A kinetic characterization of the gill V(H+)-ATPase from two hololimnetic populations of the Amazon River shrimp Macrobrachium amazonicum.

This investigation examines the kinetic characteristics and effect of acclimation to a brackish medium (21 ‰S) on gill V(H+)-ATPase activity in two hololimnetic populations of M. amazonicum. We also investigate the cellular immunolocalization of the enzyme. Immunofluorescence findings demonstrate that the V(H+)-ATPase c-subunit is distributed in the apical pillar cells of shrimps in fresh water but is absent after acclimation to 21 ‰S for 10 days. V(H+)-ATPase activity from the Tietê River population is ≈50% greater than the Grande River population, comparable to a wild population from the Santa Elisa Reservoir, but is 2-fold less than in cultivated shrimps. V(H+)-ATPase activity in the Tietê and the Grande River shrimps is abolished after 21 ‰S acclimation. The apparent affinities of the V(H+)-ATPase for ATP (0.27 ± 0.04 and 0.16 ± 0.03 mmol L-1, respectively) and Mg2+ (0.28 ± 0.05 and 0.14 ± 0.02 mmol L-1, respectively) are similar in both populations. The absence of V(H+)-ATPase activity in salinity-acclimated shrimps and its apical distribution in shrimps in fresh water underpins the importance of the crustacean V(H+)-ATPase for ion uptake in fresh water.

Salinity-dependent modulation by protein kinases and the FXYD2 peptide of gill (Na+, K+)-ATPase activity in the freshwater shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).

The geographical distribution of aquatic crustaceans is determined by ambient factors like salinity that modulate their biochemistry, physiology, behavior, reproduction, development and growth. We investigated the effects of exogenous pig FXYD2 peptide and endogenous protein kinases A and C on gill (Na+, K+)-ATPase activity, and characterized enzyme kinetic properties in a freshwater population of Macrobrachium amazonicum in fresh water (<0.5 ‰ salinity) or acclimated to 21 ‰S. Stimulation by FXYD2 peptide and inhibition by endogenous kinase phosphorylation are salinity-dependent. While without effect in shrimps in fresh water, the FXYD2 peptide stimulated activity in salinity-acclimated shrimps by ≈50 %. PKA-mediated phosphorylation inhibited gill (Na+, K+)-ATPase activity by 85 % in acclimated shrimps while PKC phosphorylation markedly inhibited enzyme activity in freshwater- and salinity-acclimated shrimps. The (Na+, K+)-ATPase in salinity-acclimated shrimp gills hydrolyzed ATP at a Vmax of 54.9 ± 1.8 nmol min-1 mg-1 protein, corresponding to ≈60 % that of freshwater shrimps. Mg2+ affinity increased with salinity acclimation while K+ affinity decreased. (Ca2+, Mg2+)-ATPase activity increased while V(H+)- and Na+- or K+-stimulated activities decreased on salinity acclimation. The 120-kDa immunoreactive band expressed in salinity-acclimated shrimps suggests nonspecific α-subunit phosphorylation by PKA and/or PKC. These alterations in (Na+, K+)-ATPase kinetics in salinity-acclimated M. amazonicum may result from regulatory mechanisms mediated by phosphorylation via protein kinases A and C and the FXYD2 peptide rather than through the expression of a different α-subunit isoform. This is the first demonstration of gill (Na+, K+)-ATPase regulation by protein kinases in freshwater shrimps during salinity challenge.

Contrasting strategies of osmotic and ionic regulation in freshwater crabs and shrimps: gene expression of gill ion transporters.

