(Na+, K+)- ATPase kinetics in Macrobrachium pantanalense: highlighting intra- and interspecific variation within the Macrobrachium amazonicum complex.

The Macrobrachium amazonicum complex is composed of at least the Macrobrachium amazonicum and Macrobrachium pantanalense species, with the latter described from specimens originally identified as part of an endemic M. amazonicum population in the Brazilian Pantanal region. While there may be a reproductive barrier between these two Macrobrachium species, both are phylogenetically close, with small genetic distance. However, there is currently no available biochemical information of Macrobrachium pantanalense (Na+, K+)-ATPase. Here, we report the kinetic characteristics of the gill (Na+, K+)-ATPase in two populations of M. pantanalense from Baiazinha Lagoon (Miranda, MS, Brazil) and Araguari River (Uberlândia, MG, Brazil), and compare them with Macrobrachium amazonicum populations from the Paraná-Paraguay River Basin. (Na+, K+)-ATPase activities were 67.9 ± 3.4 and 93.3 ± 4.1 nmol Pi min-1 mg-1 protein for the Baiazinha Lagoon and Araguari River populations, respectively. Two ATP hydrolyzing sites were observed for the Araguari River population while a single ATP site was observed for the Baiazinha Lagoon shrimps. Compared to the Araguari River population, a 3-fold greater apparent affinity for Mg2+ and Na+ was estimated for the Baiazinha Lagoon population, but no difference in K+ affinity and ouabain inhibition was seen. The kinetic differences observed in the gill (Na+, K+)-ATPase between the two populations of M. pantanalense, compared with those of various M. amazonicum populations, highlight interspecific divergence within the Macrobrachium genus, now examined from a biochemical perspective.

Description and prevalence of gregarines infecting the amphipod Gammarus pulex, in the Water of Leith, Scotland, UK.

Gregarines are symbiotic protists that are found in a broad spectrum of invertebrates, including insects, crustaceans, and annelids. Among these the globally distributed amphipod Gammarus pulex is one of the earliest recognized hosts for aquatic gregarines and is prevalent among macroinvertebrates in freshwater environments. In this study, samples of G. pulex were collected in the Water of Leith river, Scotland, UK. Gregarines were identified using light and scanning electron microscopy as well as standard molecular techniques. We identified three septate eugregarine symbionts-Heliospora longissima, Cephaloidophora gammari, and the here newly characterized Cephaloidophora conus n. sp. (formerly Cephaloidophora sp.) associated with Gammarus pulex in the Water of Leith. Prevalences for identified gregarine species were calculated and seasonal dynamics of gregarine infections/colonization were analyzed. Prevalences were highest in autumn and spring reaching almost 50 %. While the two Cephaloidophora species showed similar colonization patterns, the prevalence of Heliospora showed an opposite trend. Identifying gregarine infection/colonization patterns is one step towards better understanding the gregarine-host relationship, as well as possible impacts of the gregarines on their hosts.

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.

Host Size Selection in the Ectoparasite Tachaea chinensis (Isopoda: Corallanidae) under Laboratory Conditions.

Tachaea chinensis is a temporary ectoparasite infesting freshwater shrimps and prawns in eastern Asia. This study investigated the host size selection by T. chinensis across common freshwater shrimps under laboratory conditions. A total of 70 isopods were allowed to select between host shrimps of different size and different species in pairwise selection experiments. In treatments involving different sizes of the same host species, T. chinensis tended to select the medium host option in all of the four treatments. Similarly, T. chinensis demonstrated greater preference towards medium host (90%) when provided with mixed host options (medium Palaemon paucidens vs small Neocaridina spp.). However, despite the increase in the infestation proportion on medium Neocaridina spp., the isopod significantly selected the small P. paucidens when provided with a choice between medium Neocaridina spp. and small P. paucidens. In manca stage (1 day after hatch) T. chinensis treatment, the isopods showed no specific preference between large and medium Neocaridina spp. These results suggest that T. chinensis is likely to show size specificity according to the developmental stage, a size specificity that ultimately ensures adequate space for isopods' growth while maintaining a minimum risk of predation.

Mixture Toxicity of Three Unconventional Gas Fracking Chemicals, Barium, O-Cresol, and Sodium Chloride, to the Freshwater Shrimp Paratya australiensis.

