Elasmobranch pericardial function. 1. Pericardial pressures are not always negative

Acute studies have led to the generalization that negative pericardial pressure is necessary for optimal cardiac function in elasmobranchs. We chronically instrumented horn sharks with pericardial catheters to test the hypothesis that ejection of pericardial fluid through the pericardioperitoneal canal (PPC) during routine handling could have accounted in part for previous measurements of exclusively negative pressures (–0.3 to –9.1 cm H₂O) in elasmobranchs. Maximum and minimum pericardial pressures measured immediately following routine handling (acute pressures) were more negative than those measured in resting horn sharks at intervals from 1 to 27 days following handling (chronic pressures). Chronic pericardial pulse pressure was less than acute. Entirely positive pericardial pressures were observed on occasion. Handling of chronically catheterized horn sharks resulted in ejection of 21 per cent (range=10–26, n=5) of the initial pericardial fluid volume through the PPC and reduced pericardial pressure. Operating pericardial fluid volume of horn sharks averaged 2.0 ml.kg^–1 (range=1.6–2.6, n=9). The PPC opened after 4.3±0.2 ml.kg^–1 (x±S.E.) of elasmobranch saline had been slowly infused into the pericardium, corresponding to an average pressure of 1.3±0.2 cm H₂O (n=10). The presence of the PPC plus a comparatively large pericardial fluid volume allows horn sharks to regulate pericardial pressure. Our analysis of pericardial pulse pressure, which can be an index of cardiac activity, suggests in contrast to previous studies that the elasmobranch heart can have relatively high stroke volumes at pericardial pressures near ambient. Thus, for venous return in resting or even moderately active elasmobranchs, it is more important that pericardial pressure be pulsatile than at a mean level which is negative.     

Regulation of cardiac function in the horn shark by changes in pericardial fluid volume mediated through the pericardioperitoneal canal

The California horn shark (Heterodontus francisci), instrumented with a pericardial catheter and a ventral-aortic flow probe, was studied to determine the effect of complete pericardial chamber evacuation on the time course for restitution of pericardial fluid-volume and pressure, and the effects of both fluid removal and its restitution on cardiac output. Prior to evacuation, pericardial pressure was –0.02±0.02 kPa, and cardiac output was 18±2 ml min^–1 kg^–1. Evacuation reduced pericardial pressure to –0.73±0.14 kPa, and increased cardiac output to 23±4 ml min^–1 kg^–1. The time course for restoration of post-evacuation pressure is described by a non-linear asymptotic function. A large percentage of the pericardial pressure and volume recovery occurred within the first hour, while, complete restoration of pre-withdrawal conditions required about 11 h. Pericardial pressure-volume relationships, determined by incremental infusion of small volumes of elasmobranch saline into the pericardium, confirm previous findings that the operating pericardial pressure in the horn shark is at or near ambient pressure and that both pericardial fluid volume and cardiac stroke volume influence horn shark pericardial pressure.     

Elasmobranch pericardial function 2. The influence of pericardial pressure on cardiac stroke volume in horn sharks and blue sharks

The importance of negative pericardial pressure to heart function in clasmobranchs has been questioned due to the discovery of positive pericardial pressures in healthy horn sharks (Heterodontus francisci). We therefore implanted electromagnetic flow probes on the ventral aorta of horn sharks and blue sharks (Prionace glauca) and assessed stroke volume and pericardial pressure as pericardial fluid volume (PFV) was varied to test the hypothesis that elasmobranchs are capable of maintaining a relatively large stroke volume at pericardial pressures near and above ambient. Stroke volume was maximum between zero and 25% maximum PFV (maximum PFV: the volume of pericardial fluid required to open the pericardioperitoneal canal), where pericardial pressure was most negative. At 50% maximum PFV (pericardial pressure near or slightly above ambient) stroke volume was 70% and 98% of its maximum in horn sharks and blue sharks, respectively. At a larger PFV, stroke volume declined drastically, reaching zero where both PFV and pericardial pressure were maximum. Thus, at a pericardial pressure apparently associated with resting or mild activity, stroke volume is a relatively large proportion of the apparent maximum. Increased circulatory demands associated with strenuous activity may induce ejection of pericardial fluid through the perieardioperitoneal canal, which then lowers pericardial pressure. The lowered pericardial pressure causes an increase in stroke volume, indicating that control is in part effected by changing pericardial pressure.     

