Min Air Exposure Research Articles

Variations of physiological and innate immunological responses in goldfish (Carassius auratus) subjected to recurrent acute stress

This study was undertaken to investigate the influence of repeated acute stress on the physiological status and non-specific immune response of goldfish, Carassius auratus. The acute stress was a succession of a 3 min-chasing period followed by a 2 min-air exposure. The goldfish in triplicate tanks were subjected 3 times daily to this stress for one (S3) or three (S9) days. A separate group of unstressed fish was used as control for each sampling time. Blood samples were collected 12, 48 and 120 h after the last stress procedure. Variations of globulin levels, plasma anti-protease and bactericidal activities were not significant in the present study. The haematological parameters and plasma total protein and albumin strongly declined in S9 fish 12 h post-stress compared to control fish. However, plasma cortisol, glucose and lactate levels in both S3 and S9 transiently increased compared to the control fish. Similarly, plasma peroxidase activity transiently increased in both stressed groups 12 h after stress. An increase in plasma lysozyme and complement activities suggested a hormesis-like effect with one-day acute stress improving the immunological response of goldfish while an extension of the stress period to three days impaired physiology and immunity for up to 5 days. This study revealed that recurrent acute stress could immunosuppress goldfish as usually expected of chronic stress.

Effects of dietary arachidonic acid on cortisol production and gene expression in stress response in Senegalese sole (Solea senegalensis) post-larvae

Dietary fatty acids, particularly arachidonic acid (ARA), affect cortisol and may influence the expression of genes involved in stress response in fish. The involvement of ARA on stress, lipid, and eicosanoid metabolism genes, in Senegalese sole, was tested. Post-larvae were fed Artemia presenting graded ARA levels (0.1, 0.4, 0.8, 1.7, and 2.3%, dry matter basis), from 22 to 35 days after hatch. Whole-body cortisol levels were determined, before and 3 h after a 2 min air exposure, as well as the expression of phospholipase A2 (PLA 2 ), cyclooxygenase-2 (COX-2), steroidogenic acute regulatory protein (StAR), glucocorticoid receptors (GRs), phosphoenolpyruvate carboxykinase (PEPCK), and peroxisome proliferator-activated receptor alpha (PPARα). Relative growth rate (6.0-7.8% day(-1)) and survival at the end of the experiment (91-96%) and after stress (100%) were unaffected. Fish reflected dietary ARA content and post-stress cortisol increased with ARA supply up to 1.7%, whereas 2.3% ARA seemed to enhance basal cortisol slightly and alter the response to stress. Results suggested that elevating StAR transcription might not be necessary for a short-term response to acute stress. Basal cortisol and PLA 2 expression were strongly correlated, indicating a potential role for this enzyme in steroidogenesis. Under basal conditions, larval ARA was associated with GR1 expression, whereas the glucocorticoid responsive gene PEPCK was strongly related with cortisol but not GR1 mRNA levels, suggesting the latter might not reflect the amount of GR1 protein in sole. Furthermore, a possible role for PPARα in the expression of PEPCK following acute stress is proposed.

Finding the best estimates of metabolic rates in a coral reef fish

Metabolic rates of aquatic organisms are estimated from measurements of oxygen consumption rates ( ) through swimming and resting respirometry. These distinct approaches are increasingly used in ecophysiology and conservation physiology studies; however, few studies have tested whether they yield comparable results. We examined whether two fundamental measures, standard metabolic rate (SMR) and maximum metabolic rate (MMR), vary based on the method employed. Ten bridled monocle bream (Scolopsis bilineata) were exercised using (1) a critical swimming speed (Ucrit) protocol, (2) a 15 min exhaustive chase protocol and (3) a 3 min exhaustive chase protocol followed by brief (1 min) air exposure. Protocol 1 was performed in a swimming respirometer whereas protocols 2 and 3 were followed by resting respirometry. SMR estimates in swimming respirometry were similar to those in resting respirometry when a three-parameter exponential or power function was used to extrapolate the swimming speed- relationship to zero swimming speed. In contrast, MMR using the Ucrit protocol was 36% higher than MMR derived from the 15 min chase protocol and 23% higher than MMR using the 3 min chase/1 min air exposure protocol. For strong steady (endurance) swimmers, such as S. bilineata, swimming respirometry can produce more accurate MMR estimates than exhaustive chase protocols because oxygen consumption is measured during exertion. However, when swimming respirometry is impractical, exhaustive chase protocols should be supplemented with brief air exposure to improve measurement accuracy. Caution is warranted when comparing MMR estimates obtained with different respirometry methods unless they are cross-validated on a species-specific basis.

