young, 5 mm
Elysia obtusa Baba, 1938
|Maximum size: 22 mm.
moderately tall parapodia that meet in a frilly
margin. There are widely scattered papillae that become much more
prominent on the parapodial margin. It is usually bright yellow with
minute rust-brown flecks, scattered white spots, and a white marginal
band on the parapodia. Some animals, however, have dark interior
pigment. (Note 1) Rarely, there may be a more extensive dusting of white flecks on the interior of the parapodia and rhinophores.
Elysia obtusa is a
moderately rare plakobranchid found on shallow rocky
It occurs in highly protected to moderately protected locations from
intertidal to depths of 1.5 m (5 ft). Mature animals are nocturnally
The lack of consistent dark pigment suggests that it does not
store chloroplasts. A 7.5 mm animal laid a tightly coiled, pale
orange egg mass. It had evenly spaced "knobs" on the outer surface of
whorls that were filled with dark orange extra-capsular yolk. Hatching
occurred in about seven days in the laboratory. The extra-capsular yolk
remained in the egg mass after hatching.
Big Island, Maui,
French Frigate Shoals and Pearl & Hermes Reef: widely distributed in the Indo-Pacific
This species was previously lumped with Atlantic animals under the name Elysia flava
Verrill, 1901 and it is listed under that name in many older
sources. It was first recorded in Hawaii from Hekili Point, Maui by CP
on May 9,
1992. Recent DNA results from Kaneohe Bay (and elsewhere) suggest that
there may be two cryptic species lumped under the name in the
Indo-Pacific (though only one in Hawaii) making use of the name for the
Hawaiian population uncertain. (Gustav Paulay, pers. com.).
CP: 7.5 mm: Hekili Point, Maui; April 16, 2006.
Observations and comments:
An animal with dark pigment changed to "all yellow" after laying eggs
suggesting that the dark color may be due to some compound involved in
egg laying (a precursor to the extra-capsular yolk?) rather than
retained chloroplasts. (see photos)