Effect of different diets on digestive enzyme activities,in vitrodigestibility, and midgut gland structure in juvenile crayfish,Cherax quadricarinatus

Feeding and Amines Stimulate the Growth of the Salivary Gland following Short-Term Starvation in the Black Field Cricket, Teleogryllus commodus

The salivary gland of the black field cricket, Teleogryllus commodus Walker changed size between being starved and fed. Crickets without access to food for 72 h showed a reduction in both wet and dry mass of the glands compared with the glands from continuously fed animals at 72 h. Glands returned to size following ingestion within 10 min. Salivary glands of starved crickets (72 h) were incubated in saline containing either serotonin (5-HT) or dopamine (DA). Glands increased to pre-starvation size after 1 h incubation in situ with either 10^-4 moles L^-1 5-HT or 10^-4 moles L^-1 DA, although lower concentrations (10^-5 moles L^-1) did not affect gland size. From immunohistochemistry, amines appeared to shift from zymogen cells during starvation to parietal cells following feeding. High-performance liquid chromatography showed that serotonin concentration is higher than dopamine in the salivary gland removed from starved and fed crickets, but the quantity of these compounds was not dependent upon feeding state; the amine quantities increased as gland size increased. Further work is necessary to determine what might be the stimulus for gland growth and if dopamine and serotonin play a role in the stimulation of salivary gland growth after a period of starvation.

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.

Title: CO2 and HCl-induced seawater acidification impair the ingestion and digestion of blue mussel Mytilus edulis

Anthropogenic CO₂ emissions lead to seawater acidification that reportedly exerts deleterious impacts on marine organisms, especially on calcifying organisms such as mussels. A 21-day experiment focusing on the impacts of seawater acidification on the blue mussel, Mytilus edulis, was performed in this study, within which two acidifying treatments, CO₂ enrichment and HCl addition, were applied. Two acidifying pH values (7.7 and 7.1) and the alteration of the key physiological processes of ingestion and digestion were estimated. To thoroughly investigate the impact of acidification on mussels, a histopathological study approach was adopted. The results showed that: (1) Seawater acidification induced either by CO₂ enrichment or HCl addition impaired the gill structure. Transmission electron microscope (TEM) results suggested that the most obvious impacts were inflammatory lesions and edema, while more distinct alterations, including endoplasmic reticulum edema, nuclear condensation and chromatin plate-like condensation, were placed in the CO₂-treated groups compared to HCl-treated specimens. The ciliary activity of the CO₂ group was significantly inhibited simultaneously, leading to an obstacle in food intake. (2) Seawater acidification prominently damaged the structure of digestive glands, and the enzymatic activities of amylase, protease and lipase significantly decreased, which might indicate that the digestion was suppressed. The negative impacts induced by the CO₂ group were more severe than that by the HCl group. The present results suggest that acidification interferes with the processes of ingestion and digestion, which potentially inhibits the energy intake of mussels.