Description: As with all Polynoids, this
species is mostly benthic, few if any of the segments are longer than wide
when contracted, the dorsal surface has clearly visible elytra,
and all of the neurosetae are simple. Arctonoe pulchra has
at least 20 pairs of elytra, elytra
are on segments 2, 4, 5, then every other segment to 23, 26, 29, then every
other segment to the end of the body. The edges of the elytra
are smooth (photo), and they nearly meet along the
animal's dorsal midline. It has no prominent nuchal fold and the
lateral prostomial antennae are inserted slightly ventral to the edge of
the prostomium, may have few or sometimes no notosetae. The neurosetae
are falcate, with pointed tips, and hooked. Most individuals are
brick red, and the species has no dark band across segments 7 and 8.
Up to 7 cm long.
Arctonoe pulchra (Johnson, 1897)
Common name(s): Red commensal scaleworm
|Synonyms: Polynoe pulchra, Acholoe
sp., Halosydna sp.
|Arctonoe pulchra, about 2 cm long. Was living on the sea
californicus caught near Rosario.
|(Photo by: Dave Cowles, July 2006)
How to Distinguish from Similar Species:Arctonoe
vittata has a band of dark pigment extending across segments 7
and 8. Arctonoe fragilis
has ruffled or folded margins on the elytra.
Geographical Range: Gulf of Alaska to Baja California,
Mexico; uncommon in California
Depth Range: Lower intertidal to 275 m
Habitat: Symbiotic with several invertebrates
including sea stars such as Solaster
foliata, and Dermasterias
imbricata, sea cucumbers such as Parastichopus
californicus and P. parvimensis, and other animals such
aspera, Megathura crenulata and terebellid polychaetes such
as Loimia montagui.
Biology/Natural History: This species
is attracted by the smell of its host (if the host is uninjured), but can
learn to live with a new species. Its body color is usually close
to that of its host. It eats detritus. Adults are territorial
and will try to drive other individuals off their host. They may
injure or kill one another in fights over a host.
Members of Family Polynoidae,
unlike most other errant polychaetes, have parapodia specialized for walking
rather than as paddles. Their longitudinal muscles, which caused
lateral undulations in other polychaetes, are poorly developed and they
don't undulate much. As a result, although they can walk efficiently
they are poor swimmers.
and Carlton, 1975
and O'Clair, 1998
et al., 1985
General Notes and Observations: Locations, abundances,
The edges of the elytra on this species are smooth, as seen in this
closeup photo. This individual also has a red spot on each elytrum.
et al. says all members of the species have this spot (but that A.
vittata do not), while O'Clair
and O'Clair say that some individuals may not have the spot.
Authors and Editors of Page:
Dave Cowles (2006): Created original page