Physiological responses to hyper-saline waters in sailfin mollies (Poecilia latipinna)

We examined the ionoregulatory physiology and biochemistry of the teleost sailfin molly (Poecilia latipinna), an inhabitant of salt marshes along the gulf coast, during exposure to hyper-saline waters (salinity range 35-95 ppt). Mollies were able to tightly control plasma Na(+) and Cl(-) concentrations and tissue water levels up to 65 ppt, but at higher salinities plasma ion levels began to rise and muscle water content dropped. Still, even at the highest salinity (90 ppt) plasma Na(+) and Cl(-) levels were only 32% and 39%, respectively, above levels at 35 ppt. Drinking rates at 60 ppt climbed 35%, while gut Na(+)/K(+)-ATPase (NAK) activity rose 70% and branchial NAK activity jumped 200%. The relatively small rise in drinking rate, in the face of a more than doubling of the osmotic gradient, suggests that a reduction in branchial water permeability significantly limited water loss and associated salt load. At 80 ppt, a salinity where plasma ion levels just begin to rise, drinking rate rose more rapidly, but gut and gill NAK activity did not, suggesting that mollies employed other pathways (perhaps renal) of salt excretion. At higher salinities, plasma ion levels continued to rise and muscle water content fell slightly indicating the beginnings of internal osmotic disturbances. To evaluate the energetic costs of hyper-salinity on mollies we measured the rate of O(2) consumption and found it rose with salinity, in sharp contrast to virtually all species previously examined. Interestingly, despite higher metabolism, growth was unaffected by hyper-salinity.     

Effects of salinity on physiological conditions in juvenile common snook Centropomus undecimalis

This study describes the effects of different salinities on oxygen consumption, ammonia excretion, osmotic pressure, apparent heat increment, postprandial nitrogen excretion, and oxygen:nitrogen ratio in juvenile common snook Centropomus undecimalis. Oxygen consumption of fish fasting and fish feeding was statistically different in relation with salinity. Fish maintained at 0, 25, and 35 ppt invested more energy processing feed than fish maintained at 12 ppt. Fasting fish had lower ammonia excretion than feeding fish and excretion was reduced at high salinities. Snook can change the energetic substrate in function with salinity, from a mixture of protein and lipids and carbohydrates at 35 ppt to a more acute preference for proteins at lower salinities. This species changes osmotic plasma concentrations at extreme experimental salinities. The different salinities were the snook inhabits (0-36 ppt), have a direct effect on the physiology, inducing changes on the oxygen consumption, nitrogen excretion, changes on the energetic substrate and plasma osmotic pressure.     

Aerial and aquatic respiration of the Australian desert goby, Chlamydogobius eremius

