Righting Response and Escape Response in Opsanus tau Are Temperature Dependent.

We sought to establish baseline values for two basic reflex behaviors and for ventilation rate in the toadfish, Upsanus tau, over a range of temperatures. Righting response and escape response were chosen as measureable reflexes indicative of activity level in these animals. Between September, 1996, and January, 1997, ten fish were held in an isolated tank at ambient temperature in the Marine Resources Center at the Marine Biological Laboratory in Woods Hole, Massachusetts. The animals were subjected to a series of behavioral tests as the ambient water decreased in temperature. Fish were acclimated a minimum of 24 hours at each temperature before testing. Tests were conducted in an experimental tank, 65 cm wide x 100 cm long x 10 cm deep, and filled with water at the same temperature to which the animals had been acclimated. Trials were recorded with a video camera mounted on a tripod above the tank. During testing, a single animal was placed in the tank, and righting response, escape response, and the ventilation rate were quantified consecutively. The righting response was measured as follows. A fish was held ventral side up for several seconds and then released. The animal could then attempt to right itself. These trials were scored on an incremental scale of five levels based on the number of attempts required by the animal to right itself and on the effort exerted (4, successful on first attempt with accessory tail movement; 3, successful on first attempt with minimal tail movement; 2, successful after multiple attempts; 1, unsuccessful attempts; and 0, no attempts). The escape response was quantified by probing and pinching the animal posterior to the last dorsal spine with toothed forceps. Three levels of pressure (probe, hold, hold, and pull) were applied to all animals with a 30-s recovery period between stimuli. From these three trials, a single escape response score was generated. Escape responses were divided into high velocity (220 cm/s) and low velocity (~20 cm/s) responses. The stimulus of least force to which the animal responded at high velocity was the basis for scoring. If the animal did not exhibit a high velocity response to the first two levels of stimulus, the score was determined using the strongest stimulus applied (animal held and pulled with forceps). In general, scoring, using an incremental scale, was based on response velocity relative to the type of stimulus eliciting that response (4, escape velocity 2 20 cm/s when touched with forceps; 3, same velocity when held with forceps; 2, same velocity when held and tugged with