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The ice fly Diamesa steinboecki Goetghebuer, 1933 (Diptera: Chironomidae: Diamesinae) is exclusive to glacier-fed streams in the East Palaearctic region and is threatened by extinction due to global warming and glacier retreat. To date, no data are available on its thermal tolerance or ability to develop a heat shock response (HSR) or involve other biomarkers when exposed to higher-than-natural temperatures (i.e., >4–6 °C). Our study aimed to investigate the warmth resistance of IV-instar larvae of D. steinboecki in terms of (1) ability to survive heat shock and (2) gene expression of four genes known to be involved in the detoxification/stress response (cytochrome p450 (Cyp450), heat shock protein 70 (hsp70), hsp70 with intron and heat shock protein cognate 70 (hsc70)). Larvae were exposed to short-term shocks for 1 h at increasing temperatures (26, 28, 30, 32, 34, 36, 38, and 40 °C) to estimate the lethal temperature, obtaining high values (LT10 = 38.1 °C, LT50 = 39.2 °C, LT99 = 40.3 °C), suggesting a strong heat resistance up to 38 °C and a very rapid decline in survival thereafter. Moreover, gene expression analysis by real-time PCR was performed on larvae from the control (at 2 °C) and larvae found alive after the previous treatment at 26, 28, 30, 32, 34, 36, and 38 °C. Modulation of the expression was observed only for hsc70 and hsp70 genes. Specifically, hsc70 resulted in constitutive overexpression, even at 26 °C when all larvae were found alive without evidence of suffering. By contrast, hsp70 showed up and downregulation according to the specific temperature, suggesting the activation of an HSR at 28 °C, when some larvae were found alive but suffering (almost paralyzed). The results suggest that, based on LTs, D. steinboecki is more thermally tolerant than other Diamesa species (e.g., D. tonsa) from cold freshwaters, but, as in these, hsp70 and hsc70 are involved in surviving short-term heat shock. This makes the ice fly from the Alps different from Belgica antarctica and other cold-adapted organisms living in extremely cold habitats that, constantly exposed to cold, have lost the ability to develop an HSR. Further research is needed to investigate the response to prolonged exposure to temperatures higher that the natural one, giving new insights into the biological response to climate change of alpine species threatened by extinction. [ABSTRACT FROM AUTHOR]

The deep-sea hydrothermal vent ecosystem is one of the extreme chemoautotrophic environments. Shinkaicaris leurokolos Kikuchi and Hashimoto, 2000, and Alvinocaris longirostris Kikuchi and Ohta, 1995, are typically co-distributed and closely related alvinocaridid shrimps in hydrothermal vent areas with different ecological niches, providing an excellent model for studying the adaptive evolution mechanism of animals in the extreme deep-sea hydrothermal vent environment. The shrimp S. leurokolos lives in close proximity to the chimney vent discharging high-temperature fluid, while A. longirostris inhabits the peripheral areas of hydrothermal vents. In this study, full-length transcriptomes of S. leurokolos and A. longirostris were generated using a combination of single-molecule real-time (SMRT) and Illumina RNA-seq technology. Expression analyses of the transcriptomes showed that among the top 30% of highly expressed genes of each species, more genes related to sulfide and heavy metal metabolism (sulfide: quinone oxidoreductase, SQR; persulfide dioxygenase, ETHE1; thiosulfate sulfurtransferase, TST, and ferritin, FRI) were specifically highly expressed in S. leurokolos, while genes involved in maintaining epibiotic bacteria or pathogen resistance (beta-1,3-glucan-binding protein, BGBP; endochitinase, CHIT; acidic mammalian chitinase, CHIA, and anti-lipopolysaccharide factors, ALPS) were highly expressed in A. longirostris. Gene family expansion analysis revealed that genes related to anti-oxidant metabolism (cytosolic manganese superoxide dismutase, SODM; glutathione S-transferase, GST, and glutathione peroxidase, GPX) and heat stress (heat shock cognate 70 kDa protein, HSP70 and heat shock 70 kDa protein cognate 4, HSP7D) underwent significant expansion in S. leurokolos, while CHIA and CHIT involved in pathogen resistance significantly expanded in A. longirostris. Finally, 66 positively selected genes (PSGs) were identified in the vent shrimp S. leurokolos. Most of the PSGs were involved in DNA repair, antioxidation, immune defense, and heat stress response, suggesting their function in the adaptive evolution of species inhabiting the extreme vent microhabitat. This study provides abundant genetic resources for deep-sea invertebrates, and is expected to lay the foundation for deep decipherment of the adaptive evolution mechanism of shrimps in a deep-sea chemosynthetic ecosystem based on further whole-genome comparison. [ABSTRACT FROM AUTHOR]