Author: outoftheblueocean

Entoprocts vs. Ectoprocts – What’s the difference?

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Perhaps the more important question is: “Wait, which ones are bryozoans again?”

Entoproct and ectoproct are separated by just one letter–and the similar terms reflect how similar they look to one another!

Here are some example images of entoprocts (also known as kamptozoans): https://commons.wikimedia.org/wiki/Category:Barentsia

Kampto- refers to the Greek word for bending, as they often bend back and forth on their stalks!

Ectoprocts are our bryozoans! Scientists now tend to refer to ectoprocts as bryozoans, although the term ectoproct still floats around in some circles. You can see how entoprocts do look rather similar to the bryozoans. Like bryozoans, brachiopods, and phoronids, entoprocts have a ring of ciliated tentacles, which captures food. Some will consider the entoprocts’ ciliated tentacles to be a lophophore (as in the lophophorates: bryozoans, brachiopods, and phoronids), and others won’t.

There are definite differences between ectoprocts and endoprocts both etymologically and anatomically, though…

The shared root word “-proct” refers to the anus of the organisms. “Ento” means “within” and “ecto” means “outside”. This refers to the location of the anus in both groups–in entoprocts, the anus is within the ring of ciliated tentacles (lophophore), and in ectoprocts, the anus is outside the lophophore.

There are other differences too–

Ectoprocts/bryozoans have a true body cavity, known as a coelom. On the other hand, entoprocts do not have a true coelom at any point during their development.

Entoprocts have solid tentacles, whereas bryozoan tentacles are hollow. The cilia on the tentacles creates a current that allows for more efficient feeding–in entoprocts, the current runs from the base to the tip of the tentacles, whereas the current runs from the tip to the base of the tentacles in bryozoans.

Genetically, entoprocts and ectoprocts don’t seem to be very related….or maybe they are! A recent paper, “Polyzoa is back: The effect of complete gene sets on the placement of Ectoprocta and Entoprocta“, suggests that we may want to combine Ectoprocts and Entoprocts back into the Polyzoa group. Guess what? The Bryozoa/Ectoprocta are ALSO known as the Polyzoa on their own! We have had a lot of different names for these organisms…

Where will the ectoprocts & entoprocts end up taxonomically? That remains to be seen as more research is done! But, for now, we are working with Phylum Bryozoa and Phylum Entoprocta!

Source/for further reading: Invertebrate Zoology by Ruppert, Fox, & Barnes

What is a bryozoan?

On By outoftheblueoceanLeave a comment

I think it’s prudent to start off this blog by addressing the question most people ask me directly after asking me “what’s your favorite animal?”

So…what is a bryozoan?

Bryozoans get their name from two root words, “bryo” and “zoa”. “Bryo” refers to moss–bryophytes are mosses and relatives! “Zoa” refers to animals, so bryozoans are officially called “moss animals.” This is rather accurate, all things considered, as bryozoans often look like mosses and are indeed animals.

(Perhaps it is more prudent to refer to mosses as “moss plants,” given their word root origins?)

Beyond that, bryozoan taxonomy has a varied history and is the subject of another post. But suffice it to say that bryozoans are now generally grouped within Phylum Bryozoa. Phylum Bryozoa is the newest phylum to come about in evolutionary time!

Each bryozoan group is actually a colony! Much like corals, bryozoan colonies are made up of many individuals which share resources. However, they are absolutely not corals!

Bryozoan individuals are called zooids and each feeding zooid has a ring of ciliated tentacles–cilia are like little hairs (although they are not hairs at all). A ring of ciliated tentacles is called a lophophore!

Bryozoan zooids have the capacity to specialize into different zooid types that carry out different functions! Not all zooids have lophophores.

Bryozoans show a variety of growth forms, depending on the species: encrusting, upright, gelatinous mounds…

Bryozoans can live in marine, fresh, and brackish water, depending on the species!

Still want more bryozoan information? Good! I’ll be posting information about interesting species, bryozoan anatomy, taxonomy, and more on this blog!

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Source: Invertebrate Zoology by Ruppert, Fox, & Barnes