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PubMed1999

Convective oxygen transport and tissue oxygen consumption in Weddell seals during aerobic dives.

Unlike their terrestrial counterparts, marine mammals stop breathing and reduce their convective oxygen transport while performing activities (e.g. foraging, courtship, aggressive interactions, predator avoidance and migration) that require sustained power output during submergence. Since most voluntary dives are believed to remain aerobic, the goal of this study was to examine the potential importance of the dive response in optimizing the use of blood and muscle oxygen stores during dives involving different levels of muscular exertion. To accomplish this, we designed a numerical model based on Fick's principle that integrated cardiac output (Vb), regional blood flow, convective oxygen transport (Q(O2)), muscle oxymyoglobin desaturation and regional rates of oxygen consumption (VO2). The model quantified how the optimal matching or mismatching of QO2 to VO2 affected the aerobic dive limit (ADL). We chose an adult Weddell seal Leptonycotes weddellii on which to base our model because of available data on the diving physiology and metabolism of this species. The results show that the use of blood and muscle oxygen stores must be completed at the same time to maximize the ADL for each level of VO2. This is achieved by adjusting Vb (range 19-94 % of resting levels) and muscle QO2 according to the rate of muscle oxygen consumption (VMO2). At higher values of VMO2, Vb and muscle perfusion must increase to maintain an appropriate QO2/VO2 ratio so that available blood and muscle oxygen stores are depleted at the same time. Although the dive response does not sequester blood oxygen exclusively for brain and heart metabolism during aerobic dives, as it does during forced submersion, a reduction in Vb and muscle perfusion below resting levels is necessary to maximize the ADL over the range of diving VO2 (approximately 2-9 ml O2 min-1 kg-1). Despite the reduction in Vb, convective oxygen transport is adequate to maintain aerobic metabolism and normal function in the splanchnic organs, kidneys and other peripheral tissues. As a result, physiological homeostasis is maintained throughout the dive. The model shows that the cardiovascular adjustments known as the dive response enable the diving seal to balance the conflicting metabolic demands of (1) optimizing the distribution and use of blood and muscle oxygen stores to maximize the ADL over the normal range of diving VO2 and (2) ensuring that active muscle receives adequate oxygen as VMO2 increases.

Aerobiosis↗
PubMed2000

Foraging energetics and diving behavior of lactating New Zealand sea lions, Phocarctos hookeri.

The New Zealand sea lion, Phocarctos hookeri, is the deepest- and longest-diving sea lion. We were interested in whether the diving ability of this animal was related to changes in its at-sea and diving metabolic rates. We measured the metabolic rate, water turnover and diving behavior of 12 lactating New Zealand sea lions at Sandy Bay, Enderby Island, Auckland Islands Group, New Zealand (50 degrees 30'S, 166 degrees 17'E), during January and February 1997 when their pups were between 1 and 2 months old. Metabolic rate (rate of CO(2) production) and water turnover were measured using the (18)O doubly-labeled water technique, and diving behavior was measured with time/depth recorders (TDRs). Mean total body water was 66.0+/-1.1 % (mean +/- s.d.) and mean rate of CO(2) production was 0. 835+/-0.114 ml g(-)(1 )h(-)(1), which provides an estimated mass-specific field metabolic rate (FMR) of 5.47+/-0.75 W kg(-)(1). After correction for time on shore, the at-sea FMR was estimated to be 6.65+/-1.09 W kg(-)(1), a value 5.8 times the predicted standard metabolic rate of a terrestrial animal of equal size. The mean maximum dive depth was 353+/-164 m, with a mean diving depth of 124+/-36 m. The mean maximum dive duration was 8.3+/-1.7 min, with an average duration of 3.4+/-0.6 min. The deepest, 550 m, and longest, 11.5 min, dives were made by the largest animal (155 kg). Our results indicate that the deep and long-duration diving ability of New Zealand sea lions is not due to a decreased diving metabolic rate. Individual sea lions that performed deeper dives had lower FMRs, which may result from the use of energetically efficient burst-and-glide locomotion. There are differences in the foraging patterns of deep and shallow divers that may reflect differences in surface swimming, time spent on the surface and/or diet. Our data indicate that, although New Zealand sea lions have increased their O(2) storage capacity, they do not, or cannot, significantly reduce their at-sea metabolic rates and are therefore likely to be operating near their physiological maximum.