The 96-h acute toxicity of barium (Ba2+ ), o-cresol, and sodium chloride (NaCl) to Paratya australiensis was assessed in single, binary, and ternary combinations in addition to three biochemical assays: glutathione S-transferase, acetylcholinesterase, and sodium-potassium adenosine triphosphatase. The 96-h lethal concentrations that expressed 50% mortality (LC50) in the single-toxicant exposures were Ba2+ = 23.4 mg/L, o-cresol = 12.2 mg/L, and NaCl = 4198 mg/L. Mortality from o-cresol exposure occurred between 11 and 22 mg/L, whereas Ba2+ was more gradual across 10-105 mg/L, and most of the NaCl mortality occurred between 2050 and 4100 mg/L. Toxic units were used to assess the binary and ternary interactions of the toxicants. A more than additive effect was observed for most combinations in the binary chemical exposures, with the ternary combinations yielding highly synergistic interactions. Greater synergism was observed with the 96-h LC50 of o-cresol in combination with the three concentrations of NaCl (1025, 2050, and 3075 mg/L) compared with Ba2+ , with toxic units of 0.38, 0.48, and 0.10 (o-cresol) and 0.71, 0.67, and 0.50 (Ba2+ ). No notable enzyme activity trends were observed in the enzyme biomarker responses from both individual and mixture exposures. Although acute single-species toxicity tests tend to underestimate the effects of Ba2+ , o-cresol, and NaCl on populations, communities, and ecosystems in seminatural (e.g., mesocosms) and natural systems, there are currently no published acute toxicity data available for P. australiensis and the three toxicants used in the present study. The present study shows that chemicals with different toxicity mechanisms can potentially lead to more synergistic responses. Environ Toxicol Chem 2023;42:481-494. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects of ammonia on gill (Na+, K+)-ATPase kinetics in a hololimnetic population of the Amazon River shrimp Macrobrachium amazonicum.

Water quality is essential for successful aquaculture. For freshwater shrimp farming, ammonia concentrations can increase considerably, even when culture water is renewed frequently, consequently increasing the risk of ammonia intoxication. We investigated ammonia lethality (LC50-96 h) in a hololimnetic population of the Amazon River shrimp Macrobrachium amazonicum from the Paraná/Paraguay River basin, including the effects of exposure to 4.93 mg L-1 total ammonia concentration on gill (Na+, K+)-ATPase activity. The mean LC50-96 h was 49.27 mg L-1 total ammonia, corresponding to 1.8 mg L-1 un-ionized ammonia. Except for NH4+ affinity that increased 2.5-fold, that of the gill (Na+, K+)-ATPase for ATP, Mg2+, Na+, K+ and ouabain was unchanged after ammonia exposure. Western blotting of gill microsomal preparations from fresh caught shrimps showed a single immunoreactive band of ≈110 kDa, corresponding to the gill (Na+, K+)-ATPase α-subunit. Ammonia exposure increased (Na+, K+)-ATPase activity by ≈25%, coincident with an additional 130 kDa α-subunit immunoreactive band, and increased K+-stimulated and V(H+)-ATPase activities by ≈2.5-fold. Macrobrachium amazonicum from the Paraná/Paraguay River basin is as tolerant to ammonia as are other Amazon River basins populations, showing toxicity comparable to that of marine crustaceans.

Microinjection-based CRISPR/Cas9 mutagenesis in the decapoda crustaceans Neocaridina heteropoda and Eriocheir sinensis.

CRISPR/Cas9 technology has been applied to many arthropods. However, application of this technology to crustaceans remains limited because of the unique characteristics of embryos. Our group has developed a microinjection system to introduce the CRISPR/Cas9 system into Neocaridina heteropoda embryos (one-cell stage). Using the developed method, we mutated the target gene Nh-scarlet (N. heteropoda scarlet), which functions in eye development and pigmentation. The results showed that both eye color and shape were altered in individuals in which Nh-scarlet was knocked out. Furthermore, this system was also successfully applied to another decapod crustacean, Eriocheir sinensis. DNA sequencing revealed that the zoeae with red eyes had an edited version of Es-scarlet. This study provides a stable microinjection method for freshwater crustaceans, and will contribute to functional genomics studies in various decapods.

Locomotor behavior of Neocaridina palmata: a study with leachates from UV-weathered microplastics.

