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Abstract

The first description of a gutless marine oligochaete was published in 1977 (Jamieson 1977), but it was not until 1979 that the reduction of a mouth and gut in this species and several other marine tubificid worms was recognized (Erséus 1979a,b; Giere 1979). At the time, the only other free-living worms known to lack a mouth or gut were pogonophores (now called Frenulata) that were most commonly found buried deep in the reducing sediments of continental slopes. Extensive studies on these very long and thin pogonophore worms indicated that their high surface areas enabled them to gain their nutrition from the uptake of dissolved organic compounds from the environment (Southward and Southward 1980). It was therefore assumed that the gutless oligochaetes that are also quite thin (0.1–0.2 mm) and relatively long (up to 2–3 cm), also gain their nutrition through the diffusive uptake of organic compounds from the sediment pore waters.