Animals↗
PubMed1999

Buoyancy and diving behavior in mosquito pupae.

Mosquito pupal diving behavior has been studied mostly in Aedes aegypti and in this species pupal buoyancy varies relative to several factors. The research reported herein addresses the 2 following questions. Does diving behavior vary among different mosquito genera and species? How is diving behavior influenced by variation in buoyancy? Depth and duration of dive, and dive pattern, were compared among Ae. aegypti, Culex pipiens, Anopheles stephensi, Aedes albopictus, and Aedes triseriatus. In response to the stimulation associated with transferring pupae between containers, diving behavior varied dramatically among the different genera studied. Culex pipiens and An. stephensi make short-duration, shallow dives and remain positively buoyant. The 3 aedine species studied make longer-duration dives, typically to a depth at which they become neutrally or negatively buoyant. Buoyancy reduction effects were studied in the 3 aedine species. Normally buoyant pupae tend to dive to greater depths and for longer periods of time than reduced-buoyancy pupae. Aedine pupal diving behavior clearly is closely regulated relative to buoyancy variation. To the earlier hypotheses that pupal behavior may help avoid predation and be energy-conserving, we add the suggestion that the diving behavior displayed by the container-breeding aedine pupae we studied represents an adaptation that helps keep them from being washed from their container habitat by overflowing water during rainfall. We also suggest that the diving behavior of all the species studied may help pupae survive heavy, pelting rainfall by enabling them to avoid the mechanical shock of a direct hit by a raindrop, which could cause disruption of the gas in the ventral air space, thereby causing the loss of hydrostatic balance and drowning.

Aedes↗
PubMed2001

Thermal status of saturation divers during operational dives in the North Sea.

The principal aim of the present study was to monitor the core temperature (Tc) of a population of saturation divers conducting routine deep dives at different locations in the United Kingdom sector of the North Sea and to assess whether current dive procedures are adequate in preventing deleterious decreases in Tc. A total of 30 divers, with an average (SD) of 19.3 (6.6) yr of experience as saturation divers, participated in the study. The survey included 59 dives conducted at six locations (Scott Field, Norfra Pipeline, Hudson Field, Pierce Field, Forties Field, and Bruce Field) from four Diver Support Vessels (Rockwater 1, Semi 2, Bar Protector, and Discovery). The depth of the dives monitored ranged from 54 to 160 meters of seawater (msw), and the duration of the dives from 31 min to 7 h 30 min. before each dive, divers were requested to ingest a radio pill and strap a data logger to their abdomen. Upon returning to the chamber within the Diver Support Vessel following a dive, they provided subjective ratings of thermal perception (7 point scale) and thermal comfort (4 point scale) for the period just before, during, and immediately after the dive. In 55 dives, Tc of saturation divers working at depths to 160 msw for up to 6 h with water temperatures ranging from 4 degrees to 6 degrees C increased above the pre-dive core temperature of 37.4 degrees (0.620+/-0.6 degrees C). In four dives there was a decrease in Tc: 2 divers had a 0.2 degrees C fall in Tc, and 2 bellmen had a decrease of 0.4 degrees and 1.0 degrees C. The subjective responses of divers indicated that they were thermally neutral (neither warm nor cold) and comfortable before and immediately after the dives. The current practice of providing thermal protection with hot water suits to saturation divers working in the North Sea is adequate for preventing the risk of hypothermia and maintaining thermal comfort.

Adult↗
PubMed2003

Incidence and risk factors for symptoms of decompression sickness among male and female dive masters and instructors--a retrospective cohort study.

