Pleurobranchus mamillatus Quoy & Gaimard, 1832
|Maximum size: about 76 mm. (probably gets much larger)
large species with tall, conical tubercles on the central portion of
the notum that may be somewhat contractile. There are irregular arcs or
rings of small, rounded
tubercles surrounding the larger ones. The lateral portion of the notum
is thinner with fewer large tubercles and the rhinophores are deeply
enfolded. The color ranges from mottled burnt-orange and cream to dark
violet-red. The underside is light orange in mottled animals while the
notum has bright violet-white spots in all forms (a trait that
from Pleurobranchus grandis).
has been dredged from about 100 m (328 ft) and photographed from HURL
92-138 m (302-453 ft). However, a single animal was found by PF at 8 m (25 ft) in a Halimeda kanaloana
bed indicating that they occasionally enter shallow water. The notum of
that animal was completely covered with sand when found. (see photo)
Maui, Oahu, Raita Bank and Pioneer Bank: widely
distributed in the Indo-Pacific.
It was first
in Hawaii from Oahu by Terry Gosliner. It's misspelled in some sources as "Pleurobranchus mammalatus". (note 1)
Photo: PF: about 76 mm: Maalaea Bay, Maui; Oct. 15, 2020.
Observations and comments:
1: Most animals from elsewhere in
the Indo-Pacific have violet-white arcs on their notums while all known
Hawaiian animals have violet-white spots. However, Japan shows a mixture
of animals with arcs and spots suggesting that Hawaii might have been
colonized from that direction. Perhaps, the dominance of spotted animals
in Hawaii is due to "founder's effect"? Meanwhile, the smaller
tubercles seem better developed in Hawaiian animals than in most
specimens from elsewhere (often resembling the tubercles of Pleurobranchus hilli, a species that lacks both spots and arcs). So, the DNA
should probably be checked...