ECOMORPHOLOGICAL DIET PREDICTIONS - AN ASSESSMENT USING INLAND SILVERSIDE (MENIDIA-BERYLLINA) AND LONGEAR SUNFISH (LEPOMIS-MEGALOTIS) FROM LAKE TEXOMA

The functions of an organism's morphological structures indicate the o rganism's potential resource use (fundamental niche). While this infor mation often is also used to predict differences in actual resource us e (realized niche) among individuals or species, such predictions may not be accurate because the maximum abilities may not be useful to the organism under specific conditions or in specific environments. We in vestigated the importance of six previously studied morphologically ba sed performance abilities/constraints in structuring the diet of Menid ia beryllina (inland silverside) and Lepomis megalotis (longear sunfis h) in Lake Texoma, a reservoir in the Red River basin (Oklahoma-Texas, USA). Of the six morphological characteristics measured (number of gi ll rakers, length of gill rakers, space between gill rakers, eye lens diameter, mouth size, mouth protrusibility), only one characteristic f or M. beryllina (mouth size) and three for L. megalotis (space between rakers, mouth size, and raker length) correlated with the gut content s as predicted by previous functional morphology studies. This indicat es that caution should be exercised when making untested predictions a bout the ecology of an organism based on its functional morphology.