Meeting Abstract
15.3 Jan. 4 Resource allocation in coral reef sponges: the trade-off between reproduction and chemical defense COWART, J. D.*; PAWLIK, J. R.; Univ. of North Carolina Wilmington ; Univ. of North Carolina Wilmington jdc1234@uncw.edu
Sponges have evolved effective methods to avoid, discourage or tolerate predation. Chemically defended sponges live relatively free from predation. In contrast, coral reef predators commonly graze upon sponges that lack chemical defenses. Why then do chemically undefended sponges persist on coral reefs? They may be allocating energy otherwise used for the production and maintenance of secondary metabolites to increased sexual reproduction. To test this hypothesis, tissue from 2 chemically defended (Amphimedon compressa and Ircinia campana) and 2 chemically undefended (Iotrochota birotulata and Xestospongia muta) Florida reef sponges were monitored using histological methods for the presence of eggs, embryos and larvae. Fecundity was calculated using the average densities of eggs, embryos and larvae in a 0.5 cm2 area of tissue in 3 individuals per species prior to spawning. The average egg sizes for the chemically defended sponges were 270.6 ± 15.7 µm and 481.1 ± 67.1 µm (mean ± SD) respectively, while those for the chemically undefended sponges were 492.5 ± 40.5 µm and 92.4 ± 7.0 µm respectively. The chemically defended sponges produced fewer offspring (1.3 ± 1.4 eggs and 0.3 ± 0.5 eggs in a 0.5 cm2 area of adult tissue respectively) than the chemically undefended sponges (4.6 ± 1.4 eggs and 19.1 ± 5.7 eggs in a 0.5 cm2 area of adult tissue respectively). These preliminary trends suggest that chemically undefended sponges are allocating energy otherwise used for the production and maintenance of secondary metabolites to increased sexual reproduction. Continued monitoring of a total of 10 Florida reef sponge species (5 chemically defended and 5 chemically undefended) will provide additional information supporting or negating our hypothesis.
