Observations on the Ecology of the Marine Nematode Monhystera filicaudata Allgen, 1929

Abstract

The marine nematode Monhystera filicaudata Allgen, 1929 was isolated from sediment of a Rhode Island estuary and maintained in the laboratory in culture. Information is presented which suggests that this nematode feeds primarily on detritus, bacteria, and dinoflagellates. Experiments using the elimination products of the bay scallop, Aequipecten irradians, as food are described. Maturation time of this nema- tode at 20-25 C required 24-35 days. The total disappearance of the remains of dead nematodes from sub-cultures is noted, and information is presented which suggests they were selectively fed upon by colorless euglenoids also present in the culture medium. There is little information on the ecology of free-living marine nematodes. As part of a study of the meiofauna of New England estuaries, the nematode Monhystera filicaudata Allgen, 1929 was isolated from sediment of the Petta- quamscutt River estuary in Rhode Island in the winter of 1963. Although rare in the environment from which it was collected, this species was easily maintained in laboratory culture, and information on its feeding habits, life history, and decomposition by marine microorganisms is presented here. MATERIALS AND METHODS Five to ten ml sediment samples were dispersed in 50 ml of filtered (Millepore HA- pore size, 0.45 v,) estuarine water in 125 ml Erlenmeyer flasks, to which were added pieces of decaying Zostera marina Linne and its aufwuchs. The flasks were stoppered with cotton plugs. The aufwuchs consisted of filamentous blue-green algae, pennate diatoms, ciliates (mostly Stylonichia spp. and Euplotes spp.), bacteria, colorless euglenoids, and several unknown dinoflagellates. Within ten weeks the nematode fauna, which had originally consisted of about 25 species, was comprised solely of M. filicaudata in large numbers. Ten such flasks were maintained as stock cultures at room temperature (20-25 C) under continuous fluorescent illumination, which enhanced growth of the dinoflagellates. An additional ten flasks were maintained in the dark at room temperature; the nematodes grew well under both conditions. Sub-cultures were made from these stock cultures for the observations noted below.