The effect of sub-lethal doses of dieldrin on the ventilatory and cardiac activity in two species of shrimps

The effect of dieldrin on the heart and ventilatory activity in the shrimps Macrobranchium faustinum and Macrobrachium amazonicum was studied over 4 and 7 day exposure periods, respectively. In M. faustinum, ventilatory rate increased by 43% and heart rate by 14.4%. In M. amazonicum, the ventilatory and heart rates decreased by 21 and 6%, respectively. In M. amazonicum ventilatory reversal frequency, an index of respiratory stress, was 6.7 times higher than the control values. All the changes, except for M. amazonicum heart rate were significant at the 0.01 level of probability.     

Reproductive cycle of Macrobrachium amazonicum females (Crustacea, Palaemonidae).

Macrobrachium amazonicum is considered a favorite Brazilian species of freshwater prawn for cultivation as a result of its quick development and because it is easy to maintain in captivity. The aim of this work is to describe the sexual cycle stages and determine maturation age of the female M. amazonicum, which was collected monthly from June, 2002 to May, 2003 in the Jaguaribe River, Itai?aba, Ceará. A monthly sample of water was also collected to determine the following parameters: temperature, dissolved oxygen, pH and salinity. A monthly sample of females was selected among the individuals caught, to determine the total weight (W(T)), carapace length (L( C)) and abdomen+telson length (L(A+T)) and to register the number of non-ovigerous females (NOF) and ovigerous females (OF). Determining ovarian maturation stages of M. amazonicum was done in a laboratory by observing macroscopic characters such as coloring, size, location and appearance of ovarians examined by transparent carapace. The first maturation age was determined from the relative frequency of the total length (L(T)) of young and adult females. The environmental parameters of the Jaguaribe River did not hold any influence in the number of individuals collected. A total of 1,337 prawns were sampled, 513 males (38.4%) and 824 females (61.6%). The proportion between males and females in the studied population was of 1:1.6. Among the collected females, 492 (50.7%) did not carry eggs in their abdomens (NOF) and 332 (40.3%) carried eggs in their abdomens (OF). There was no record of intact females. Non-ovigerous females with mature ovaries were recorded throughout all the months of collection. The female ovaries were classified as immature (IM), rudimentary (RU), intermediary (IN) and mature (M). M. amazonicum females reach their first sexual maturity between 4.5 and 5.5 cm of total length.     

Yeasts from Macrobrachium amazonicum: a focus on antifungal susceptibility and virulence factors of Candida spp

In the present study, it was sought to compare yeast microbiota of wild and captive Macrobrachium amazonicum and evaluate the antifungal susceptibility and production of virulence factors by the recovered isolates of Candida spp. Additionally, cultivation water was monitored for the presence of fungi. Overall, 26 yeast isolates belonging to three genera and seven species were obtained, out of which 24 were Candida spp., with Candida famata as the most prevalent species for both wild and captive prawns. From cultivation water, 28 isolates of filamentous fungi were obtained, with Penicillium spp., Cladosporium spp. and Aspergillus spp. as the most frequent genera. Eight out of 24 Candida spp. isolates were resistant to azole derivatives, out of which four were recovered from wild-harvested prawns. As for production of virulence factors, three (12.5%) and eight (33.3%) isolates presented phospholipase and protease activity, respectively. This is the first comparative study between wild and captive prawns and the first report on yeast microbiota of M. amazonicum. The most relevant finding was the high percentage of resistant Candida spp., including from wild individuals, which suggests the occurrence of an environmental imbalance in the area where these prawns were captured.     

The distribution of freshwater shrimps (Atyidae and Palaemonidae) in Jamaica

The distribution of freshwater shrimps in Jamaica is presented. Atya innocous, Atya lanipes, Atya scabra, Micratya poeyi and Macrobrachium heterochirus were found only in the high-gradient streams characteristic of eastern and north-eastern parishes. Macrobrachium acanthurus, Jonga serrei , and Potimirim mexicana were found only in the low-gradient streams characteristic of western and southwestern parishes. Macrobrachium faustinum, Macrobrachium carcinus , and Xiphocaris elongata were distributed throughout Jamaica. Oxygen, temperature, and current speed were the physical features of the streams most likely influencing this distribution. It was observed that species in high-gradient streams had larvae which required high salinity for development, and those in low-gradient streams had larvae with low salinity requirements. It is argued that larval salinity preferences during the marine planktonic stage of the life history could allow larvae to select an appropriate river prior to its being invaded by juveniles.     