Dietary supplementation with the microalgae Parietochloris incisa increases survival and stress resistance in guppy (Poecilia reticulata) fry

Dietary enrichments with the arachidonic acid (ARA)-rich microalga, Parietochloris incisa, on the survival of guppy (Poecilia reticulata) fry were examined. Diets were applied via Artemia enrichment to fish from two commercial farms for 34 and 36 days of experimental period (trials 1 and 2, respectively). In trial 1, Artemia nauplii were enriched with dry biomass of whole algal cells at 0 (control), 0.1, 0.2 and 0.4 mg mL−1. Fry fed with Artemia enriched with 0.4 mg mL−1 demonstrated the lowest mortality rates (24% and 1% in farms 1 and 2, respectively) compared with controls (36% and 13% in farms 1 and 2, respectively). In trial 2, fry were fed with Artemia, enriched with whole algal cells (0.4 mg ml−1), algal hexane extract (HE; containing primarily ARA-rich triacylglycerols and β-carotene; 0.19 mg ml−1) or the extraction residue (0.28 mg ml−1). Acute stress (5 min air exposure) was applied after 18 days. The lowest mortality was recorded in the whole alga-fed group (av. 26% and 2.6% in farms 1 and 2, respectively), with a slightly, but not significantly higher mortality in the HE-fed group (av. 29% and 6.2% in farms 1 and 2, respectively). Elevated lysozyme was associated with the reduced mortality. Overall, the use of P. incisa as a dietary supplement for guppy fry during their first month of life enhanced their survival and stress resistance.

Species specificity in the magnitude and duration of the acute stress response in Mediterranean marine fish in culture

The aim of the present study was to examine the species-specific stress response for seven Mediterranean fishes in culture. Also, to evaluate the method of measuring free cortisol concentration in the rearing water as a non-invasive and reliable indicator of stress in marine species, of aquaculture importance. Gilthead sea bream, Sparus aurata (Sparidae); common dentex, Dentex dentex (Sparidae); common Pandora, Pagellus erythrinus (Sparidae); sharpsnout sea bream, Diplodus puntazzo (Sparidae); dusky grouper, Epinephelus marginatus (Serranidae); meagre, Argyrosomus regius (Sciaenidae) and European sea bass, Dicentrarchus labrax (Moronidae) were subjected to identical acute stress (5–6 min chasing and 1–1.5 min air exposure) under the same environmental conditions and samples were analyzed by the same procedures. Results indicated that there was a clear species-specificity in the magnitude, timing and duration of the stress response in terms of cortisol, glucose and lactate. European sea bass showed a very high response and dusky grouper and meagre a very low response, except plasma glucose concentrations of dusky grouper which was constantly high, while sharpsnout sea bream presented a protracted stress response, up to 8 h. The present study confirmed that free cortisol release rate into the water can be used as a reliable stress indicator.

