<Session 5: Wildlife Tracking I>Simultaneous measurements of breaths and energy expenditure reveal the dive tactics of sea turtles

19–22 May 2022 Kyoto, JapanAir-breathing divers are assumed to have evolved to apportion their time between surface and underwater periods to maximize the benefit gained from diving activities. However, whether they change their time allocation depending on the aim of the dive is still unknown. This may be particularly crucial for 'surfacers' because they dive for various purposes in addition to foraging. In this study, we counted breath events at the surface and estimated oxygen consumption during resting, foraging, and other dives in 11 green turtles (Chelonia mydas) in the wild. Breath events were counted by a head-mounted acceleration logger or direct observation based on an animal-borne video logger, and oxygen consumption was estimated by measuring overall dynamic body acceleration. Our results indicate that green turtles maximized their submerged time, following this with 5-7 breaths to replenish oxygen for resting dives. However, they changed their dive tactic during foraging and other dives; they surfaced without depleting their oxygen content, followed by only a few breaths for effective foraging and locomotion. These dichotomous surfacing tactics would be the result of behavioral modifications by turtles depending on the aim of each dive

Preliminary result of the relationship between the breathing frequency and dynamic body acceleration

March 5-6, 2009, Bangkok, ThailandIn this study, the relationship between the breathing frequency and the dynamic body acceleration (DBA) of one hatchery-reared loggerhead turtle Carretta carretta was examined using acceleration data loggers. Two acceleration data loggers (M190L-D2GT, W1000-3MPD3GT, Little Leonard, Japan) were attached on the lower-beak and carapace of a hatchery-reared loggerhead turtle, respectively. Breathing was successfully detected from the angle and depth of the beak-attached data logger and DBA, which has been used as an index of activity levels (Wilson et al., 2006), was calculated from the forward acceleration of the carapace-attached logger. There was a positive correlation between the DBA in the previous dive and the breathing frequency; the relationship was exponential. The result suggests that the number of breaths increased exponentially after a more active dive

Pulmonary ventilation–perfusion mismatch : a novel hypothesis for how diving vertebrates may avoid the bends

© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Proceedings of the Royal Society B: Biological Sciences 285 (2018): 20180482, doi:10.1098/rspb.2018.0482.Hydrostatic lung compression in diving marine mammals, with collapsing alveoli blocking gas exchange at depth, has been the main theoretical basis for limiting N2 uptake and avoiding gas emboli (GE) as they ascend. However, studies of beached and bycaught cetaceans and sea turtles imply that air-breathing marine vertebrates may, under unusual circumstances, develop GE that result in decompression sickness (DCS) symptoms. Theoretical modelling of tissue and blood gas dynamics of breath-hold divers suggests that changes in perfusion and blood flow distribution may also play a significant role. The results from the modelling work suggest that our current understanding of diving physiology in many species is poor, as the models predict blood and tissue N2 levels that would result in severe DCS symptoms (chokes, paralysis and death) in a large fraction of natural dive profiles. In this review, we combine published results from marine mammals and turtles to propose alternative mechanisms for how marine vertebrates control gas exchange in the lung, through management of the pulmonary distribution of alveolar ventilation (Embedded Image) and cardiac output/lung perfusion (Embedded Image), varying the level of Embedded Image in different regions of the lung. Man-made disturbances, causing stress, could alter the Embedded Image mismatch level in the lung, resulting in an abnormally elevated uptake of N2, increasing the risk for GE. Our hypothesis provides avenues for new areas of research, offers an explanation for how sonar exposure may alter physiology causing GE and provides a new mechanism for how air-breathing marine vertebrates usually avoid the diving-related problems observed in human divers.Funding to support a portion of this work was obtained by the Fundación Oceanogràfic and by the Office of Naval Research (ONR YIP Award no. N000141410563 and Award no. N000140811220)

Measuring Energy Expenditure in Sub-Adult and Hatchling Sea Turtles via Accelerometry

Measuring the metabolic of sea turtles is fundamental to understanding their ecology yet the presently available methods are limited. Accelerometry is a relatively new technique for estimating metabolic rate that has shown promise with a number of species but its utility with air-breathing divers is not yet established. The present study undertakes laboratory experiments to investigate whether rate of oxygen uptake (o2) at the surface in active sub-adult green turtles Chelonia mydas and hatchling loggerhead turtles Caretta caretta correlates with overall dynamic body acceleration (ODBA), a derivative of acceleration used as a proxy for metabolic rate. Six green turtles (25–44 kg) and two loggerhead turtles (20 g) were instrumented with tri-axial acceleration logging devices and placed singly into a respirometry chamber. The green turtles were able to submerge freely within a 1.5 m deep tank and the loggerhead turtles were tethered in water 16 cm deep so that they swam at the surface. A significant prediction equation for mean o2 over an hour in a green turtle from measures of ODBA and mean flipper length (R2 = 0.56) returned a mean estimate error across turtles of 8.0%. The range of temperatures used in the green turtle experiments (22–30°C) had only a small effect on o2. A o2-ODBA equation for the loggerhead hatchling data was also significant (R2 = 0.67). Together these data indicate the potential of the accelerometry technique for estimating energy expenditure in sea turtles, which may have important applications in sea turtle diving ecology, and also in conservation such as assessing turtle survival times when trapped underwater in fishing nets

The Behaviour of Immature and Female Hawksbill Turtles (Eretmochelys imbricata) at Sea