Inter- and intra-individual variation in resting oxygen consumption in post-larvae of the giant freshwater prawn,Macrobrachium rosenbergii (De Man)

In a study of the factors that influence metabolic rate in the giant freshwater prawn Macrobrachium rosenbergii, resting oxygen consumption (ROC) was measured in 90 post-larvae ranging in size from 0.1 to 2.8 g. As in many other animal species, ROC was strongly negatively related to body weight. A stressful event (anaesthesia with or without tagging) caused a sharp increase in the ROC that disappeared over a time scale of hours. As has been demonstrated for other species of crustaceans, ROC was highest in prawns in the pre-moult stage. Individual differences in ROC among prawns handled in the same way and in the same moult stage persisted over a period of hours, but not over days. It remains unclear, therefore, whether early differences in resting metabolic rate can explain the conspicuous differences in growth rate that are found in this species during the first few weeks of life and that profoundly influence subsequent life history events.     

Molecular Analysis of the Freshwater Prawn Macrobrachium olfersii (Decapoda,Palaemonidae) Supports the Existence of a Single Species throughout Its Distribution

Macrobrachium olfersii is an amphidromous freshwater prawn, widespread along the eastern coasts of the Americas. This species shows great morphological modifications during ontogenesis, and several studies have verified the existence of a wide intraspecific variation. Because of this condition, the species is often misidentified, and several synonyms have been documented. To elucidate these aspects, individuals of M. olfersii from different populations along its range of distribution were investigated. The taxonomic limit was established, and the degree of genetic variability of this species was described. We extracted DNA from 53 specimens of M. olfersii, M. americanum, M. digueti and M. faustinum, which resulted in 84 new sequences (22 of 16S mtDNA, 45 of Cythocrome Oxidase I (COI) mtDNA, and 17 of Histone (H3) nDNA). Sequences of three genes (single and concatenated) from these species were used in the Maximum Likelihood and Bayesian Inference phylogenetic analyses and COI sequences from M. olfersii were used in population analysis. The genetic variation was evaluated through the alignment of 554 bp from the 16S, 638 bp from the COI, and 338 bp from the H3. The rates of genetic divergence among populations were lower at the intraspecific level. This was confirmed by the haplotype net, which showed a continuous gene flow among populations. Although a wide distribution and high morphological intraspecific variation often suggest the existence of more than one species, genetic similarity of Caribbean and Brazilian populations of M. olfersii supported them as a single species.     

Gill (Na+,K+)-ATPase in diadromous, freshwater palaemonid shrimps: species-specific kinetic characteristics and alpha-subunit expression

To better comprehend physiological adaptation to dilute media and the molecular mechanisms underlying ammonia excretion in palaemonid shrimps, we characterized the (Na+,K+)-ATPase from Macrobrachium amazonicum gills, disclosing high- (K(0.5) = 4.2+/-0.2 micromol L(-1); V = 33.9+/-1.9 U mg(-1)) and low-affinity (K(0.5) = 0.144+/-0.010 mmol L(-1); V = 232.9+/-15.3 U mg(-1)) ATP hydrolyzing sites. Stimulation by Na+ (K(0.5) = 5.5+/-0.3 mmol L(-1); V = 275.1+/-15.1 U mg(-1)), Mg2+ (K(0.5) = 0.79+/-0.06 mmol L(-1); V = 261.9+/-18.3 U mg(-1)), K+ (K(M) = 0.88+/-0.04 mmol L(-1); V = 271.8+/-10.9 U mg(-1)) and NH4(+) (K(M) = 5.0+/-0.2 mmol L(-1); V = 385.9+/-15.8 U mg(-1)) obeys single saturation curves, activity being stimulated synergistically by NH4(+) and K+. There is a single K+ binding site, NH4(+) binding to a second, exclusive site, stimulating activity by 33%, modulating K+ affinity. (Na+,K+)-ATPase activity constitutes approximately 80% of total ATPase activity (K(Iouabain) = 147.5+/-8.9 micromol L(-1)); Na+-, K+-, Ca2+-, V- and F(o)F(1)-ATPases are also present. M. amazonicum microsomal fractions possess approximately 2-fold less (Na+,K+)-ATPase alpha-subunit than M. olfersi, consistent with a 2.6-fold lower specific activity. These differences in (Na+, K+)-ATPase stimulation by ATP and ions, and specific activities of other ATPases, suggest the presence of distinct biochemical adaptations to life in fresh water in these related species.     

