, but the mechanisms 38 through which it impacts chill tolerance are unclear, and low doses of CAPA have been 39 demonstrated to cause anti-diuresis in other insects, including dipterans. Here, we provide 40 evidence that low (fM) and high (µM) doses of CAPA impair and improve chill tolerance, 41 respectively, via two different effects on Malpighian tubule ion and water transport. While low 42 doses of CAPA are anti-diuretic, reduce tubule K + clearance rates and reduce chill tolerance, 43 high doses facilitate K + clearance from the haemolymph and increase chill tolerance. By 44 quantifying CAPA peptide levels in the central nervous system, we estimated the maximum 45 achievable hormonal titres of CAPA, and found evidence to suggest that CAPA may function as 46 an anti-diuretic peptide in Drosophila. We provide the first evidence of a neuropeptide that can 47 negatively affect cold tolerance in an insect, and the first evidence of CAPA as an anti-diuretic 48 peptide in this ubiquitous insect model. 49 et al., 2017a;Djamgoz, 1987; MacMillan et al., 2014;Rheuben, 1972). Over minutes to hours, 64 suppressed ion transport allows for the net movement of Na + and water down their concentration 65 50

No abstract

Animal welfare assessment relies on valid and practical indicators of affect. In mice, the most widely used research vertebrates, lying still with eyes open, inactive-but-awake (IBA) in the home cage, has potential to be one such indicator. IBA is elevated in barren, conventional housing compared with well-resourced, enriched housing, and predicts immobility in Forced Swim Tests, a common measure of ‘helplessness’ in depression research. In Experiment 1, using females from three strains (C57BL/6, Balb/c and DBA/2), we first replicated past findings, confirming higher levels of IBA in conventional cages and a positive relationship between IBA and helplessness. We then extended this research to three other signs of depression: changes in weight and sleep, and reduced hippocampal volume. Here, IBA positively covaried with body mass index, with sleep in DBA/2s and conventionally housed BALB/cs, and negatively covaried with hippocampal volume in conventionally housed C57BL/6s. In Experiment 2, we sought to refine the phenotype of IBA to improve its accuracy as a welfare indicator. Here, scoring IBA performed in hunched postures appeared to improve its accuracy as an indicator in Balb/c mice. Additional research is now needed to further refine the phenotype of IBA and to confirm whether it reflects states consistent with depression, or instead other underlying poor welfare conditions.