Variations in collagen fibrils network structure and surface dehydration of acid demineralized intertubular dentin: Effect of dentin depth and air-exposure time

The aim was to characterize the variations in the structure and surface dehydration of acid demineralized intertubular dentin collagen network with the variations in dentin depth and time of air-exposure (3, 6, 9 and 12 min). In addition, to study the effect of these variations on the tensile bond strength (TBS) to dentin. Phosphoric acid demineralized superficial and deep dentin specimens were prepared. The structure of the dentin collagen network was characterized by AFM. The surface dehydration was characterized by probing the nano-scale adhesion force (F(ad)) between AFM tip and intertubular dentin surface as a new experimental approach. The TBS to dentin was evaluated using an alcohol-based dentin self-priming adhesive. AFM images revealed a demineralized open collagen network structure in both of superficial and deep dentin at 3 and 6 min of air-exposure. However, at 9 min, superficial dentin showed more collapsed network structure compared to deep dentin that partially preserved the open network structure. Total collapsed structure was found at 12 min for both of superficial and deep dentin. The value of the F(ad) is decreased with increasing the time of air-exposure and is increased with dentin depth at the same time of air-exposure. The TBS was higher for superficial dentin at 3 and 6 min, however, no difference was found at 9 and 12 min. The ability of the demineralized dentin collagen network to resist air-dehydration and to preserve the integrity of open network structure with the increase in air-exposure time is increased with dentin depth. Although superficial dentin achieves higher bond strength values, the difference in the bond strength is decreased by increasing the time of air-exposure. The AFM probed F(ad) showed to be sensitive approach to characterize surface dehydration, however, further researches are recommended regarding the validity of such approach.

Effects of angler-induced exercise and air exposure on the mortality of mouth-hooked yellowfin bream (Acanthopagrus australis)

Two aquaria experiments were done to quantify the short-term (up to 10 days) mortality of mouth-hooked yellowfin bream (Acanthopagrus australis) after short and long playing times (5 vs 30 s) followed by different extremes in air exposure (2.5 vs 5 min). During exp. 1, 44 fish were angled from randomly-selected 5000-L holding tanks, played for 5 s, subjected to either 2.5 or 5 min air exposure and then released into replicate sea cages located in a 1050 KL pool. Appropriate numbers of controls were transferred without air exposure from an unfished 5000-L tank into separate cages in the pool. The same methodology was applied during exp. 2, except that 31 yellowfin bream were angled and played for 30 s (rather than 5 s) before being subjected to the different durations of air exposures and released. Fish were monitored for 10 and 5 days in exps. 1 and 2, respectively. Concentrations of plasma cortisol and glucose were collected from samples of fish on the first and last days of the experiments. The only mortalities were two individuals (one from each treatment) during exp. 2, attributed to clotted blood (from hook wounds) across the gill lamellae. Surviving individuals at the end of the experiments had variable elevations in plasma cortisol but not glucose, indicating acute stress responses that were probably evoked during sampling. The conclusion is that yellowfin bream are resilient to being mouth-hooked, exercised and exposed to air before being released. However, to minimise impacts, individuals should be released as soon as possible, especially when blood is present at the hook wound.

PROPOSED NEW COLOR RETENTION METHOD FOR TILAPIA FILLETS (O. NILOTICUS♀ × O. AUREUS♂) BY EUTHANATIZING WITH REDUCED CARBON MONOXIDE

ABSTRACT The conditions of color retention for tilapia fillets (O. niloticus♀ × O. aureus♂) treated by euthanatizing with reduced carbon monoxide (CO) were investigated. Live tilapias were first exposed to water saturated with CO. After a certain amount of CO-saturated water had been pumped through the gills, the tilapias were timely picked out and killed following the industry guidelines. The color value of fillets was measured by colorimeter to evaluate the color retention. The results showed that (1) temperature did not have a significant effect on the color of the fillets; (2) the optimal conditions were a ratio of 3:1, v/w between water and fish, a CO flow rate of 80 mL/min and 10 min CO injection followed by 5 min air exposure. Under these conditions, a higher a*value (redness 19.44) and a better sensory evaluation value (4.8) were obtained; and (3) the proposed method shortened processing time by 30–35 min, reduced the frequency of sterilization to only once, significantly lowered microbial counts from 82.33 × 102 to 56.33 × 102 and reduced the CO requirement 25-fold, which has significant occupation, health, safety, and environmental implications. PRACTICAL APPLICATIONS Color retention for tilapias is conventionally accomplished by treating fillets with CO. Recently, euthanatizing tilapias with CO has been assumed to be an effective way to shorten processing time and to lessen product handling process. Many factories have been searching for a way to solve the problem of color retention for tilapias or other red muscle treatment, but there has been a lack of information on how euthanasia affects fish quality, especially red muscle color. The objective of this experiment was to explore the application of the new method.