Owing to their extraordinary niche diversity, the Crustacea are ideal for comprehending the evolution of osmoregulation. The processes that effect systemic hydro-electrolytic homeostasis maintain hemolymph ionic composition via membrane transporters located in highly specialized gill ionocytes. We evaluated physiological and molecular hyper- and hypo-osmoregulatory mechanisms in two phylogenetically distant, freshwater crustaceans, the crab Dilocarcinus pagei and the shrimp Macrobrachium jelskii, when osmotically challenged for up to 10 days. When in distilled water, D. pagei survived without mortality, hemolymph osmolality and [Cl-] increased briefly, stabilizing at initial values, while [Na+] decreased continually. Expression of gill V-type H+-ATPase (V-ATPase), Na+/K+-ATPase and Na+/K+/2Cl- symporter genes was unchanged. In M. jelskii, hemolymph osmolality, [Cl-] and [Na+] decreased continually for 12 h, the shrimps surviving only around 15-24 h exposure. Gill transporter gene expression increased 2- to 5-fold. After 10 days exposure to brackish water (25‰S), D. pagei was isosmotic, iso-chloremic and iso-natriuremic. Gill V-ATPase expression decreased while Na+/K+-ATPase and Na+/K+/2Cl- symporter expression was unchanged. In M. jelskii (20‰S), hemolymph was hypo-regulated, particularly [Cl-]. Transporter expression initially increased 3- to 12-fold, declining to control values. Gill V-ATPase expression underlies the ability of D. pagei to survive in fresh water while V-ATPase, Na+/K+-ATPase and Na+/K+/2Cl- symporter expression enables M. jelskii to confront hyper/hypo-osmotic challenges. These findings reveal divergent responses in two unrelated crustaceans inhabiting a similar osmotic niche. While D. pagei does not secrete salt, tolerating elevated cellular isosmoticity, M. jelskii exhibits clear hypo-osmoregulatory ability. Each species has evolved distinct strategies at the transcriptional and systemic levels during its adaptation to fresh water.

Protein requirement for initial rearing phase of pacific white shrimp in biofloc system / Exigência proteica para a fase inicial do camarão-branco-do-pácífico em sistema de bioflocos

This study evaluated the protein requirement of Litopenaeus vannamei post-larvae during the initial rearing phase in a biofloc system. Five different diets were evaluated with increasing concentrations of crude protein: 31.28, 36.29, 41.57, 46.34, and 51.74 g 100 g-¹ CP. Post-larvae (0.16 ± 0.01 g) were stocked at a density of 450 PL m-³ in 400 L tanks. Water quality parameters were maintained within the limits recommended for shrimp farming. After 38 days, a regression analysis revealed that levels of CP content (65.29–72.83%), EE (10.45–11.65%) and body N (10.45–11.64%) increased with increasing protein levels in the diet. A similar trend was observed in the biofloc sludge with respect to CP and N. Survival exceeded 80%, and the shrimp with diets containing 31.28 to 46.34 g 100 g-¹ CP presented an increase in final weight (1.52–2.61 g), productivity (0.69–1.10 kg m-³), weight gain (1.38–2.44 g), and feeding efficiency (77.28–101.68%), whereas these indices decreased to 51.74 g 100 g-¹ CP. Crude protein content from 44.26 to 47.12 g 100 g-¹ provided the best growth performance during the initial rearing phase of Pacific white shrimp L. vannamei in a biofloc system.

Esse estudo avaliou a exigência proteica do Litopenaeus vannamei na fase inicial de cultivo em sistema de bioflocos. Cinco dietas com quantidades crescentes de proteína bruta (31,28; 36,29; 41,57; 46,34 e 51,74 g 100 g-¹ PB) foram avaliadas. As pós-larvas (0,16 ± 0,01 g) foram estocadas na densidade de 450 PL m-³ em tanques de 400 L. A qualidade de água manteve-se dentro dos limites adequados para o cultivo. Após 38 dias, uma análise de regressão revelou que teores de PB (65,29–72,83%), EE (10,45–11,65%) e N corporal (10,45–11,64%) aumentaram com os níveis crescente de proteína na dieta. A mesma análise foi realizada para o lodo do bioflocos, que apresentou aumento crescente de PB e N. A sobrevivência foi superior a 80% e os camarões alimentados com dietas contendo 31,28 à 46,34g 100 g-¹ PB obtiveram aumento no peso final (1,52–2,61 g), produtividade (0,69–1,10 kg m-³), ganho em peso (1,38–2,44 g) e eficiência alimentar (77,28–101,68%), enquanto esses índices decresceram no tratamento 51,74 g 100 g-¹ PB. O conteúdo de proteína bruta entre 44,26 à 47,12 g 100 g-¹ PB proporcionou o melhor desempenho de crescimento durante a fase inicial do cultivo do camarão-branco-do-pacífico L. vannamei em bioflocos.

