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Environmental and Endocrine Regulators of Stress Effects in Teleost Fishes.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Environmental and Endocrine Regulators of Stress Effects in Teleost Fishes./
作者:	Honeycutt, Jamie Lynn.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2018,
面頁冊數:	152 p.
附註:	Source: Dissertations Abstracts International, Volume: 80-05, Section: B.
Contained By:	Dissertations Abstracts International80-05B.
標題:	Biology. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=11007111
ISBN:	9780438598058

Environmental and Endocrine Regulators of Stress Effects in Teleost Fishes.
Honeycutt, Jamie Lynn.

Environmental and Endocrine Regulators of Stress Effects in Teleost Fishes. - Ann Arbor : ProQuest Dissertations & Theses, 2018 - 152 p.

Source: Dissertations Abstracts International, Volume: 80-05, Section: B.

Thesis (Ph.D.)--North Carolina State University, 2018.

This item must not be sold to any third party vendors.

The adaptive stress response is mediated by the endocrine stress axis whereby catecholamines and glucocorticoids promote production of energy substrates essential for re-establishing homeostasis. Here we utilize two teleost fish models to examine two overarching research goals: 1) the role catecholamines, cortisol, and glucose might play in regulating leptin (LepA), an important hormone controlling energy homeostasis in the Mozambique tilapia (Oreochromis mossambicus), and 2) the impact of environmental stressors, namely temperature, on nursery habitat sex ratios and sex determination in southern flounder (Paralichthys lethostigma), a species that exhibits both genetic and environmental sex determination. Leptin is a cytokine critical for regulating energy expenditure in vertebrates, yet it is unclear how the hormone interacts with the endocrine stress axis, particularly in fishes. We evaluated the actions of epinephrine, cortisol, and glucose in regulating leptin in the liver, the primary site of hormone production in the tilapia. Both cortisol and epinephrine stimulate LepA secretion from hepatocytes. While epinephrine had no effect on mRNA, cortisol suppresses lepa mRNA levels. Epinephrine stimulates both leptin synthesis and secretion in vivo. Leptin is directly sensitive to glucose as hepatic synthesis and secretion declines as ambient glucose levels rise. By contrast, glucose injection increases lepa mRNA levels by 14-fold, indicating that there are likely other systemic factors regulated by glucose that may enhance lepa mRNA. These data show that tilapia LepA is negatively regulated by rises in extracellular glucose at the level of the hepatocyte but stimulated by hyperglycemia in vivo. The increase in LepA in response to cortisol and epinephrine suggests that classic stress hormones may augment leptin to help promote glucose mobilization as part of the integrated, adaptive stress response. Southern flounder is a valuable commercial and recreational species found in the southeast United States. The fisheries are dependent on females due to sexually dimorphic growth, with females growing larger and faster relative to males. Southern flounder like other Paralichthids exhibit environmental sex determination (ESD), where factors in the environment such as temperature and background color, can influence phenotypic sex and masculinize populations. Impacts of the environment on sex occurs during early juvenile development and sex reversal is limited to the female genotype. To evaluate the effects of the environment and ESD on wild juvenile southern flounder populations, we examined spatial and temporal variation in sex ratios across a range of nursery habitats in North Carolina. Data show that northern habitats averaged optimal temperatures near 23°C during the sex determining window and produced the greatest abundance of females, while southern habitats consistently produced male skewed sex ratios (up to 94% male) and were associated with warmer temperatures. Other water quality parameters such as salinity and dissolved oxygen did not appear to have a correlation with male skewed sex ratios, suggesting that temperature is likely the key factor influencing sex ratio bias across habitats. Temperature profiles recorded in different nursery areas experienced similar patterns of temperature fluctuation over time yet showed relatively consistent differences in temperature that averaged a maximum difference near 4°C among sites. In one northern nursery habitat that produced 1:1 sex ratios, the average temperature over the sex determination period was 23.2°C, consistent with the permissive temperature that yields 1:1 sex ratios in the laboratory. We mimicked this temperature profile ± 4°C and show that the patterns of temperature variation observed in NC nursery habitats produce similar sex ratios under controlled laboratory conditions. These studies suggest that warmer water temperatures found in some nursery habitats produce male-biased sex ratios, which could impact the management of this important fishery that largely depends on females.

ISBN: 9780438598058Subjects--Topical Terms:

522710
Biology.

Environmental and Endocrine Regulators of Stress Effects in Teleost Fishes.
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