Effects of Chronic Aluminum Exposure on Swimming and Cardiac Performance in Rainbow Trout, <Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>

Rainbow trout were exposed to 0–80 μg l⁻¹ aluminum (Al) at pH 5.2 in synthetic soft water, for up to 8 weeks. Trout were submitted to an incremental swimming test to quantify their aerobic swimming capacity (U_crit). After a simple, non-invasive cardiac surgery to install Doppler flow probes, their heart rate, cardiac output and stroke volume were measured while swimming at increasing water velocities. Fish exposed to Al accumulated significant amounts of Al at the gills (0–80 μg g⁻¹) and in their liver (5–60 μg g⁻¹) and had decreases in swimming capacity, ranging from 11 to 21%. Analysis of cardiac parameters during swimming revealed that increases in heart rate were used in trout exposed to the highest concentrations of Al to increase cardiac output, whereas control fish tended to increase cardiac output through increases in stroke volume.     

The effect of demand feeding on swimming speed and feeding responses in Atlantic salmon Salmo salar L., gilthead sea bream Sparus aurata L. and European sea bass Dicentrarchus labrax L. in sea cages

Abstract Using underwater cameras, data were collected on the feeding behaviour and swimming speeds of Atlantic salmon Salmo salar L., gilthead sea bream Sparus aurata L. and European sea bass Dicentrarchus labrax L. in sea cages. Comparisons were made between the behaviours of fish fed on demand using interactive feedback systems and those of fish fed under the standard feeding practice of each farm (control). In all three species, swimming speeds were similar before feeding , but they were significantly higher in the control regimes during feeding. When fed on demand, sea bass had reduced swimming speed just before and during feeding compared with that observed during the non‐feeding periods. Higher proportions of feeding fish were observed in the control regime cages than in fish fed on demand for all three species, indicating a greater feeding intensity during meals in the control regimes. This was further supported by observations of an increase in the density of sea bass in the upper water in the control cages during feeding. The results suggest decreased levels of competition between the on demand‐fed fish during feeding, which might be hypothesized to lead to improved growth and production efficiency in aquaculture.     

Performance of the heat of the hagfish,Eptatretus cirrhatus

The maximum power output of isolated perfused ventricles of the hafish (Eptatretus cirrhatus) averaged 0.367±0.031 mW g^–1 (n=9), considerably high than estimates for the heart of the Atlantic hagfish (Myxine glutinosa). Maximal minute volumes averaged 21.55±1.28 ml min^–1kg^–1, with a mean stroke volume of 0.71±0.14 ml kg^–1 body weight, values which are similar to those reported for many teleost and elasmobranch hearts.Ventricular output showed the characteristic dependence upon atrial filling pressure up to an optimum filling pressure ofc. 4 mm Hg. At output pressures exceeding 14 mm Hg the stroke volume and power output fell sharply. At these afterloads, the ventral aorta remained distended following semilunar valve closure and so the volume of fluid ejected on ventricular systole was reduced. There was little change in the frequency of the heart as either input or output pressures were varied.     