三种沼虾的COI基因序列变异及其分类地位探讨(英文)

罗氏沼虾(Macrobrachium rosenbergii)和日本沼虾(M.nipponense)经在我国得到广泛的养殖,产生巨大的经济效益.祁连沼虾(M. qilianensis)是自然分布在我国甘肃省的土著虾种,因其外部形态符合沼虾属的特征,而被前人归入沼虾属.为了从分子生物学的角度理解罗氏沼虾、日本沼虾与祁连沼虾的遗传差异,为合理开发和利用沼虾资源提供理论基础,作者对这3种沼虾的线粒体COI基因序列进行研究.从甘肃、浙江等地分别采集这三种沼虾的样本各10尾,共30尾,其中祁连沼虾是野生样本,而罗氏沼虾和日本沼虾都是养殖样本.通过PCR方法扩增线粒体COI基因,并测序.通过比对,获得一致序列649 bp.在30个样本中共检测到169个变异位点,占总变异的26.04%;共检测到7种单倍型.3种沼虾的核苷酸多态性分别为:罗氏沼虾0.411%、日本沼虾0.092%、祁连沼虾0.031%.野生的祁连沼虾遗传多样性远远低于养殖的罗氏沼虾和日本沼虾.三种沼虾单倍型之间的Kimura双参数遗传距离在19.87%～23.84%,三者之间的遗传距离较大,提示三者均为有效种.为进一步确定这三种沼虾在长臂虾科的分类地位, 我们从NCBI数据库中下载了长臂虾科的其它种类的COI序列进行系统发生分析.用NJ法构建的分子系统树显示:日本沼虾和罗氏沼虾与沼虾属的其它种类聚成一枝,而祁连沼虾与同亚科的脊尾白虾(Exopalaemon carinicauda)和长角长臂虾(Palaemon debilis)较沼虾属另10种虾的遗传距离近,即祁连沼虾与白虾属及长臂虾属聚成另一枝.凶此,COI序列的结果不支持祁连沼虾归入沼虾属.但其分类地位应该综合多方面证据重新进行分析确定.     

Resting Metabolic Rate and Social Status in Juvenile Giant Freshwater Prawns, Macrobrachium rosenbergii

Forty post-larval giant freshwater prawns ( Macrobrachium rosenbergii ) were weighed, measured, marked and placed in groups of 4. Social interactions were screened daily, moults were recorded and the nature and stability of dominance interactions characterised. Half of the prawns were screened for resting oxygen consumption before group formation. In most groups, one or two individuals ('dominants') consistently won the majority of interactions in which they were involved, while others ('subordinates') consistently lost; the remainder were classified as of intermediate social status. Prawns lost more fights on the day before a moult, but despite this, rank was retained after moults. Neither initial size nor growth rates varied with status, but prawns that became dominant had significantly higher resting metabolic rates before group formation than those that became subordinate. Thus in M . rosenbergii the outcome of aggressive interactions can be predicted from the metabolic physiology of the animals although whether the relationship is causal remains to be determined.     

