Doriprismatica atromarginata (Cuvier, 1804)
|Maximum size: 90 mm.
has a high, narrow body with a mantle that covers the
foot almost entirely (except for places where the margin folds and at
the tip of the posterior end). Body color ranges from
toasted-marshmallow brown to brownish black. The highly convoluted
mantle margin is usually cream-colored and always possesses a striking
black line. The rhinophore clubs and gill tips are black as well. The
foot is cream. Hawaiian animals tend to be darker brown than those in
other parts of its range.
While common in some parts of the world, such as Australia and
Indonesia, Doriprismatica atromarginata
is rarely sighted in Hawaii with only a few encounters in the main Hawaiian
Islands. In most cases, several individuals were found feeding on a large black/brown sponge, Spongia oceania. (Note
1) They were
in moderately exposed, rocky habitats ranging from 2-12 m (6-40 ft).
The egg mass is white and hatches in about 10 days.
Maui, Oahu and French Frigate Shoals: widely distributed in the
was first recorded in Hawaii from French Frigate Shoals before
Johnson, pers. com.). The species name means black margin and, in the
5th printing, Hoover, 2006 lists it as Glossodoris atromarginata (corrected in 2019 printing) and refers to it as the "black-margin
on Spongia oceania with
feeding damage: found by Michelle White; Molokini Islet, Maui; Nov. 6,
Observations and comments:
1: On June 20 and June 29, 2008 we
watched a pair of D.
atromarginata attempt to feed on their host sponge. The
nudibranch would begin to
oral tube and place it on the sponge but, within a few seconds, it
quickly recoil as if in pain and would remain in a reared back
position for about 30 seconds before slowly placing its mouth on the
sponge again. Sometimes instead of recoiling quickly it would pull back
a little less vigorously,
and attached to its mouth/head would be a long
thin polychaete! When
nudibranch pulled back a centimeter or so, the polychaete would
apparently let go and withdraw into the sponge. We watched this for 30
minutes each time and polychaetes continually attacked both nudibranchs
on their heads and undersides wherever they attempted to feed. At
times the nudibranchs would assume a "bridge" posture with only the tip
of the foot and the head touching the sponge, seemingly in an attempt
to prevent worms from attacking the foot and body. In spite of constant
attacks, the nudibranchs seemed to be able to consume a tiny bit of
sponge with each attempt as evidenced by many small scars. (see photos)
Perhaps, the polychaetes were defending their host sponge in a manner
analogous to Trapezia spp.
defending Pocillopora spp.
from crown of thorns sea stars? For further discussion of such
interactions with another species of dorid see the Sea Slug Forum.