Creek Creatures

The temperatures may be well below freezing, but as long as the water remains ice free, I can enjoy watching aquatic creatures going about their business on the bottom of the creek.  On this sunny day, Caddisflies were busy dragging their stone casings around as they grazed algae and other morsels from the rocky stream bottom.

If I’m going to observe aquatic animals in the creek, it’s got to be done in the winter and spring.  Lack of water in the summer and fall makes it difficult to find those animals that maintain an aquatic existence.  During the wet phase, the creek is full of easily observed life.  I assume that these species are adapted to life in an environment that annually cycles between wet and dry.

Caddisflies use sand to adorn the silken sack in which they spend their larval stage.  This camouflage allows them to blend quite well into the rocky creek bottom.

Patterning of the mayfly larvae makes them hard to notice as they move across the substrate.  Their shape resists the drag of the passing water and allows them to avoid being easily swept downstream.

The creek supports several species of snails.  Snails spend the dry season beneath stones or buried in the gravel stream bottom.

Snails feed on algae scraped from the rocks.  Consumed material moves quickly through the snail’s gut and is expelled as nutrient rich pellets.  This process converts the energy of the algae into a form usable by many other organisms.  Without animals like the snail, there would be no fuel to sustain the animal life of the stream.

There were a lot of tiny creatures that I wasn’t able to identify.  I imagine that they will become more recognizable as they grow.  Temperature was at 23 degrees and wind was about 15 mph so I didn’t remove any of these animals from the water.  I didn’t think exposure to that cold air would do them any good and I didn’t want to freeze my fingers in the process of capturing and examining the little guys.

Isopods were a childhood favorite of mine.  I was intensely interested in paleontology and in my mind the aquatic isopod was as close as I could get to a living trilobite.  I used to keep a few in a jar on my dresser and spent hours watching them.  Watching these scavengers forage across the rock face reminded me of those days spent observing my captive specimens.

These animals spend most of their time hidden beneath the rocks.  It was interesting to see them out going about their normal business in the bright sunlight.

Planaria have always survived in the smaller tributaries, but it was just a few years ago that I first saw them in the main creek that passes through Blue Jay Barrens.  Planaria need clean, well oxygenated water and disappear quickly if water quality deteriorates.  Concentrations of cattle in the watershed above Blue Jay Barrens used to add a high nutrient load to the water, causing rapid growth of algae in the creek.  The cattle have gone and the water quality is more typical of a natural stream.  This has allowed the planaria to successfully move from the tributaries to the main creek.

Planarian

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.

Intermittent Stream

During the winter, little water courses that have remained dry through the summer and fall begin to flow. Areas that haven’t had open water for half a year now have an abundance of small pools.

The water has filtered down through the soil on the wooded hillsides and appears as a narrow stream. The water is clear and clean. Winter birds prefer this water source over all others.

Storm runoff carries away leaves that have fallen into the stream channel. The water will continue to flow until mid spring and then things will again be dry. This type of seasonal flow defines an intermittent stream.

The small intermittent streams at Blue Jay Barrens are very nutrient poor and generally don’t support any algae or other plant life. Rain runoff removes sediment from the narrow channel so the substrate is generally rock. Several types of aquatic insects will lay their eggs in these streams in early spring.

There are some animal species that live exclusively in these tiny watercourses. A common one here is the flatworm know as the planarian. Planarians lay two types of eggs; one thin shelled that hatches soon after being laid and a second that is hard shelled and able to survive through the summer dry period. The eggs are hatching now, but the worms won’t be noticeable until late winter. Until then, I’ll just enjoy the sight of super clear water that flows in these streams.