The Effect of Hypoxia and Hyperoxia on Growth and Expression of Hypoxia‐Related Genes and Proteins in Spotted Gar Lepisosteus oculatus Larvae and Juveniles

Abstract

We studied the molecular responses to different water oxygen levels in gills and swim bladder of spotted gar (Lepisosteus oculatus), a bimodal breather. Fish at swim-up stage were exposed for 71 days to normoxic, hypoxic, and hyperoxic water conditions. Then, all aquaria were switched to normoxic conditions for recovery until the end of the experiment (120 days). Fish were sampled at the beginning of the experiment, and then at 71 days of exposure and at 8 days of recovery. We first cloned three hypoxia-related genes, hypoxia-inducible factor 2α (HIF-2α), Na(+) /H(+) exchanger 1 (NHE-1), and NHE-3, and uploaded their cDNA sequences in the GeneBank database. We then used One Step Taqman® real-time PCR to quantify the mRNA copies of target genes in gills and swim bladder of fish exposed to different water O2 levels. We also determined the protein expression of HIF-2α and neuronal nitric oxide synthase (nNOS) in the swim bladder by using confocal immunofluorescence. Hypoxic stress for 71 days significantly increased the mRNA copies of HIF-2α and NHE-1 in gills and swim bladder, whereas normoxic recovery for 8 days decreased the HIF-2α mRNA copies to control values in both tissues. We did not found significant changes in mRNA copies of the NHE-3 gene in either gills or swim bladder in response to hypoxia and hyperoxia. Unlike in normoxic swim bladder, double immunohistochemical staining in hypoxic and hyperoxic swim bladder using nNOS/HIF-2α showed extensive bundles of HIF-2α-positive nerve fibers in the trabecular musculature associated with a few varicose nNOS immunoreactive nerve terminals.

Spatial distribution and activity patterns as welfare indicators in response to water quality changes in European sea bass, Dicentrarchus labrax

“…TAN concentrations in the High TAN condition corresponded to a concentration of NH3 of 1.6 mg.L -1 ( half of the LC50, Person-Le Ruyet et al, 1995). Oxygen saturations chosen during the Hyperoxia and Hypoxia conditions were previously described to affect fish physiology and behaviour during chronic exposure without being lethal (Chapman and Mckenzie, 2009;Espmark and Baeverfjord, 2009;Rimoldi et al, 2016). Both concentrations of oxygen and TAN used in the present study were quite extreme but can occasionally occur (or even co-occur) in aquaculture conditions in case of technical failures.…”

“…Interestingly, fish from High TAN, Hyperoxia and Hypoxia conditions spent less time in the periphery area than control fish, which suggest that they were not displaying anxiety-like behaviour contrary to control fish in response to handling. High TAN, Hyperoxia and Hypoxia are known to directly affect fish survival (Magaud et al, 1997;Person-Le Ruyet and Boeuf, 1998;Shimps et al, 2005;Rimoldi et al, 2016). Indeed, fish survival can be impacted in many ways following their exposure to one of these stressors.…”

Survival, Growth, and Development in the Early Stages of the Tropical Gar Atractosteus tropicus: Developmental Critical Windows and the Influence of Temperature, Salinity, and Oxygen Availability

“…The first experiment consisted of a temperature challenge to the embryos and larvae with temperatures of 33 • C and 36 • C. These temperatures are near the upper thermal limits for larvae of this species [37] and above its optimal incubation temperature (28-30 • C) [86]. In the second experiment, fish were exposed to hypoxia (~30% air saturation) and hyperoxia (117% air saturation; Figure 6), since Lepisosteids can tolerate environments with variable dissolved oxygen levels [77,122,123]. The third experiment consisted of exposure to salinities of 4.0 ppt and 6.0 ppt, because Lepisosteids can tolerate euryhaline environments and little information is available on early life stages under these conditions, especially regarding developmental critical windows.…”

First demonstration of the neuroepithelial cells and their chemical code in the accessory respiratory organ and the gill of the sharptooth catfish, Clarias gariepinus: A preliminary study

“…Only previous studies (Lauriano et al, 2015;Porteus et al, 2015;Rimoldi et al, 2016;Zaccone et al, 2003) have reported the presence of nNOS in the neuroepithelial cells, the putative oxygen receptor of fish and their associated innervation in the gill, larval skin and respiratory gas bladder in fish. The role of gasotransmitters NO, hydrogen disulphide (H2S), carbon monoxide (CO) has been studied in carotid body O 2 sensing.…”

“…No study has yet assessed the role of NO in O 2 chemoreception in air-breathing fishes. Only previous studies (Lauriano et al, 2015;Porteus et al, 2015;Rimoldi et al, 2016;Zaccone et al, 2003) have reported the presence of nNOS in the neuroepithelial cells, the putative oxygen receptor of fish and their associated innervation in the gill, larval skin and respiratory gas bladder in fish. Porteus et al (2015) have also demonstrated that NO has an inhibitory effect on the hypoxic ventilatory response in adult zebrafish, but an excitatory effect on the hypoxic ventilation response of larvae.…”