The cardiovascular responses of the freshwater turtleTrachemys scriptato warming and cooling

Abstract

Seven freshwater turtles Trachemys scripta were instrumented with flow probes and cannulated for blood pressure measurements. The turtles were warmed from 24 to 34°C, and cooled down to 24°C, with and without atropine. Animals exhibited a hysteresis of heart rate and blood flow to both the pulmonary and systemic circulations, which was not cholinergically mediated. Blood pressure remained constant during both warming and cooling, while systemic resistance decreased during heating and increased during cooling, indicating a barostatic response. There was a large right-to-left (R-L) shunt during warming and cooling in untreated animals, which remained relatively constant. Atropinisation resulted in a large L-R shunt, which decreased during warming and increased during cooling. Nevertheless, heating rates were the same in untreated and atropinised animals, and cooling rates were significantly longer in atropinised animals, indicating that shunt patterns contribute little to heat exchange.

Embryonic hypoxia programmes postprandial cardiovascular function in adult common snapping turtles (Chelydra serpentina)

“…In 5-year-old snapping turtles, fasted and postprandial _ Q pul values (∼21-31 ml min −1 kg −1 ; Fig. 4A) were within the range for other turtle species at similar temperatures (∼15-56 ml kg −1 min −1 ; West et al, 1992;Wang and Hicks, 1996a;Hicks and Wang, 1998;Galli et al, 2004). However, _ Q sys of fasted N21 snapping turtles (6.54±0.90 ml kg −1 min −1 ; Fig.…”

“…However, _ Q sys of fasted N21 snapping turtles (6.54±0.90 ml kg −1 min −1 ; Fig. 4B) was considerably lower than values previously reported for other species (∼17-73 ml kg −1 min −1 ; Wang and Hicks, 1996a;Hicks and Wang, 1998;Galli et al, 2004). This was partially the result of a low _ Q RAo (Fig.…”

“…Prior studies have also reported a net systemic blood flow pattern [i.e. right-left (R-L) shunt] in T. scripta (Wang and Hicks, 1996a;Hicks and Wang, 1998;Crossley et al, 2000;Krosniunas and Hicks, 2003;Galli et al, 2004;Keen et al, 2016). However, we are among the first to assess intracardiac shunting in the snapping turtle (Steggerda and Essex, 1957), and it is unclear whether the direction of shunting is similarly variable in this species.…”

“…Over half a century ago, anaesthetized snapping turtles (8-14 kg) were shown to demonstrate a large net L-R shunt, through the use of a dye-dilution technique (Steggerda and Essex, 1957). The presence of this pulmonary shunt has been more extensively described in red-eared slider turtles, Trachemys scripta (White and Ross, 1966;Comeau and Hicks, 1994;Hicks et al, 1996;Crossley et al, 1998;Overgaard et al, 2002b;Krosniunas and Hicks, 2003;Galli et al, 2004), and is attributed to low vagal tone and/or high adrenergic stimulation (Hicks, 1994;Hicks and Comeau, 1994;Hicks and Wang, 1998;Wang et al, 2001b;Overgaard et al, 2002b). Shunt ratio ( _ Q pul = _ Q sys ) is dependent on the relationship of pulmonary to systemic vascular resistance in turtles (Crossley et al, 1998).…”

“…5B). To date, studies of _ Q in surgically recovered, conscious turtles have reported total systemic flow only (Wang and Hicks, 1996a;Hicks and Wang, 1998;Krosniunas and Hicks, 2003;Galli et al, 2004;Stecyk et al, 2004), so it is unclear whether this phenomenon is common to turtles, or whether it is unique to snapping turtles. However, _ Q RAo has been reported to be roughly double that of _ Q LAo in anaesthetized T. scripta .…”