Combined effects of temperature and diet on the performance of larvae produced by young and old Palaemon serratus females.

Seasonal variations in environmental conditions determine the success of decapod larval development, and females transmit more energy in sub-optimal conditions to maximise the fitness of their offspring. The objective of this study was to focus on the combined effects of temperature (14, 18 and 22 °C) and food quality on the performance of larvae produced by 5 young (0+) and 5 old (I+) Palaemon serratus females. We prepared 3 diets based on Artemia, in decreasing order of total fatty acid content: freshly hatched nauplii (N), unenriched metanauplii (M) and metanauplii enriched with a mixture of microalgae (ME). At hatching, the larvae produced by I+ females had a higher biomass but a similar fatty acid concentration to those produced by 0+ females. Larvae survived better and developed relatively faster as temperature increased, and the longer they waited to metamorphose, the greater their weight at metamorphosis. These performances were diet-dependent, with more survival and more growth in less time with diet N than with the other two. Larvae from I+ females performed better than those from 0+ females, especially under the most stressful conditions. The greater biomass of the larvae of I+ females seems to have enabled them to follow a shorter, and therefore faster, development path than those of 0+ females. The larvae's diet also had an impact on post-metamorphic composition: larvae eating a diet richer in fatty acids produced richer juveniles and those eating a poorer diet produced juveniles with slightly more essential fatty acids. This study supports the high plasticity of caridean shrimp larval development and the importance of maternal effects on the fitness of offspring.

N-acetyl-ß-D-glucosaminidase measurement on the freshwater amphipod Gammarus fossarum: development, biological variability and application in an ecotoxicological approach.

Due to its role in the crustacean moulting process, N-acetyl-ß-D-glucosaminidase (NAGase) is interesting to monitor the good proceeding of the moult cycle, as well as relevant in assessing changes in the moulting process caused by stressors. The present study aimed to measure the NAGase activity to monitor the moulting process of the freshwater amphipod Gammarus fossarum. Firstly, an optimised protocol measuring the NAGase activity was made, allowing a robustness and reproducibility of measurements. Then, intrinsic variability of NAGase response was checked under two physiological factors: the gammarid moult cycle and gender. For both genders, a significative increase of activity was observed during premoult, instead of a basal activity detected during postmoult and intermoult. However, the NAGase female profile was preconised to study since it was defined with more precision. Finally, a 16-day exposure of female gammarids to different levels of treated or non-treated wastewater effluents was made. If delays of tissue development appeared on effluent exposed specimens, NAGase activity was similar between the different conditions. This apparent desynchronization between tissue and molecular activities accentuates the diagnostic of moult impairment and raises the interest to use markers at different organisational levels.

Effects of Chemical Compounds on the Activity of the N-acetyl-ß-D-Glucosaminidase of the Marine Prawn, Palaemon serratus: Screening In Vitro.

N-acetyl-ß-D-glucosaminidase (NAGase) is important for crustaceans because the enzyme activity is necessary for the molting process. The present study aimed to assess the sensitivity of Palaemon serratus NAGase activity to a set of compounds of diverse chemical families in the context of in vitro exposures. Compounds representing different chemical families were selected according to their abundance, impact in the environment, and relevance as disruptors of the molting process. In a first step, four solvents (dimethylsulfoxide [DMSO], methanol, acetone, and ethanol) were tested to determine their suitability to dissolve hydrophobic compounds without affecting NAGase activity. Exclusively, ethanol had no effect on enzyme activity and on the integrity of the proteins present in the enzyme extract. The 18 other compounds were tested and four of these compounds, pentoxifylline, fenoxycarb, dithiocarbamate, and RH5849, showed a specific alteration on the activity of NAGase, without affecting the protein content. However, cadmium, zinc, and glyphosate showed a nonspecific alteration, affecting both the enzyme activity and the proteins, whereas ibuprofen exclusively altered the protein content. Finally, 10 of the 22 tested compounds (including DMSO, acetone, and methanol) showed a direct alteration of NAGase activity. Environ Toxicol Chem 2023;42:846-858. © 2023 SETAC.

N-acetyl-ß-d-glucosaminidase activity in Palaemon serratus - Methodological optimisation and intrinsic variability.

Chitinolytic enzymes fulfil a key role in the moulting process of crustaceans, in degrading the endocuticle during apolysis. Measuring the enzyme activity is an interesting manner to monitor the moult process at sub-individual level, complementary to the classical observation of the integument morphogenesis, ecdysis success, or moult cycle duration. The present study aimed to optimise the methodology of using N-acetyl-ß-D-glucosaminidase (NAGase) activity to monitor moulting in the marine prawn Palaemon serratus, and to compare NAGase activity levels along the moult cycle of both male and female specimens. First, to optimise protocols for five different organs, different reaction medium compositions were tested, considering the type buffer, concentration of the substrate, and the load in enzymatic extract. Second, levels of NAGase activity were closely monitored during eight moulting stages in male prawns. Variations in NAGase activity were observed during the moult cycle, with an increase in activity in the late premoult phase of approximately 2.4-fold the level of the intermoult phase. This response profile was observed for each tested organ. The levels of NAGase activity of male and female specimens were compared during three stages of the premoult phase. The patterns observed for both sexes were similar for all the tested organs.

Additive effect of calcium depletion and low resource quality on Gammarus fossarum (Crustacea, Amphipoda) life history traits.

Gammarus fossarum is an often-abundant crustacean detritivore that contributes importantly to leaf litter breakdown in oligotrophic, mainly heterotrophic, headwater streams. This species requires large amounts of Ca to moult, thus allowing growth and reproduction. Because resource quality is tightly coupled to the organism's growth and physiological status, we hypothesised that low Ca concentration [Ca] and low food resource quality (low phosphorus [P] and/or reduced highly unsaturated fatty acid [HUFA] contents) would interactively impair molecular responses (gene expression) and reproduction of G. fossarum. To investigate the effects of food resources quality, we experimentally manipulated the P content of sycamore leaves and also used diatoms because they contain high amounts of HUFAs. Three resource quality treatments were tested: low quality (LQ, unmanipulated leaves: low P content), high quality 1 (HQ1; P-manipulated leaves: high P content), and high quality 2 (unmanipulated leaves supplemented with a pellet containing diatoms: high P and HUFA content). Naturally, demineralised stream water was supplemented with CaSO4 to obtain three Ca concentrations (2, 3.5, and 10.5 mg Ca L-1). For 21 days, pairs of G. fossarum were individually exposed to one of the nine treatments (3 [Ca] × 3 resource qualities). At the individual level, strong and significant delays in moult stage were observed in gammarids exposed to lower [Ca] and to lower resource quality, with additive effects lengthening the duration of the reproductive cycle. Effects at the molecular level were investigated by measuring expression of 12 genes involved in energy production, translation, or Ca or P homeostasis. Expression of ATP synthase beta (higher in HQ2), calcified cuticle protein (higher in HQ1 and HQ2), and tropomyosin (higher in HQ2 compared to HQ1) was significantly affected by resource quality, and significant additive effects on Ca transporting ATPase expression were induced by [Ca] and resource quality (higher for low [Ca] and higher resource quality). These results highlight the potential drastic deleterious effects of water [Ca] depletion on G. fossarum physiology, populations, and ecosystem functioning, especially in oligotrophic environments.