Sep 30, 2010


This column is about an interesting but obscure natural phenomena that we often see in our lakes in summertime. Earlier this summer, some visitors to our area saw what was described as a “globulous gelatinous mass” in Sharbot Lake, and I was asked if I could shed any light on what it might be. I had seen a number of “blobs” in Bobs Lake in the past, and as my curiosity had led me to do a little investigation to find out more about them, I had a pretty good idea that this was another example of what I had seen.

I am referring to greenish, roughly softball-sized masses that on first glance resemble a mass of what could be fish or frog’s eggs. Often formed around submerged sticks or plant stems, they tend to be found in warm, shallow, still water bodies, a few inches below the surface of the water. They appear to be mostly made up of a translucent jelly-like substance, but divided into a large number of similar sized “cells” or individual units, not unlike the cells of a honeycomb. Each cell seems to have a darker spot in the centre.

It turns out that these blobs are actually colonies of small invertebrate aquatic animals called bryozoans – more specifically a colonial freshwater bryozoan called a Phylactolaemata.  A good way to think of these animals is as a group of identical jellyfish-like creatures that all live together in a single blob-like structure.  Bryozoans come from one of the most obscure corners of the animal world, and aren't closely related to anything else.  Some people also describe them as like the small animals that make up corals (called “polyps”) but without the hard calcite structures that coral polyps create for themselves. Like all bryozoans, they filter-feed by means of a "crown" of tentacle-like appendages that extend out into the water to trap food.

The life cycle of these creatures appears to be quite complex. Each individual member of the colony is called a “zooid”, all of which are clones of the founding member of the colony. The colonies reproduce sexually, with each member functioning as both male and female at the same time – making them what is known as simultaneous hermaphrodites. They also reproduce asexually in a way that enables a colony to survive the variable and uncertain conditions of freshwater environments. Throughout summer and autumn they produce tiny disc-shaped bodies called statoblasts – groups of cells contained in shell-like structures that function as "survival pods". Statoblasts can remain dormant for considerable periods, and while dormant, can survive harsh conditions such as freezing and drying out. They can be transported across long distances by animals, floating vegetation, currents and winds. When conditions improve, the shells open and the cells inside develop into a zooid that tries to form a new colony. A study estimated that one small group of colonies produced 800,000 statoblasts. Fortunately for us, not all statoblasts become new colonies, or our lakes would have little room for anything other than bryozoans!

One last interesting feature of these curious creatures is worthy of note: They don’t appear to have a common name other than “freshwater bryozoans”. This strikes me as an opportunity for some creative naming. If anybody would like to submit a possible name for these curious creatures, I’d be happy to publish it in the next column. Who knows, the name may even stick!

 

Please feel free to report any observations to Lorraine Julien at This email address is being protected from spambots. You need JavaScript enabled to view it.  or Steve Blight at This email address is being protected from spambots. You need JavaScript enabled to view it.

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