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Photos by urbpan. A small colony attached to a stick is pulled out of the water to be examined. Location: Ward's Pond, Boston.

Urban species #260: Freshwater bryozoan Pectinatella magnifica

A football-sized clump of gelatinous material in a pond may not be an egg mass. You may encounter a colony of animals called bryozoans, or as that obsolete scientific name translates, "moss animals". Bryozoans make cockroaches look like spring chickens: their fossil record extends back 500 million years. The vast majority of the thousands of species in this group live in salt water, with only 50 or so found in fresh water. This one, Pectinatella magnifica (with no good common name but sometimes referred to as "blobs") is the one most often seen in urban waterways. I have seen it in Spectacle Pond at Mt. Auburn Cemetery in Cambridge Mass., and recently found it in Ward's Pond in Boston. It also apparently occurs in the waters of the Connecticut and Potomoc rivers. Bryozoans have a similar ecology to corals. Hundreds of thousands of individual animals (or "zooids" in zoological jargon) live together, secreting a jelly-like matrix, growing quickly in favorable conditions. Favorable conditions include water temperatures of 68 degrees or more (20 degrees or more celcius) and large amounts of food: single-celled algae, bacteria, and other microorganisms, conditions not uncommon in urban ponds in summer. Each zooid has tiny tentacles with which it grabs food particles. Rapidly growing bryozoan colonies are alarming to some people, and may create problems when they form on intake pipes and other structures. However, it seems that their presence and growth may potentially be a good indicator of water quality.

Found in Pleasure Bay, South Boston. Photos by cottonmanifesto.


( 15 comments — Leave a comment )
Sep. 20th, 2006 01:49 am (UTC)
God! Nature produces the most BIZARRE organisms! It's all so miraculous...

And I've seen those before, and wondered what they were. Thank you much for enlightening me. This blog is amazing.
Sep. 20th, 2006 01:55 am (UTC)

They remind me of fish eggs.
Sep. 20th, 2006 01:55 am (UTC)
That is so cool. Amazing. Gorgeous. Can't find just one word for it. I've never seen something like that, or even imagined it. Let alone think it would live literally less than a mile away. It almost seems like they should have a"hive mind". Do they? Or are they too primitive for that? (Can you tell yet that I'm not a creature-ologist at all?)
Sep. 20th, 2006 02:12 am (UTC)
Their nervous system is pretty simple:
The nervous system is composed of a single bilobed ganglion at the base of the lophophore near the pharynx. This has a number of nerves leading off from it to the internal organs and muscles, it also connects to a nerve net in the body wall and the nerve ring which supplies nerves to the tentacles of the lophophore.

No mention of how or if the zooids coordinate their activities.
Sep. 20th, 2006 02:48 am (UTC)
I don't think I've ever seen or heard of these before. How weird and squishy and cool!
Sep. 20th, 2006 02:58 am (UTC)
Freshwater bryozoan? Cool!

I've studied a bit of paleobiology, and in last semester's Paleobiology Seminar, my class plucked some fossil bryozoans out of Paleozoic outcrops in Missori. They generally resembled this morphotype (and often had crinoid stem pieces intermixed in the matrix, as in the picture). Bryozoans are neat, strange animals.

Wow, the saltwater bryozoan looks really familiar. I think I've seen that species before in one of my marine labs, and we had to memorize the Latin binomial... I want to say it's Botryllus schlosseri, but I'm not 100% sure.
Sep. 20th, 2006 03:29 am (UTC)
Another wonderful post! Thank you!
Sep. 20th, 2006 05:23 am (UTC)
are they related to sea squirts? Puget sound is having a sea squirt problem: apparently they suffocate everything they cover.
Sep. 20th, 2006 09:41 am (UTC)
Only inasmuch as they are squishy things that live in the water. Sea squirts are actually our closest invertebrate relatives.


I suppose a sessile existance is common to many unrelated marine animals, all of which can be inconvenient to human industry: barnicles, zebra mussels, sea squirts, bryozoans, and so on.
Sep. 20th, 2006 08:01 am (UTC)
neat!!! i like them
Sep. 20th, 2006 11:57 am (UTC)
I've only ever encountered them in fossils. It's cool to see live ones!
Sep. 20th, 2006 01:26 pm (UTC)
i had to cut bryozoans from my ocean invertebrates book because i just couldn't make sense of them to kids. (you manage to make sense of them quite well, though, which is exciting) my consultant was not pleased with my decision, but geez! so many ocean invertebrates out there to include in one 48-page book!
Sep. 20th, 2006 05:32 pm (UTC)
May. 7th, 2007 02:12 am (UTC)
Bryozoan in Florida Pond
I was researching this jelly-like mass, and its name. I ran across your site and thank you for the name and brief info you gave on the bryozoan. Would love more info if you have any. My pond is a spring fed pond with just the right temps. aparently. This bryozoan has multiplied tremendously in the last 2 years. It does not seem to affect the fish population from what i can tell. Honestly I would like it to disappear if you know what i mean. I have a hard time enjoying the sight of it. Thanks Wj
May. 7th, 2007 10:53 am (UTC)
Re: Bryozoan in Florida Pond
Sorry, I don't really know any more than what I've written here. If it bothers you, you may want to look in to whether the pond is getting an excess of nutrients, from fertilizer runoff, Canada geese, or some other source.

It's a harmless colony of animals, if that makes you feel any better!
( 15 comments — Leave a comment )


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