Regulation of cardiac output and gut blood flow in the sea raven,Hemitripterus americanus

Coeliac artery blood flow (F_ca) before and after feeding was recorded in the sea raven. To obtain basic information about the scope of cardiovascular adjustment in the sea raven, a separate series of experiments was performed, in which ventral (P_va), and dorsal (P_da) aortic blood pressure, heart rate (HR) and cardiac output (jaz) were monitored during rest and encouraged exercise.Measurements of coeliac artery flow showed that visceral blood flow is substantial, particularly after feeding, and variations in the visceral vascular conductance affect P_da directly. Simultaneous recordings of intestinal and dorsal aortic blood pressures showed no measurable difference in the two arterial pressures, refuting the idea of a vascular control at the level of the main coeliac artery. Thus, in the sea raven, the adrenergic tonus affecting the visceral vasculature presumably acts at the arteriolar level.Sea ravens encouraged to exercise increased theirjaz by 64%; 32% through HR and 25% through stroke volume. The increase injaz during encouraged exercise was sufficient to produce an elevation of both P_va and P_da, despite an increase of systemic vascular conductance, -adrenoceptor blockade with sotalol, however, severely impaired the increase injaz during exercise, and the change in P_da was reversed.During rest there were both an adrenergic and a cholinergic tonus affecting the HR, as revealed by the effects of injected pharmacological antagonists. Swimming activity decreased the cholinergic tonus, while the adrenergic tonus increased.     

Influence of exercise on the distribution of enzymes in trout white muscle and kinetic properties of AMP-deaminase from free and bound fractions

Effects of exercise on the distribution of phosphofructokinase (PFK), fructose-1,6-biphosphatase (FBPase), and AMP-deaminase between free and particulate-bound fractions was analyzed in white skeletal muscle of rainbow trout Oncorhynchus mykiss. With a widely used technique for the separation of free and bound enzyme fractions (homogenization in low ionic strength, high sucrose buffer), the data showed that the amount of bound PFK increased from 64 to 95% during burst swimming whereas other enzymes were unaffected. Since this data for AMP-deaminase contrasted with earlier reports, different methods of separating free and bound enzyme were evaluated. A clear effect of exercise on AMP-deaminase binding occurred when high ionic strength media (either KCl or KF) were used; in extraction media containing 150 mM KCl, the percent bound rose from 30% in controls to 97% after 1 min burst swimming. Exercise also produced stable changes to AMP-deaminase kinetic properties, including for the bound enzyme (compared with the free) a 2-fold higher K_m AMP, a 3-fold higher K_i for inorganic phosphate, and a 60% increase in K_a ADP after 1 min burst exercise. The data suggest that AMP-deaminase in working skeletal muscle is subject to combined controls by allosteric effectors, post-translational modification, and distribution between free and bound states.     

Mortality due to a retained circle hook in a longfin mako shark Isurus paucus (Guitart‐Manday)

A female longfin mako shark Isurus paucus (Guitart‐Manday, 1966) was found moribund on the Atlantic Ocean beach near Canaveral National Seashore, Florida; the shark died shortly after stranding. Macroscopic lesions included a partially healed bite mark on the left pectoral fin, a clefted snout, pericardial effusion and a pericardial mass surrounding a 12/0 circle fishing hook. The heart, pericardial mass, gills, ovary, oviduct, shell gland, epigonal organ, liver, kidney and intrarenal and interrenal glands were processed for histopathology and examined by brightfield microscopy. Microscopic examination revealed chronic proliferative and pyogranulomatous pericarditis and myocarditis with rhabdomyolysis, fibrosis and thrombosis; scant bacteria and multifocal granular deposits of iron were found intralesionally. In addition, acute, multifocal infarcts within the epigonal organ and gill filaments were found in association with emboli formed by necrocellular material. The ovary had high numbers of atretic follicles, and the liver had diffuse, severe hepatocellular degeneration, multifocal spongiosis and moderate numbers of melanomacrophage cells. This report provides evidence of direct mortality due to systemic lesions associated with retained fishing gear in a prohibited shark species. Due to the large numbers of sharks released from both recreational and commercial fisheries worldwide, impact of delayed post‐release mortality on shark populations is an important consideration.     