UNLABELLED: The aim was to determine the incidence of symptoms of decompression sickness (DCS) in dive masters and instructors in relation to number of dives and possible risk factors. STUDY DESIGN: Retrospective cohort study of dive masters and instructors in Sweden. STUDY BASE: All dive masters and instructors listed with PADI, NAUI and CMAS in Sweden as of January 1st 1999 (2380 divers). METHODS: The dive masters and instructors received a validated questionnaire on diving activities and symptoms of DCS in 1999. 1516 men and 226 women answered, i.e. 73% of the initial study base. RESULTS: DCS symptoms were reported by 190 divers. The incidence of DCS symptoms was 1.52 for males and 1.27 for females per 1000 dives. Dive masters, divers not performing decompression-stop dives, divers not practicing advanced diving and divers with a low number of total lifetime dives had a higher proportion (p < 0.05) of DCS symptoms per 1000 dives. There were no major differences in DCS symptom incidence related to sex, age, asthma, overweight or alcohol abuse in this study.

Adult↗
PubMed1998

Diving speeds and angles of a gyrfalcon (Falco rusticolus)

An optical tracking device recorded the three-dimensional paths of 11 dives by a 1.02 kg gyrfalcon, trained to dive to a falconer. The dives started at altitudes up to 500 m above the ground and were inclined at angles of 17-62 degrees from the horizontal. The falcon controlled its speed during the dives, rather than simply falling from the sky, and the dives had three phases. During the first (acceleration) phase, the falcon accelerated to speed limits between 52 and 58 m s-1 in the seven fastest dives, evidently with minimum drag, because its accelerations were close to those predicted from theory for minimum drag. The falcon then began a constant-speed phase by increasing drag by a factor of 1.3-4.8 while still 100-350 m above the ground in most dives. The constant-speed phase lasted no more than a few seconds, and the falcon then began a deceleration phase by increasing its drag further, this time by factors of 1.7-3. 2, and decelerating with a mean value of -0.95 times gravitational acceleration. During all three phases, the dive angle was nearly constant or increased during the deceleration phase, and the falcon made no changes in its body shape that were obvious through the tracking device telescope except to reduce its wing span as it accelerated. The falconer, however, was close to the falcon at the end of the dive and could see that, during the deceleration phase, the falcon held its wings in a cupped position, apparently with a high angle of attack and therefore high drag. At the end of the deceleration phase, the falcon dropped its legs, spread its toes and finally spread its wings as it approached the falconer. Although the speeds reported here are the fastest ever measured with known accuracy in animals, the falcon could theoretically have reached more than 70 m s-1 if it had continued to accelerate with minimum drag until close to the ground. Even at this speed, it would have had enough altitude to pull out of the dive before crashing into the ground. Several authors have estimated that diving falcons reach speeds of more than 70 m s-1, and wild falcons may reach such speeds when they make long, steep dives upon birds flying high in the air.

Journal Article↗
PubMed2001

Effects of ambient cold and depth on lung function in humans after a single scuba dive.

This study evaluated the subacute respiratory effects of diving, to try to separate the effects of ambient temperature from those of depth. In the first experiment 10 healthy men made a compressed-air dive to 50 m that exposed them to cold. They were compared with 10 matched control subjects who underwent the same dive profile but were exposed to a comfortable temperature. In the second experiment 16 healthy subjects made randomized cold dives to both 50 m and 10 m. Pulmonary function tests were made before, after 1 h, and 24 h after the dives. In the first experiment there was an increase in residual volume (P < 0.05) and a decrease in forced expiratory volume at 1 s (FEV1), in forced vital capacity (FVC) and in mid-expiratory flow at 75% of FVC (MEF75) 1 h after the cold dives (P < 0.05). In the second experiment significant increases in specific airways resistance (sR(AW)) (P < 0.05) and decreases in FEV1 (P<0.01), in MEF75 (P<0.05), and in mid-expiratory flow at 25% of FVC (P<0.05), were obtained after the 50 m-dives, whereas SR(AW) increased after the 10 m-dives (P<0.05). The respiratory pattern observed 1 h after cold dives to 50 m indicated airway narrowing. The changes after cold dives to 10 m, however, were of minor magnitude. Both cold and depth seemed to contribute to the adverse effects of a single compressed-air dive on pulmonary function.

