Vol. 39: 81-85,1987
MARINE ECOLOGY - PROGRESS SERIES
Published July 27

Comparison of the ultrastructure of the food-concentrating filter of two appendicularians

Don Deibel, C. V. L. Powell

Newfoundland Institute for Cold Ocean Science, and Marine Sciences Research Laboratory, Memorial University of Newfoundland,

St. John's, Newfoundland AlC 5S7, Canada

ABSTRACT: Houses of Oikopleura longicauda were removed from preserved zooplankton samples and prepared for transmission electron microscopy. Pore size and fiber diameter of the food-concentrating filter were determined for comparison with similar measurements on larger oikopleurids from cold ocean waters. The filter was composed of 3 types of fibers arranged in a regular rectangular array. In accordance with nomenclature used previously, we identified microfibers, nodulated fibers, and smooth fibers. There were dense nodes where microfibers and nodulated fibers crossed. Mean pore size was 0.15 ± 0.02 x 0.61 ± 0.13 µm (± SD), with a mean width-to-length ratio of 0.25 ± 0.03 and mean porosity of 0.85 ± 0.01. Mean pore size is similar to that of Oikopleura dioica, a temperate-ocean oikopleurid of similar body size, but is smaller than that of Oikopleura vanhoeffeni, a large, cold-ocean oikopleurid. The microfibers of O. longicauda were 17.1 ± 2.6 nm in diameter, while the nodulated fibers were 38.9 ± 8.8 nm in diameter, and the smooth fibers 48.1 ± 10.2 nm in diameter. All 3 fiber types formed branches, which contributed to high variance of mean pore size.