Physiological, anatomical and behavioural adaptations enable the Australian desert goby, Chlamydogobius eremius, to live in mound springs and temporary aquatic habitats surrounding the south-eastern rim of the Lake Eyre drainage basin in the harsh inland of Australia. This study describes the desert goby's respiratory and metabolic responses to hypoxic conditions and its use of buccal air bubbles for gas exchange at the water surface. Oxygen consumption for C. eremius is significantly higher in water than in air under normoxic and hypoxic conditions. In water, total oxygen consumption (V(O(2))) increases from normoxic conditions (253 microl g(-1) h(-1)) to 8% ambient O(2) concentration (377 microl g(-1) h(-1)), then decreases with increasing hypoxia of 4% O(2) (226 microl g(-1) h(-1)) and at 2% O(2) (123 microl g(-1) h(-1)). In air (fish were moist but out of water), V(O(2)) progressively decreases from normoxic conditions to hypoxic conditions (21% O(2), V(O(2)) is 169 microl g(-1) h(-1) to 39 microl g(-1) h(-1) at 2% O(2)). These data indicate oxygen-conforming patterns with increasing hypoxia both in air and in water below 8% O(2). In water, opercular movement rates remain unchanged with increasing hypoxia (139 min(-1) at 21% O(2), 154 min(-1) at 8%, 156 min(-1) at 4% and 167 min(-1) at 2%) but in air, opercular movement rates are significantly lower than in water, corresponding with the lower metabolic rate (71 min(-1) at 21% O(2), 53 min(-1) at 8%, 96 min(-1) at 4% and 64 min(-1) at 2%). Chlamydogobius eremius can use a buccal air bubble for aerial O(2) uptake, most probably in response to increased aquatic hypoxia. In air, C. eremius relies more on the buccal bubble as an oxygen source with increasing hypoxia up to an ambient O(2) of 4% (7.1% of V(O(2)) at 21% O(2); 14.5% at 8% O(2); and 27.1% at 4% O(2)), then when the available supply of O(2) is further reduced, it decreases (15% of V(O(2)) at 2% O(2)) and respiration across the skin again makes a higher relative contribution. The Australian desert goby has a higher metabolic rate in higher salinities (336 microl g(-1) h(-1) in 35 ppt, 426 microl g(-1) h(-1) in 70 ppt) than in freshwater (235 microl O(2) g(-1) h(-1)), presumably because of the increased metabolic cost of osmoregulation. There was no significant difference in V(O(2)) for fish in air that had come from varying salinities.     

Ontogeny of energetics in leatherback (Dermochelys coriacea) and olive ridley (Lepidochelys olivacea) sea turtle hatchlings

Changes in activity related oxygen consumption were measured in leatherback and olive ridley sea turtle hatchlings over their first month after emergence from the nest. Leatherbacks emerged with 75-90 KJ of energy in the residual yolk for growth and activity whereas olive ridleys emerged with 45 KJ. In leatherbacks (n=8), resting mass-specific oxygen consumption rates decreased by 53% over the first post-hatching month (0.34+0.03 mL O(2) h(-1) g(-1) to 0.16+0.01 mL O(2) h(-1) g(-1), respectively), while for ridleys (n=8) the fall was 35% (0.20+0.03 mL O(2) h(-1) g(-1) to 0.13+0.01 mL O(2) h(-1) g(-1), respectively). Olive ridley factorial aerobic scope doubled (1.93+0.30 to 3.97+0.51) over the first month but there was no significant increase in leatherback factorial aerobic scope (1.39+0.21 to 1.60+0.13). Leatherback hatchlings gained on average 20% initial body mass (7.68+1.66 g) over the first week, with 70 to 80% of this increase due to water accumulation. Olive ridleys gained 14% (1.83+0.16 g) in initial mass over the first week of age. We propose that the differences in aerobic scope and energy reserves are related to differences in early life ecological stratagems of these species.     

Toxic effects of mercury on the hard clam,Meretrix lusoria,in various salinities

1. The 96-hr lc₅₀ values for juvenile hard clams, Meretrix lusoria, were 328, 392 and 194 μg/l Hg in 10, 20 and 30 ppt salinities at 25 ± 1°C, respectively; for adult hard clams 341 and 140 μg/l Hg in 20 and 30 ppt salinities, respectively.2. Acclimatizing the adult clams to low salinity of 10 ppt lessened the toxicity of mercury. However, juvenile animals appeared to be more sensitive to mercury poisoning after 96 hr exposure in 10 ppt salinity.3. All embryos exposed to 40 μg/l Hg and above died within 30 hr. In the control, 44% of hatched embryos had developed into D-stage larvae, while those exposed to 20 μg/l Hg were still in the trochophore stage. Most of the retarded larvae developed into abnormal forms within 30 hr at 28°C in 15 ppt salinity.4. In order to maintain water quality and protect natural resources, the recommended safe level of mercury is 0.046 (0.039–0.053) μg/l Hg, based on the estimated 30-hr EC₅₀ for the clam embryos, with an application factor of 0.01.     

