Summary 1. Freshwater fishes are the most northerly of freshwater ectotherms, followed by frogs. North American snakes, turtles, and salamanders do not range farther north than southernmost Canada. 2. Freezing desiccation main challenges during terrestrial hibernation ectotherms. Oxygen depletion, water balance, ionic balance major problems for air breathing ectotherms that hibernate underwater. 3. The importance accumulation energy stores overwintering among depends upon length severity...

A BASIC program is given that fits two-segmented straight lines. It applicable for analysis of data concerning the physiological response an organism to varying environmental conditions where regulate some parameter over a range relevant variable (zone regulation) and fail more stressful conformation). The identifies as example critical point shift from metabolic regulation O2 consumption conformation occurs (Pc, tension). discussion presented relative merits our method Nickerson, Facey,...

ABSTRACT Survival and blood acid-base status were measured on freshwater turtles (Chrysemys picta bellii Gray) that submerged at 3 °C in either aerated (high O2) or Na-equilibrated (low water. Results from catheterized turtles, without access to air under these conditions, non-catheterized which apnoeic (in high O2 low water) water with air, are compared. Under the most adverse conditions (catheterized, submerged, O2), survival duration was 126 ± 14 (X s.E.) days, 2 of 10 so treated still...

The painted turtle, Chrysemys picta, is currently recognized as a continentally distributed polytypic species, ranging across North America from southern Canada to extreme northern Mexico. We analyzed variation in the rapidly evolving mitochondrial control region (CR) 241 turtles 117 localities this range examine whether turtle represents species based on molecular analysis. found strong support for novel hypothesis that C. p. dorsalis sister group all remaining Chrysemys, with falling into...

Six species of darters (Etheostoma) were studied in the field and laboratory to relate respiration habitat selection. The ranged preference from a fast—water form (Etheostoma rufilineatum) slow—water fusiforme). Field measurements showed that winter O_2 tensions not limiting distribution when these compared with critical determinations made at low temperature (10 degrees C). However, summertime ambient levels as 3.3 ppm [= 7.33 kilopascals or 55 mm Hg], level was 1.0—1.7 below wintertime...

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ABSTRACT Plasma [Na+], [K+], and [Cl-] were measured on blood sampled periodically from turtles submerged in Na-equilibrated (low-O2) or air-equilibrated (high-O2) water. osmolality total [Ca2+] [Mg2+] selected samples. Previously we reported that a severe metabolic acidosis developed under these conditions; low-O2 turtles, plasma [lactate-], rising to over 200 m-equiv/1, was only partially buffered by [HCO3-], which fell 40 5 m-equiv/1. The balance of the buffering accomplished changes...

ABSTRACT Carp (Cyprinus carpio) were exposed to environmental water pH (pHw) step changes from 7·4 5·1, 5·1 4·0 and 3·5. pH, , lactate in dorsal aortic blood, [Na+], [K+] [Cl−] plasma, base loss, ammonia excretion determined as a function of time after each pHw change. At the measured blood acid-base electrolyte parameters remained essentially unchanged; however, was increased by factor 2. When lowered an additional severe increase ‘net loss’, expressed difference between loss excretion,...

ABSTRACT Western Painted Turtles, Chrysemys picta bellii (N = 5), were maintained submerged and apneic for 90 days: days 0–21 in severely hypoxic water ( 0–5 mmHg), 22–43 aerated ∼ 160 44–90 again water. From day onward, the was turtles allowed access to air ; temperatures at 3 °C. Arterial blood samples taken periodically analysed , pH, [Na+], [K+], [Cl−], [lactate−], [glucose] haematocrit. Plasma [HCO3−] calculated all total plasma calcium measured on from two animals. Each exposure low...

ABSTRACT The critical O2 tension (Pcrit) is the lowest PO2 at which an animal can maintain some benchmark rate of uptake (ṀO2). This has long served as a comparator hypoxia tolerance in fishes and aquatic invertebrates, but its usefulness this role, particularly when applied to fishes, recently been questioned. We believe that Pcrit remains useful provided it determined using proper methods clearly defined. Here, we review available for each three steps determination: (1) measuring most...

The responses to prolonged diving in a representative of each the four families North American freshwater turtles (Chelydridae, Emydidae, Kinosternidae, Trionychidae) were investigated. For submerged at 10 C anoxic (N₂-equilibrated) and normoxic (aerated) water, we found: (1) Survival times anoxia (days) 2.6 (Trionyx), 5.2 (Sternotherus), 8.5 (Chelydra), 17.0 (Chrysemys); corresponding survival normoxia >100, 14.2, 29.3. differences between water significant all species except Chelydra. (2)...