Weathering of plastics leads to the formation of increasingly smaller particles with the release of chemical compounds. The latter occurs with currently unknown environmental impacts. Leachate-induced effects of weathered microplastics (MPs) are therefore of increasing concern. To investigate the toxicity of the chemical mixtures from such plastics, we exposed the freshwater shrimp Neocaridina palmata to enriched leachates from unweathered and artificially weathered (UV-A/B light) MPs (≤1 mm) from recycled low-density polyethylene (LDPE-R) pellets and from a biodegradable, not fully bio-based starch blend (SB) foil. We analyzed the individual locomotor activity (moved distance and frozen events) on day 1, 3, 7 and 14 of exposure to five leachate concentrations equivalent to 0.40-15.6 g MPs L-1, representing the upper scale of MPs that have been found in the environment. The median moved distance did not change as a function of concentration, except for the unweathered SB treatment on day 14 that indicated hyperactivity with increasing concentrations. Significant impacts were solely detected for few concentrations and exposure days. Generally, no consistent trend was observed across the experiments. We further assessed the baseline toxicity of the samples in the Microtox assay and detected high bioluminescence inhibitions of the bacterium Aliivibrio fischeri. This study demonstrates that neither the recycled nor the biodegradable material are without impacts on test parameters and therefore cannot be seen as safe alternative for conventional plastics regarding the toxicity. However, the observed in vitro toxicity did not result in substantial effects on the behavior of shrimps. Overall, we assume that the two endpoints examined in the atyid shrimp N. palmata were not sensitive to chemicals leaching from plastics or that effects on the in vivo level affect other toxic endpoints which were not considered in this study.

Association of the alga Cladogonium sp. with a multifactorial disease outbreak in dwarf shrimp (Neocaridina davidi).

This study outlines a multifactorial disease outbreak in a population of the freshwater shrimp Neocaridina davidi, with the focus on a rarely described parasitic alga. Within this multifactorial disease outbreak, low but consistent mortality was observed. During microscopic examination, an infection of the shrimp with bacterial and fungal-like agents was diagnosed. Furthermore, the green alga Cladogonium sp. was found in pleopodal regions. The alga compromised the body surface of the shrimp, and its rhizoids penetrated the chitin shell and reached into the subcutaneous tissue. This might be a first indication of a parasitic lifestyle. In addition to a morphological description, sequencing data are presented which allow the taxonomic classification of the organism within the order Trentepohliales.

Macrobrachium/ Spence Bate, 1868 (Decapoda: Palaemonidae): New records, range extension and geographic distribution in the Northeastern Caatinga amp; Coastal Drainages, and São Francisco hydrographic ecoregions, Northeast of Brazil.

This study constitutes the most comprehensive effort ever done to assess the faunal diversity of the Macrobrachium genus within two ecoregions that encompass part of the northeastern Brazil: the Northeastern Caatinga Coastal Drainages, and the São Francisco (Lower-middle and Lower portions). Through sampling in several of their hydrographic basins, bibliographic research, and consulting scientific collections, our results reveal the occurrence of five species along these ecoregions: Macrobrachium acanthurus, M. amazonicum, M. carcinus, M. jelskii and M. olfersii. We also provide the first record of these species for several river basins in both ecoregions. Additionally, we confirm the occurrence of M. carcinus from Rio Grande do Norte State and provide updated distribution maps for each species in the studied area. This carcinofauna survey may form the basis for future evaluations of eventual anthropic impacts on biological diversity resulting from projects being implemented in these regions, which involve the São Francisco interbasin water transfer.

Impact of dietary lipid level on esterase enzyme activities in the non-target freshwater shrimp Macrobrachium borellii exposed to chlorpyrifos.

This study increases our understanding of how diet-driven phenotypic plasticity can help non-target aquatic invertebrates deal with chlorpyrifos (CPO) exposure. A bioassay was performed over 6 days with the freshwater shrimp Macrobrachium borellii. Experimental treatments included CPO-treated shrimps (10 µg L-1) were fed with (i) a lipid-rich diet, (ii) a lipid-medium diet, or (iii) a lipid-poor diet. Control shrimps (no CPO exposure) received the same diets as detailed above. Cholinesterases and carboxylesterases were determined as an indicator of CPO exposure. Results showed that diets with a medium-to-high lipid content were important inducers of esterase activity, while shrimps exposed to CPO under a lipid-poor diet showed a significant enzymatic inhibition. This diet-dependent esterase induction suggests that the intake of fatty dietary items mitigates the esterase enzyme inhibition caused by CPO exposure.

The Hillstream Decapod Crustaceans of Shenzhen, China, with Description of a New Species of Freshwater Crab (Crustacea: Brachyura: Potamidae) in the Genus Megapleonum Huang, Shih & Ahyong, 2018.

