Metabolic effects of epinephrine on the crab Neohelice granulata

A brief and updated introduction to the neuroendocrine system of crustaceans

The neuroendocrine system of crustaceans is complex and regulates many processes, such as development, growth, reproduction, osmoregulation, behavior, and metabolism. Once stimulated, crustaceans' neuroendocrine tissues modulate the release of monoamines, ecdysteroids, and neuropeptides that can act as hormones or neurotransmitters. Over a few decades, research has unraveled some mechanisms governing these processes, substantially contributing to understanding crustacean physiology. More aspects of crustacean neuroendocrinology are being comprehended with molecular biology, transcriptome, and genomics analyses. Hence, these studies will also significantly enhance the ability to cultivate decapods, such as crabs and shrimps, used as human food sources. In this review, current knowledge on crustacean endocrinology is updated with new findings about crustacean hormones, focusing mainly on the main neuroendocrine organs and their hormones and the effects of these molecules regulating metabolism, growth, reproduction, and color adaptation. New evidence about vertebrate-type hormones found in crustaceans is included and discussed. Finally, this review may assist in understanding how the emerging chemicals of environmental concern can potentially impair and disrupt crustacean's endocrine functions and their physiology.

The impact of chasing stress on the metabolism of the Atlantic Ghost Crab Ocypode quadrata (Fabricius, 1787)

Ocypode quadrata, a Ghost crab species found along the western Atlantic coast, is considered a bioindicator of anthropogenic impact on sandy beaches. Ghost Crabbing, a touristic activity in which ghost crabs are chased just for fun, is a potentially threatening activity for this crab. In crustaceans, metabolites such as glucose and lactate, and the gene expression of crustacean hyperglycemic hormone (CHH) and heat shock proteins (HSPs) increase when the animals are exposed to several types of stress, including alterations in temperature, salinity, or exposure to xenobiotics. This work was developed to identify if being chased by humans would affect these markers of stress in this species of crab. The effects of chasing stress on hemolymph and tissue metabolites and the gene expression levels of CHH and HSP70 were investigated. The levels of lactate in the hemolymph of stressed crabs were six times higher than those of control crabs immediately after chasing and decreased progressively during recovery, indicating an active anaerobic metabolism during the stress. On the contrary, glucose levels in the hemolymph of the stressed crabs increased progressively from 30 to 60 min after chasing, indicating an inverse correlation between glucose and lactate and the conversion of lactate to glucose by gluconeogenesis. In stressed crabs, the levels of triglycerides in the hemolymph decreased 30 min after chasing, while the opposite tended to occur in the hepatopancreas, indicating that during recovery, the crabs use triglycerides as energy source to sustain aerobic metabolism. Finally, this study demonstrates that ghost crabs are stressed by minimum human contact and that "ghost crabbing" must not be encouraged as a tourist activity.

Arylalkalamine N-acetyltransferase-1 acts on a secondary amine in the yellow fever mosquito, Aedes aegypti

Arylalkylamine N-acetyltransferase (aaNAT) in Aedes aegypti is primarily involved in cuticle pigmentation and formation. The reported arylalkylamine substrates are all primary amines. In this study, we report a novel substrate, a secondary amine, of Ae. aegypti aaNAT1. The recombinant aaNAT1 protein exhibited high activity to a secondary amine, epinephrine, which has not been reported for any aaNATs previously. Structure-activity relationship study demonstrated that aaNAT1 has an epinephrine binding site, and molecular docking and dynamic simulation showed that epinephrine is quite stable in the active cavity. Further functional studies demonstrated that epinephrine affected mosquito fecundity, egg hatching and development. The new biochemical function of aaNAT1 in metabolizing epinephrine could reduce some negative effects of the compound in the mosquito.

Effect of different doses of the catecholamine epinephrine on antioxidant responses of larvae of the flesh fly Sarcophaga dux

The production and use of pharmaceutical products have increased over the past decades, and several are considered potential or proved hazardous wastes. When contaminating the environment, they can severely impact biodiversity. The catecholamine epinephrine (adrenaline) is no exception. Epinephrine can be administered as growth promoter in cattle, and is used for anaphylaxis treatment in human. While a range of studies has examined the effects of this catecholamine on vertebrate tissues, and evidenced that it can disrupt the oxidative stress status, the effects epinephrine could have on insects have remained poorly considered. Here, we examined the physiological effects of different concentrations (0, 25, 50, and 100 μg/mL) of epinephrine on larvae of the flesh fly Sarcophaga dux. Following experimental treatments, levels of H₂O₂, GSH, CAT, GPx, and CEH were measured from the fat body, cuticle, gut, and hemolymph of 3rd instars. Significant differences are reported for these physiological endpoints among the considered body compartments, and epinephrine concentrations. Epinephrine treatments did not increase reactive oxygen species production (H₂O₂ amounts), except for gut tissues. Increased levels of GSH suggest that epinephrine may have enhanced glucose metabolism and flux towards the pentose phosphate pathway, while reducing glutamine oxidation. CAT activity was slightly increased when the concentration of epinephrine was higher. The decreased GPx activity in the fat body was consistent with GSH variations. In sum, the injection of epinephrine seemed to elicit the antioxidant response in S. dux larvae, in turn attenuating ROS production.