Protein requirement for initial rearing phase of pacific white shrimp in biofloc system / Exigência proteica para a fase inicial do camarão-branco-do-pácífico em sistema de bioflocos

This study evaluated the protein requirement of Litopenaeus vannamei post-larvae during the initial rearing phase in a biofloc system. Five different diets were evaluated with increasing concentrations of crude protein: 31.28, 36.29, 41.57, 46.34, and 51.74 g 100 g-¹ CP. Post-larvae (0.16 ± 0.01 g) were stocked at a density of 450 PL m-³ in 400 L tanks. Water quality parameters were maintained within the limits recommended for shrimp farming. After 38 days, a regression analysis revealed that levels of CP content (65.29–72.83%), EE (10.45–11.65%) and body N (10.45–11.64%) increased with increasing protein levels in the diet. A similar trend was observed in the biofloc sludge with respect to CP and N. Survival exceeded 80%, and the shrimp with diets containing 31.28 to 46.34 g 100 g-¹ CP presented an increase in final weight (1.52–2.61 g), productivity (0.69–1.10 kg m-³), weight gain (1.38–2.44 g), and feeding efficiency (77.28–101.68%), whereas these indices decreased to 51.74 g 100 g-¹ CP. Crude protein content from 44.26 to 47.12 g 100 g-¹ provided the best growth performance during the initial rearing phase of Pacific white shrimp L. vannamei in a biofloc system.(AU)

Esse estudo avaliou a exigência proteica do Litopenaeus vannamei na fase inicial de cultivo em sistema de bioflocos. Cinco dietas com quantidades crescentes de proteína bruta (31,28; 36,29; 41,57; 46,34 e 51,74 g 100 g-¹ PB) foram avaliadas. As pós-larvas (0,16 ± 0,01 g) foram estocadas na densidade de 450 PL m-³ em tanques de 400 L. A qualidade de água manteve-se dentro dos limites adequados para o cultivo. Após 38 dias, uma análise de regressão revelou que teores de PB (65,29–72,83%), EE (10,45–11,65%) e N corporal (10,45–11,64%) aumentaram com os níveis crescente de proteína na dieta. A mesma análise foi realizada para o lodo do bioflocos, que apresentou aumento crescente de PB e N. A sobrevivência foi superior a 80% e os camarões alimentados com dietas contendo 31,28 à 46,34g 100 g-¹ PB obtiveram aumento no peso final (1,52–2,61 g), produtividade (0,69–1,10 kg m-³), ganho em peso (1,38–2,44 g) e eficiência alimentar (77,28–101,68%), enquanto esses índices decresceram no tratamento 51,74 g 100 g-¹ PB. O conteúdo de proteína bruta entre 44,26 à 47,12 g 100 g-¹ PB proporcionou o melhor desempenho de crescimento durante a fase inicial do cultivo do camarão-branco-do-pacífico L. vannamei em bioflocos.(AU)

Distribution patterns, carbon sources and niche partitioning in cave shrimps (Atyidae: Typhlatya).

Cave shrimps of the Typhlatya genus are common and widespread in fresh, brackish and marine groundwater throughout the Yucatan Peninsula (Mexico). These species are ideal models to test niche partitioning within sympatric species in oligotrophic systems. Nevertheless, their food sources remain unidentified, and despite their frequency and functional importance, distribution and abundance patterns of these species within caves have not been fully recognized. Here, we describe the abundance of three Typhlatya species in different temporal and spatial scales, investigate changes in water conditions, and potential sources of carbon as an indication of food origin. Species composition and abundance varied markedly in space and time revealing patterns that differed from one system to another and in relation to environmental parameters. Isotope analysis showed that each species reflects a particular δ13C and Δ14C fingerprint, suggesting they feed in different proportions from the available carbon sources. Overall, our findings suggest a niche partitioning of habitat and feeding sources amongst the three Typhlatya species investigated, where environmental characteristics and physiological differences could play an important role governing their distribution patterns.

Effects of macroconsumers on benthic communities: Rapid increases in dry-season accrual of calcium in a tropical karst stream.

