Hallaxa cf. fuscescens (Pease, 1871)
|Maximum size: 6 mm.
a soft-bodied species with irregular tubercles on its notum. It lacks the fine, secondary tubercles of Actinocyclus verrucosus
and has about half as many branchial plumes as that species. The dark
pigment on the tubercles is diffuse rather than sharply margined. The
rhinophores have white tips and the underside is flecked with brown.
Natural history: Hallaxa cf. fuscescens is known from a single animal found just off the beach at a highly protected site with a depth of < 1 m (< 3 ft).
Distribution: Oahu: perhaps, widely distributed in the Indo-Pacific.
Originally misidentified as a juvenile Actinocycus verrucosus,
its DNA proved divergent from that species (Gustav Paulay, pers. com.). On
reexamination, it was found to match many of the photos labelled Hallaxa fuscescens.
Other photos, however indicate either high variability for that species
or the possibility of further splits. And, the original description by
Pease is somewhat ambiguous. So, we're opting to "cf" pending further
work. It was first found in Hawaii during the 2017 MarineGeo at Kaneohe Bay, Oahu by R. Ravinesh on May 20, 2017.
Photo: Invert Team: 6 mm: 2017 MarineGeo; Coconut Island, Kaneohe Bay, Oahu; May 20, 2017.
Observations and comments:
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