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underside
 


rhinophores

 

branchia

 

crawling




 
Hallaxa
cf. fuscescens (Pease, 1871)
 
Hallaxa cf. fuscescens
Maximum size:  6 mm.

Identification:  This is 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.

Taxonomic notes:  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 recorded 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:

Note 1:  ( )
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