Abstract
Using scanning electron microscopy, we examined the undigested contents of fecal pellets from hand-collected Oikopleura vanhoeffeni Lohmann. Our goals were to compare the size of food in fecal pellets to the pore size of the incurrent filters, and to compare the size and type of food in fecal pellets to the size and type of food available in the environment. We collected O. vanhoeffeni in coastal waters of Newfoundland in May 1983, during the spring diatom bloom, and in January 1984, when diatoms were rare. Because the pore size of the incurrent filters was large (X̄ = 169 × 88 μm), O. vanhoeffeni was able to ingest the large, armored cells and diatom chains present during the spring bloom. The largest cells in fecal pellets were smaller than the mean pore width of the incurrent filters. The largest single cell in fecal pellets was the silicoflagellate Distephanus speculum (48 μm in diameter). Many tabular chains of pennate diatoms in fecal pellets were >40 μm long. Spinous Chaetoceros socialis were ingested. In January, the fecal pellet contents were dominated by coccoliths along with common dinoflagellates and diatoms. Each fecal pellet was surrounded by a peritrophic membrane.