Effect of cadmium on survival,osmoregulation and gill structure of the Sunda prawn,Macrobrachium sintangense (de Man), at different salinities

The prawn Macrobrachium sintangense is likely to be subjected to occasional exposure to combined metal and saline stressors in its natural environment. This research evaluated the acute toxicity (96?h LC₅₀) of cadmium (Cd) on the prawn M. sintangense, with respect to the osmoregulatory capacity (OC) of prawns and to document histological changes in the gills after exposure to sublethal Cd concentrations at different salinities. The 96?h LC₅₀ of Cd to M. sintangense decreased with increasing salinity. The 96?h LC₅₀ values were 89.12 (72.53–109.50), 681.26 (554.20–837.46) and 825.37 (676.99–1006.27) μg CdL^?1 at 0, 10 and 20 ppt, respectively. The OC of prawns exposed to 30?μg?CdL^?1 at 0 ppt and to 300?μg?CdL^?1 at10 ppt decreased significantly compared with that of control prawns exposed to 0 and 10 ppt respectively. Swelling, hyperplasia and necrosis of gill lamellae resulting in the loss of marginal canals were observed in the gills of prawns exposed to 30?μg?CdL^?1 at 0 ppt and to 300?μg?CdL^?1 at 10 ppt for 7?days.     

The effects of temperature and salinity on the swimming ability of whiteleg shrimp, Litopenaeus vannamei

Swimming endurance of whiteleg shrimp, Litopenaeus vannamei exposed to various temperatures (15, 20, and 25 degrees C) and salinities (15, 32, and 40 per thousand) was determined in a swimming channel against one of five flow velocities (5.41, 6.78, 8.21, 10.11, and 11.47 cm s(-1)) for up to 9000 s. No shrimp swam the full 9000 s throughout the experiment. The swimming endurance decreased as swimming speed was increased at any of the temperatures and salinities tested and was significantly affected by temperature and salinity (P<0.05). The power model (nu x t(b) = a) showed a better fit to the relationship between swimming endurance (t, in s) and swimming speed (nu, in cm s(-1)) at any of the temperatures and salinities tested. The swimming ability index (SAI), defined as SAI = integral(0)(9000) vdt x 10(-4) (cm), was found to be temperature- and salinity-dependent in L. vannamei. The optimum temperature and salinity and corresponding maximum SAI were Topt = 21.3 degrees C and SAI(max21.3) = 7.37 cm; Sopt = 27.6 per thousand and SAI(max27.6) = 7.47 cm, respectively. The range of temperatures and salinities within which SAI is >90% of the maximum was estimated between 17.6 and 24.9 degrees C and between 18.5 and 36.7 per thousand, respectively. The results suggest that the power model fits well to the observed endurance estimates and the SAI is a good index to quantitatively describe the overall swimming ability of L. vannamei. Furthermore, temperature and salinity can limit the swimming performance of L. vannamei.     

Survival and development of horseshoe crab (Limulus polyphemus) embryos and larvae in hypersaline conditions

The horseshoe crab Limulus polyphemus spawns in the mid- to upper intertidal zone where females deposit eggs in nests below the sediment surface. Although adult crabs generally inhabit subtidal regions of estuaries with salinities from 5 to 34 ppt, developing embryos and larvae within nests are often exposed to more extreme conditions of salinity and temperature during summer spawning periods. To test whether these conditions have a negative impact on early development and survival, we determined development time, survival, and molt cycle duration for L. polyphemus embryos and larvae raised at 20 combinations of salinity (range: 30-60 ppt) and temperature (range: 25-40 degrees C). Additionally, the effect of hyperosmotic and hypoosmotic shock on the osmolarity of the perivitelline fluid of embryos was determined at salinities between 5 and 90 ppt. The embryos completed their development and molted at salinities below 60 ppt, yet failed to develop at temperatures of 35 degrees C or higher. Larval survival was high at salinities of 10-70 ppt but declined significantly at more extreme salinities (i.e., 5, 80, and 90 ppt). Perivitelline fluid remained nearly isoosmotic over the range of salinities tested. Results indicate that temperature and salinity influence the rate of crab development, but only the extremes of these conditions have an effect on survival.     

