Yellowfin tuna, Thunnus albacares (Bonnaterre, 1788) and bigeye tuna, Thunnus obesus (Lowe, 1839) are two of the most economically important tuna species in the world. However, identification of their juveniles, especially at sizes less than 40 cm, is very difficult, often leading to misidentification and miscalculation of their catch estimates. Here, we applied the mitochondrial DNA control region D-loop, a recently validated genetic marker used for identifying tuna species (Genus Thunnus), to discriminate juvenile tunas caught by purse seine and ringnet sets around fish aggregating devices (FADs) off the Southern Iloilo Peninsula in Central Philippines. We checked individual identifications using the Neighbor-Joining Method and compared results with morphometric analyses and the liver phenotype. We tested 48 specimens ranging from 13 to 31 cm fork length. Morpho-meristic analyses suggested that 12 specimens (25%) were bigeye tuna and 36 specimens (75%) were yellowfin tuna. In contrast, the genetic and liver analyses both showed that 5 specimens (10%) were bigeye tuna and 43 (90%) yellowfin tuna. This suggests that misidentification can occur even with highly stringent morpho-meristic characters and that the mtDNA control region and liver phenotype are excellent markers to discriminate juveniles of yellowfin and bigeye tunas.
Acute hepatopancreatic necrosis disease (AHPND), caused by a toxin‐producing Vibrio parahaemolyticus strain, has become a serious threat to shrimp aquaculture. The need to regulate antibiotic use prompted the development of alternative ways to treat infections in aquaculture including the use of chicken egg yolk immunoglobulin (IgY) for passive immunization. This study evaluated the protective effect of IgY against AHPND infection in Litopenaeus vannamei (Boone). IgY was isolated from eggs laid by hens immunized with recombinant PirA‐like (rPirA) and PirB‐like (rPirB) toxins. Whole‐egg powders having IgY specific to rPirA (anti‐PirA‐IgY) and rPirB (anti‐PirB‐IgY) and IgY from non‐immunized hen (control‐IgY) were mixed with basal diets at 20% concentrations and used to prefeed shrimp 3 days before the bacterial challenge test. Survival rates of the challenged shrimp fed the anti‐PirA‐IgY, anti‐PirB‐IgY and control‐IgY diets were 86%, 14% and 0%, respectively. Only the feed containing anti‐PirA‐IgY protected shrimp against AHPND. Increasing the concentration of rPirA antigen to immunize hens and lowering the amount of egg powder in feeds to 10% consistently showed higher survival rates in shrimp fed with anti‐PirA‐IgY (87%) compared with the control (12%). These results confirm that addition of anti‐PirA‐IgY in feeds could be an effective prophylactic method against AHPND infection in shrimp.
With the emergence of several infectious diseases in shrimp aquaculture, there is a growing interest in the use of feed additives to enhance shrimp immunity. Recently, the use of 5-aminolevulinic acid (5-ALA), a non-protein amino acid that plays a rate-limiting role in heme biosynthesis, has received attention for its positive effect on immunity in livestock animals. To evaluate the effect of 5-ALA in the Pacific white shrimp, Litopenaeus vannamei, we conducted microarray analysis, a Vibrio parahaemolyticus immersion challenge test, an ATP level assay, and gene expression analysis of some hemoproteins and genes associated with heme synthesis and degradation. Out of 15,745 L. vannamei putative genes on the microarray, 101 genes were differentially expressed by more than fourfold (p < 0.05) between 5-ALA-supplemented and control shrimp hepatopancreas. 5-ALA upregulated 99 of the 101 genes, 41 of which were immune- and defense-related genes based on sequence homology. Compared to the control, the 5-ALA-supplemented group had a higher survival rate in the challenge test, higher transcript levels of porphobilinogen synthase, ferrochelatase, catalase, nuclear receptor E75, and heme oxygenase-1 and higher levels of ATP. These findings suggest that dietary 5-ALA enhanced the immune response of L. vannamei to V. parahaemolyticus, upregulated immune- and defense-related genes, and enhanced aerobic energy metabolism, respectively. Further studies are needed to elucidate the extent of 5-ALA use in shrimp culture.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.