Feeding ecology of free-living aquatic nematodes

Abstract

The buccal cavity structure of free-living aquatic nematodes indicates 4 feeding groups: deposit feeders, epistrate feeders, scavengers and predators. This is in contrast to a previous classification which united omnivores and predators and separated deposit feeders into selective and nonselective groups. The new classification shows that the previous view that heavy predator pressure plays a major role in the structuring of meiobenthic communities has been much overemphasized. Most predatory species in the previous classification are herein recognized as 'garbage collectors', i.e. species with scavenging feeding habits. The actual feeding behaviour of epistrate-feeding specles shows that they are able to break open cell membranes of food items in the buccal cavity and suck out the cell contents (juice feeders), in contrast to deposit-feeding species which swallow the whole food item (particulate feeders), indicating different sets of digestive enzymes. Buccal cavity morphology within predators indicates 2 feeding types. Trans-epidermal uptake of dissolved organic matter is suggested as an additional food supply for thiobiotic species [mainly deposit feeders), hence indicahng mixotrophy. Size, shape, quality and quantity of food items may to some extent explain coexistence of congeners. Nematode mobility and mucus release may attract potential food or keep food sources in optimal condition, i.e. gardening.