Thursday, March 08, 2018

Sand trap

Another find on the same flat beach:

Unidentified sponge, as found at the top of the intertidal zone.

At home, dried and cleaned up. Sand still fills many of the pores. 7 inches diameter.

The sponge had evidently been ripped out of its home and tossed up by the waves. It was still damp, and on the underside, where the sunshine didn't reach, it was orange. The green spots seem to be the green algae that grows on everything. Once the sponge was dry, the orange colour disappeared.

Sponges are difficult to identify, especially out of context. (The Encyclopedia lists 26 undetermined sponges after their photos of named species.) I think this may possibly be an Orange Finger sponge, Neoesperiopsis rigida, a sponge I remember seeing on the underside of a local dock. They may be quite varied in shape and colour: INaturalist has a series of photos demonstrating this: pale orange, pink, brownish, but not green; long and skinny, or in rounded clumps.

A sponge is an animal that is basically a filtration device. The "fingers" are hollow; water flows in through the porous walls and is pumped out through the larger upper opening. Food particles, tiny plankton, shreds of organic material, get filtered out along the way.

A closer look at some of the "fingers".

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