An analysis of the energetic cost of the branchial and cardiac pumps during sustained swimming in trout

Experimental data are available for the oxygen cost of the branchial and cardiac pumps in fish. These data were used to theoretically analyze the relative oxygen cost of these pumps during rest and swimming in rainbow troutSalmo gairdneri. Efficiency of the heart increases with activity and so the relative oxygen cost of the cardiac pumps decreased from 4.6% at rest to 1.9% at the critical swimming speed. The relative oxygen cost of the branchial pump is significant in the resting and slowly swimming fish, being 10 to 15% of total oxygen uptake. However, when swimming trout switch to a ram mode of ventilation, a considerable saving in oxygen cost is accrued by switching the cost of ventilation from the branchial to the tail musculature. Thus, the relative oxygen cost of the branchial and cardiac pumps actually decreases at critical swimming speed compared to rest and therefore is unlikely to be a major limiting factor in maximum oxygen delivery to the tissues.     

Efficacy of feeding tiger puffer Takifugu rubripes on moon jellyfish with respect to nutritional composition and behavioural traits

Although jellyfish blooms are serious nuisances for fisheries and other industries, the utilization and nutritional value of by‐catch jellyfish has drawn public attention. Here, we evaluated the efficacy of feeding tiger puffer Takifugu rubripes with moon jellyfish Aurelia sp. using 20‐day rearing experiments. Feeding on jellyfish had no positive effect on growth performance, although it significantly reduced neutral lipids and increased proportions of polar lipids, n?3 and n?6 highly unsaturated fatty acids (HUFAs), especially arachidonic and docosahexaenoic acids, and taurine. Supplemental feeding on jellyfish plus pellets elevated activity and responsiveness in the fish, with no effect on burst swimming speed or prevention of aggressive biting by siblings. The present research suggests that feeding on jellyfish improves body composition and some behaviours in tiger puffers. As cultured fish tend to accumulate excessive amounts of lipids from lipid‐rich pellets that can induce an unhealthy condition, and behavioural deficits of hatchery‐reared fish reduce survival after release in the wild, we propose the use of jellyfish as a supplemental diet in the nursery production of tiger puffer. Moreover, feeding on jellyfish can overcome deficiencies in alternative soy‐material feeds by supplying phospholipid, HUFAs, or taurine.     

Behaviour and physiology of mountain whitefish ( Prosopium williamsoni) relative to short‐term changes in river flow

Despite the growing recognition that river flow can have an effect on the growth, distribution and survival of fishes, little is known about the underlying mechanisms to explain this effect. Furthermore, there are few examples of integrated measures of behaviour and physiology to study the responses of fish to river hydrology. Here, axial swimming muscle electromyograms were logged as a sensitive indicator of activity from 19 mountain whitefish ( Prosopium williamsoni) across a large range of hourly discharge magnitudes (mean = 621 m³·s^?1, range = 0–1770 m³·s^?1) in a hydropeaking reach of the Columbia River, Canada. Hourly mean discharge had a significant positive effect on swimming muscle activity. However, a large amount of the variance was unexplained, possibly due to social interactions, feeding and/or flow‐refuging behaviours. Fluctuating flows were no more energetically costly than stable flows. Discharge magnitude had a significant positive effect on blood cortisol concentrations. Yet, cortisol concentrations were low overall (mean ± SD = 1.60 ± 0.09 ng·ml^?1), suggesting that the small observed response could be the result of routine physiological processes rather than a stress response per se. Based on low blood lactate concentrations, mountain whitefish were not swimming exhaustively (i.e., anaerobic burst‐type swimming) at high flows.     

