Meeting Abstract

P3.56  Sunday, Jan. 6  Feeding Rates of the Freshwater Amphipod Hyalella azteca for Aquatic Vascular Plants and Macroalgae SCRIBER, K.E.*; AMSLER, C.D.; MCCLINTOCK, J.B.; University of Alabama at Birmingham KEVSCRYB@UAB.EDU

Numerous factors influence the feeding preferences of fresh water and marine invertebrates. Most consumers discriminate between the plants and animals they consume. This study tests the null hypothesis that there is no difference in the palatability of the common omnivorous freshwater amphipod Hyalella azteca for sympatric aquatic vegetation; vascular plants and green algae. Non-choice feeding assays were utilized to measure feeding rates (palatability) on exposed foliage of three species of vascular plants and two species of green algae. Statistical analysis indicated high variation in the palatability of the three vascular plants, with Vallisneria americana being least palatable (<12% consumed, mean mass per unit time). The remaining two vascular plants were moderately palatable (mean range = 34.6 –41.9% of mass consumed). The two species of green alga were both palatable (mean range = 37–48 % of mass consumed) and feeding rates were similar to those on the two moderately palatable vascular plants. In order to evaluate one factor responsible for differences in food palatability, penetrometry was used to measure food toughness. As both green algae were filamentous they were not subjected to penetrometry. Measurements of Force (Newtons/mm2) for the three vascular plants indicated that the force required to penetrate the least palatable species, V. americana, was significantly greater than that the other two species. Ongoing studies are examining additional metrics for food quality (protein content and chemical defense). The present study indicates that at least one measure of food quality, toughness, may have an influence on food palatability in the common and ecologically important freshwater amphipod H. azteca.