Temperature dependence of cardiac performance in the lobsterHomarus americanus

Abstract

SUMMARY The lobster Homarus americanus inhabits ocean waters that vary in temperature over a 25°C range, depending on the season and water depth. To investigate whether the lobster heart functions effectively over a wide range of temperatures we examine the temperature dependence of cardiac performance of isolated lobster hearts in vitro. In addition, we examined whether modulation of the heart by serotonin depends on temperature. The strength of the heartbeat strongly depends on temperature, as isolated hearts are warmed from 2 to 22°C the contraction amplitude decreases by greater than 60%. The rates of contraction and relaxation of the heart are most strongly temperature dependent in the range from 2 to 4°C but become temperature independent at warmer temperatures. Heart rates increase as a function of temperature both in isolated hearts and in intact animals, however hearts in intact animals beat faster in the temperature range of 12–20°C. Interestingly, acute Q10 values for heart rate are similar in vivo and in vitro over most of the temperature range, suggesting that temperature dependence of heart rate arises mainly from the temperature effects on the cardiac ganglion. In contrast to earlier reports suggesting that the strength and the frequency of the lobster heartbeat are positively correlated, we observe no consistent relationship between these parameters as they change as a function of temperature. Stroke volume decreases as a function of temperature. However, the opposing temperature-dependent increase in heart rate partially compensates to produce a relationship between cardiac output and temperature in which cardiac output is maximal at 10°C and significantly decreases above 20°C. Serotonin potentiates contraction amplitude and heart rate in a temperature-independent manner. Overall, our results show that although the parameters underlying cardiac performance show different patterns of temperature dependence, cardiac output remains relatively constant over most of the wide range of environmental temperatures the lobster inhabits in the wild.

Impact of anthropogenic ocean acidification on thermal tolerance of the spider crab <i>Hyas araneus</i>

“…This pattern is similar to the pattern of oxygen consumption within thermal tolerance windows as seen in the squat lobster Munida rugosa (Zainal et al, 1992) and in other marine invertebrates, e.g. the lugworm, Arenicola marina (Wittmann et al, 2008).…”

“…The earliest limits of the thermal tolerance range with ecological relevance (Pörtner and Knust, 2007) are reflected by high and low pejus temperatures (T p ). Warming leads to rising oxygen demand that can initially be met by oxygen supply through enhanced ventilation and heart rate (Zainal et al, 1992;. The upper T p indicates the point, where ventilation and heart rates level off and remain constant indicating capacity limitation.…”

“…A drop in heart rate characterizes the critical temperature as it coincides with the onset for anaerobic metabolite accumulation Melzner et al, 2006). As P e O 2 levels depend on oxygen consumption and are controlled by ventilation and heart rate the determination of critical thermal maxima in different crab species from heart rate measurements (Ahsanullah and Newell, 1971;Cuculescu et al, 1998;Stillman and Somero, 1996;Worden et al, 2006) would likely match critical thermal limits according to the concept of oxygen and capacity limited thermal tolerance.…”

Master of all trades: thermal acclimation and adaptation of cardiac function in a broadly distributed marine invasive species, the European green crab,Carcinus maenas

“…Because C. maenas lives almost exclusively in shallow subtidal habitats, water temperature data provide a valid measure of body temperature (McGaw, 2003;Worden et al, 2006). Long-term temperature data were also collated for each site, using SST analyses created by the NOAA/NWS National Centers for Environmental Prediction, based on AVHRR satellite data and buoy observations (Reynolds et al, 2007).…”

Inter-animal variability in the effects of C-type allatostatin on the cardiac neuromuscular system in the lobster Homarus americanus

“…The peptide was applied to the preparation for 8-12min at a flow rate of 5mlmin -1 . Because the cardiac system exhibits its maximum output at 10°C (Worden et al, 2006), the temperature was maintained at 9-11°C using an in-line Peltier temperature regulator (CL-100 bipolar temperature controller and SC-20 solution heater/cooler, Warner Instruments, Hamden, CT, USA). After each peptide application, the preparation was washed with fresh saline for 45-60min, allowing contractions to return to baseline before additional peptide applications at different concentrations.…”