Water worms

When searching for macro fauna in a small pool in the province of Limburg, The Netherlands, the worms on the video were found alongside many other organisms. These worms belong to the Oligochaeta, a subclass within the ringworm taxonomy. There are species that live in the soil on land and species that live in the water.

Oligochaeta are well-segmented worms and most have a large body cavity that is used as a hydro skeleton. Usually each segment has little bundles of chaeta or ‘bristles’ on the outside, The bundles can contain one to several hairs and contain muscles to pull them in and out of the body. This allows the worm to get a grip on the ground or mud while it nestles into it. When digging, the body moves peristaltically, alternately it contracts and stretches forward.

Most Oligochaeta feed on dead organic material. The digestive tract is essentially a tube that runs over the body. For many species, the pharynx helps the worm to easily absorb food. For many species that live in the water, the pharynx can be turned inside out and placed as a sucking cup over food before it is pulled back in.

Most Oligochaeta have no gills or similar structures and simply breathe through their moist skin. Only a few aquatic Oligochaeta have eyes, and even then these are only simple light-sensitive organs. Nevertheless, their skin has individual photoreceptors, allowing the worm to detect the presence of light and to dig away from it.