Species loss from upper trophic levels can result in some major changes in community structure and ecosystem functions. Here, we experimentally excluded macroconsumers (e.g., fish and shrimp) in a Brazilian karst tropical stream during the dry season to investigate if their loss affected the accrual of calcium, dry mass (DM) and ash-free dry mass (AFDM) of sediment, benthic invertebrates, and chlorophyll-a. We found that the exclusion of macroconsumers decreased accrual of calcium. The absence of fish and shrimp may have promoted increased grazing by mayflies and snails in the electrified treatment as expressed by the depressed calcium accrual and shift in periphyton community composition. However, the exclusion of macroconsumers had no effect on DM and AFDM, chlorophyll-a, or total abundance of invertebrates. Our findings shed new light on the impact of macroconsumer loss and consequences for calcium accrual in karstic streams.

Aquaporin in different moult stages of a freshwater decapod crustacean: Expression and participation in muscle hydration control.

Crustaceans, during their moult cycle, at the stages of both pre-moult and post-moult, need water uptake. This movement of water creates a challenge for the regulation of cell volume. The cells of freshwater decapods require a high regulatory capacity to deal with hyposmotic stresses, given the need to face dilution of the haemolymph during their moult cycles. This study investigated the variation in the expression of water channels (aquaporins) along the moult cycle of a freshwater palaemonid shrimp, focusing on their role in cell volume regulation. Moults in Palaemonetes argentinus have been investigated along three stages of its moult cycle: intermoult, late pre-moult and recent post-moult. For the evaluation of tissue volume regulation, the weight of isolatedmuscle, subjected to isosmotic and hyposmotic salines, was followed for 60min. The expression of AQP during the different moult stages was evaluated by immunocytochemistry. Muscle from the three moult stages in isosmotic conditions showed the same pattern of tissue volume regulation. When muscle from animals in pre-moult and intermoult were submitted to hyposmotic stress they swell, followed by volume regulation, while in post-moult the regulation is compromised. The difference in volume regulatory control between pre-moult and post-moult may be related to a possible regulation of water channels, as AQP expression was equal at these stages. This study presents novel findings for crustaceans in general, in the demonstration that AQP expression changes during the moult cycle of a decapod crustacean, together with the regulation of cell volume with the participation of AQPs.

Exploring developmental gene toolkit and associated pathways in a potential new model crustacean using transcriptomic analysis.

The crustaceans are one of the largest, most diverse, and most successful groups of invertebrates. The diversity among the crustaceans is also reflected in embryonic development models. However, the molecular genetics that regulates embryonic development is not known in those crustaceans that have a short germ-band development with superficial cleavage, such as Macrobrachium olfersi. This species is a freshwater decapod and has great potential to become a model for developmental biology, as well as for evolutionary and environmental studies. To obtain sequence data of M. olfersi from an embryonic developmental perspective, we performed de novo assembly and annotation of the embryonic transcriptome. Using a pooling strategy of total RNA, paired-end Illumina sequencing, and assembly with multiple k-mers, a total of 25,636,097 pair reads were generated. In total, 99,751 unigenes were identified, and 20,893 of these returned a Blastx hit. KEGG pathway analysis mapped a total of 6866 unigenes related to 129 metabolic pathways. In general, 21,845 unigenes were assigned to gene ontology (GO) categories: molecular function (19,604), cellular components (10,254), and biological processes (13,841). Of these, 2142 unigenes were assigned to the developmental process category. More specifically, a total of 35 homologs of embryonic development toolkit genes were identified, which included maternal effect (one gene), gap (six), pair-rule (six), segment polarity (seven), Hox (four), Wnt (eight), and dorsoventral patterning genes (three). In addition, genes of developmental pathways were found, including TGF-ß, Wnt, Notch, MAPK, Hedgehog, Jak-STAT, VEGF, and ecdysteroid-inducible nuclear receptors. RT-PCR analysis of eight genes related to embryonic development from gastrulation to late morphogenesis/organogenesis confirmed the applicability of the transcriptome analysis.

Tide-related biological rhythm in the oxygen consumption rate of ghost shrimp (Neotrypaea uncinata).

The effects of tidal height (high and low), acclimation to laboratory conditions (days in captivity) and oxygen level (hypoxia and normoxia) were evaluated in the oxygen consumption rate (OCR) of the ghost shrimp Neotrypaea uncinata We evaluated the hypothesis that N. uncinata reduces its OCR during low tide and increases it during high tide, regardless of oxygen level or acclimation. Additionally, the existence of an endogenous rhythm in OCR was explored, and we examined whether it synchronized with tidal, diurnal or semidiurnal cycles. Unexpectedly, high OCRs were observed at low tide, during normoxia, in non-acclimated animals. Results from a second, longer experiment under normoxic conditions suggested the presence of a tide-related metabolic rhythm, a response pattern not yet demonstrated for a burrowing decapod. Although rhythms persisted for only 2 days after capture, their period of 12.8 h closely matched the semidiurnal tidal cycle that ghost shrimp confront inside their burrows.

