young, 8 mm
with egg mass
Gymnodoris bicolor (Alder and Hancock,
|Maximum size: 22 mm (Kay,
background color of this species varies from cream through orange
to pale pink. It's decorated with small orange spots. The branchia form
a horseshoe-shaped circle around the anus and the oral tentacles are
broad. It can be distinguished from the similar appearing Gymnodoris
sp. #2 by its lack of nipple-like tips on its rhinophores and its
broad oral tentacles. It can be distinguished from the nearly identical
Gymnodoris citrina be the
location of its genital opening (immediately behind the branchia
in G. bicolor and well
forward of the branchia in G. citrina)
by its more rounded oral tentacles.
is a moderately common species found in protected to moderately exposed
rocky habitats at depths of < 1 to 10 m (< 3 to 33 ft). Like G. citrina, it feeds on other
species of Gymnodoris. (Kay, 1979) (Note 1) It
lays an orange spiral egg mass that hatches in about eight days in the
Big Island, Maui, Oahu, Kauai and French Frigate Shoals.
was first reported from Hawaii in Kay & Young, 1969.
orange: Hekili Point, Maui; Oct. 19, 2001.
Observations and comments:
1: On July 4, 2012 an 8-10 mm Gymnodoris bicolor was offered a Noumeaella
rehderi, an Elysia sp. #6 and a Gymnodoris alba (or G. sp. #7?), all around 3-4 mm in length. It ignored the first two (even with repeated contact) but immediately ate the G. alba.