Influence of swimming speed on metabolic rates of juvenile pacific bluefin tuna and yellowfin tuna

Bluefin tuna are endothermic and have higher temperatures, heart rates, and cardiac outputs than tropical tuna. We hypothesized that the increased cardiovascular capacity to deliver oxygen in bluefin may be associated with the evolution of higher metabolic rates. This study measured the oxygen consumption of juvenile Pacific bluefin Thunnus orientalis and yellowfin tuna Thunnus albacares swimming in a swim-tunnel respirometer at 20 degrees C. Oxygen consumption (Mo2) of bluefin (7.1-9.4 kg) ranged from 235+/-38 mg kg(-1) h(-1) at 0.85 body length (BL) s(-1) to 498+/-55 mg kg(-1) h(-1) at 1.80 BL s(-1). Minimal metabolic rates of swimming bluefin were 222+/-24 mg O(2) kg(-1) h(-1) at speeds of 0.75 to 1.0 BL s(-1). Mo2 of T. albacares (3.7-7.4 kg) ranged from 164+/-18 mg kg(-1) h(-1) at 0.65 BL s(-1) to 405+/-105 mg kg(-1) h(-1) at 1.8 BL s(-1). Bluefin tuna had higher metabolic rates than yellowfin tuna at all swimming speeds tested. At a given speed, bluefin had higher metabolic rates and swam with higher tailbeat frequencies and shorter stride lengths than yellowfin. The higher M dot o2 recorded in Pacific bluefin tuna is consistent with the elevated cardiac performance and enhanced capacity for excitation-contraction coupling in cardiac myocytes of these fish. These physiological traits may underlie thermal-niche expansion of bluefin tuna relative to tropical tuna species.     

Effects of environmental hypoxia on oxygen consumption rate and swimming activity in juvenile white sturgeon, Acipenser transmontanus, in relation to temperature and life intervals

Routine oxygen consumption rates (MO₂) and swimming activity rates of juvenile white sturgeon were determined using closed respirometers at life-interval-appropriate temperatures: 10° C (0.2 g mean wet weight), 16° C (1.9 g mean wet weight), and 20° C (63.1 g mean wet weight) under normoxic (PO₂ > 140 mmHg) and moderately hypoxic (PO₂=80 ± 5.0 mmHg) water conditions. At all temperatures and body sizes, hypoxia significantly depressed (p < 0.05) MO₂ (57% mean reduction) and swimming activity (70% mean reduction). Overall mean MO₂ was 228 µg O₂ g^-1 wet weight h^-1 (normoxia) and 99 µg O₂ g^-1 wet weight h^-1 (hypoxia). Thus, juvenile white sturgeon appear to decrease overall energy expenditures (hypometabolism) during hypoxia via reductions in spontaneous swimming activity. This is a life style that may increase survival during widespread or prolonged environmental hypoxia.     

Effect of salinity on osmoregulatory patch epithelia in gills of the blue crab Callinectes sapidus

In euryhaline crabs, ion-transporting cells are clustered into osmoregulatory patches on the lamellae of the posterior gills. To examine changes in the branchial osmoregulatory patch in the blue crab Callinectes sapidus in response to change in salinity and to correlate these changes with other osmoregulatory responses, crabs were acclimated to a range of salinities between 10 and 35 ppt. When crabs that had been acclimated to 35 ppt were subsequently transferred to 10 ppt, both the size of the osmoregulatory patch on individual gill lamellae and the specific activity of Na+, K+-ATPase in whole-gill homogenates increased only after the first 24 h of exposure to dilute seawater. Enzyme activity and size of patch area increased gradually and reached their maxima (increasing by 200% and 60%, respectively) 6 days following transfer to 10 ppt seawater and then remained at these levels. Patch size at acclimation varied inversely with the salinity for seawater dilutions below 26 ppt (the isosmotic point of the crab), although it did not vary in salinities at or above 26 ppt. Thus, the size of the patch clearly is modulated with acclimation salinity, but it increases only in those salinities in which the crab hyperosmoregulates. An increase in the total RNA/DNA ratio in gill homogenates, the lack of mitotic figures in the lamellae, and the lack of incorporation of bromodeoxyuridine into nuclei of lamellar epithelial cells during acclimation to dilute seawater were interpreted as evidence that no cell proliferation had occurred and that increases in the size of the osmoregulatory patch occurred through differentiation of existing gas exchange cells or of undifferentiated epithelial cells into ion-transporting cells.     

