Meeting Abstract

39.2  Monday, Jan. 5  Three dimensional excape response of white spotted ratfish, Hydrolagus colliei. DICKSON, Juleen*; MAIA, Anabela; DOMENICI, Paolo; University of Rhode Island; University of Rhode Island; CNR-IAMC jdickson@mail.uri.edu

Escape responses are vital to the survival of prey during predator-prey interactions. This study documented the kinematics of the escape responses of white spotted ratfish, Hydrolagus colliei (Chimaeriformes). Three H. colliei (345-460 mm TL) were trawled off the coast of San Juan Island, WA and housed in flow-through aquaria at the University of Washington, Friday Harbor Laboratories. Escape responses were elicited with a forceful tap on the caudal region and recorded using a high speed camera at 250 fps. The video sequences were digitized for both lateral and dorsal views. Escape responses generally included a large vertical excursion which corresponded to 77% of the horizontal displacement. Large vertical excursions in escape locomotion is relatively unusual in fish, although they have been observed in Carnegiella strigata and Xenomystus nigri. The potential advantages of this type of response may lie in eluding predators that have little vertical maneuverability. The average latency time to response was about 200 ms, which is higher than the latency values commonly observed in teleosts (10-50 ms). This was unexpected, since ratfish are the only chondrichthyans whose adults are known to have Mauthner cells. The average head turning rate during stage 1 (initial formation of C-shape) was 517.16 deg.s^-1 (mean+SEM), which is in line with results on other fishes. Maximum acceleration was 116+31 m s^-2 and maximum speed was 8.52+1.15 BL s^-1. Pectoral fin analyses indicate that right and left fin abduction are not simultaneous, but rather alternate over time. Maximum pectoral fin velocities were usually during stage 1. Overall, locomotor performance appears to be higher than that observed in previously studied chondrichthyan species.