Use of a treadmill to study the relationship between walking, ventilation and heart rate in the lobster Homarus americanus

Abstract

A passive treadmill was designed and built that measures the speed of lobster walking, while simultaneously recording heart and scaphognathite pumping rates. The treadmill only moved when the lobster voluntarily walked either forward or backward. Lobsters (n = 5) on the treadmill typically walked in bouts lasting an average of 5 min (range 8 s to 53 min). During these bouts, the mean walking rate was 0.9 0.6 m/min (n = 100 bouts from 5 lobsters), and the maximum speed recorded was 2.5 m/min. At the onset of walking, and sometimes 5–10 s before, the heart and ventilation rates rapidly increased. Ventilation rate increased more than heart rate during walking (ventilation rate: 194% increase; heart rate: 69% increase) and returned to baseline faster (4.5 3.9 min) than heart rate (6.6 3.9 min) after a bout. Heart and ventilation rates during walking do not appear to be related to the duration of the bout. Heart and ventilation rates were positively correlated with the average walking speed attained in 3 of the 5 lobsters tested. Heart rate, in particular, appeared to have an upper limit of approximately 90–100 beats/min, regardless of walking duration or speed.