Blob-like lifeforms: sponges, ascidians and encrusting algae
How to tell them apart?
updated Apr 2020
These kinds of lifeforms are often mistaken for one another.
They take on various blob-like or other irregular shapes. And are often quite colourful.






Colonial ascidians are smooth and slimy. Sponges tend to be rough, although some are smooth. Tends to be smooth, taking on the shape of whatever it is encrusting. Sometimes appears branch-like or knobbly when covering dead corals.
Colonial ascidians tend to 'collapse' when exposed out of water. They inflate again once they are submerged. Sponges don't 'collapse' when exposed out of water and most retain their rigid shape. Coralline algae doesn't 'collapse' when exposed out of water.
Colonial ascidians tend to have many tiny holes of the same size, although some may have a few large holes. Sponges usually a few larger holes, with tiny holes over the rest of the body. Coralline algae doesn't have holes.
Colonial ascidians are complex animals belonging to Phylum Chordata, Class Ascidiacea. Sponges are simple animals belonging to Phylum Porifera. Coralline algae are seaweeds.
More comparisons

Some zoanthids look like mats of
thick rubber or blobs of jelly
when exposed at low tide.

Other zoanthids look like blobs of jelly
when exposed at low tide.

Banded bead anemones tuck in their
tentacles at low tide and look like blobs.

Corallimorphs tuck in their
tentacles at low tide and look like blobs.

Peacock anemone with tentacles
tucked in at low tide.

Peacock anemone with tentacles
tucked in at low tide.

Siphon of a buried razor clam.

Burrowing sea anemone with tentacles tucked in.

Ascidians are blob-like animals!

This is a brown seaweed.

This is a green seaweed.

This is a green seaweed.

Jellyfishes stranded on the shore
look like blobs.

The white thing is the egg capsule
of the Noble volute.

Out of water, sea slugs
look like blobs.

These white cylinders are the egg capsules of a cephalopod (squid, cuttlefish or octopus).

This string of black blobs are the egg capsules of a cephalopod (squid, cuttlefish or octopus).
 
 
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