Immune protection by Rhizophora apiculata in clownfish against Vibrio alginolyticus

Study on amyloodiniosis outbreak in captive-bred percula clownfish (Amphiprion percula) and improved control regimens

The amyloodiniosis outbreak was documented with high mortality of percula clownfish (Amphiprion percula) and subsequently, various therapeutics were evaluated to control the infection. The affected fish exhibited symptoms such as discoloration of the skin and jerky movement with severe respiratory stress. Microscopic examination of the gill and body surface of the infested moribund fish showed the presence of brown coloured spherical shaped trophonts with the size range of 150-300 µM. Copper sulphate (10 ppm) and hydroxychloroquine phosphate (10 ppm) treatment with 14 days of continuous bath showed 76 ± 5.3 and 66 ± 4.3% survival rates. However, formalin (10 ppm) and malachite green (10 ppm) treated groups showed a survival of 41 ± 1.7 and 32.7 ± 1.2% respectively. The present results suggest that, use of copper sulphate to treat amyloodiniosis in clownfish will relatively more effective than other treatment options. The findings will be helpful to mitigate amyloodiniosis in marine finfish aquaculture, particularly marine ornamentals.

Effects of dietary administration of fenugreek seeds on metabolic parameters and immune status of gilthead seabream (Sparus aurata L.)

Medical plants could be used as a prophylactic method in aquaculture because they are considered safe and so very promising alternatives to the use of chemicals. The aim of the present work was to examine the effects of dietary fenugreek (Trigonella foenum graecum) seeds administered for 8 weeks on the metabolic and immune status of gilthead seabream (Sparus aurata L.). Four experimental groups were designated: one receiving a basal diet (control) and three fed powdered fenugreek seeds incorporated in the fish feed at 1%, 5% and 10%. The results show that significant decreases in aspartate aminotransferase, creatine kinase, potassium and the albumin/globulin ratio were detected in the serum of fish fed 10% fenugreek compared with the values recorded in control fish. As regards the immune status, fish fed the 5% supplemented diet had higher haemolytic complement and peroxidase activities than the control fish whilst antiprotease activity was higher in fish fed the 1% fenugreek level respect to control fish and the fish fed the highest fenugreek supplementation rate. Interestingly, the results also revealed a significant enhancement of most of the cellular immune parameters studied, especially in fish fed the highest level of fenugreek (10%). However, the bacteriostatic activity of serum against fish pathogenic and non-pathogenic bacteria was non-affected to any significant extent in fish fed the supplemented diets. Overall, the results suggest that the high level of dietary fenugreek tested in this work (10%) did not negatively affect any of the metabolic parameters measured in serum but increased some of them. In addition, the inclusion of fenugreek seeds in the gilthead seabream diet at 5% or 10% improved the humoral and cellular immune activities, respectively. Further studies are needed to better understand the effects of this natural product, which may be suitable for use as a feed additive in fish aquaculture.

The response of fish to immunostimulant diets

In order to maintain fish health and to improve performance immunostimulants have been used as dietary additives to improve weight gain, feed efficiency, and/or disease resistance in cultured fish. In aquaculture, non-specific immunostimulants have been widely used probably due to the limited knowledge of the immune response in fish and the ease of their application. Many studies have been carried out to assess the effect of dietary immunostimulants in fish including algal derivatives, herb and plant extract containing diets using a wide range of downstream analytical techniques. Many immunostimulants are based upon tradition and folklore transferred through generations and specific to certain geographical regions rather than known biological properties. However, there are studies in which it is possible to observe a clear and direct dose-dependent stimulatory effect upon the immune system. Other dietary supplements used contain PAMPs (Pathogen Associated Molecular Patterns) as immunostimulants whose recognition depends upon PRR (pathogen recognition receptor) interactions including the TLRs (Toll-like receptor). Despite the growing interest in the use of immunostimulants across the aquaculture industry the underlying mechanisms of ligand recognition, extract composition and activation of the fish immune response remains fragmented. In this review we focus upon the last 15 years of studies addressing the assessment of: (1) plant, herb and algae extracts; and (2) PAMPs, upon non-specific immune parameters of activation and immunostimulant diet efficacy.