Polybranchia orientalis (Kelaart, 1858)
|Maximum size: 90 mm.
thin, leaf-like cerata with serrated edges. The
body is cream with white flecks. The cerata are usually edged with
flecks and often have greenish centers.
is a moderately common species found in the low intertidal and
subtidally to depths of 5 m (16 ft). It occurs in highly protected to
moderately protected rocky habitats. It's nocturnal but can be found
under rocks during the day. When disturbed, it can autotomize its
central cerata. (Note 1) According to Kay (1979)
the egg mass consists of "cylindrical, transparent, gelatinous coils".
Maui, Oahu and Midway: widely distributed in the Indo-Pacific.
listed as Branchophyllum
pellucida (Pease, 1860) in Kay, 1979. There is some possibility
that animals with and without greenish centers in there cerata are
different species. It was probably first reported from Hawaii in Pease,
1860 (as Polybranchia pellucida). It may also be the animal referenced in the text at the bottom of page 185 in Edmondson, 1946.
found by CP; Hekili Point, Maui; Sept. 1990.
Observations and comments:
1: Two animals found in 1985 and
1988 autotomized their central cerata abruptly when touched with a bare
finger. In one case, the cerata were observed to exude a rubber
glue-like mucus and twitch for at least half an hour after being
dropped, presumably serving to distract or entangle a potential
predator. Two other animals of the "greenish centered form" that were
handled with probes or spoons didn't
autotomize there cerata suggesting that they can discriminate between
casual contact and a potential threat. Branches of the digestive gland
appear to be concentrated in the lateral cerata that aren't
autotomized. Specimens of the pale form (lacking greenish centers in
their cerata) seem to be less sensitive, seldom (if ever?) autotomizing
their cerata during handling.