Acute stress response of Kootenai River white sturgeon Acipenser transmontanus Richardson reflected in peritoneal fluid and blood plasma

To evaluate whether stress‐response indicators in blood plasma (BP) are similarly reflected in the peritoneal fluid (PF) white sturgeon Acipenser transmontanus were stressed by a 30 min air exposure and pH, PCO2, osmolality, cortisol, glucose and lactate levels measured. Changes in certain stress indicators in the BP (pH, PCO2, osmolality and glucose) also occurred in the PF, while stressor‐induced changes in cortisol and lactate were restricted to the BP. Data suggest that PF is a modified ultrafiltrate of the blood and potentially a useful indicator of animal stress.

Effect of UV Irradiation on Cut Cantaloupe: Terpenoids and Esters

Recent studies demonstrated that ultraviolet (UV) radiation enhanced terpenoids and decreased esters in thin-sliced cantaloupe. In preliminary studies treating fresh juices with UV, terpenoid compounds that normally were not isolated, or found in minute quantities, were elevated and only low molecular weight alcohols, ketones, and aldehydes decreased. Subsequently terpenoid induction/oxidation in UV-treated cut cantaloupe was reinvestigated. UV exposure increased the concentrations of terpenoids in cantaloupe tissue. However, UV exposure alone was not the sole factor responsible for enhanced terpenoids. UV-enhanced terpenoid production appears to be both cultivar- and maturity-dependent. Concomitant decreases in the ester content of UV-treated samples occurred using a previously published system. Yet, we established that almost identical ester losses occurred in thinly sliced laminar tissue receiving 60 min UV or air exposure in an open system. Tissue samples that were exposed to UV in a closed system often did not suffer correspondingly equal ester loss. Marked tissue warming (4.3 +/- 0.5 degrees C in 60 min) occurred during UV treatments in thin-sliced tissue. Ester loss from cantaloupe tissue was caused by the experimental procedure, but not by UV treatment per se. These findings are supported by the observation that UV is not responsible for chemical transformations to ester bonds, esterase, and lipase decrease in stored cut cantaloupe, and no lipid oxidation volatiles were observed in thin-sliced control tissue, while oxidized terpenoids were recovered. Information gathered indicates that improper cutting, handling, sanitation treatment, and storage can radically alter the desirable volatile aroma profile in cut cantaloupe, and potentially lead to decreased consumer acceptance.

Characterization of the Physiological Stress Response in Lingcod

AbstractThe goal of this study was to describe the duration and magnitude of the physiological stress response in lingcod Ophiodon elongatus after exposure to brief handling and sublethal air stressors. The response to these stressors was determined during a 24‐h recovery period by measuring concentrations of plasma cortisol, lactate, glucose, sodium, and potassium. Lingcod were subjected to brief handling followed by either a 15‐min or a 45‐min air stressor in the laboratory. After the 15‐min stressor, an increase in cortisol or glucose could not be detected until after 5 min of recovery. Peak concentrations were measured after 30 min for cortisol and after 60 min for glucose and lactate. Glucose and lactate had returned to basal levels after 12 h, whereas cortisol did not return to basal levels until after 24 h of recovery. Immediately following a 45‐min air stressor, all measured parameters were significantly elevated over levels in prestressor control fish. Cortisol concentrations tended to increase and reached a measured peak after 8 h of recovery, whereas glucose and lactate reached a measured peak after 1 h of recovery. Cortisol and lactate returned to basal levels within 24 h. Glucose, however, remained elevated even after 24 h of recovery. Plasma ions initially increased during the first hour of recovery, and the concentrations then declined to a level below that measured in control fish for the remainder of the 24‐h recovery period. In addition, we evaluated the effect of fish size on the stress response. There was no significant difference between the stress response of smaller (41–49‐cm [total length] and larger (50–67‐cm) lingcod after 45 min air exposure. In general, both the magnitude and duration of the primary and secondary stress responses in lingcod are comparable to those of salmonids.

