Dondice occidentalis (Engel, 1925)
One of two species of Dondice living in Caribbean waters, Dondice occidentalis is the more colorful of the two. The color of D. occidentalis is dramatically different from is sister species Dondice parguerensis featured in a previous Nudibranch of the Week, having a bright yellow to red medial stripe on its head and body to its tail, with wide white bands occurring to each side of this stripe. A tinge of light, almost Hermissenda-like blue can be seen on the body. The species is also smaller in size than D. parguerensis, reaching only about 30 mm length, and has fewer ceratal groups (it has six, while D. parguerensis has eight).
The photo shown here was taken by Jeff Hamann, of El Cajon, California, while on our March 1992 collecting trip to Belize, Central America. This specimen was collected on Ranguana Caye on a hydroid species, however other specimens were observed at other Cayes along the Honduran barrier reef.
These two species give some credence to the hypothesis suggesting the mechanisms of aposomatic coloration. Dondice parguerensis is neutral and cryptic in color, not needing to broadcast warning coloration as it lives entire adult life protected by the stinging tentacles of the jellyfish, Cassiopea, while Dondice occidentalis must display warning colors due to its more vulnerable existence, lacking the protective umbrella from another source. D. occidentalis is warning its wanton predators of the presence of stinging nematocysts, stored at ready in the cnidosacs at the tip of each of its cerata.
Taxonomic information courtesy of Dave Behrens
David W. Behrens
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