"tail" & foot
young & feeding
Oxynoe sp. #1
|Maximum size: 47 mm (including "tail").
species has a thin, transparent shell that's covered by undivided
parapodia. The body is papillate and
the foot extends well beyond the posterior margin of the shell. The
posterior portion of the foot appears to increase in relative length as it grows. (Note 1) It is
light olive-green with yellow flecks and white blotches. The body is
decorated with gold-ringed, blue ocelli that have dark blue dots in
their centers. (Note 2) Blue ocelli are also present on the body under the shell (showing through the shell in young animals).
Natural history: Numerous Oxynoe sp. #1 were recently found, on Maui, in patches of Caulerpa taxifolia growing in a patchy Halimeda kanaloana bed
at a depth of about 9 m (29-30 ft). The lack of records between the 1800s and
2021 suggests that the species may be very sporadic in occurrence. (Note 3) It feeds on Caulerpa taxifolia
and lays flattened, cream egg masses. It's
diurnally active and uses it's flexible foot margins to grasp the Caulerpa's fronds. (see photos) (Note 4)
Maui and Oahu: also known from the western Pacific and French Polynesia.
Taxonomic notes: Oxynoe sp. #1 is a close match for "Oxynoe sp. 2" in Gosliner, et. al. (2018). The genus was first reported from Hawaii by Adams in 1855 (described as Lophocercus krohnii).
His description, however, was based only on the shell. Morch, in 1863,
reported the genus from the "Sandwich Islands" using the name Lophocercus viridis
Pease 1861 (since changed to Oxynoe viridis and originally
described as "from the Pacific Islands"). Neither the shell description
by Adams nor the Morch record can be clearly assigned to either "Oxynoe sp. 2" or O. viridis
as illustrated in Gosliner, et. al.
(2018). Therefore, although it's possible that the older records were a
different species, we're lumping the new animals with them by "process
of elimination." If it becomes possible at some point to separate them,
Katherine Shepherd and Jenna Szerlag should be credited with the first
record of Oxynoe sp. #1.
Photo: Rebecca Bicker: Maalaea Bay, Maui; Feb. 14, 2021.
Observations and comments:
Gosliner, et. al. (2018), referring to the genus, mentions that the
elongate "tail" can be used as a propeller to swim away if they are
disturbed and can be autotomized to distract predators. Secretion of
milky, defensive fluid is also mentioned. Autotomization and
regeneration might be an alternative explanation for the variation in
The blue spots with gold rings aren't as precisely matched to the blue and gold ocelli found in the sea hares Stylocheilus
striatus and Phycophila euchlora as are the markings in some other possible mimics.
But, perhaps they are close enough so that
Oxynoe sp #1 is
still deriving some benefit from the resemblance (since the sea hares
are known to concentrate toxins from the cyanobacteria they eat)?
Previous Oahu records from the 1800s lack habitat data.
Note 4: On Feb. 14, 2021 Katherine Shepherd and Jenna Szerlag found 10 animals on a 4 m (15 ft) diameter patch of Caulerpa taxifolia growing in a patchy Halimeda kanaloana
bed. They ranged from 17 to 40 mm in length and could "stretch out
longer." They were observed feeding actively on the
Caulerpa and crawling between clumps. Several were resting on egg masses.