Effects of Cu on plasma cortisol and cortisol secretion by adrenocortical cells of rainbow trout ( Oncorhynchus mykiss)

Fish are exposed to multiple stressors, often acting concurrently, in their environment. To evaluate the potential of Cu to act as a chemical stressor, rainbow trout ( Oncorhynchus mykiss) were exposed to Cu (30 or 80 μg/l) for 30 days in the laboratory and they were subjected to a physical stressor (1 min air exposure) before sampling. Physiological stress indicators in the whole fish as well as cortisol secretion by adrenocortical cells in vitro were measured. Fish exposed to Cu had a lower condition factor, hepatosomatic index, plasma glucose, hepatic glycogen and gill Na +/K +-ATPase activity compared to controls. Exposure to Cu did not have an effect on basal plasma cortisol (fish sampled without air exposure stress) however, the air exposure-induced increase in plasma cortisol was lower in fish exposed to Cu. Cortisol secretion stimulated by ACTH in vitro was greater in adrenocortical cells isolated from fish exposed to Cu in vivo but in vitro exposure to Cu consistently impaired cortisol secretion. Our results indicate that Cu at high concentrations disrupts cortisol secretion through a direct toxic effect on adrenocortical cells while low concentrations resulting from a 30-day exposure to environmentally relevant Cu concentrations enhances cortisol secretion in response to ACTH in vitro.

The effects of incidental trawl capture of juvenile snapper (Pagrus auratus) on yield of a sub-tropical line fishery in Australia: an assessment examining habitat preference and early life history characteristics

Abstract Juvenile snapper ( Pagrus auratus ), predominantly 0+ year old (5–20 cm fork length), were an abundant incidental bycatch in Moreton Bay prawn trawls, with catch rates averaging 100 fish h −1 at some locations. Discard mortality of these juveniles, was high (over 85% mortality after 15 min of air exposure) and under a worst case scenario models predicted that incidental capture of juvenile snapper in prawn trawls from southern Moreton Bay alone could be responsible for the loss of a greater tonnage of snapper than is taken by the total Queensland commercial line fishery. The predicted mean loss was approximately 30 tonnes compared to an annual commercial line catch of 100 tonnes. Juvenile snapper were found associated with several substrates including sand, mud, rubble and soft coral/algal beds in Moreton Bay with population densities not significantly different among the habitat types. Juvenile snapper had not previously been associated with coral habitat. Despite the lack of difference in abundance related to the sampled habitat types, juveniles were more common in the shallower ( −1 ) in subtropical Moreton Bay were higher than those in temperate areas.

A first insight into stress-induced neuroendocrine and immune changes in the octopus Eledone cirrhosa

A number of cephalopod species present substantial ecological and economical importance; however, data on the physiology of stress and on regulatory processes linking stress to immune defence against pathogens remain extremely scarce in these organisms. The present study examined the influence of a 5 min air exposure, a common perturbation associated with handling in aquaculture settings and fisheries, on neuroendocrine and immune parameters in the octopus Eledone cirrhosa. Measurements of circulating concentrations of noradrenaline and dopamine, two hormones that are released in the haemolymph during stress in bivalves and gastropods, showed that the 5 min air exposure represents a real stress to octopus. Indeed, blood levels of both hormones increased by about 2–2.5-fold in stressed animals. Concomitantly, a significant decrease in the number of circulating haemocytes was observed, whereas haemocyte phagocytotic activity and superoxide anion production increased transiently between 5 and 60 min after the beginning of the stress. These results provide a first insight into the effects of stress on catecholamine levels and immune functions in cephalopods and suggest that stress and immunity may be associated in these organisms.

