| Bivalves were in Big and Marijilda Canyon creeks, and oligochaetes were only in Moonshine, Wet Canyon, and Lower Grant creeks. |
| For example, bacterial endosymbionts as found in the giant vent Pogonophora are also present in many meiofaunal oligochaetes, nematodes and flatworms. |
| Fossil oligochaetes are much rarer, and there are almost no fossil hirudineans known. |
| The littoral zone was dominated by oligochaetes, gastropods, sphaerid clams, and chironomid larvae. |
| The oligochaetes include earthworms and a group of related, mostly freshwater, species of annelids. |
| The burrowing activities of oligochaetes can often prevent tubicolous polychaetes from becoming established in a particular habitat. |