Freshwater decapod crustaceans are often ecologically important keystone species in their habitats. The freshwater hillstream decapods of Shenzhen City, Guangdong, China, were systematically surveyed for the first time from June to September 2019. We identified a total of 19 decapod species from 10 genera and six families. Of these, one Macrobrachium species and one potamid species could not be assigned to any known species. The latter clearly belongs to the monotypic genus Megapleonum Huang, Shih & Ahyong, 2018, and resembles the type species M. ehuangzhang in general external morphology. Striking differences in male gonopodal morphology along with genetic evidence based on mitochondrial 16S rDNA sequences strongly suggest that this species is distinct from the type species and it is herein described as Megapleonum shenzhen n. sp. Our survey data sheds light on the biodiversity of hillstream decapods in Shenzhen and highlights areas of conservation interest.

Screening of antibiotic resistance genes in pathogenic bacteria isolated from tiny freshwater shrimp (Macrobrachium lanchesteri) and "Kung Ten", the uncooked Thai food.

OBJECTIVE: This study aimed to isolate and identify of pathogenic bacteria in tiny freshwater shrimp (Macrobrachium lanchesteri) and in Kung Ten, which is an unusual Thai cuisine that eaten alive shrimp directly. Antimicrobial susceptibility test and identification of antibiotic resistance genes for isolated bacteria were conducted. MATERIALS AND METHODS: Eighty of fresh shrimp samples and forty of Kung Ten salads were collected from four fresh markets, which were located in Bangkok and Nonthaburi province (N = 120). The isolation, identification, and antimicrobial susceptibility test of pathogenic bacteria were done following the Clinical and Laboratory Standards Institute guidelines. Antibiotic-resistant bacteria were screened for ß-lactamase relating genes, such as AmpC (MOX and ACC genes), bla CTX-M, and Int1 genes. RESULTS: The number of bacterial isolates in tiny freshwater shrimp and Kung Ten salad was 136 and 65, respectively. Aeromonas caviae, A. hydrophilla, Proteus penneri, Proteus vulgaris, and Klebsiella pneumoniae were commonly found. Ampicillin, amoxicillin/clavulanic, cefuroxime, tetracycline, and trimethoprim/sulfamethoxazole resistance were observed, and common antibiotic-resistant bacteria were A. caviae, P. vulgaris, Enterobacter Aerogenes, and K. pneumoniae. A. caviae, P. penneri, K. Pneumoniae, and A. hydrophilla were positive for MOX gene; bla CTX-M, and Int1 genes; ACC and Int1 genes; and ACC gene, respectively. CONCLUSION: Raw or uncooked shrimps in Kung Ten salad may a risk in foodborne diseases due to positive for pathogenic bacterial isolates. However, hygienic control on food preparation is difficult to apply because of the difficulty of changing in local Thai food behavior.

Genetic structure of Australian glass shrimp, Paratya australiensis, in relation to altitude.

Paratya australiensis Kemp (Decapoda: Atyidae) is a widely distributed freshwater shrimp in eastern Australia. The species has been considered as an important stream organism for studying genetics, dispersal, biology, behaviour and evolution in atyids and is a major food source for stream dwelling fishes. Paratya australiensis is a cryptic species complex consisting of nine highly divergent mitochondrial DNA lineages. Previous studies in southeast Queensland showed that "lineage 4" favours upstream sites at higher altitudes, with cooler water temperatures. This study aims to identify putative selection and population structure between high elevation and low elevation populations of this lineage at relatively small spatial scales. Sample localities were selected from three streams: Booloumba Creek, Broken Bridge Creek and Obi Obi Creek in the Conondale Range, southeast Queensland. Six sample localities, consisting of 142 individuals in total were sequenced using double digest Restriction Site Associated DNA-sequencing (ddRAD-seq) technique. Among the 142 individuals, 131 individuals shared 213 loci. Outlier analysis on 213 loci showed that 27 loci were putatively under selection between high elevation and low elevation populations. Outlier analysis on individual streams was also done to test for parallel patterns of adaptation, but there was no evidence of a parallel pattern. Population structure was observed using both the 27 outliers and 186 neutral loci and revealed similar population structure in both cases. Therefore, we cannot differentiate between selection and drift here. The highest genetic differentiation was observed between high elevation and low elevation populations of Booloumba Creek, with small levels of differentiation in the other two streams.

[Nutritional components of five main products of freshwater shrimp in Anhui Province].