Influence of air exposures and thermal treatments on the secondary electron yield of copper

The variation of the secondary electron yield (SEY) of sputter-cleaned oxygen-free high-conductivity copper has been studied as a function of air exposure duration at room temperature. After short air exposures of some seconds the maximum SEY (δmax) of clean copper is reduced from 1.3 to less than 1.2, due to the oxidation of the copper surface. Prolonged air exposure increases the SEY steadily until, after about 8 days of atmospheric exposure, δmax is higher than 2. Air exposures at higher temperatures have been found to be effective in reducing the SEY of technical copper surfaces. A 5 min air exposure of copper at 350 °C followed by a 350 °C bakeout under vacuum reduces δmax to about 1.05, which is lower than the value of pure copper and that of Cu2O.

COLD ACCLIMATIZATION IN ACTIVE ANTARCTIC SCUBA DIVERS 1203

The purpose of this investigation was to determine whether the cold exposure associated with polar scuba diving operations could result in measurable cold acclimatization in humans. Antarctic-cold-exposed (ACE) subjects (n=4; male) lived in semi-permanent structures in an isolated field camp (77°S 163°E) during the austral spring, conducting 4.9±0.6(4.3-5.9) dives per week for biological research (water -1.9°C; air -36.7 to -5.8°C). Matched bi-weekly-tested (BWT) subjects remained in the U.S. throughout the study period (autumn). Physiological responses to standardized peripheral (30 min digit immersion, 4°C water bath) and whole body (90 min air exposure, 5°C, supine, rest) cold tests were evaluated at two week intervals for six weeks. Analysis of variance (Group × Trial × Time) indicated significant but subtle Group × Trial interactions(p<0.05) in mean digit temperature during the peripheral tests and in mean rectal and mean skin temperatures and mean heart rate during the whole body tests (accounting for 16.4, 8.0, 1.5 and 7.7% of dependent score variability[eta squared], respectively). From the first to fourth trial, the ACE group demonstrated decreased mean digit and rectal temperatures, increased mean skin temperature and decreased mean heart rate (-0.83, -0.16 and +0.36°C and-6.0 bpm, respectively). The BWT group demonstrated increased digit, rectal and mean skin temperatures and heart rate (+0.53, +0.25 and +0.64°C and+5.5 bpm). ACE group changes in digit and rectal temperature and heart rate are consistent with hypothermic adaptation. The elevated mean skin temperature may indicate a concomitant attenuation of the vasoconstrictive responses. BWT group changes are consistent with metabolic adaptation, potentially induced by a combination of the cold testing and naturally occurring seasonal acclimatization. Given the modest changes, it is unclear whether the cold adaptation demonstrated by the divers working under polar conditions has any operational importance.

Effect of End-Point Temperature and Storage Time on Color and Denaturation of Myoglobin in Broiler Thigh Meat

This study investigated the effect of end-point cooking temperature (EPT, 60, 66, 71, 77, and 82 C), sampling time (0 or 30 min), and storage time after cooking (0,5, and 10 d) at 2 C on color values and percentage denatured myoglobin (PDM) of broiler thigh meat. As EPT increased, L* values, b* values, and PDM increased but a* values decreased. As storage time increased, L* and a* values decreased and PDM increased. Time of color measurement (immediately after cutting into the interior of the sample 0 vs 30 min after cutting) had a significant effect on L* and b* values. At 0 d storage 30 min sampling, a* values were redder than 0-min values from 60 through 71 C, no different at 77 C and redder at 0 than 30 min at 82 C EPT, suggesting that myoglobin is more susceptible to oxidative denaturation (reddish-brown pigment) at higher EPT after air and light exposure. At 5 d, 77 and 82 C a* values were less red after 30 min air and light exposure, suggesting that myoglobin was more susceptible to oxidative denaturation at higher EPT after storage. These results will help the meat processor identify and incorporate process factors that will lower the reddish-pink color defect in cooked poultry meat.