Adult↗
PubMed1983

Respiratory adaptations in diving mammals.

This report examines the evidence for the presence of oxygen stores in the lungs, blood and systemic musculature of diving mammals, the modifications in the respiratory functions of blood that may be important in utilizing the lung and blood oxygen stores, and the potential importance of the oxygen stores and the respiratory functions of blood in supporting short-duration, aerobic dives. Increasing oxygen stores by increasing lung volume does not occur in diving mammals. The long-duration diving whales have small lung volumes which results in lung collapse during dives and the seals dive following partial expiration which produces the same effect. The short-duration diving dolphins, porpoises and rodents have lung volumes comparable to terrestrial mammals, dive following inspiration and appear to use the lungs as an oxygen store. Adaptations in the oxygen affinity of the blood parallel the modifications in lung volume. Where the lungs do not represent a potential oxygen store the oxygen affinity is low, maximizing the unloading of oxygen while maintaining a high tissue oxygen tension. Where the lungs do represent an oxygen store, the affinity is high, maximizing the uptake of oxygen from the alveolar space. Increases in the concentration of respiratory pigment in the blood and in muscle are important adaptations in diving mammals. The blood oxygen stores in diving mammals vary from near normal to over three times normal for terrestrial mammals while the muscle oxygen stores vary from near normal to nearly ten times normal. The degree to which the blood and muscle oxygen stores are increased can be equated to the duration of the dive and demands for oxygen; longer duration divers and those with higher metabolic demands have greater oxygen stores than divers that remain submersed for shorter periods or have lower rates of oxygen utilization.

Animals↗
PubMed2006

Body cooling and the diving capabilities of muskrats (Ondatra zibethicus): a test of the adaptive hypothermia hypothesis.

We tested the hypothesis that immersion hypothermia enhances the diving capabilities of adult and juvenile muskrats by reducing rates of oxygen consumption (V O2). Declines in abdominal body temperature (T(b)) comparable to those observed in nature (0.5-3.5 degrees C) were induced by pre-chilling animals in 6 degrees C water. Pre-chilling did not reduce diving V O2 of any animal tested in 10 degrees C or 30 degrees C water, irrespective of the nature of the dive. Most behavioural indices of dive performance, including average and cumulative dive times, were unaffected by T(b) reduction in adults, but depressed in hypothermic juveniles (200-400 g). Hypothermia reduced diving heart rate only on short (<25s) dives (16% reduction, P=0.01), but did not affect the temporal onset of diving bradycardia. Post-immersion V O2 was higher for pre-chilled than for normothermic muskrats, but the difference became insignificant on longer (>90 s) dives. Our findings suggest that the mild hypothermia experienced by muskrats in nature has minimal effect on diving and post-immersion metabolic costs, and thus has little impact on the dive performance of this northern semi-aquatic mammal.

Acclimatization↗
PubMed2006

Aerobic dive limit. What is it and is it always used appropriately?

The original definition of aerobic dive limit (ADL) was the dive duration after which there is an increase in post-dive concentration of lactate in the blood of Weddell seals freely diving in the field. The only other species in which such measurements have been made is the emperor penguin. For all other species, aerobic dive limit has been calculated (cADL) by dividing usable oxygen stores with an estimation of the rate of oxygen consumption during diving. Unfortunately, cADL is often referred to as the aerobic dive limit, implying that it is equivalent to that determined from the measurement of post-dive blood lactate concentration. However, this is not so, as at cADL all of the usable oxygen would have been consumed, whereas Weddell seals and emperor penguins can dive for at least 2-3 times longer than their ADL. Thus, at ADL, there is still some usable oxygen remaining in the stores. It is suggested that to avoid continued confusion between these two terms, the former is called diving lactate threshold (DLT), as it is somewhat analogous to the lactate threshold in exercising terrestrial vertebrates. Possible explanations of how some species routinely dive beyond their cADL are also discussed.

Animals↗
PubMed2005

Blood glucose changes and adjustments of diet and insulin doses in type 1 diabetic patients during scuba diving (for a change in French regulations).

