Abstract
Salinity is one of the important environmental factors affecting survival and growth of aquatic animals. However, the impact of low-salinity stress on M. rosenbergii post-larvae at different development stages remains elusive. Therefore, the aim of this study was to explore the underlying mechanisms of hypotonic stress at different development stages of M. rosenbergii post-larvae through transcriptome analysis and antioxidant parameters detection. The salinity of the control group was 15 psu (S15) and the hypotonic stress group was 6 psu (S6). Samples were collected at 7 days-post-hatch (dph), 14 dph and 21 dph larvae. The results showed that hypotonic stress caused oxidative damage in post-larvae evidenced by decreased glutathione peroxidase (GSH-Px); superoxide dismutase (SOD); anti-superoxide anion free radical (ASAFR); and increased malondialdehyde (MDA); nitric oxide (NO); and inducible nitric oxide synthase (iNOS) levels. Transcriptome analysis showed that there were 1428, 1187, 132 DEGs including 301, 366, 4 up-regulated genes and 1127, 821, 128 down-regulated genes at 7 dph, 14 dph and 21 dph larvae under hypotonic stress, respectively. Furthermore, GO and KEGG enrichment indicated that hypotonic stress led to dysregulation of immune signals including lysosome and autophagy in the 7 dph larvae. The autophagy-related genes including beclin 1-associated autophagy-related key regulator (Barkor); ubiquitin-like modifier-activating enzyme ATG7 (ATG7); Beclin; autophagy-related protein 13 (ATG13); nuclear receptor-binding factor 2 (Nrbf2); ubiquitin-like-conjugating enzyme ATG3 (ATG3); vacuole membrane protein 1 (VMP1); and autophagy-related protein 2 (ATG2) decreased at 7 dph, and 14 dph larvae, and then increased at 21 dph larvae under hypotonic stress. In the 14 dph and 21 dph larvae, the renin-angiotensin system was activated. In conclusion, our data indicated that hypotonic stress reduced the antioxidant capacity and impaired the immune system in post-larvae, but as development progresses, the adaptability of post-larvae to hypotonic stress gradually increased, and might reach a new homeostasis through the RAS signaling pathway.
Highlights
Salinity is a vital environment factor that affects survival, growth, and distribution of many aquatic organisms and mainly affects the physiology of various aquatic animals [1,2].Under salinity fluctuations, some of the aquatic animals required more energy to adjust the osmotic pressure balance between their body fluid and the environment [3,4]
At 14 dph and 21 dph larvae, the superoxide dismutase (SOD) activity in the S6 group was significantly lower than that of the S15 group (p < 0.05), while they showed no significant differences at 7 dph larvae (p > 0.05)
Our results demonstrated that hypotonic stress reduced antioxidant and immune capacity at different development stages of M. rosenbergii post-larvae
Summary
Salinity is a vital environment factor that affects survival, growth, and distribution of many aquatic organisms and mainly affects the physiology of various aquatic animals [1,2].Under salinity fluctuations, some of the aquatic animals required more energy to adjust the osmotic pressure balance between their body fluid and the environment [3,4]. Salinity is a vital environment factor that affects survival, growth, and distribution of many aquatic organisms and mainly affects the physiology of various aquatic animals [1,2]. A series of studies showed that salinity affected the feeding behavior, growth, and health of Macrobrachium nipponense [5], Litopenaeus vannamei [6], and Nephrops norvegicus [7], indicating that water salinity is an important factor in the growth and survival of crustacean species. The way in which aquatic animals respond to ambient salinity stress is quite complex and extends from behavior to the molecular level [8]. To achieve ion homeostasis during salinity stress, aquatic animals must activate appropriate signal transduction pathways and send messages to specific target molecules by signal transducers to restore homeostasis [9,10]. Information about the signal transduction events for osmoregulation in crustacean species is limited
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