Polybranchia samanthae Madrano, Krug, Gosliner, Kumar & Valdes, 2018
|Maximum size: about 50 mm (rough estimate from photo).
This species has broad, thin, leaf-like cerata with serrated edges. The
cerata are finely papillate and often edged with
white flecks. A short, opaque-white line extends from the tip to the
center of each ceras's inner face where it surrounds a
green patch. White pigment is also present on the rhinophore tips, head
and pericardium. The cerata usually have more acute tips than in Polybranchia jensenae.
Natural history: Polybranchia samanthae
is a moderately rare species found in the low intertidal to 6 m (20
ft). It occurs in protected to moderately exposed rocky habitats.
It's nocturnal but can be found under rocks during the day. When
disturbed, it can autotomize its central cerata. (Note 1)
Maui, Oahu and Kauai: widely distributed in the Indo-Pacific.
Taxonomic notes: Members of this genus were first described from Hawaii by Pease in 1860 under the name Polybranchia pellucida. Kay (1979) used the name Branchophyllum
pellucida. However, Medrano, et. al.
(2018) states that their descriptions are insufficient to distinguish
between Polybranchia jensenae and P. samanthae.
So, one or both were probably first reported from Hawaii in Pease,
1860 or Kay, 1979. One or the other may also have been the animal
referenced in the text at the bottom of page 185 in Edmondson, 1946.
about 50 mm (rough estimate from photo): 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 that were
handled with probes or spoons didn't
autotomize their 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 Polybranchia jensenae seem to be less sensitive, seldom autotomizing
their cerata during gentle handling.