Meeting Abstract

9.2  Thursday, Jan. 3  Ventilation Mechanics in Resting and Swimming Spiny Dogfish DOLCE, J.*; WILGA, C.; Univ. of Rhode Island jdol6206@postoffice.uri.edu

Oxygen consumption rates increase with swimming velocity in many fishes. As a result, ram ventilating fishes often enlarge the gape and opecular openings while swimming; however, modulation of suction ventilation mechanics during swimming has not been studied. To investigate this, gill arch and slit kinematics and pressure profiles were compared at rest and while swimming at 0.5 BL s-1 in spiny dogfish, a suction ventilating species. Sonometric crystals were placed on the upper and lower jaw, the hyoid and branchial arches one through five, and gill slits one, three, and five. Pressure transducers were implanted in the pharyngeal cavity and parabranchial cavities one, three, and five. Gape cycle increases but gape distance decreases when swimming compared to that at rest. The relative distances between the arches narrow during swimming compared to that at rest. Gill slit one has a larger maximum opening width than slit three at rest, and this relationship remains the same during swimming. In contrast, the relative distance between arches four and five and the maximum opening width of slit five doubles during swimming. The arches and slits move nearly in unison at rest, but show temporal variation during swimming. Parabranchial pressure is the same at rest as during swimming. These results suggest the arches and slits may be separated into two functional units that play different roles in ventilation. The distance between the branchial arches are adjusted when swimming compared to that at rest such that no change in pressure occurs in the parabranchial chambers and more water is directed through slit five. The suction ventilation mechanism is modulated by increasing the opening width of slit five and associated arches to serve as an exit valve for water entering the posterior region of the pharyngeal cavity during swimming.