Physiological and behavioral responses of the mud snails Hydrobia glyca and Hydrobia ulvae to extreme water temperatures and salinities: implications for their spatial distribution within a system of temperate lagoons

Physiological responses (oxygen consumption) and behavioral responses (feeding and activity) of the mud snails Hydrobia ulvae and Hydrobia glyca at different salinities (20 per thousand-80 per thousand) and temperatures (20 degrees and 30 degrees C) were studied. After 24 h under experimental conditions, both Hydrobia species already showed maximal activities (>90%) for a wide salinity range (30 per thousand-70 per thousand), with significant differences in activity between species only outside the usual salinity range of the studied lagoon. In contrast, egestion rates of H. glyca were significantly higher at the lowest salinities tested (30 per thousand and 40 per thousand) irrespective of water temperature, whereas egestion rates of H. ulvae were always significantly higher (57% on average) at 20 degrees C than at 30 degrees C and at the usual salinities found in the field (40 per thousand and 50 per thousand). Both species showed an oxyregulatory response to dissolved oxygen concentrations ranging from saturation to 1.5 mg O(2) L(-1), although specific oxygen consumption rates were significantly higher at 30 degrees C than at 20 degrees C (Q(10)=1.47+/-0.08 for H. ulvae and Q(10)=12.1+/-0.06 for H. glyca) and at the lowest salinities (30 per thousand-50 per thousand for H. ulvae and 30 per thousand-40 per thousand for H. glyca). On average, specific rates were higher for the smaller-sized H. glyca (1.64+/-0.03 microg O(2) mg(-1) ash-free dry weight [AFDW]) than for H. ulvae (1.35+/-0.03 microg O(2) mg(-1) AFDW). Despite the overlapping of their tolerances to high temperatures and salinities, the observed interspecies differences could play a certain role in the distribution of H. ulvae and H. glyca in the studied habitat. In particular, the decreasing feeding activity but increasing respiration of H. ulvae at 30 degrees C for salinities that usually occur in the studied lagoon could represent disadvantages to H. glyca during the warm period.     

The increase in human plasma antioxidant capacity after apple consumption is due to the metabolic effect of fructose on urate, not apple-derived antioxidant flavonoids

Regular fruit consumption lowers the risk of cardiovascular diseases and certain cancers, which has been attributed in part to fruit-derived antioxidant flavonoids. However, flavonoids are poorly absorbed by humans, and the increase in plasma antioxidant capacity observed after consumption of flavonoid-rich foods often greatly exceeds the increase in plasma flavonoids. In the present study, six healthy subjects consumed five Red Delicious apples (1037 +/- 38 g), plain bagels (263.1 +/- 0.9 g) and water matching the carbohydrate content and mass of the apples, and fructose (63.9 +/- 2.9 g) in water matching the fructose content and mass of the apples. The antioxidant capacity of plasma was measured before and up to 6 h after food consumption as ferric reducing antioxidant potential (FRAP), without or with ascorbate oxidase treatment (FRAPAO) to estimate the contribution of ascorbate. Baseline plasma FRAP and FRAPAO were 445 +/- 35 and 363 +/- 35 microM trolox equivalents, respectively. Apple consumption caused an acute, transient increase in both plasma FRAP and FRAPAO, with increases after 1 h of 54.6 +/- 8.7 and 61.3 = 17.2 microM trolox equivalents, respectively. This increase in plasma antioxidant capacity was paralleled by a large increase in plasma urate, a metabolic antioxidant, from 271 +/- 39 microM at baseline to 367 +/- 43 microM after 1 h. In contrast, FRAP and FRAPAO time-dependently decreased after bagel consumption, together with urate. Consumption of fructose mimicked the effects of apples with respect to increased FRAP, FRAPAO, and urate, but not ascorbate. Taken together, our data show that the increase in plasma antioxidant capacity in humans after apple consumption is due mainly to the well-known metabolic effect of fructose on urate, not apple-derived antioxidant flavonoids.     

