Ontogenetic changes in energetic reserves, digestive enzymes, amino acid and energy content of Lithodes santolla (Anomura: Lithodidae): Baseline for culture

Effects of contaminants and flooding on the physiology of harvested estuarine decapod crustaceans: A global review and meta-analysis

Contaminants are transported into estuaries during rainfall events, impacting the physiology of harvested species, and thereby threatening fisheries sustainability. Decapods are among the most economically important groups harvested from estuaries, but are at high risk of contaminant exposure. We conducted a systematic review and meta-analysis evaluating the physiological responses of harvested estuarine decapods to contaminants and flooding. A total of 138 research articles were identified, with global research efforts corresponding to the geographic distribution of crustacean harvesting. From these studies, 305 acute toxicity values for metals, polcyclic aromatic hydrocarbons (PAHs) and pesticide chemical classes were extracted and 341 sublethal effect sizes (log-response ratios; LnRRs) calculated using 91 physiological measures across seven response categories. At sublethal environmentally relevant concentrations, exposure to various metals, pesticide chemical classes and PAHs consistently elicited negative effects on decapod physiology (LnRR range: -0.67 to -0.07). Key physiological processes impacted by contaminant exposure included nutritional condition, osmoregulation, oxidative stress defences, acetylcholinesterase activity, metabolism and growth (LnRR range: -0.73 to -0.10), with a general trend for greater effects later in ontogeny. With new agricultural and industrial chemicals continually being marketed, our meta-analysis highlights the need for regulatory testing on harvested species prior to registration for use in catchment areas. Under future climatic variability, harvested estuarine decapods may be increasingly exposed to contaminants, with implications for fisheries and global food security.

Effects of Dietary L-TRP on Immunity, Antioxidant Capacity and Intestinal Microbiota of the Chinese Mitten Crab (Eriocheir Sinensis) in Pond Culture

L-tryptophan (L-TRP) is an essential amino acid for the normal growth of crustaceans. As a nutritional supplement and antioxidant, L-TRP has the function of immune and antioxidant capacity regulation. From July to November, the effects of L-TRP on the immunity, antioxidant capacity and intestinal microflora of the Chinese mitten crab (Eriocheir sinensis) in pond culture were investigated. After feeding an L-TRP diet for 30 (named as August), 60 (named as September) and 106 (named as November) days, respectively, the activities of the immune and antioxidant enzymes in the hepatopancreas and hemolymph were evaluated, and the intestinal microbiota were profiled via high-throughput Illumina sequencing. The results showed that supplementation of L-TRP significantly increased the activities of AKP in the hepatopancreas in September, and significantly increased the activities of ACP in the hepatopancreas in August and September, and the hemolymph’s ACP activities also significantly increased in August and November (p < 0.05). Similarly, the activities of SOD, AOC and POD in the hepatopancreas significantly increased in September and November (p < 0.05) after feeding the L-TRP diet; meanwhile, the activities of SOD and AOC in the hemolymph also significantly increased in August (p < 0.05). However, in August, the L-TRP diet resulted in a significant increase in MDA activity in the hepatopancreas and hemolymph (p < 0.05). In addition, the results of the intestinal microbiota analysis showed that Firmicutes, Bacteroidetes and Proteobacteria were the dominant phyla in August, September and November, and Patescibacteria was the dominant phylum in September and November. After feeding the L-TRP diet, the richness of Cyanobacteria and Desulfobacterota significantly increased in August (p < 0.05), and the richness of Actinobacteriota significantly decreased in September (p < 0.05). Moreover, the L-TRP supplementation significantly reduced the abundance of ZOR0006 in the Firmicutes in September (p < 0.05). In conclusion, dietary L-TRP could improve the immunity and antioxidant ability and impact the intestinal health of E. sinensis at the early stage of pond culturing. However, long-term feeding of an L-TRP diet might have no positive impact on the activities of the immune, antioxidant enzymes and intestinal microbiota.

Understanding the Digestive Peptidases from Crustaceans: from Their Biochemical Basis and Classical Perspective to the Biotechnological Approach

Scientific studies about decapod crustaceans' digestive physiology have increased, being an important topic with novel results in the last years. This revision aims to show how the study of crustacean peptidases has evolved, from the classical biochemical characterization studies to the assessment of their usefulness in biotechnological and industrial processes, with emphasis on commercial species of interest to world aquaculture and fisheries. First studies determined the proteolytic activity of the midgut gland crude extracts and evaluated the optimum biochemical properties of specific enzymes. Peptidase's identity was determined using inhibitors and specific protein substrates on tube tests and electrophoresis gels. Later, various studies focused on the characterization of purified peptidases and their gene expression. Recently, the integrated mechanisms of enzyme participation during the digestive process of food protein have been established using novel techniques. Scientific research has revealed some of the potential biotechnological applications of crustacean peptidases in the food industry and other processes. However, the knowledge field is enormous, and there is much to explore and study in the coming years.