Improving aeration for efficient oxygenation in sea bass sea cages. Blood, brain and gill histology

Abstract

An air diffusion based system (Airx) was developed to control the dissolved oxygen levels in aquaculture sea cages. The system was introduced and then tested for 37 days in a sea bass sea cage (aerated cage). A second sea bass sea cage, without the AirX, was used as a control. Oxygen levels were measured in both cages at the start of the trial, before the AirX system was introduced, and during the working period of the AirX system. Fish samples were collected 15 days after the AirX system was introduced and at the end of the experiment. Blood smears were prepared and examined microscopically. Erythrocyte major axis, minor axis and area of fish erythrocytes were measured. Leucocyte differentiation was also examined. In the control cage, the fish had significantly larger red blood cells when compared with the red blood cells of the fish in the aerated cage. Histological examination of the gills and brain revealed no morphological differences or alterations between the two groups of fish. This study demonstrated that an air diffuser system could improve the water quality of fish farmed in sea cages and enhance sea bass physiological performance, especially if DO levels fall below 60% oxygen saturation.

Water Oxygen Content Affects Distribution of T and B Lymphocytes in Lymphoid Tissues of Farmed Sea Bass (Dicentrarchus Labrax)

“…Contrarily, in our analysis by flow cytometry and immuno-histochemistry, the B-cells seemed to diminish in thymus (just a trend, not statistically significant) and gut (p < 0.05) in the HO group as compared to the NO group. Recently, a study in aquaculture has revealed that the oxygen treatment of ≥70% of saturation improves the quantity and the performance of the oxygen-releasing of red blood cells; however, contrary to our findings, no histological differences were revealed in lymphocyte number [25]. In the present research, we evidenced both in flow cytometry analysis and immuno-histochemistry, a significant increment of T-cells in the organs normally enriched of lymphocytes of type "T" [18], such as thymus, gut, and gills.…”

“…Immuno-histochemistry was performed as previously described [25]. Tissues were sampled from thymus, head kidney, spleen, intestine (middle segment 2-cm long, taken 3 cm caudally to opening of bile duct), and gills (portion of mucosae adherent to the gill arch, comprehensive of primary and secondary lamellae) and were fixed in Bouin's fluid for 7 h at 4 • C, dehydrated in graded alcohols at 4 • C, cleared in toluene and embedded in paraffin wax.…”

The impact of different rearing condition on gilthead seabream welfare: Dissolved oxygen levels and stocking densities

“…This pattern was observed for stoking density trial, but not for oxygen trial. The different variation pattern could be a result of cell volume increase instead of number (Berillis et al, ), since red blood cells swelling has been described for fish under stressful conditions (Brill et al, ). However, no significant differences were observed for red cell volume on the blood smears analysed for the present study (data not shown).…”

Lymphoid Tissue in Teleost Gills: Variations on a Theme

“…These lamellae are hollowed flap-shaped structures where an intense blood flow runs in-between supportive cells called pillar cells. A typical branchial epithelium is mainly composed of pavement cells in-between which reside chloride cells (also called mitochondria-rich cells), mucous cells and neuroepithelial cells [3,8]. Filaments are compartmentalized, the external or efferent side of a filament is differentiated from the inner or afferent side and the interlamellar region is positioned in-between.…”