Selenium status in psoriasis and its relationship with alcohol consumption

The aim of the study was to examine the influence of alcohol consumption on the severity of psoriasis and selenium (Se) concentration and Se-dependent gluathione peroxidase activity in plasma (pl-GSH-Px) and in erythrocytes (RBC-GSH-Px) in psoriatic patients. Thirty-five in-patients with psoriasis lasting <10 mo and 42 with psoriasis lasting >3 yr constituted groups 1 and 2, respectively. The severity of psoriasis was assessed using the PASI scoring system and the consumption of alcohol, using a structured questionnaire. The Se concentration was 47.11±11.61 μg/L in group 1 and 38.69±13.22 μg/L in group 2 (p<0.05), the pl-GSH-Px was 0.15±0.04 U/mL and 0.14±0.04 U/mL (p>0.05), and the RBC-GSH-Px was 13.97±4.27 U/g Hb and 13.16±3.85 U/g Hb (p>0.05), respectively. In excessive drinkers (<10% of patients, all males), the Se concentration was 32.84±10.88 μg/L, the pl-GSH-Px was 0.15±0.03 U/mL, and the RBC-GSH-Px was 11.64±3.32 U/g Hb. A low RBC-GSH-Px correlated to the consumption of high-grade alcoholic beverages (R=−0.45, p<0.05) and to the PASI value (R=−0.37, p<0.05) in group 2. Depressed Se concentration and Se-dependent GSH-Px can be related to the severity and a duration of psoriasis. The excessive consumption of alcohol is associated with severity of the disease and with low activity of GSH-Px in erythrocytes in patients with long-lasting psoriasis.     

The effects of temperature and swimming speed on instantaneous fuel use and nitrogenous waste excretion of the Nile tilapia.

The effects of acclimation temperature (30 degrees, 20 degrees, and 15 degrees C) and swimming speed on the aerobic fuel use of the Nile tilapia (Oreochromis niloticus; 8-10 g, 8-9-cm fork length) were investigated using a respirometric approach. As acclimation temperature was decreased from 30 degrees C to 15 degrees C, resting oxygen consumption (Mo2) and carbon dioxide excretion (Mco2) decreased approximately twofold, while nitrogenous waste excretion (ammonia-N plus urea-N) decreased approximately fourfold. Instantaneous aerobic fuel usage was calculated from respiratory gas exchange. At 30 degrees C, resting Mo2 was fueled by 42% lipids, 27% carbohydrates, and 31% protein. At 15 degrees C, lipid use decreased to 21%, carbohydrate use increased greatly to 63%, and protein use decreased to 16%. These patterns at 30 degrees C and 15 degrees C in tilapia paralleled fuel use previously reported in rainbow trout acclimated to 15 degrees C and 5 degrees C, respectively. Temperature also had a pronounced effect on critical swimming speed (UCrit). Tilapia acclimated to 30 degrees C had a UCrit of 5.63+/-0. 06 body lengths/s (BL/s), while, at 20 degrees C, UCrit was significantly lower at 4.21+/-0.14 BL/s. Tilapia acclimated to 15 degrees C were unable or unwilling to swim. As tilapia swam at greater speeds, Mo2 increased exponentially; Mo2min and Mo2max were 5.8+/-0.6 and 21.2+/-1.5 micromol O2/g/h, respectively. Nitrogenous waste excretion increased to a lesser extent with swimming speed. At 30 degrees C, instantaneous protein use while swimming at 15 cm/s ( approximately 1.7 BL/s) was 23%, and at UCrit (5.6 BL/s), protein use dropped slightly to 17%. During a 48-h swim at 25 cm/s (2.7 BL/s, approximately 50% UCrit), Mo2 and urea excretion remained unchanged, while ammonia excretion more than doubled by 24 h and remained elevated 24 h later. These results revealed a shift to greater reliance on protein as an aerobic fuel during prolonged swimming.     