OBJECTIVE: In France, diabetic subjects were not allowed to dive. The principal risk is hypoglycemia during immersion. However scuba diving is allowed in many countries. To follow blood glucose changes, food intake and insulin adjustments in type 1 diabetic patients when diving, and to propose specific guidelines for such patients willing to practice recreational scuba diving. METHODS: Fifteen well-controlled (mean HbA1c: 7.2%) type 1 diabetic patients without complications were volunteer to dive under strict medical monitoring. They dove 8 times in 4 days in autumn at a depth of 20 meters, in 12 degrees C to 16 degrees C water. A strict protocol based on blood glucose was implemented to prevent hypoglycaemia. RESULTS: No case of hypoglycemia was observed and no faintness was reported underwater. Mean blood glucose before diving was 200 mg/dl (11 mmol/l). There was a mean fall in blood glucose of 40 mg/dl (2.2 mmol/l) during dives, a mean decrease in daily insulin doses by 19.3% on the last day. Daily energy intake was 3,225 Kcal in average. A continuous glucose monitoring (CGMS) was performed in one patient and showed a rather stable glycemia during immersion but a decrease within the 8 hours after. CONCLUSION: When respecting a strict protocol to prevent hypoglycaemia, the risk of hypoglycaemia appears quite low. We recommend an ideal glycemic goal of 200-250 mg/dl (11-13.75 mmol/l) before immersion, a higher reduction of insulin doses (-30%) and taking carbohydrates on board in any case. The present data have recently led the French diving federation (FESSM) to allow type 1 diabetic patients to dive with some restrictive qualification requirements: dives within the "safety curve" (no decompression curve), in above 14 degrees C water, depth limited to the median space range (6 to 20 meters), plus mandatory guidance by a diving instructor.

Blood Glucose↗
PubMed2003

Retention of safe diving skills.

This study investigated diving skill maintenance over an eight-month retention period following an intervention program. Thirty-four recreational swimmers with poor diving skills were measured before and immediately after a diving skills intervention program. Twenty-two returned for follow-up evaluation. Treadwater, Deck and Block dives were video-recorded, and maximum depth, distance, velocity, entry angle and flight distance were compared. Underwater hand and arm positions were examined. Pre-intervention, a breaststroke arm action before maximum depth occurred in 18% of all dives and 38% of Treadwater dives. This was eliminated post-intervention, improving head protection. The Treadwater dive elicited the greatest mean maximum depth, and ANOVA showed depth for this entry decreased (improved) following intervention and remained shallower at follow-up. Deck and Block dives also became shallower following intervention. As seven 10-minute skills sessions resulted in shallower dives with safer hand and arm positions, including safe diving skills in learn-to-swim programs can provide a diving spinal cord injury prevention strategy.

Adult↗
PubMedDate not supplied

Energetic costs of surface swimming and diving of birds.

The energetic costs of swimming at the surface (swimming) and swimming underwater (diving) are compared in tufted ducks (Aythya fuligula) and three species of penguins, the gentoo (Pygoscelis papua), the king (Aptenodytes patagonicus), and the emperor (Aythya forsteri). Ducks swim on the surface and use their webbed feet as paddles, whereas penguins tend to swim just below the surface and use their flippers as hydrofoils, the latter being much more efficient. Penguins are more streamlined in shape. Thus, the amount of energy required to transport a given mass of bird a given distance (known as the cost of transport) is some two to three times greater in ducks than in penguins. Ducks are also very buoyant, and overcoming the force of buoyancy accounts for 60% and 85% of the cost of descent and remaining on the bottom, respectively, in these birds. The energy cost of a tufted duck diving to about 1.7 m is similar to that when it is swimming at its maximum sustainable speed at the surface (i.e., approximately 3.5 times the value when resting on water). Nonetheless, because of the relatively short duration of its dives, the tufted duck dives well within its calculated aerobic dive limit (cADL, usable O(2) stores per rate of O(2) usage when underwater). However, these three species of penguins have maximum dive durations ranging from 5 min to almost 16 min and maximum dive depths from 155 to 530 m. When these birds dive, they have to metabolise at no more than when resting in water in order for cADL to encompass the duration of most of their natural dives. In gentoo and king penguins, there is a fall in abdominal temperature during bouts of diving; this may reduce the oxygen requirements in the abdominal region, thus enabling dive duration to be extended further than would otherwise be the case.