Active metabolism in larval and juvenile fish: ontogenetic changes,effect of water temperature and fasting

Oxygen consumption, ammonia excretion and fish swimming speed were measured in fish induced to swim by optomotor reaction in a circular metabolism chamber. The relationship between the swimming speed and fish metabolism described by exponential equations allowed the extrapolation to the standard metabolism, i.e. at zero swimming speed. The partitioning of the catabolised protein in the energy supply was estimated based on AQ (volume of ammonia/ volume of oxygen) values. Weight specific standard metabolism, as expressed by the ammonia excretion rate, decreased by one order of magnitude in coregonids as the fish grew from 20 to 780 mg body weight. The slope of the relationship between oxygen uptake and swimming speed decreased in coregonid ontogenesis. In salmon, after 12 days of fasting 28% of energy used was derived from protein, whilst coregonid juveniles utilized mostly lipid. Active swimming in fasted juveniles of coregonid, as well as in salmon, led to the accelerated utilization of protein as a source of energy, based on AQ coefficients. In juveniles acclimated to a range of water temperatures from 14 to 26°C, the changes in standard or active metabolic rate (expressed as oxygen uptake or ammonia excretion) were described by Q₁₀ coefficients. They were generally higher for the ammonia excretion rate than for the oxygen uptake rate and for active metabolism than for standard metabolism. Utilization of protein as energy for swimming differed significantly between the species, being in general one order of magnitude higher in coregonids than in salmon. The use of protein for swimming activity tended to decrease during coregonid ontogenesis.     

不同运动状态下鳙幼鱼的游泳特性研究

为了探究鱼类反复运动疲劳后游泳能力和游泳行为的变化,以鳙(Aristichthys nobilis)幼鱼为研究对象,利用环形水槽实验装置,采用流速递增法,通过LoliTrack视频软件分析鱼类游泳行为,研究不同运动状态下鳙幼鱼的游泳特性变化情况。结果表明,鳙幼鱼疲劳前耗氧率随游泳速度的增大显著增加,且临界游泳速度恢复过程中最大耗氧率小于突进游泳速度恢复过程中最大耗氧率。视频分析显示,摆尾频率与游泳速度呈线性正相关关系。同时发现,在2组反复疲劳运动状态下,连续进行2次临界游泳速度测定过程中,鳙幼鱼频繁使用爆发-滑行游泳行为,而在经过突进游泳速度测试后转入临界游泳速度测定过程中,实验鱼并未使用这一游泳行为。经过一次临界游泳速度测试后,第二次临界游泳速度显著大于突进游泳速度测试后的临界游泳速度(P0.05),第一次突进游泳速度与第二次突进游泳速度无显著差异(P0.05)。无氧运动消耗导致鳙幼鱼有氧运动能力显著下降,而有氧运动消耗过程对无氧运动能力无显著影响。     

Developmental temperature stress and parental identity shape offspring burst swimming performance in sockeye salmon (Oncorhynchus nerka)

Abstract – The persistent effects of embryonic temperature stress and individual parentage on fry swimming performance were examined in a cross‐fertilisation experiment using sockeye salmon (Oncorhynchus nerka). A fixed‐velocity test of burst swimming was used to assess the endurance capacity and behavioural performance of individual fry from 10 offspring families incubated at 12, 14 or 16 °C to hatch and then reared through yolk absorption and exogenous feeding stages in a common posthatch environment (average 6.9 °C). Fry burst swim time (BST) was influenced by an interaction between incubation temperature and family identity. Average BST was longer for fry from the 12 °C prehatch treatment compared to 14 and 16 °C, although differences were largely attributable to temperature effects on average fry size. Behavioural observations revealed that fish incubated at 16 °C performed more poorly, having a larger proportion of individuals that required stimulation to swim, fatigued more frequently or were classified as ‘nonswimmers’. Within all three incubation temperature treatments, mean BST varied significantly among offspring families, independent of fry mass and length. An interesting relationship was observed within the 16 °C treatment, whereby families with higher survivorship were characterised with lower mean BSTs. Collectively, these findings demonstrate that exposure to high temperatures in early sockeye salmon development can result in persistent, parentally mediated effects on fry performance. As such, these results provide important insight into how elevated temperature events during egg incubation may affect early life history selection processes and survival in stages beyond when the stressor is experienced.     