The stress response and the plasma disappearance of corticosteroid and glucose in a marine teleost, the sea raven

The objective of the study was to examine the physiological response to stress in a marine species with a sluggish life-style. The sea raven (Hemitripterus americanus), a marine benthic predator, did not produce elevated catecholamine levels when handled for blood removal, which facilitated repeated blood sampling from the same fish without cannulation. However, this species did release catecholamines in response to an acute stress (1 min of air exposure followed by 1 min of chasing), suggesting a high threshold (degree of external stimulation) for catecholamine release in this species. Plasma cortisol concentration increased significantly only after 1 h and remained elevated 4 h post-stress, showing a delayed response compared with salmonids. Plasma glucose concentration increased significantly at 0.5 h post-stress and remained elevated even at 24 h, while lactate levels dropped between 4 and 24 h post-stress. The delayed cortisol increase may not be due to altered plasma clearance, as no change in the plasma disappearance or tissue uptake of cortisol-derived radioactivity occurred with confinement stress in this species. Also, confinement stress did not alter the plasma disappearance or tissue uptake of radioactivity derived from glucose, indicating a higher production of glucose during stress. Food deprivation significantly increased the plasma disappearance and tissue uptake of both cortisol- and glucose-derived radioactivity in the sea raven. These results indicate that the hormonal response to stress in the sea raven is different from that of salmonids. This altered response may be an adaptation to prevent excess energy mobilization in a species with an inactive life-style and low metabolic activity.

Size and hematological impact of the splenic erythrocyte reservoir in rainbow trout,Oncorhynchus mykiss

Fish were sampled individually, at rest, following air exposures of up to 8 min, during recovery from a 5 min air exposure or after a 5 minute chase. The spleen was photographedin vivo at rest and following 5 min air exposure in one fish. The effect of individual versus serial sampling from the same tank and of MS222 anaesthesia was also examined. Spleen hemoglobin content (SpHb), spleen somatic index (100 × spleen weight/body weight; SSI), blood hemoglobin concentration (Hb), and hematocrit (Ht), were measured. Mean cell hemoglobin concentration (MCHC), erythrocyte reservoir size, and relative contributions of reservoir release, erythrocyte swelling, and plasma water loss to hemoconcentration were calculated. The splenic reservoir contained 0.54 g Hb/kg body (21% of total body Hb), most of which it released between 1 and 3 minutes after the onset of air exposure. The spleen released more than 95% of the erythrocytes it contained at rest within 8 min. The release accounted for 31% of the 5.65 g/dl rise in Hb and 23% of the 26.6% observed increase in Ht after 8 minutes of air exposure. The balance of the increase was caused by erythrocyte swelling and fluid shifts reducing plasma volume. Animals exercised for 5 min showed changes similar to those in fish air exposed for 5 min. Recovery of all parameters was complete in 3 to 6 h, with the exception of MCHC which recovered in 30 min. Serial sampling produced a decrease in SpHb, and R1Wt and induced a significant hemoconcentration. MS222 did not cause erythrocyte release, but failed to prevent it after handling. Many previous reports of Ht and Hb in resting fish are probably high because they were taken under conditions that would cause the spleen to release its contents.

Carbon dioxide excretion in the jeju, Hoplerythrinus unitaeniatus, a facultative air-breathing teleost

The facultative air breather Hoplerythrinus unitaeniatus utilizes a modified swim bladder as an accessory breathing organ. Dorsal aortic blood and bladder [Formula: see text] and [Formula: see text], and blood pH values were measured while in water, after 20 min air exposure, and 20 min after returning the fish to water. In water the dorsal aortic [Formula: see text] is 31 mmHg(1 mmHg = 133.322 Pa), [Formula: see text] is 11 mmHg, and pH is 7.81. After 20 min air exposure both pH and [Formula: see text] fell, [Formula: see text] increased, and the bladder gas exchange ratio, R, 0.21 in water, increased to 0.40. In water there is no difference between mean [Formula: see text] levels in blood and bladder; however, upon air exposure [Formula: see text] levels increase and large differences develop between the blood and lung. Carbonic anhydrase infusion reduces these differences and also increases the R value for the bladder. In water carbonic anhydrase infusion is without effect on CO2 levels in the blood or the bladder. The results are consistent with the hypothesis that CO2 excretion into the air bladder during air exposure is limited by the velocity of the plasma bicarbonate dehydration reaction.