Aerobiosis↗
PubMed2006

A phylogenetic analysis of the allometry of diving.

The oxygen store/usage hypothesis suggests that larger animals are able to dive for longer and hence deeper because oxygen storage scales isometrically with body mass, whereas oxygen usage scales allometrically with an exponent <1 (typically 0.67-0.75). Previous tests of the allometry of diving tend to reject this hypothesis, but they are based on restricted data sets or invalid statistical analyses (which assume that every species provides independent information). Here we apply information-theoretic statistical methods that are phylogenetically informed to a large data set on diving variables for birds and mammals to describe the allometry of diving. Body mass is strongly related to all dive variables except dive:pause ratio. We demonstrate that many diving variables covary strongly with body mass and that they have allometric exponents close to 0.33. Thus, our results fail to falsify the oxygen store/usage hypothesis. The allometric relationships for most diving variables are statistically indistinguishable for birds and mammals, but birds tend to dive deeper than mammals of equivalent mass. The allometric relationships for all diving variables except mean dive duration are also statistically indistinguishable for all major taxonomic groups of divers within birds and mammals, with the exception of the procellariiforms, which, strictly speaking, are not true divers.

Animals↗
PubMed2004

Nutritional status changes in humans during a 14-day saturation dive: the NASA Extreme Environment Mission Operations V project.

Ground-based analogs of spaceflight are an important means of studying physiologic and nutritional changes associated with space travel, and the NASA Extreme Environment Mission Operations V (NEEMO) is such an analog. To determine whether saturation diving has nutrition-related effects similar to those of spaceflight, we conducted a clinical nutritional assessment of the NEEMO crew (4 men, 2 women) before, during, and after their 14-d saturation dive. Blood and urine samples were collected before, during, and after the dive. The foods consumed by the crew were typical of the spaceflight food system. A number of physiologic changes were observed, during and after the dive, that are also commonly observed during spaceflight. Hemoglobin and hematocrit were lower (P < 0.05) after the dive. Transferrin receptors were significantly lower immediately after the dive. Serum ferritin increased significantly during the dive. There was also evidence indicating that oxidative damage and stress increased during the dive. Glutathione peroxidase and superoxide dismutase decreased during and after the dive (P < 0.05). Decreased leptin during the dive (P < 0.05) may have been related to the increased stress. Subjects had decreased energy intake and weight loss during the dive, similar to what is observed during spaceflight. Together, these similarities to spaceflight provide a model to use in further defining the physiologic effects of spaceflight and investigating potential countermeasures.

Adult↗
PubMed2001

Can eustachian tube ventilatory function impairment after oxygen diving be influenced by application of free radical scavenger vitamins C and E?

OBJECTIVES/HYPOTHESIS: To evaluate the influence of free radical scavenger vitamins C and E on eustachian tube ventilatory function changes related to oxygen dives. STUDY DESIGN: Prospective, randomized, double-blind, placebo-controlled study of middle ear impedance changes of oxygen divers being orally treated with free radical scavenger vitamins C and E. METHODS: Fifteen divers were allocated to two groups. Before diving on oxygen on consecutive days (days 1 and 2), divers in group 1 took a daily dose of 1 g ascorbic acid and 600 International Units d-alpha-tocopherol and divers in group 2 were given placebo. Before diving and 2 and 24 hours after diving on days 1 and 2, middle ear impedance was measured. RESULTS: Impedance decreased overnight after dive 1 (P =.04) but not after dive 2 (P =.31). No impedance differences were found between groups after the dive on day 1 (P =.83). Twenty-four hours after the dive on day 1 and after the dive on day 2, impedance values in both groups were different (P =.02 vs. P =.07), emphasizing slightly more negative pressures in the vitamin group. CONCLUSION: Vitamins C and E did not reduce eustachian tube ventilatory function impairment overnight after the dive on day 1, suggesting no evidence of free radical-mediated toxicity affecting the eustachian tube or middle ear mucosa. Repetitive oxygen dives may cause tissue adaptation suggesting other than antioxidant defense mechanisms.

