Nutrient Acquisition By a Respiratory Epithelium in the Sea Cucumber, Thyonella gemmata

Many sea cucumbers (phylum Echinodermata) exhibit arborescent respiratory structures which emerge from the digestive system and ascend into the body coelom. These "respiratory trees" are accepted as the primary site of respiratory gas exchange for these animals. However, several studies have suggested the respiratory trees are also involved in feeding. We investigated the potential role of the respiratory trees of Thyonell a gemmata to remove dissolved organic matter from seawater. Specimens were incubated in seawater containing labeled proteins Omg/mL) for times up to 24 hours and then the trees were removed. To assess the presence of the absorbed label, tissue samples w ere examined using light and fluorescence microscopy. In both whole mounts and tissue cross sections ( lJlm), the label was detected within the cells of the respiratory trees. Although there was variability in the presence of label among experimental animals, no equivalent label was detected in unexposed animals. The respiratory trees of T. gemmata appear to be involved in nutrient acquisition and may account for a significant amount of the total nutrient uptake.Originally presented in the John Wesley Powell Student Research Conference - April 14, 2007 and used with permission.