young, 2 mm
Elysia pusilla (Bergh, 1872)
|Maximum size: 14 mm.
a small species with low parapodia that end well before the tip
of the foot. The body and parapodia range from bright green through mottled
green and white to solid white. Occasionally, they have faint blue flecks. There are small,
papillae on the parapodia and rhinophores.
Elysia pusilla may
well be the most common plakobranchid found in Hawaiian waters however
it's seldom seen by
divers since it rarely leaves its host algae (on which it's
superbly camouflaged). It feeds on various species of the green alga Halimeda and may be found on Halimeda discoidea and Halimeda opuntia growing in
protected to highly exposed rocky habitats as well as in Halimeda
kanaloana beds in deeper, sandy habitats. We've recorded it from
depths of < 1 to 12 m (< 3 to 39 ft). Mature animals are
resting animals assume a highly flattened posture with the parapodia
tightly appressed to the host algae. (see photo) Rarely, they will secrete a milky fluid when disturbed. Egg masses are tightly coiled,
flattened, yellow spirals. The eggs are closely associated with a
reticulated mass of opaque-cream extra-capsular yolk. The eggs hatch in
about 6 days in the
laboratory and the extra-capsular yolk disappears during development
suggesting that its role is primarily nutritional.
Maui, Oahu, Kauai and French Frigate Shoals: widely distributed in the
Indo-Pacific; also in the eastern Pacific.
the species listed as Elysia
halimedae MacNae, 1954 in Kay, 1979. Some authors list it as Elysiella pusilla. The name
means weak or little.
Photo: CP: 8
mm: Maalaea Bay, Maui; May 4, 2006.
Observations and comments:
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