Wednesday, March 31, 2010


One of my favorite animals is a flatworm, commonly called a planarian. I was first introduced to this creature in seventh grade biology where we sliced them a dozen different ways to demonstrate their ability to regenerate body parts. We managed to produce one individual with two heads and this not only appealed to my love of all things biological; it shared a common thread with some of my favorite monster movies.

Planarians require cool, clean water in which to survive. This intermittent stream provides an ideal environment during the winter and spring. Planarians have reached their adult size and are busy producing eggs that will span the dry season this summer.

Planarians are most noticeable when they move about on the rock bottom of the stream. Most will hide beneath the rocks during the day and venture out after dark. This one was doing just that until I turned over his rock. They feed on living or dead animal matter and are particularly attracted to red meat. I doubt that they come across many steak dinners.

Often, planarians are mistaken for leeches. Leeches normally move by extending the front part of the body and then pulling in the back, like an inchworm. Planarians glide across the substrate on a mass of locomotive cilia located on their ventral surface.

Two light sensitive areas appear as eyes atop the wedge shaped head. I haven’t yet identified these planarians to species. One day, when they appear to be particularly abundant, I’ll have to bring a couple inside for closer examination and an attempt at running them through the keys.

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