Meeting Abstract

P1.146  Monday, Jan. 4  Bite Force and In Vivo Stimulation of the Loggerhead Sea Turtle (Caretta caretta) Adductor Mandibulae Complex MARSHALL, CD*; HIGGINS, BM; FLANAGAN, JP; KANE , EA; NEUENHOFF, RD; Texas A and M University; NOAA Galveston ; The Houston Zoo; Clemson University; Pacific States Marine Fisheries Commission marshalc@tamug.edu

Voluntary bite force measurements can vary according to the motivation state of subjects. To test whether voluntary bite force data collected for loggerheads were within the physiological range of maximum performance, and to characterize tetanic muscle fusion of the adductor mandibulae complex, we conducted an in vivo muscle stimulation study in 3 loggerhead turtles. All subjects were deeply anesthetized and bipolar stimulation electrodes were inserted percutaneously into the body of the adductor mandibulae muscle complex bilaterally. Bite force plates of a “bite meter” incorporating a Kistler force transducer (type 9312A) were placed between the jaws of the subjects. A hand-held charge amplifier with output to a channel on Biopac MP150 system recorded the stimulus response of the force transducer. Stimulator output was recorded onto a second channel. Force output curves were visualized using Acknowledge software. Stimulations included single twitch (500 ms), square-wave stimulus trains of 10-70 Hz, and ramping voltages from 5 to 30V. Stimulus train frequency and voltage was varied until tetanic fusion was attained, as represented by bite force output curves. Maximum train rate, voltage, and bite force at tetanus for each of the 3 subjects were: Cc2005-82 (SCL=43.1cm; 11kg): 20Hz, 20V, 81.8N; Cc2003-45 (SCL=49.3 cm; 18.6kg): 17Hz, 20V, 114N; Cc2004-28 (SCL=57.1; 23.7kg): 17Hz, 30V, 194N. Maximum bite forces measured during stimulation trials were in accordance with voluntary bite force measurements collected previously.