Molecular characterization and organ-specific expression of the gene that encodes betaine aldehyde dehydrogenase from the white shrimp Litopenaeus vannamei in response to osmotic stress.

Crustaceans overcome osmotic disturbances by regulating their intracellular concentration of ions and osmolytes. Glycine betaine (GB), an osmolyte accumulated in response to hyperosmotic stress, is synthesized by betaine aldehyde dehydrogenase (BADH EC 1.2.1.8) through the oxidation of betaine aldehyde. A partial BADH cDNA sequence from the white shrimp Litopenaeus vannamei was obtained and its organ-specific expression during osmotic stress (low and high salinity) was evaluated. The partial BADH cDNA sequence (LvBADH) is 1103bp long and encodes an open reading frame for 217 protein residues. The amino acid sequence of LvBADH is related to that of other BADHs, TMABA-DH and ALDH9 from invertebrate and vertebrate homologues, and includes the essential domains of their function and regulation. LvBADH activity and mRNA expression were detected in the gills, hepatopancreas and muscle with the highest levels in the hepatopancreas. LvBADH mRNA expression increased 2-3-fold in the hepatopancreas and gills after 7days of osmotic variation (25 and 40ppt). In contrast, LvBADH mRNA expression in muscle decreased 4-fold and 15-fold after 7days at low and high salinity, respectively. The results indicate that LvBADH is ubiquitously expressed, but its levels are organ-specific and regulated by osmotic stress, and that LvBADH is involved in the cellular response of crustaceans to variations in environmental salinity.

Physiological responses of the ghost shrimp Neotrypaea uncinata (Milne Edwards 1837) (Decapoda: Thalassinidea) to oxygen availability and recovery after severe environmental hypoxia.

Hypoxia is a common and widespread phenomenon in aquatic ecosystems, imposing a significant challenge for the animals that inhabit such waters. In different habitats, however, the characteristics of these hypoxic events may differ, therefore imposing different challenges. We investigated the tolerance of adult ghost shrimp Neotrypaea uncinata (an intertidal mudflat dweller) to different partial pressures of oxygen (pO2), severe hypoxia (2 kPa) and recovery from hypoxia after different exposure times, mimicking the natural tidal cycle (6 h and 12 h). We calculated critical oxygen tension and categorize the adult ghost shrimps as oxyregulators (R value=75.27%). All physiological measurements (metabolic rate, oxyhemocyanin, hemolymph protein and lactate concentrations) were affected by exposure to low partial pressures of oxygen, but most of them recovered (with exception of metabolic rate) control values (21 kPa) after 6h under normoxic conditions. Low metabolic rate, high release of hemolymphatic proteins and anaerobic metabolism are suggested as response mechanisms to overcome hypoxic events during low tide.

Effects of both ecdysone and the acclimation to low temperature, on growth and metabolic rate of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda, Parastacidae) / Efectos de ecdisona y de la aclimatación a baja temperatura, sobre el crecimiento y la tasa metabólica de juveniles de la langosta de agua dulce Cherax quadricarinatus (Decapoda, Parastacidae)

Se evaluaron las reservas energéticas, el crecimiento y la tasa metabólica de langostas juveniles de agua dulce Cherax quadricarinatus (von Martens, 1868), aclimatadas durante 16 semanas tanto a 25ºC (temperatura cercana al óptimo) como a 20ºC (temperatura marginal para la especie). Adicionalmente, se evaluó el efecto modulador de la ecdisona sobre la aclimatación. Luego de 12 semanas de exposición, la ganancia en peso de ambos grupos experimentales aclimatados a 25ºC (control: C25, y tratados con ecdisona: E25) fue significativamente mayor que la de los grupos aclimatados a 20ºC (C20 and E20). Se verificó una compensación total en la tasa metabólica, luego de la aclimatación desde 25 a 20ºC, tanto para el grupo control como para el tratado con ecdisona. Solamente se observó un valor de Q10 significativamente mayor en el grupo aclimatado a 20ºC y tratado con ecdisona. En ambos grupos aclimatados a 20ºC, se determinó un reducción en la reservas de glucógeno, tanto en hepatopancreas como en músculo, así como un menor contenido de proteína en músculo. Correspondiente, la glucemia resultó siempre más elevada en esos grupos, que también mostraron un mayor nivel de lípidos en el hepatopancreas, siendo mayor el nivel de lípidos en músculo sólo para los juveniles aclimatados a 20ºC y tratados con ecdisona.