Administration, Oral↗
PubMed1986

The diving response in man: effects on sympathetic activity in muscle and skin nerve fascicles.

Multi-unit recordings of muscle-nerve sympathetic activity (m.s.a) or skin-nerve sympathetic activity (s.s.a) were made in the left peroneal nerve of sixteen healthy volunteers during simulated diving by immersion of the face in a tub of water. The procedure was varied by the use of different water temperatures, by diving with snorkel breathing, by apnoea without diving, and by apnoea with a stream of air against the face instead of immersion in water. Diving for 12 s elicited a pronounced activation of m.s.a., the mean increase from control periods being 360%. The response was stronger with lower water temperatures. Immersion of the whole face evoked a stronger increase in m.s.a. than immersion of mouth and nose only. Diving without apnoea elicited a significant but weaker increase in m.s.a., whereas apnoea only for 12 s did not influence the sympathetic outflow. Cool air against the face during apnoea for 12 s was associated with a significant increase in m.s.a. The increase in m.s.a. usually occurred before the bradycardia. On emersion, m.s.a. ceased abruptly, whereas the bradycardia persisted for a few seconds. Mental arithmetic during diving did not change the m.s.a. response but reduced the bradycardia. M.s.a. increased despite increasing blood pressure levels. On emersion, m.s.a. did not reappear until the pre-diving blood pressure level was attained. S.s.a was inhibited on diving, with concomitant vasodilatation in the skin as recorded in the big toe. It is concluded that the response of m.s.a. to diving is initiated by a central 'pattern recognition' of an input from facial receptors, that this input and the effects of apnoea, acting by mutual reinforcement, maintain the strong sympathetic outflow, and that the mechanism releasing m.s.a. on diving overrides the normal blood pressure regulatory function of m.s.a. Diving exerts differentiated influence on different parts of the sympathetic nervous system, as illustrated by the inhibition of s.s.a.

Adult↗
PubMed2003

Unconventional ventral attachment of time-depth recorders as a new method for investigating time budget and diving behaviour of seabirds.

We tested the use of commercially available electronic time-depth recorders (TDRs) to quantify activities and thus total time budgets of seabirds. This new method involved first fitting TDRs onto the birds' bellies (not on their backs), and, secondly, analysing continuous recordings of temperature, light and pressure to differentiate activities on land and at sea. The birds studied were 12 common guillemots (Uria aalge) rearing chicks at Hornøya, in northern Norway. The method successfully recorded five different activities: at the colony, flying, diving, and resting or active at the sea surface. Overall, common guillemots spent 68% of their time at the colony and 32% at sea. While at sea, the birds spent the majority (77%) of their time at the surface, during which they were active 64% of the time, and rested only 13%. Birds engaged in the costly behaviours of flying and diving for shorter times (11% and 12% of their time at sea, respectively). The method allowed us to differentiate between two types of trips to sea based on the presence (foraging trips: 77% of the total number of trips) or absence (non-foraging trips: 23%) of dives. On average, foraging trips lasted 3.2 h, but most trips were shorter (<1 h), during which the mean estimated travel distance from the colony was 11 km. Diving occurred in bouts of 7.7+/-6.6 dives (mean +/- S.D.). The mean maximum dive depth was 10.2+/-7.6 m (deepest dive: 37 m), and the mean dive duration and post-dive intervals were 38.7+/-21.3 s (longest dive: 119 s) and 20+/-12 s, respectively. Direct and indirect evidence suggests that common guillemots had no difficulty in finding food during the study period, and that the TDRs had minimal effects on the birds' behaviour and physiology. The method is easy to use in the field and is applicable to many other flying seabird species; it is therefore an efficient way of collecting information on time budgets and diving behaviour in the context of various ecological and monitoring studies.

Animals↗