Stored product insects show high adaption to hypoxia and hypercapnia, but the underlying mechanism is still unclear. Herein, a comparative transcriptome on 4th adzuki bean weevil (Callosobruchus chinensis) instar larvae was studied to clarify the response mechanisms to hypoxia (HA) and hypoxia/hypercapnia (HHA) using NextSeq500 RNA-Seq. Transcript profiling showed a significant difference in HA or HHA exposure both quantitatively and qualitatively. Compared with control, 631 and 253 genes were significantly changed in HHA and HA, respectively. Comparing HHA with HA, 1135 differentially expressed genes (DEGs) were identified. The addition of hypercapnia made a complex alteration on the hypoxia response of bean weevil transcriptome, carbohydrate, energy, lipid and amino acid metabolism were the most highly enriched pathways for genes significantly changed. In addition, some biological processes that were not significantly enriched but important were also discussed, such as immune system and signal transduction. Most of the DEGs related to metabolism both in HHA and HA were up-regulated, while the DEGs related to the immune system, stress response or signal transduction were significantly down-regulated or suppressed. This research reveals a comparatively full-scale result in adzuki bean weevil hypoxia and hypoxia/hypercapnia tolerance mechanism at transcription level, which might provide new insights into the genomic research of this species.

The effect of short-term (5 days) exposure to CO2-acidified seawater (year 2100 predicted values, ocean pH = 7.6) on key aspects of the function of the intertidal common limpet Patella vulgata (Gastropoda: Patellidae) was investigated. Changes in extracellular acid–base balance were almost completely compensated by an increase in bicarbonate ions. A concomitant increase in haemolymph Ca2+ and visible shell dissolution implicated passive shell dissolution as the bicarbonate source. Analysis of the radula using SEM revealed that individuals from the hypercapnic treatment showed an increase in the number of damaged teeth and the extent to which such teeth were damaged compared with controls. As radula teeth are composed mainly of chitin, acid dissolution seems unlikely, and so the proximate cause of damage is unknown. There was no hypercapnia-related change in metabolism (O2 uptake) or feeding rate, also discounting the possibility that teeth damage was a result of a CO2-related increase in grazing. We conclude that although the limpet appears to have the physiological capacity to maintain its extracellular acid–base balance, metabolism and feeding rate over a 5 days exposure to acidified seawater, radular damage somehow incurred during this time could still compromise feeding in the longer term, in turn decreasing the top-down ecosystem control that P. vulgata exerts over rocky shore environments.

The lungs of the naked mole-rat Heterocephalus glaber were morphologically (qualitatively) and morphometrically (quantitatively) investigated in adult captive in-burrow body-temperature-maintained (CBTMA) and captive cold-exposed animals (CCEA). The observations were compared with those of field (burrow-dwelling) animals (FA) examined in an earlier study. The lungs of the captive animals were morphologically (qualitatively) similar to those of the field mole-rats. Conspicuous paedomorphic features, i.e. a preponderant double pulmonary capillary arrangement, incomplete differentiation of alveolar pneumocytes, and extension of a cuboidal epithelium to the immediate vicinity of the alveoli, were observed. The prevalent pulmonary underdevelopment was attributed to the relatively low metabolic rate of the poikilothermic naked mole-rat, a species that has evolved in a thermally stable environment. Measurable differences and similarities were found between the lungs of the captive naked mole-rats themselves (i.e. the CBTMA and the CCEA) and between the captive and the field ones. Genetic factors may help explain the conserved pulmonary structural features while environmental (gaseous) change from a hypoxic–hypercapneic (an oxygen deficient–high carbon dioxide concentration) to a normoxic–normocapnic atmosphere and the thermal shift respectively may have enforced pulmonary transformations between the CBTMA and the FA and between the CCEA and the CBTMA. Paradoxically, the CCEA had a significantly lower mass-specific total morphometric pulmonary diffusing capacity of 0.024 compared with that of 0.102 mlO2.s−1.mbar−1.kg−1 in the CBTMA. The observed morphometric differences indicate that the lung of the naked mole-rat, though morphologically unchanged, is intrinsically tractable to environmental shifts in its habitat. Studies on captive naked mole-rats should not be indiscriminately taken to be representative of the species.

The partial pressure of carbon dioxide in the arterial blood (PaCO2) is usually tightly regulated, yet it varies among healthy people at rest (range ∼32–44 mmHg) as well as within an individual during many natural life situations. The present study examined whether modest changes in end-tidal PCO2 (PetCO2; a noninvasive measure of PaCO2) affect electroencephalographic (EEG) activity, cognitive function, and vigilance. Nine adults were ventilated mechanically using a mouthpiece; respiratory rate and breath size were held constant while PetCO2 was set to levels that produced minimal discomfort. Despite discrete changes in EEG, neither acute PetCO2 increases (mean = 47 mmHg) nor decreases (mean = 30 mmHg) from resting levels (mean = 38 mmHg) affected performance on cognitive tasks, latency or amplitude of the N1, P2, or P3 event-related potential, or alertness. Modest changes in PetCO2 may cause significant alterations in the EEG without disturbing cognitive function.