Growth, metabolic rate, and energy reserves of Cherax quadricarinatus (von Martens, 1868) juveniles were evaluated in crayfish acclimated for 16 weeks to either 25ºC (temperature near optimum) or 20ºC (marginal for the species). Additionally, the modulating effect of ecdsyone on acclimation was studied. After 12 weeks of exposure, weight gain of both experimental groups acclimated to 25ºC (control: C25, and ecdysone treated: E25) was significantly higher than that of those groups acclimated to 20ºC (C20 and E20). A total compensation in metabolic rate was seen after acclimation from 25ºC to 20ºC; for both the control group and the group treated with ecdysone. A Q10 value significantly higher was only observed in the group acclimated to 20ºC and treated with ecdysone. A reduction of glycogen reserves in both hepatopancreas and muscle, as well as a lower protein content in muscle, was seen in both groups acclimated to 20ºC. Correspondingly, glycemia was always higher in these groups. Increased lipid levels were seen in the hepatopancreas of animals acclimated to 20ºC, while a higher lipid level was also observed in muscle at 20ºC, but only in ecdysone-treated crayfish.

Effects of both ecdysone and the acclimation to low temperature, on growth and metabolic rate of juvenile freshwater crayfish Cherax quadricarinatus (Decapoda, Parastacidae) / Efectos de ecdisona y de la aclimatación a baja temperatura, sobre el crecimiento y la tasa metabólica de juveniles de la langosta de agua dulce Cherax quadricarinatus (Decapoda, Parastacidae)

Se evaluaron las reservas energéticas, el crecimiento y la tasa metabólica de langostas juveniles de agua dulce Cherax quadricarinatus (von Martens, 1868), aclimatadas durante 16 semanas tanto a 25ºC (temperatura cercana al óptimo) como a 20ºC (temperatura marginal para la especie). Adicionalmente, se evaluó el efecto modulador de la ecdisona sobre la aclimatación. Luego de 12 semanas de exposición, la ganancia en peso de ambos grupos experimentales aclimatados a 25ºC (control: C25, y tratados con ecdisona: E25) fue significativamente mayor que la de los grupos aclimatados a 20ºC (C20 and E20). Se verificó una compensación total en la tasa metabólica, luego de la aclimatación desde 25 a 20ºC, tanto para el grupo control como para el tratado con ecdisona. Solamente se observó un valor de Q10 significativamente mayor en el grupo aclimatado a 20ºC y tratado con ecdisona. En ambos grupos aclimatados a 20ºC, se determinó un reducción en la reservas de glucógeno, tanto en hepatopancreas como en músculo, así como un menor contenido de proteína en músculo. Correspondiente, la glucemia resultó siempre más elevada en esos grupos, que también mostraron un mayor nivel de lípidos en el hepatopancreas, siendo mayor el nivel de lípidos en músculo sólo para los juveniles aclimatados a 20ºC y tratados con ecdisona.(AU)

Growth, metabolic rate, and energy reserves of Cherax quadricarinatus (von Martens, 1868) juveniles were evaluated in crayfish acclimated for 16 weeks to either 25ºC (temperature near optimum) or 20ºC (marginal for the species). Additionally, the modulating effect of ecdsyone on acclimation was studied. After 12 weeks of exposure, weight gain of both experimental groups acclimated to 25ºC (control: C25, and ecdysone treated: E25) was significantly higher than that of those groups acclimated to 20ºC (C20 and E20). A total compensation in metabolic rate was seen after acclimation from 25ºC to 20ºC; for both the control group and the group treated with ecdysone. A Q10 value significantly higher was only observed in the group acclimated to 20ºC and treated with ecdysone. A reduction of glycogen reserves in both hepatopancreas and muscle, as well as a lower protein content in muscle, was seen in both groups acclimated to 20ºC. Correspondingly, glycemia was always higher in these groups. Increased lipid levels were seen in the hepatopancreas of animals acclimated to 20ºC, while a higher lipid level was also observed in muscle at 20ºC, but only in ecdysone-treated crayfish.(AU)

Daily variations of the antioxidant defense system of the lithodid crab Lithodes santolla.

