Meeting Abstract
P1.99 Thursday, Jan. 3 Under pressure: ventilation and feeding in the white-spotted ratfish, Hydrolagus collei (Chimaeroidea) FERRY-GRAHAM, L.A.*; NEWAY, A.L.; QUARANTA, K.L.; PERLMAN, B.M.; California State Universities/Moss Landing Marine Labs; California State Universities/Moss Landing Marine Labs; California State Universities/Moss Landing Marine Labs; California State Universities/Moss Landing Marine Labs lfgraham@mlml.calstate.edu
Holocephalans are the only aquatic vertebrates with a fused upper jaw and a non-suspensory hyoid. These features, along with robust tooth plates, arose coincident with a durophagous foraging habit. However, extant species show a trend towards reduction of the tooth plates and consume softer prey, captured putatively via suction. This implies that suction is being generated in a mechanical system where the upper jaw cannot protrude and the hyoid cannot depress, posing serious limitations on suction generation as we have come to understand it based upon studies of elasmobranchs and actinopterygians. As a first attempt at understanding this problem, we measured intra-oral pressures in 9 individuals of H. collei during ventilation and prey capture. Transducers were implanted in the oro- and parabranchial cavities, and pressure was recorded during several modes of ventilation (i.e., at rest, fins sculling, quiescent swimming), as well as during prey capture. We observed a consistent trend across ventilatory modes whereby a single pump dominated; i.e., only the pressure pump phase of the two-pump/suction-pressure model appeared to function consistently. Pressure inside the orobranchial cavity dropped by as much as 1000 Pa during capture of mussel pieces and small crabs, however, suggesting that some suction could be generated. A subset of these strikes were recorded using high-speed video which revealed that the labial folds on either side of the mouth descend to create a small, tubular mouth opening. A small, laterally enclosed mouth opening is associated with increased suction production in other aquatic lineages and the labial folds may be convergent in this sense.