Das Verhalten sowohl adulter Weibchen als auch juveniler Karettschildkröten (Eretmochelys imbricata) auf See wurde aufgezeichnet und die Tauchgänge in Abhängigkeit von unterschiedlichen extrensischen und intrensischen Bedingungen analysiert. In den zwei Karibischen Untersuchungsgebieten wurden an den freilebenden Karettschildkröten Geräte befestigt, die Wassertemperatur, Lichtintensität, Schwimmgeschwindigkeit, Tiefe, Himmelsrichtung und Lage im Raum in Messintervallen zwischen 0.25 und 30 sek aufzeichneten. Während der Reproduktionsphase führten adulte Weibchen Ruhetauchgänge durch, die unabhängig vom Tagesrhythmus waren. Lediglich kurz vor der Eiablage zeigte sich ein nachtaktiver Rhythmus. Während eines Hurrikans war das Verhalten des betroffenen Weibchens kurzfristig verändert und die Wassertemperatur mittelfristig erniedrigt. Immature Karettschildkröten zeigten einen deutlich tagaktiven Rhythmus mit kürzeren, aktiven Tauchgängen am Tag und langen Ruhetauchgängen in der Nacht. Nach Beendigung der Nistsaison suchten die untersuchten Weibchen Nahrungsgründe in verschiedenen Himmelsrichtungen und Entfernungen zwischen 70 und 360 km auf. Im grundsätzlichen Tauchverhalten adulter Weibchen ausserhalb der Reproduktionsphase wurde Tagaktivität nachgewiesen. Die erhobenen Daten zeigen eine Abhängigkeit der Tauchdauer von der saisonal schwankenden Wassertemperatur und von der Körpermasse des Tieres

Exertional Myopathy in a Juvenile Green Sea Turtle ( Chelonia mydas

A juvenile female green sea turtle (Chelonia mydas) was found entangled in a large mesh gillnet in Pamlico Sound, NC, and was weak upon presentation for treatment. Blood gas analysis revealed severe metabolic acidosis and hyperlactatemia. Plasma biochemistry analysis showed elevated aspartate aminotransferase and creatine kinase, marked hypercalcemia, hyperphosphatemia, and hyperkalemia. Death occurred within 24 hours of presentation despite treatment with intravenous and subcutaneous fluids and sodium bicarbonate. Necropsy revealed multifocal to diffuse pallor of the superficial and deep pectoral muscles. Mild, multifocal, and acute myofiber necrosis was identified by histopathological examination. While histological changes in the examined muscle were modest, the acid-base, mineral, and electrolyte abnormalities were sufficiently severe to contribute to this animal’s mortality. Exertional myopathy in reptiles has not been well characterized. Sea turtle mortality resulting from forced submergence has been attributed to blood gas derangements and seawater aspiration; however, exertional myopathy may also be an important contributing factor. If possible, sea turtles subjected to incidental capture and entanglement that exhibit weakness or dull mentation should be clinically evaluated prior to release to minimize the risk of delayed mortality. Treatment with appropriate fluid therapy and supportive care may mitigate the effects of exertional myopathy in some cases

High resting metabolic rates with low thermal dependence induce active dives in overwintering Pacific juvenile loggerhead turtles

UTokyo FOCUS Articles掲載「三陸のウミガメは寒冷地仕様 高い休止代謝速度と低い温度依存性によって冬季でも活動性を維持」https://www.u-tokyo.ac.jp/focus/ja/articles/a_00627.htmlUTokyo FOCUS Articles "Cold never bothered me anyway Pacific sea turtles\u27 metabolisms stay active over winter" https://www.u-tokyo.ac.jp/focus/en/articles/z0508_00003.htm

Editorial. Tolerancia a la anoxia y estrés en tortugas marinas

La anoxia es una condición estresante que es extremadamente dañina para la mayoría de los mamíferos, en tanto lidera la supresión de actividad eléctrica en el córtex cerebral, silenciando los receptores ampa y nmda e inhibiendo las señales pos-sináptica y pre-sináptica de las neuronas, lo que conduce en pocos minutos a la muerte cerebral (Hochachka et al., 1996; Pérez-Pinzón et al., 1992). En contraste, vertebrados ectotérmicos están extremadamente bien adaptados para sobrevivir a las limitaciones de oxígeno (Hochachka &amp; Lutz, 2001): por ejemplo, las tortugas dulceacuícolas, Trachemys y Crysemys, permanecen en el fondo de lagos o estanques durante el invierno por hasta dos semanas entre 16 y 18 °C y de 12 a 18 semanas a 3 °C (Krivoruchko &amp; Storey, 2015). Los estudios realizados sobre esta condición en estas tortugas han identificado la expresión de genes que explican, en buena parte, esta adaptación (Keenan et al., 2015).&nbsp;&nbsp

Improving estimates of diving lung volume in air-breathing marine vertebrates

The air volume in the respiratory system of marine tetrapods provides a store of O2 to fuel aerobic metabolism during dives; however, it can also be a liability, as the associated N2 can increase the risk of decompression sickness. In order to more fully understand the physiological limitations of different air-breathing marine vertebrates, it is therefore important to be able to accurately estimate the air volume in the respiratory system during diving. One method that has been used to do so is to calculate the air volume from glide phases - periods of movement during which no thrust is produced by the animal - which many species conduct during ascent periods, when gases are expanding owing to decreasing hydrostatic pressure. This method assumes that there is conservation of mass in the respiratory system, with volume changes only driven by pressure. In this Commentary, we use previously published data to argue that both the respiratory quotient and differences in tissue and blood gas solubility potentially alter the mass balance in the respiratory system throughout a dive. Therefore, near the end of a dive, the measured volume of gas at a given pressure may be 12-50% less than from the start of the dive; the actual difference will depend on the length of the dive, the cardiac output, the pulmonary shunt and the metabolic rate. Novel methods and improved understanding of diving physiology will be required to verify the size of the effects described here and to more accurately estimate the volume of gas inhaled at the start of a dive.Publisher PDFPeer reviewe