The effects of progressive exercise on cardiovascular function in elite athletes: focus on oxidative stress

Some side-effects of excessive physical training are ascribed to reactive oxygen species production. In this work we investigated the effects of progressively imposed maximal physical effort (levels I to V), using progressive maximal exercise test, on peripheral blood lactate, NO (through NO2-), superoxide anion (O2-) and methemoglobin (MetHb) in a group of 19 elite soccer players. Blood lactate (mmol/L) was increased (4.55, level V vs. resting level, 1.95). The basal production of NO2- was in the direct relation with O2 consumption. Significant increase (p<0.05) in O2- values at effort level I (4.18) as compared to the resting value (4.01), and the significant increase (p<0.01 or p<0.05) in the MetHb (%) was found between II (18.79) and III (19.63) or between II and IV (19.24) effort levels, respectively. The regression lines of NO2- and O2- crossed at the level of the respiratory compensation point (RC), suggesting that RC could be of a crucial importance not only in the anaerobic and aerobic metabolism but in mechanisms of signal transductions as well. The results could be of the theoretical interest and also useful in designing an athlete training strategy.     

Glucocorticoid responses to stress in castrate and testosterone-replaced rams

Stress is an important contributor to cardiovascular disease and to reduced immunity and fertility. As the role of androgens in stress is uncertain, we investigated the effects of testosterone (T) on hormonal responses to stress in conscious Romney Marsh wethers. Six T-treated sheep and six control sheep were stressed by exposure to a psychological and a metabolic stimulus. Baseline glucose levels were significantly lower in the treated animals compared with controls (p=0.002). T treatment significantly attenuated ACTH (p<0.01) and cortisol (p<0.05) responses to metabolic stress. Following psychological stress, ACTH responses were significantly lower in treated sheep compared with controls (p<0.05), but differences in mean cortisol responses did not reach significance. There were no significant differences in epinephrine or norepinephrine responses following either stressor. We conclude that T replacement in wethers lowers glucose and attenuates responses to metabolic and psychological stress. While the implications of these results for human physiology require further studies, they suggest that male hypogonadism may play a role in determining the risk of cardiovascular disease and diabetes.     

Time-Dependent Effects of Training on Cardiovascular Control in Spontaneously Hypertensive Rats: Role for Brain Oxidative Stress and Inflammation and Baroreflex Sensitivity

Baroreflex dysfunction, oxidative stress and inflammation, important hallmarks of hypertension, are attenuated by exercise training. In this study, we investigated the relationships and time-course changes of cardiovascular parameters, pro-inflammatory cytokines and pro-oxidant profiles within the hypothalamic paraventricular nucleus of the spontaneously hypertensive rats (SHR). Basal values and variability of arterial pressure and heart rate and baroreflex sensitivity were measured in trained (T, low-intensity treadmill training) and sedentary (S) SHR at weeks 0, 1, 2, 4 and 8. Paraventricular nucleus was used to determine reactive oxygen species (dihydroethidium oxidation products, HPLC), NADPH oxidase subunits and pro-inflammatory cytokines expression (Real time PCR), p38 MAPK and ERK1/2 expression (Western blotting), NF-κB content (electrophoretic mobility shift assay) and cytokines immunofluorescence. SHR-S vs. WKY-S (Wistar Kyoto rats as time control) showed increased mean arterial pressure (172±3 mmHg), pressure variability and heart rate (358±7 b/min), decreased baroreflex sensitivity and heart rate variability, increased p47^phox and reactive oxygen species production, elevated NF-κB activity and increased TNF-α and IL-6 expression within the paraventricular nucleus of hypothalamus. Two weeks of training reversed all hypothalamic changes, reduced ERK1/2 phosphorylation and normalized baroreflex sensitivity (4.04±0.31 vs. 2.31±0.19 b/min/mmHg in SHR-S). These responses were followed by increased vagal component of heart rate variability (1.9-fold) and resting bradycardia (−13%) at the 4th week, and, by reduced vasomotor component of pressure variability (−28%) and decreased mean arterial pressure (−7%) only at the 8th week of training. Our findings indicate that independent of the high pressure levels in SHR, training promptly restores baroreflex function by disrupting the positive feedback between high oxidative stress and increased pro-inflammatory cytokines secretion within the hypothalamic paraventricular nucleus. These early adaptive responses precede the occurrence of training-induced resting bradycardia and blood pressure fall.     

