Meeting Abstract

1.5  Wednesday, Jan. 4  Suction among pickers: Jaw mechanics and dietary breadth in the beach-spawning grunion sisters (Leuresthes) compared to their relatives (Teleostei: Atherinopsidae) HIGGINS, B.A.*; HORN, M.H.; California State Univ., Fullerton; California State Univ., Fullerton

We compared jaw mechanics and dietary breadth in the sister atherinopsids Leuresthes tenuis (California grunion) and L. sardina (Gulf grunion) along with three other members of the Atherinopsini to test whether the two grunion species have evolved a novel jaw protrusion that might be associated with feeding narrowly on abundant prey near spawning beaches. Quantitative comparison of cleared-and-stained specimens of five members of the atherinopsine clade showed that, compared to Colpichthys regis (false grunion), Atherinops affinis (topsmelt), and Atherinopsis californiensis (jacksmelt), L. tenuis and its sister L. sardina have longer (5.1% vs 0.9%), more downwardly directed (-37 vs. +0.1 degrees) premaxillary protrusion, expanded dentary and premaxillary bones, greater lower jaw rotation (65.3 vs 13.8 degrees), and greater premaxillary-vomer spacing (36.6% vs 20.9%). L. tenuis showed the most divergence in these features. High-speed video analysis indicates that L. tenuis protrude their jaws faster than A. affinis. For dietary analysis, adult L. tenuis and A. affinis were collected offshore, simultaneously with zooplankton samples to represent prey availability. L. tenuis fed heavily on mysid crustaceans, and, as predicted, had a narrower diet than A. affinis in the same habitat, as shown by higher L selectivity (0.5 vs. 0.1) and lower H’ diversity (0.81 vs. 1.58), and J evenness (0.48 vs. 0.80) values. Information available on As. californiensis and C. regis indicate that these species have broad diets associated with benthic feeding. The diet of L. sardina remains largely unstudied. L. tenuis appears to have evolved a method of jaw protrusion unlike close (cyprinodontiform) and more distant (perciform) relatives.