Effects of crustacean hyperglycaemic hormone RNA interference on regulation of glucose metabolism in Litopenaeus vannamei after ammonia-nitrogen exposure

To unveil the adaptation of Litopenaeus vannamei to elevated ambient ammonia-N, crustacean hyperglycaemic hormone (CHH) was knocked down to investigate its function in glucose metabolism pathway under ammonia-N exposure. When CHH was silenced, haemolymph glucose increased significantly during 3-6 h, decreased significantly during 12-48 h and recovered to the control groups' level at 72 h. After CHH knock-down, dopamine (DA) contents reduced significantly during 3-24 h, which recovered after 48 h. Besides, the expressions of guanylyl cyclase (GC) and DA1R in the hepatopancreas decreased significantly, while DA4R increased significantly. Correspondingly, the contents of cyclic AMP (cAMP), cyclic GMP (cGMP) and diacylglycerol (DAG) and the expressions of protein kinase A (PKA), protein kinase G (PKG), AMP active protein kinase α (AMPKα) and AMPKγ were significantly down-regulated, while the levels of protein kinase C (PKC) and AMPKβ were significantly up-regulated. The expressions of cyclic AMP response element-binding protein (CREB) and GLUT2 decreased significantly, while GLUT1 increased significantly. Moreover, glycogen content, glycogen synthase and glycogen phosphorylase activities in hepatopancreas and muscle were significantly increased. Furthermore, the levels of key enzymes hexokinase, pyruvate kinase and phosphofructokinase in glycolysis (GLY), rate-limiting enzymes citrate synthase in tricarboxylic acid and critical enzymes phosphoenolpyruvate carboxykinase, fructose diphosphate and glucose-6-phosphatase in gluconeogenesis (GNG) were significantly decreased in hepatopancreas. These results suggest that CHH affects DA and then they affect their receptors to transmit glucose metabolism signals into the hepatopancreas of L. vannamei under ammonia-N stress. CHH acts on the cGMP-PKG-AMPKα-CREB pathway through GC, and CHH affects DA to influence cAMP-PKA-AMPKγ-CREB and DAG-PKC-AMPKβ-CREB pathways, thereby regulating GLUT, inhibiting glycogen metabolism and promoting GLY and GNG. This study contributes to further understand glucose metabolism mechanism of crustacean in response to environmental stress.

Physiological and biochemical responses of Mediterranean green crab, Carcinus aestuarii, to different environmental stressors: Evaluation of hemocyte toxicity and its possible effects on immune response

Effects of natural stressors such as copper (Cu²⁺), temperature, hypoxia, chloroform and adrenaline on physiological and biochemical responses were investigated in the Mediterranean green crab Carcinus aestuarii from tidal shallow waters of Narta Lagoon, Albania. For this purpose, hemolymph glucose levels, total and differential hemocyte count, in normal and eye-stalked individuals, exposed to above mentioned stressors like, were assessed. In addition, lysosomal membrane stability was evaluated as biomarker of hemocyte toxicity, with possible implications on crab immune response. Hemolymph glucose levels were significantly increased in all treatment groups with 1.25-to 3.5-fold above baseline levels of 37.8 ± 2.7 mgdL^-1. Response times were being manifested within 30-120 min following exposure and recovery happened within 2 h of restoration of pretreatment conditions. Total hemocyte count (THC) and differential hemocyte count (DCH) showed a significant decrease for all stressors, except for copper, were an increase of semi-granular hemocyte fraction were recorded. Meanwhile, significant reduction of neutral red retention time (NRRT), in both eyestalk-ablated and exposed animals, were recorded, indicated the loss of hemocyte lysosomal membrane integrity. The responsiveness of hemolymph blood levels to all stressors, the decrease in total hemocyte count, as well as the loss of lysosomal membrane integrity demonstrated that exposure to environmentally realistic stressors placed a heavy metabolic load on C. aestuarii, modulating their immune competence and overall physiological wellness. Overall, results suggest that monitoring cellular and biochemical parameters like hemolymph glucose titres, TCH, DHC and NRRT, may be useful and sensitive means of evaluating the crustacean's ability to cope with the wide variety of environmental stressors through modulation of the immune parameters.

Point-of-care testing for measuring haemolymph glucose in invertebrates is not a valid method

Blood glucose is widely used as a physiological parameter for vertebrates and invertebrates. However, its measurement in the field is often difficult due to the need for expensive and non-portable equipment. Point-of-care (POC) devices, originally intended for human use, are increasingly being used for measuring blood parameters of animals in the field. In this regard, POC glucose meters are becoming valuable tools for conservation physiologists, as glucose can be a useful indicator of stress response. In invertebrates, the use of POC glucose meters is still scarce, and no study yet has evaluated their usability in crustaceans and molluscs. We tested if a POC device can be used to measure haemolymph glucose in two widely used models, Leptuca thayeri and Perna perna, compared with a standard laboratory method. The device was unable to measure glucose in P. perna haemolymph due to equipment inaccuracy and low glucose concentration in this species (10.13 ± 6.25 mg/dL). Additionally, despite the device being capable of measuring glucose in L. thayeri haemolymph, Bland-Altman plots showed a strong bias and wide limits of agreement, and Lin's concordance correlation coefficient showed a weak concordance between methods. When simulating experimental conditions, POC results differed from those found using the standard method. We conclude that POC glucose meters are unsuitable for assessing glucose in mussels and should not be used in crabs as results are inaccurate.