Madrella ferruginosa Alder & Hancock, 1864

This appears to be Madrella ferruginosa, although the ID is not certain. Many specimens have been found at Kwajalein Atoll, all on the leeward lagoon reef. All were on or very near clumps of Halimeda algae upon which their food, a dark brown to black species of bryozoan, was growing. Specimens ranged from about 10 to 20mm in length. They are most easily found by putting one's hand into the algae and shaking a bit. If specimens of Madrella are in there, they will often give off a yellow-orange fluid that forms a cloud around the disturbed Halimeda clump. The fluid is probably some kind of defensive secretion and is apparently picked up from the prey bryozoan. If a colony of the encrusting bryozoan is broken or crushed, it gives off the same yellow-orange color.

Some individuals have more greenish coloration than others.

The next two photos show Madrella on its dark-colored prey bryozoan.

Below is an egg mass from Madrella ferruginosa.

Created 20 January 2007
Updated 12 July 2008