Oligochaetes (family Tubificidae)

Description

There are four recognized families of marine oligochaetes: Naididae, Tubificidae, Megascolecidae, and Enchytraeidae. All are cylindrical, segmented, bilaterally symmetrical, and hermaphroditic annelids (Cook and Brinkhurst 1973) lacking parapodia or head appendages. Tubificid oligochaetes were positively identified in this study, so the following information will focus on this family unless otherwise indicated. Tubificids are thread-like and grow to approximately 60 millimeters in length (Gosner 1978), and all adult oligochaetes are distinguishable by a clitellum (girdle) that functions in reproduction (Erseus 1998).

Background

Distribution. Tubificids are found in the intertidal and subtidal zones along most coastlines. They were found throughout New York/New Jersey Harbor (this study), and tended to occur in sandy sediments.

Feeding. Oligochaetes feed on detritus and algae consumed with bottom sediments. Tubificids are head-down deposit feeders and can significantly modify sediment structure where they occur in high densities (Fisher 1982).

Life Cycle

Oligochaetes are hermaphrodites and, therefore, produce both male and female gametes. Mating generally occurs between individuals resulting in fertilization of both partners' eggs. The eggs are then shed in a cocoon secreted by the clitellum. Juveniles emerge resembling small adults after weeks or months in the cocoon (Cook and Brinkhurst 1973). As they mature, the clitellum forms via thickening of the epidermis in the anterior region.

Environmental Influences

Salinity. Members of the Tubificidae family inhabit marine, brackish, and freshwater zones.

Predation. Freshwater tubificids are known to be important food sources for fish and larger invertebrates (Yozzo and Diaz 1999). Marine species are likely food resources for various bottom-feeding species of fish, such as spot (Leiostomus xanthurus) and winter flounder (Pleuronectes americanus) in New York/New Jersey Harbor (Grosslein and Azarovitz 1982).

Pollution. Oligochaetes are an important indicator of pollution because of their tolerance to organic enrichment. In enriched or oxygen-deficient areas, there are typically high densities of tubificids. For example, tubificids made up 98 percent of the fauna in highly polluted areas of San Francisco Bay in 1968 (Cook and Brinkhurst 1973).

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