Several physiological processes can induce daily variations in aerobic metabolism. Lithodes santolla is a decapod crustacean of special concern since it is a sub-Antarctic species of commercial interest. The aim of this work was to study in L. santolla the daily variations in levels of enzymatic and non-enzymatic antioxidants, lipid peroxidation and protein oxidation, and haemolymphatic pH. Males of L. santolla of commercial size were randomly dissected every 4 h during a period of 24 h. Enzymatic activities of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase and glutathione peroxidase were determined in samples of gills, muscle, hepatopancreas and haemolymph. Ascorbic acid, total glutathione, lipid peroxidation and protein oxidation were also determined in all tissues. Gills showed the highest enzymatic activity and hepatopancreas the highest concentration of non-enzymatic antioxidants. Maximum antioxidant activity was during the dark phase in gills and during the photophase in the haemolymph. Muscle showed significant daily variations, with peaks during the photophase and scotophase. Overall, an antioxidant protective mechanism is present in all tissues, where SOD and CAT represent the first line of defense. The defense mechanism in L. santolla seems to be more active during the dark phase, with slight differences among the analyzed tissues, indicating a higher metabolic rate.

Kinetic analysis of gill (Na⁺,K⁺)-ATPase activity in selected ontogenetic stages of the Amazon River shrimp, Macrobrachium amazonicum (Decapoda, Palaemonidae): interactions at ATP- and cation-binding sites.

We investigated modulation by ATP, Mg²âº, Na⁺, K⁺ and NH4⁺ and inhibition by ouabain of (Na⁺,K⁺)-ATPase activity in microsomal homogenates of whole zoeae I and decapodid III (formerly zoea IX) and whole-body and gill homogenates of juvenile and adult Amazon River shrimps, Macrobrachium amazonicum. (Na⁺,K⁺)-ATPase-specific activity was increased twofold in decapodid III compared to zoea I, juveniles and adults, suggesting an important role in this ontogenetic stage. The apparent affinity for ATP (K(M) = 0.09 ± 0.01 mmol L⁻¹) of the decapodid III (Na⁺,K⁺)-ATPase, about twofold greater than the other stages, further highlights this relevance. Modulation of (Na⁺,K⁺-ATPase activity by K⁺ also revealed a threefold greater affinity for K⁺ (K0.5 = 0.91 ± 0.04 mmol L⁻¹) in decapodid III than in other stages; NH4⁺ had no modulatory effect. The affinity for Na⁺ (K0.5 = 13.2 ± 0.6 mmol L⁻¹) of zoea I (Na⁺,K⁺)-ATPase was fourfold less than other stages. Modulation by Na⁺, Mg²âº and NH4⁺ obeyed cooperative kinetics, while K⁺ modulation exhibited Michaelis-Menten behavior. Rates of maximal Mg²âº stimulation of ouabain-insensitive ATPase activity differed in each ontogenetic stage, suggesting that Mg²âº-stimulated ATPases other than (Na⁺,K⁺)-ATPase are present. Ouabain inhibition suggests that, among the various ATPase activities present in the different stages, Na⁺-ATPase may be involved in the ontogeny of osmoregulation in larval M. amazonicum. The NH4⁺-stimulated, ouabain-insensitive ATPase activity seen in zoea I and decapodid III may reflect a stage-specific means of ammonia excretion since functional gills are absent in the early larval stages.

Evolution of osmoregulatory patterns and gill ion transport mechanisms in the decapod Crustacea: a review.