OBJECTIVE: To analyze and evaluate the nutritional composition of five main products of freshwater shrimp including crawfish, river prawn, macrobrachium, freshwater shrimp, exopalaemon modestus in Anhui Province. METHODS: Conventional and biochemical analytical method were used to detect the moisture, ash, crude protein, crude fat, amino acid, fatty acid, minerals and vitamin. RESULTS: The contents of crude protein, crude fat, ash of the five freshwater shrimp were 13. 9-20. 8 g/100 g edible, 0. 6-2. 2 g/100 g edible, 1. 5-4. 1 g/100 g edible, respectively. A total of 18 amino acids were detected, the content of which were 11600-18600 mg/100 g edible. The amount of nine essential amino acid was measured to be 5336-9342 mg/100 g edible. The main restrictive amino acids in the five kinds of shrimps were methionine and cysteine, threonine and valine. The essential amino acid indexes in five kinds of shrimps(EAAI) were 39. 62 and 31. 81, 28. 65, 44. 85, and 33. 48, respectively. Fourteen types of fatty acid were detected. The total content of fatty acid was 287-1851 mg/100 g edible. The monounsaturated fatty acid(MUFA) and the polyunsaturated fatty acid(PUFA) were 12-234 mg/100 g edible, 164-377 mg/100 g edible, respectively. Nine minerals were detected which including five microelements and four microelements. The content of calcium in river prawn, macrobrachium and exopalaemon modestus was higher than that in crawfish and freshwater shrimp. The content of phosphorus, kalium, sodium, magnesium in five freshwater shrimp were 221-296 mg/100 g edible, 196-278 mg/100 g edible, 120. 7-202. 7 mg/100 g edible, 37-95 mg/100 g edible, respectively. The content of iron, manganese, cuprum in crawfish were higher than the others. The content of zinc in river prawn and exopalaemon modestus was high. Moreover, the vitamin B_2 and E were also detected in five freshwater shrimp. The content of vitamin B_2 and E were 0. 02-0. 07 mg/100 g edible and 1. 61-3. 30 mg/100 g edible. CONCLUSION: Five main products of freshwater shrimp in Anhui belong to super nutritional value food which contained high protein, variety of amino acid, low fat, a certain amount of vitamin B_2 and E, rich in minerals.

Dopamine binding directly up-regulates (Na+, K+)-ATPase activity in the gills of the freshwater shrimp Macrobrachium amazonicum.

We examined the effects of exogenous dopamine on gill (Na+, K+)-ATPase activity in vitro in microsomal preparations from juvenile or adult freshwater shrimp, Macrobrachium amazonicum. Dopamine had no effect on enzyme activity in juveniles but stimulated activity in adult shrimp gills by ≈35%. Stimulation of the gill (Na+, K+)-ATPase in adult shrimps by 100 mmol L-1 dopamine was characterized kinetically by varying ATP, MgATP, and Na+ and K+ concentrations, together with inhibition by ouabain. Dopamine stimulated ATP hydrolysis by ≈40% obeying Michaelis-Menten kinetics, reaching VM = 190.5 ±â€¯15.7 nmol Pi min-1 mg-1 protein, KM remaining unaltered. Stimulation by Na+ (≈50%) and K+ (≈25%) revealed distinct kinetic profiles: although KM values were similar, Na+ stimulation followed cooperative kinetics, contrasting with the Michaelian kinetics seen for K+. Stimulation by MgATP increased activity by ≈30% with little change in KM. Similar saturation profiles were seen for ouabain inhibition with very similar calculated KI values. Our findings suggest that dopamine may be involved in hemolymph sodium homeostasis by directly binding to the gill (Na+, K+)-ATPase at a site different from ouabain, thus stimulating enzyme activity in an ontogenetic stage-specific manner. However, dopamine binding does not affect enzyme affinity for cations and ouabain. This is the first report of the direct action of dopamine in stimulating the crustacean gill (Na+, K+)-ATPase.

First record of Australatyaobscura Han & Klotz, 2015 (Decapoda, Atyidae) from the Ryukyu Islands, Japan.

BACKGROUND: The freshwater shrimp, Australatyaobscura Han & Klotz, has been known only from Taiwan and Panay Island, Philippines. NEW INFORMATION: An adult A.obscura was collected from a river on Ishigaki Island, Ryukyu Islands, Japan. This is the first record of the species in Japan and the northernmost specimen-supported record to date. The species is suggested as having been transported northwards by the Kuroshio Current.

