1. Characteristics and Ecology
The phylum Annelida includes 3 classes: Polychaeta, Oligochaeta, and Hirudinea. Polychaetes are an important, often predominant, component of marine and estuarine biota.1 In subtidal benthic environments, they comprise about 30% to 75% of macroinvertebrate species and individuals. They include a variety of feeding types, with the majority being either filter or detritus feeders. Polychaetes affect surface sediments because of their burrowing and irrigating habits. They are important food for snails, large crustaceans, fish, and birds. Many species of polychaetes have short life cycles.
Oligochaetes are among the most common benthic invertebrates in all types of aquatic environments. Particular species assemblages are recognized indicators of environmental quality. In grossly polluted freshwater habitats, oligochaetes dominate benthic fauna, while in estuarine areas, they and polychaete worms are often the most common benthic organisms. They feed mainly on bacteria, although other feeding types occur.1 They affect surface sediments, as do polychaetes. Oligochaetes are an important primary or alternate food for leeches, crustaceans, fish, and birds.
Hirudinea are leeches, either free-living or parasitic, that inhabit fresh or marine waters. They have not been used in toxicity testing.
2. Test Applications
The following procedures serve as guidelines for using polychaetes and oligochaetes in various toxicity tests. These procedures also can be, and have been, adapted to testing sediments.
Other toxicity tests for annelids have been published.2,3