Decapod crustaceans exhibit a wide range of osmoregulatory patterns and capabilities from marine osmoconformers to brackish and freshwater hyperregulators to terrestrial hyporegulators. The principal gill salt transport mechanisms proposed to underlie the ability of the better-known taxa to occupy these specific habitats are examined here. Traditional thinking suggests that a graduated series of successively stronger adaptive mechanisms may have driven the occupation of ever more dilute osmotic niches, culminating in the conquest of freshwater and dry land. However, when habitat and osmoregulatory parameters are analyzed quantitatively against the phylogenies of the taxa examined, as illustrated here using a palaemonid shrimp clade, their association becomes questionable and may hold true only in specific cases. We also propose a putative evolution for gill epithelial ion pump and transporter arrangement in a eubrachyuran crab clade whose lineages occupy distinct osmotic niches. By including the systematics of these selected groups, this review incorporates the notion of a protracted time scale, here termed 'phylophysiology', into decapod osmoregulation, allowing the examination of putative physiological transformations and their underlying evolutionary processes. This approach assumes that species are temporally linked, a factor that can impart phylogenetic structuring, which must be considered in comparative studies. Future experimental models in decapod osmoregulatory physiology should contemplate the phylogenetic relationships among the taxa chosen to better allow comprehension of the transformations arising during their evolution.

Effects of androgenic gland ablation on growth and reproductive parameters of Cherax quadricarinatus males (Parastacidae, Decapoda).

This work investigates the effects of androgenic gland (AG) ablation on the structure of the reproductive system, development of secondary sexual characters and somatic growth in Cherax quadricarinatus males. The AG ablation, which was performed at an early developmental stage (initial weight: 1.85±0.03 g), had no effect on the somatic growth parameters (specific growth rate and growth increment), but it prevented the re-formation of male gonopores and appendices masculinae. However, the red patch differentiation and chelae size were similar to those in control males. All the ablated animals developed a male reproductive system. Testis structure was macroscopically and histologically normal. The distal portion of the vas deferens (DVD) was enlarged in some animals, with histological alterations of the epithelium and the structure of the spermatophore. Results suggest that the higher growth in males than in females may be due to an indirect effect of the AG on energy investment in reproduction rather than to a direct effect of an androgen. This is the first report of a potential action of the AG on the secretory activity of the distal VD and the structural organization of the spermatophore. Although the AG may play a role in the development of male copulatory organs, its association with the red patch development deserves further research. The results obtained in the present study support and complement those from intersexes of the same species.

Differences in oxygen consumption and diel activity as adaptations related to microhabitat in Neotropical freshwater decapods (Crustacea).

This study evaluated oxygen consumption (MO(2)) and diel activity in Aegla longirostri, Trichodactylus panoplus and Parastacus brasiliensis (three species of freshwater decapods that occur in sympatry), under two different conditions of O(2) availability, limited and constant; and searched for the existence of a relationship between these two variables. The Kruskal-Wallis test showed that in all the species, MO(2) was higher under constant O(2) availability; T. panoplus and P. brasiliensis showed an oxygen-dependent pattern, while A. longirostri showed higher MO(2) values and less variation in the values between the treatments, indicating a higher and more oxygen-independent metabolism. P. brasiliensis was more active in constant O(2). A. longirostri was more active in limited O(2) and did not show a clear diel activity in any case, showing behavioral changes when in unfavorable conditions. The Spearman's rank correlation analysis did not indicate any relationship between MO(2) and activity. These results indicate a higher metabolism in A. longirostri. The less demanding metabolisms of P. brasiliensis and T. panoplus allow these species to occupy environments that are unavailable to A. longirostri due to differences in dissolved-oxygen concentrations.

Effects of glyphosate and polyoxyethylenamine on growth and energetic reserves in the freshwater crayfish Cherax quadricarinatus (Decapoda, Parastacidae).

Freshwater crayfish Cherax quadricarinatus have a high commercial value and are cultured in farms where they are potentially exposed to pesticides. Therefore, we examined the sublethal effects of a 50-day exposure to glyphosate acid and polyoxyethylenamine (POEA), both alone and in a 3:1 mixture, on the growth and energetic reserves in muscle, hepatopancreas and hemolymph of growing juvenile crayfish. Exposure to two different glyphosate and POEA mixtures caused lower somatic growth and decreased muscle protein levels. These effects, caused by both compounds interacting in the mixture, could also be synergistic because they were expressed even at the lowest concentration. The decrease in protein levels could be related to the greater use of other energy reserves. This hypothesis is supported by the decrease in muscle glycogen stores due to glyphosate exposure and the decrease in lipid reserves associated with exposure to POEA.