Cost of transport and optimal swimming speed in farmed and wild European silver eels (Anguilla anguilla)

A swimming speed of 0.4 meters per second (m s(-1)) is the minimal speed for European female silver eels to reach the spawning sites in the Sargasso Sea in time. As silver eels cease feeding when they start their oceanic migration, the cost of transport (COT) should be minimised and the swimming speed optimised to attain the highest energetic efficiency. In this study, we have investigated the optimal swimming speed (U(opt)) of silver eels since U(opt) may be higher than the minimal swimming speed and is more likely to resemble the actual cruise speed. A variety of swimming tests were performed to compare endurance swimming between farmed eels and wild eels, both in freshwater and in seawater. The swimming tests were run with 101 silver female eels (60-96 cm, 400-1500 g) in 22 Blazka-type swim tunnels in a climatised room at 18 degrees C with running freshwater or seawater. Tests were run at 0.5-1.0 m s(-1) with increments of 0.1 m s(-1), and either 2 h or 12 h intervals. Remarkably, both tests revealed no changes in oxygen consumption (M O2) and COT over time. U(opt) values ranged between 0.61 and 0.68 m s(-1) (0.74-1.02 BL s(-1)) for the different groups and were thus 53-70% higher than the minimal speed. At U(opt), the COT was 37-50 mg O2 kg(-1) km(-1). These relatively very low values confirm our earlier observations. COT values in seawater were about 20% higher than in freshwater. Assuming that migrating female silver eels cruise at their U(opt), they will be able to cover the distance to the Sargasso Sea in 3-4 months, leaving ample time for final maturation and finding mates.     

Hemolymph patterns of free amino acids in the brine shrimp Artemia franciscana after three days starvation at different salinities

The hemolymph pattern of free amino acids was examined in the brine shrimp, Artemia franciscana (Great Salt Lake origin). After one-month acclimation to 35 or 60 ppt salinity at 27 degrees C, the animals were transferred to 10, 35 or 60 ppt salinities to continue acclimation for 3 days without feeding at 27 degrees C. The osmolarity of one of the new media was raised by glycerol addition. In the hemolymph, 8 amino acids such as taurine, alanine, threonine, serine, lysine, glycine, arginine and leucine, comprised approximately 70% of the total content of free amino acids. This pattern suggested internal proteolysis due to starvation at high temperature. The total content of free amino acids significantly increased at 10 and 60 ppt salinities in comparison to 35 ppt. The hemolymph patterns from the 10 ppt and glycerol-added media showed a singularly high peak of taurine or alanine.     

Postprandial intestinal blood flow, metabolic rates, and exercise in Chinook salmon (Oncorhynchus tshawytscha)