The cost of chronic stress: impacts of a nonhabituating stress response on metabolic variables and swimming performance in sturgeon

Metabolic scope for activity (MSA) and critical swimming velocity (U(crit)) were measured in green sturgeon exposed to two stressors daily for 28 consecutive days. The results were compared with unstressed fish in an effort to measure the "cost" of chronic stress. Chronic stress was simulated by exposing fish to a randomized order of acute stressors: a 5-min chasing stressor, a 10-min water depth reduction stressor, or a 5-min confinement stressor. The acute cortisol response to each stressor was initially determined, and the maintenance of that response was verified in 7-d intervals during the chronic stress regime. Exposure to the chronic stress regime resulted in a 25% reduction of MSA caused by significantly increased maintenance metabolic rate (0.27+/-0.01 vs. 0.19+/-0.02 mg O(2) h(-1) g(-1), chronic and control fish, respectively) but did not affect the U(crit) of sturgeon. In addition, a 50% reduction in liver glycogen levels and a twofold increase of resting plasma glucose levels were measured in chronically stressed fish. We conclude that our chronic stress regime resulted in a significant maintenance cost to green sturgeon, possibly because of their inability to habituate to the stressors, but did not decrease their swimming performance.     

Trichoderma amazonicum, a new endophytic species on Hevea brasiliensis and H. guianensis from the Amazon basin

A new species of Trichoderma (teleomorph Hypocrea, Ascomycota, Sordariomycetes, Hypocreales, Hypocreaceae), T. amazonicum, endophytic on the living sapwood and leaves of Hevea spp. trees is described. Trichoderma amazonicum is distinguished from closely related species in the Harzianum clade (e.g. Hypocrea alni, H. brunneoviridis, H. epimyces, H. parepimyces, T. aggressivum, T. harzianum, T. pleuroticola and T. pleuroti) by morphological and ecological characteristics and phylogenetic analysis of three loci (ITS nrDNA, tef1 and rpb2). The closest relatives of this species are the facultatively fungicolous species T. pleuroticola and T. pleuroti.     

Airway responsiveness: role of inflammation, epithelium damage and smooth muscle tension

The purpose of this study was the effect of epithelium damage on mechanical responses of airway smooth muscles under different resting tension. We performed acetylcholine (ACh) (10(-5) M)-induced contraction on tracheal strips from 30 rabbits in five groups (0.5, 1, 1.5, 2 and 2.5 g) before and after epithelium removal. At low resting tension (0.5-1.5 g), the epithelium removal decreased the ACh-induced contractions. At 2 g resting tension, the epithelium removal increased the ACh-induced contractions of airways with intact epithelium about 20%. At 2.5 g resting tension, the elevation of contraction is about 25% (P<0.01). Consequently, after epithelium loss, the resting tension determines the airway smooth muscles responsiveness. In asthma, mediators such as ACh act on already contracted inflammatory airways, which results in additional increase of contraction. In contrast, low resting tension, a condition that simulates normal tidal breathing, protects from bronchoconstriction even when the epithelium is damaged.     

Time of feeding and possible associated thermoregulatory benefits in bronze mannikins Lonchura cucullata

Birds with a small body size have a high surface area to volume ratio, and this means that they have a high rate of heat loss to the environment. Birds may employ behavioural strategies in order to counter this heat loss. The adjustment of feeding patterns in the short term is probably the least documented of all of these strategies. Feeding results in the specific dynamic effect (SDE) which increases the metabolic rate of animals after a feeding bout. This increase in metabolic rate has been reported to possibly substitute for thermoregulatory costs in a variety of endotherms, including house wrens (Troglodytes aedon) and a variety of finch species. The thermoneutral zone was described for bronze mannikins, Lonchura cucullata (T(lc)=33.7 degrees C), and the bronze mannikins' post-absorptive physiology was described within this thermoneutral zone. Bronze mannikin mean basal metabolic rate (0.043+/-0.0038 S.E. ml O(2) min(-1) g(-1)), daytime resting metabolic rates (0.0549+/-0.0088 S.E. ml O(2) min(-1) g(-1)), and diurnal metabolic responses were described. The SDE in bronze mannikins was demonstrated within the thermoneutral zone, and was quantified. The mean magnitude of the SDE was 26.42% of mean total metabolism of post-absorptive birds. The magnitude of this SDE was independent of meal size and bird body mass. Assuming a 100% substitution, the presence of the SDE may afford bronze mannikins a maximum thermoregulatory energy saving of approximately 71.76 J g(-1) over a 300-min period.     

