A Different Kind of Pretty

Tonight’s post is not too pretty in the visual sort. But, it is pretty interesting if you take the time to study available information.     

Late last night, when I was wading the river by moonlight, I thought I noticed a bryozoan colony on a stick where I was accessing the river. Rather than me trying to provide the scientific info on bryozoans, I will share this from the Missouri Department of Conservation:

Bryozoans are microscopic aquatic invertebrates that live in colonies. The colonies of different species take different forms, building exoskeletons (outer protective structures) similar to those of corals. Most colonies are attached to a structure such as a rock or submerged branch. Freshwater bryozoans’ exoskeletons are gelatinous (like jelly) or chitinous (like the “shells” of insects). Therefore, some colonies take the form of rounded, jellylike masses, while others resemble antlers or mosses (bryophyte means “moss animal”), or trace delicately like vines across rocks, or create furry-looking colonies. The species that creates the round, jellylike masses most often seen in Missouri is Pectinatella magnifica.

With enough magnification, you can see tiny individual bryozoans (zooids). Each zooid is attached to a surface at its base. Its body has an outer sleevelike structure (a cystid) and a mass of organs (a polypide) that moves within it. An opening at the top of the cystid permits the polypide to slide outward toward the water, exposing a headlike structure (lophophore) crowned with tentacles, which filter food from water. At the slightest disturbance, the polypide and tentacles retract instantly.

Reproduction

Bryozoans can reproduce in several ways. Zooids can “clone” themselves by budding, but they can also create eggs and sperm and reproduce sexually. Larval forms undergo complete metamorphosis. Within their bodies, freshwater bryozoans form hard, round statoblasts, which function like seeds. In winter or during drought, the colonies die, but the dissolving dead zooids free the statoblasts, which can disperse widely. These endure until conditions permit new growth. Each statoblast can create a new colony.

Ecosystem Connections

Bryozoans eat microscopic organisms and are eaten by several larger aquatic predators, including fish and insects. Snails graze on them, too. Like mussels and other filter feeders, bryozoans gradually cleanse the water as they feed. Also, their presence usually indicates good water quality.   (Great news for our section of the Wapsipinicon River!)  

As I said, bryozoans may not be pretty, but they are pretty interesting!