Assimilation of Labelled Glucose from Seawater by Marine Nematodes

Abstract

RECENTLY there has been much interest in the ability of marine invertebrates to assimilate dissolved organic molecules. It has been shown that, with the notable exception of some arthropods, representatives of most phyla can freely absorb amino-acids and simple sugars through the body wall and subsequently assimilate them into macromolecules^1–3. All the experimental work to date, however, has been conducted on macrobenthic animals, although the meiobenthos would probably benefit most from this food source in view of their large surface area/volume ratio. Nematodes are among the commonest meiobenthic animals and, in spite of the fact that their thick cuticle might be expected to preclude absorption in rather the same way as the exoskeleton of arthropods, it was decided to test them for possible uptake. Glucose was considered to be a likely substance for assimilation because the main energy store in nematodes is glycogen⁴, and concentrations of 10⁻⁶–<10⁻⁸ glucose are known to be present in seawater⁵. The nematode chosen for the experiment was the oncholaimid Pontonema vulgare (Bastian) because it is large, easily identifiable, and can be readily obtained from Laminaria holdfasts on the rocks below the Dove Marine Laboratory in Northumberland.