Browsing by Author "Hazlerigg, David"
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- Modulation of intestinal growth and differentiation by photoperiod and dietary treatment during smoltification in Atlantic salmon (Salmo salar, L.)Publication . Fernandes Duarte, Vilma Vanessa; Gaetano, Pasqualina; Striberny, Anja; Hazlerigg, David; Jørgensen, Even H.; Fuentes, Juan; Campinho, Marco AntónioAtlantic salmon undergo smoltification, a process that prepares the fish to enter and thrive in seawater (SW). Several physiological changes occur during smolting, especially in osmoregulatory tissues, the gill, the kidney, and the intestine. Here we characterized the effects on intestinal morphogenesis of two different, commonly used smoltification regimes during the end of the freshwater phase, photoperiod and/or the addition of salt and amino acid supplements in the diet. We focused on intestinal morphological differentiation, i.e., external perimeter, absorptive perimeter, tissue thickness, and villi density. In addition, we quantified cell proliferation (PCNA positive) and Na+, K+-ATPase (NKA) and Na+, K+,2Cl- (NKCCs) co-transporters expression and enterocyte apicobasal distribution by immunohistochemistry. These analyses show that the anterior and posterior intestines have different developmental dynamics during smoltification. In both intestinal regions, photoperiod and dietary treatment increased the absorptive perimeter. In addition, diet and photoperiod treatments differentially stimulated NKA protein expression in the anterior intestine. NKCC apical-basolateral expression in the enterocytes increased after SW entry in the anterior and posterior intestines. In conclusion, our results show that, as smoltification progresses, the anterior intestine responds more readily to experimental conditions than the posterior intestine. In our study, photoperiod and dietary treatment seem to enhance the development of the capacity to tolerate SW.
- Photoperiod and dietary treatment in freshwater modulate the short-term intestinal response to seawater in atlantic salmon (salmo salar)Publication . Gaetano, Pasqualina; Fernandes Duarte, Vilma Vanessa; Striberny, Anja; Hazlerigg, David; Jørgensen, Even H.; Campinho, Marco António; Fuentes, JuanStimulation and timing of smoltification are essential for successful Atlantic salmon (Salmo salar) aquaculture. This study investigated intestinal responses during dietary and photoperiod manipulation in freshwater (FW) and after a subsequent seven days residence in seawater (SW). "Small" and "large" Atlantic salmon parr (-40 g and -130 g respectively) were treated in FW for 12 weeks and thereafter transferred to SW for seven days. During the FW phase, fish underwent two different light conditions, 24 L:0D - 24 L ("LL-LL" groups) and 7 L:17D - 24 L ("SP-LL" groups) or fed with either regular feed ("LL-LL C" and "SP-LL C" groups) or feed enriched with a salt mix plus free tryptophan ("LL-LL + diet" and "SP-LL + diet" groups). We analyzed Na+/K+-ATPase (NKA) activity, tissue bioelectrical properties in Ussing chambers, and intestinal fluid composition. The NKA activity showed minor variations in relation to fish size, treatments, or intestinal region (anterior or posterior). Photoperiod modulated epithelial bioelectrical properties (Isc and Rt) of the anterior and posterior intestine, particularly transepithelial resistance (Rt). Pharmacological experiments, targeting apical Na+/K+/2Cl- (NKCC2) and Na+/ Cl (NCC) co-transporters revealed intestinal region-and water salinity-dependent effects. In addition, stimu-lation of the intracellular cAMP with forskolin and IBMX showed intestinal region-, water salinity, and treatment-dependence responses with clear functional specialization of the anterior and posterior intestine. The intestinal fluid composition reflected the ability to process ingested SW and showed little variation in large fish. In sum-mary, our data suggest a better pre-adaptation of the intestine during light-stimulated smoltification (SP-LL groups), and the combination of light and diet might give, in an industrial aquaculture setting, an advantage to smaller, but not larger smolts. Intestinal fluid composition in small fish can be used as an index of intestinal function and may act as a long-term performance proxy in SW Atlantic salmon.