Resting Metabolic Rate and Social Status in Juvenile Giant Freshwater Prawns,Macrobrachium rosenbergii

Forty post-larval giant freshwater prawns (Macrobrachium rosenbergii) were weighed, measured, marked and placed in groups of 4. Social interactions were screened daily, moults were recorded and the nature and stability of dominance interactions characterised. Half of the prawns were screened for resting oxygen consumption before group formation. In most groups, one or two individuals ('dominants') consistently won the majority of interactions in which they were involved, while others ('subordinates') consistently lost; the remainder were classified as of intermediate social status. Prawns lost more fights on the day before a moult, but despite this, rank was retained after moults. Neither initial size nor growth rates varied with status, but prawns that became dominant had significantly higher resting metabolic rates before group formation than those that became subordinate. Thus in M. rosenbergii the outcome of aggressive interactions can be predicted from the metabolic physiology of the animals although whether the relationship is causal remains to be determined.     

The metabolism of social subterranean rodents: adaptation to aridity

Summary The social Damara mole-rat Cryptomys damarensis (124 g), has a mean (±SD) resting metabolic rate of 0.57±0.09 cm³ O₂ g^-1 h^-1, within a thermoneutral zone of 27–31° C. This rate of metabolism is 43% lower than that predicted by the curve for rodents, and 29% lower than that predicted by the subterranean rodent curve. These data support the hypothesis that the resting metabolic rates of social and solitary subterranean rodents are lower than those of solitary species inhabiting mesic habitats. These low resting metabolic rates may represent an energy-saving adaptation to aridity. The energetic cost of burrowing, in relation to the dispersion patterns of food in arid habitats, may explain these low metabolic rates.     

Arterial acid-base status during digestion and following vascular infusion of NaHCO(3) and HCl in the South American rattlesnake, Crotalus durissus

Digestion is associated with gastric secretion that leads to an alkalinisation of the blood, termed the "alkaline tide". Numerous studies on different reptiles and amphibians show that while plasma bicarbonate concentration ([HCO(3)(-)](pl)) increases substantially during digestion, arterial pH (pHa) remains virtually unchanged, due to a concurrent rise in arterial PCO(2) (PaCO(2)) caused by a relative hypoventilation. This has led to the suggestion that postprandial amphibians and reptiles regulate pHa rather than PaCO(2). Here we characterize blood gases in the South American rattlesnake (Crotalus durissus) during digestion and following systemic infusions of NaHCO(3) and HCl in fasting animals to induce a metabolic alkalosis or acidosis in fasting animals. The magnitude of these acid-base disturbances were similar in magnitude to that mediated by digestion and exercise. Plasma [HCO(3)(-)] increased from 18.4+/-1.5 to 23.7+/-1.0 mmol L(-1) during digestion and was accompanied by a respiratory compensation where PaCO(2) increased from 13.0+/-0.7 to 19.1+/-1.4 mm Hg at 24 h. As a result, pHa decreased slightly, but were significantly below fasting levels 36 h into digestion. Infusion of NaHCO(3) (7 mmol kg(-1)) resulted in a 10 mmol L(-1) increase in plasma [HCO(3)(-)] within 1 h and was accompanied by a rapid elevation of pHa (from 7.58+/-0.01 to 7.78+/-0.02). PaCO(2), however, did not change following HCO(3)(-) infusion, which indicates a lack of respiratory compensation. Following infusion of HCl (4 mmol kg(-1)), plasma pHa decreased by 0.07 units and [HCO(3)(-)](pl) was reduced by 4.6 mmol L(-1) within the first 3 h. PaCO(2), however, was not affected and there was no evidence for respiratory compensation. Our data show that digesting rattlesnakes exhibit respiratory compensations to the alkaline tide, whereas artificially induced metabolic acid-base disturbances of same magnitude remain uncompensated. It seems difficult to envision that the central and peripheral chemoreceptors would experience different stimuli during these conditions. One explanation for the different ventilatory responses could be that digestion induces a more relaxed state with low responsiveness to ventilatory stimuli.