#doridacea

These are pictures of the nudibranch Trapania velox. A nudibranch is a type of marine mollusc (snail) that loses its shell during metamorphoses from a planktonic larvae (veliger) to a baby sea slug. The word velox from the species name means “swift”, though this slug doesn't seem all that swift.  This nudibranch lives on the west coast of North America, from Carmel, California to Bahia Tortugas, Baja California, Mexico.  Trapania velox feeds on tiny colonial animals called entoprocts that often grow on top of encrusting sponges (epizoic).

Trapania velox is a dorid nudibranch that cannot retract its gill (phanerobranch).  The gills are feather-like projections near the top-middle of the body just behind two black and yellow appendages.  There are two other black and yellow appendages near the rhinophores.  The rhinophores (which means nose-bearer) are white and yellow and are perfoliate.  Rhinophores are used as chemical sensors, so “smell” underwater.

The eggs of Trepania velox are in laid in white ribbons.

This species of nudibranch was first described in 1901 by T.D.A Cockerell from La Jolla.  The animal in these pictures was photographed at South Casa Reef (Hospital Point), La Jolla, CA.

References

Behrens, D.W. (2005).  Nudibranch Behavior. New World Publications, Jacksonville, FL.

Behrens, D.W., and Hermosillo, A. (2005).  Eastern Pacific Nudibranchs: A Guide to the Opisthobranchs from Alaska to Central America.  Sea Challengers, Monterey, CA.

Cockerell, T.D. (1901). Three nudibranchs from California. Journal of Malacology 8:85–87.

Red-Spotted Dorid or Halo Red-Spotted Dorid (Goniobranchus heatherae) - 

This little sea slug is a dorid nudibranch which means that it is able to retract its gills into a gill pocket.  Its gills are the external "branches" that stick out near its bum.  It can grow up to 2 inches long.

This species of sea slug lives along the coast of southern Africa.  They live on the rocks of shallow waters and feed on sponges.  Some of the identifying features of the red spotted dorid are the eight butt gills and the thick rhinophores (the antennae things).  Some nudibranchs' rhinophores are smooth while most dorid nudibranch have fat, ribbed ones.  Most red spotted dorids have an opaque white band around the notum.  Species that live in the eastern areas of its region can have a yellow band next to the white one (bottom right).  The size of the spots can vary from very small to having one large red spot on its back.  

Squish.

Nembrotha yonowae

....is a species of dorid nudibranch that is found throughout the western Indo-Pacific, and is most common in the Maldives, The Philippines and Indonesia. Like other members of Nembrotha N.yonowae feeds mostly on sessile invertebrates, and has an affinity for colonial ascidians. 

Nembrotha yonowae is similar in appearance to Nembrotha cristata, but is different in coloration. Like N.cristata N.yonowae's coloration is aposematic warning predators of its toxicity.

Phylogeny

Animalia-Mollusca-Gastropoda-Doridacea-Polyceroidea-Polyceridae-Nembrothinae-Nembrotha-N.yonowae