Comparative Studies of the Proteolytic Activity of Crude Extracts from the Digestive Tract of Three Shark Species

Abstract

The level of pepsin, trypsin, chymotrypsin and leucine aminopeptidase (LAP) was measured in the digestive organs of Portuguese dogfish, leafscale gulper shark, and lowfin gulper shark. The highest pepsin activity was measured in the cardiac stomach. Trypsin was not detected in leafscale gulper shark, and chymotrypsin was mainly measured in the intestine. LAP was detected in all organs and species. The temperature optima of pepsin, trypsin and chymotrypsin were between 42 and 48°C and those of LAP in the 50-56°C range. Pepsin from Portuguese dogfish was considerably activated during pre-incubation. Trypsin, chymotrypsin and LAP from lowfin gulper shark were reasonably activated when pre-incubated but that was not evident in these proteases from Portuguese dogfish and leafscale gulper shark.     

Swimming depths of the giant jellyfish <Emphasis Type="Italic">Nemopilema nomurai</Emphasis> investigated using pop-up archival transmitting tags and ultrasonic pingers

The swimming depths of 12 individual Nemopilema nomurai with bell diameters of 0.8–1.6 m were investigated using pop-up archival transmitting tags and ultrasonic pingers, and the validity of the research method was evaluated. The N. nomurai studied frequently showed vertical movement, with the swimming depth ranging from 0 to 176 m, The mean swimming depths of most individuals were less than 40 m. The swimming depths of N. nomurai in the northern Japan Sea in the winter were mostly deeper than those of this species in the southern Japan Sea in the autumn. This result suggests that the range of the depths almost depends on the vertical structure of the ocean. Swimming depths during the nighttime were significantly deeper than those during the daytime. More specifically, during the daytime, the swimming depths in the afternoon tended to be shallower than those in the morning, while during the nighttime, the swimming depths after midnight were deeper than those before midnight.     

A basking shark (Cetorhinus maximus) tracked by satellite together with simultaneous remote sensing II: New analysis reveals orientation to a thermal front

AVHRR remote sensing data for sea surface temperature during the first successful satellite track of a basking shark, Cetorhinus maximus on 6 July 1982 is analysed using the new composite front map technique. The shark is shown to have been swimming, presumed to be filter-feeding zooplankton, in warm coastal water off the west coast of Scotland parallel to the line of a thermal front.     

Physiological and behavioral responses to hypoxia in the bonnethead shark, Sphyrna tiburo: routine swimming and respiratory regulation

We examined the effect of hypoxia on the swimming speed, respiration rate (oxygen uptake), gape and ventilation volume of the bonnethead shark, Sphyrna tiburo. We used a sonic flowmeter developed for this study to examine swimming speed changes of sharks held in artificial lagoons during diurnal dissolved oxygen changes. Sharks were observed to swim at about 34 cm s^-1 during the day but increased to about 40 cm s^-1 at night when dissolved oxygen levels fell to < 3 mg l^-1. Using a closed system respirometer we examined changes in swimming speed, respiration rate and gape at four dissolved oxygen levels. Swimming speeds averaged 24 to 25 cm s^-1 under normoxic conditions but increased to 38 to 40 cm s^-1 during hypoxia. Similarly, respiration rate increased with increasing speed and decreasing dissolved oxygen. Gape averaged about 1.0 cm under normoxic conditions and increased to a maximum of about 3.5 cm during hypoxia. Using assumed oxygen extraction efficiencies of 25, 50 and 75% and observed respiration rates, we estimated that ventilation volumes of about 25 to 470 l h^-1, depending upon oxygen concentration, would be necessary for gill ventilation. These experiments suggest that changes in swimming speed and mouth gape are important for respiratory regulation in ram ventilating sharks.