Berthellina ilisima
This specimen was identified by Yolanda Camacho. It is a Berthellina species I found at 90ft off the northern Pacific coast of Costa Rica. I found it on an underwater pinnacle, on the underside of a scallop. This species has a small internal shell. The shape of the shell is used to help identify the species.
One of the distinguishing characteristics of the Berthella and Berthellina genus is the presence of an oral hood. This structure is clearly visible in the photograph on the left. It is the trapezoid shaped translucent part of the nudibranch on its extreme anterior end.
Notospidea are also referred to as side gilled sea slugs. They have an elongate plumed gill on the right hand side of their bodies. Members of the order are voracious predators. They have strong jaws and wide radula to enable them to scrape and feed on their prey. Most species feed on sponges, but some feed on hard corals or ascidians.
Notospidea is a small sized order with relatively high variation. Their shells can be external and limpet like, small and internal, or not existent at all.
Here is a top view of this guys small internal shell. It has a similar shape to a bivalve shell, but it only has one side:
© Peter Ajtai, 2002