Taxonomic revision of the Australian species of Australatya Chace 1983 (Crustacea, Decapoda, Atyidae), and the description of a new species.

A morphological and genetic study of both newly collected and museum specimens of the east Australian freshwater shrimp genus Australatya indicates two genotypes and three morphotypes are present. One genotype and morphotype were of the known species, Australatya striolata (McCulloch McNeill 1923). The second genotype, comprising two morphotypes, is now described as a new species, Australatya hawkei sp. nov.. All Australian Australatya species and morphotypes currently have allopatric distributions. Australatya striolata is widespread along the south-eastern Australian seaboard, from Genoa River in Victoria to the Sunshine Coast in Queensland. The 'southern' morphotype of Australatya hawkei sp. nov. occurs in north Queensland, from near Mackay to about Cooktown, and its 'northern' morphotype is found on Cape York Peninsula, north from about Coen to the Iron Range, just north of Lockhart River. The once monotypic genus now includes two Australian species, Australatya striolata and A. hawkei sp. nov., and a third, A. obscura, recently described from Japan, Taiwan, and the Philippines.

Kinetic characterization of the gill (Na+, K+)-ATPase in a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum (Decapoda, Palaemonidae).

We provide a kinetic characterization of (Na+, K+)-ATPase activity in a posterior gill microsomal fraction from a hololimnetic population of the diadromous Amazon River shrimp Macrobrachium amazonicum. Sucrose density gradient centrifugation reveals two distinct membrane fractions showing considerable (Na+, K+)ATP-ase activity, but also containing other microsomal ATPases. Only a single immune-reactive (Na+, K+)-ATPase with Mr of ≈110 kDa is present that hydrolyzes ATP with VM = 130.3 ±â€¯4.8 nmol Pi min-1 mg protein-1 and K0.5 = 0.065 ±â€¯0.00162 mmol L-1, exhibiting site-site interactions. Stimulation by Na+ (VM = 127.5 ±â€¯5.3 nmol Pi min-1 mg protein-1, K0.5 = 5.3 ±â€¯0.42 mmol L-1), Mg2+ (VM = 130.6 ±â€¯6.8 nmol Pi min-1 mg protein-1, K0.5 = 0.33 ±â€¯0.042 mmol L-1), K+ (VM = 126.7 ±â€¯7.7 nmol Pi min-1 mg protein-1, K0.5 = 0.65 ±â€¯0.0079 mmol L-1) and NH4+ (VM = 134.5 ±â€¯8.6 nmol Pi min-1 mg protein-1, K0.5 = 1.28 ±â€¯0.44 mmol L-1) also obeys cooperative kinetics. Ouabain (KI = 0.18 ±â€¯0.058 mmol L-1) inhibits total ATPase activity by ≈70%. This study reveals considerable differences in the kinetic characteristics of the gill (Na+, K+)-ATPase in a hololimnetic population that appear to result from the adaptation of diadromous Macrobrachium amazonicum populations to different limnic habitats.

The complex study of complexes: The first well-supported phylogeny of two species complexes within genus Caridina (Decapoda: Caridea: Atyidae) sheds light on evolution, biogeography, and habitat.

Atyid shrimps, a key component of tropical freshwater ecosystems, face multiple anthropogenic threats and thus need special attention. With more than 300 described species, the genus Caridina is the most speciose of all the Caridea infra-order. Caridina spp. occupy diverse habitats in tropical freshwaters of the Indo-West Pacific region. Several species complexes have been recognized, based on common morphological features, but little is known about how well these morphological characteristics align with phylogenetic characteristics. Furthermore, no phylogeny of the genus Caridina published so far has provided well-resolved and supported relationships among different species, thus impeding the possibility of proposing evolutionary hypotheses. In this study we used next generation sequencing (NGS) to provide new insights into the phylogenetic relationships among the genus Caridina, focusing on two complexes: 'Caridina nilotica' and 'Caridina weberi'. We collected 92 specimens belonging to these two groups from most of their known geographical range, representing 50 species, for which we sequenced seven mitochondrial genes and two nuclear markers using ion torrent NGS. We performed a phylogenetic analysis, which yielded the first well-supported tree for the genus Caridina. On this tree were mapped the geographic ranges and the habitats used by the different species, and a time calibration was tested. We found the driving factors that most likely account for separation of clades are differences in habitat and to a lesser extent geography. This work provides new insights into the taxonomy of this group and identifies opportunities for further studies in order to fill knowledge gaps that currently impede the management and conservation of atyid species.