Nudibranchs — marine snails without shells — make wonderful photo subjects for the macro photographer. They are small, colorful, and they move slowly (as snails are wont to do). That last characteristic is particularly welcome. Most fishes are in motion almost constantly, and non-sessile invertebrates tend to scurry hither and thither. It’s nice to find a subject that is not only photogenic, but doesn’t turn tail or flat out disappear before the photographer can focus the camera’s lens!
It’s always interesting to find out and record which critters feed on what. Here are some macro photos of two sponge-eating nudibranch species feeding on their favorites. The colorful nudibranch in the first photo, at right, is Chromodoris quadricolor — also known by its common name Striped Pajama nudibranch. While we cannot see the mouth parts of the creature in this photo, or any obvious feeding damage on the sponge, the species is known to feed on these brightly colored sponges (Negombata sp.).
The individual in the first image was photographed in the Red Sea at Tiran Island.
In the image above, we see a Mediterranean nudibranch species, Peltodoris atromaculata, known by the common name Dotted Sea Slug. The nudibranch is on a brown sponge (Petrosia ficiformis), which is thought to be its primary food source. Both the sponge and the nudibranch species are found throughout the Mediterranean, including the Adriatic and Aegean Seas.
The final image, above, is much more convincing as a feeding record. Here again we have P. atromaculata, but this time the feeding scars on the sponge, P. ficiformis, are very obvious. It is not uncommon to see several of these nudibranchs feasting on a single sponge at the same time. They can leave the sponge quite scarred.
Each of the two photos of P. atromaculata is of a different individual. Both were photographed off the coast of Greece, near Cape Sounion.
Note: Although the nudibranchs in the second and third photo appear larger than the C. quadricolor in the first photo, in real life they all are about the same size: approximately 5 cm (2 in) long. The second and third photos were enlarged.