Following a relatively large meal (2% body mass of dry pellets), intestinal blood flow in chinook salmon (Oncorhynchus tshawytscha) increased significantly, up to 81%, between 14 and 29 h postprandially. Also, 15 h postprandially, oxygen consumption (M(2)) was elevated by 128% compared with a measurement of routine M(2) made after 1 wk of fasting. The postprandial increase in MO(2) (the heat increment) was 33 micromol O(2) min(-1) kg(-1). Because intestinal blood flow is known to decrease during swimming activity in fish, we therefore tested the hypothesis that swimming fish would have to make a trade-off between maximum swimming activity and digestive activity by comparing the swimming performance and metabolic rates of fed and fasted chinook salmon. As expected, MO(2) increased exponentially with swimming velocity in both fed and fasted fish. Moreover, the heat increment was irreducible during swimming, such that MO(2) remained approximately 39 micromol O(2) min(-1) kg(-1) higher in fed fish than in fasted fish at all comparable swimming speeds. However, maximum M dot o2 was unaffected by feeding and was identical in both fed and fasted fish (approximately 250 micromol O(2) min(-1) kg(-1)), and, as a result, the critical swimming speed (U(crit)) was 9% lower in the fed fish. Three days after the fish were fed and digestion was completed, MO(2) and U(crit) were not significantly different from those measured in fasted fish. The ability of salmonids to maintain feeding metabolism during prolonged swimming performance is discussed, and it is suggested that reduced swimming performance may be due to postprandial sparing of intestinal blood to support digestion, thereby limiting the allocation of blood flow to locomotory muscles.     

Behavioral aspects of cold tolerance in blackchin tilapia,Sarotherodon melanotheron,at different salinities

Synopsis Cold tolerance and behavioral responses of blackchin tilapia, Sarotherodon melanotheron, to rapidly decreasing temperatures were investigated at salinities of 5, 15, and 35 parts per thousand (ppt). Cold tolerance did not significantly differ with salinity or social rank. Mean temperatures were 10.7° C for beginning loss of equilibrium, 9.6° C for complete loss of equilibrium, and 6.9° C for death at all salinities. Behavioral activity declined with decreasing temperature and ceased between 10–12° C. Certain behavioral actions were significantly more frequent at 15 or 35 ppt salinity than at 5 ppt. The northward range expansion by introduced populations of the blackchin tilapia in the United States probably will be limited by its lower lethal temperature limits, but may also be affected by temperatures at which social behavior becomes disrupted.     

Fatty acid and lipid class composition in eyes and brain from teleosts and elasmobranchs

The effect of 17beta-estradiol (E(2)) on osmoregulatory performance was examined in the euryhaline killifish, Fundulus heteroclitus. Fish were injected once with 1, 2 and 5 microg g(-1) E(2) and, 6 h after injection, transferred from 1 ppt seawater (SW) to full strength SW (40 ppt) or from SW to 1 ppt SW. In another set of experiments, fish were injected four times on alternate days with 2 microg g(-1) E(2) and then, 6 h after the last injection, transferred from 1 ppt SW to SW or from SW to 1 ppt SW. Fish were sampled 18 h after transfer (i.e., 24 h post-injection), and plasma osmolality, Na(+) and Cl(-) concentration and gill K(+)-pNPPase activity (a reflection of the sodium pump) were examined. Transfer from 1 ppt SW to SW resulted in significantly increased plasma osmolality, but did not affect gill K(+)-pNPPase activity. A single dose of E(2) (1, 2 and 5 microg g(-1)) prior to transfer from 1 ppt SW to SW increased plasma osmolality and decreased gill K(+)-pNPPase activity in a dose-dependent manner. Prolonged treatment with E(2) increased plasma osmolality and decreased gill K(+)-pNPPase activity in 1 ppt SW-adapted fish. Transfer of fish thus treated from 1 ppt SW to SW increased plasma osmolality and did not alter gill K(+)-pNPPase activity. Transfer from SW to 1 ppt SW had no significant effect on plasma osmolality or gill K(+)-pNPPase activity. Only the highest single dose of E(2) (5 microg g(-1)) prior to transfer from SW to 1 ppt SW decreased gill K(+)-pNPPase activity. Prolonged treatment with 2 microg g(-1) E(2) decreased gill K(+)-pNPPase activity only following transfer from SW to 1 ppt SW. The results substantiate an inhibitory action of E(2) on hypoosmoregulatory capacity in this euryhaline teleost.