Description: This crab has a rostrum
composed of two broad, flattened processes (photo)
which project forward but are not turned dorsally. Its carapace
is slightly broader than long, and nearly oval in outline. The carapace
margins have spines on the anterolateral margins (photo)
but are not expanded into winglike lobes. The dorsal surface of the
The walking legs are long, and longer than the chelipeds.
of the walking legs is slightly inflated and flattened. The margins
of the merus
of the walking legs have spines. Color of adults is greenish-brown
with red granules and orange lateral spines. Pink on the ventral
side (photo). Chelipeds
have a golden iridescence, and have white fingers with red stripes and
orange at the base (photo). The walking legs
are brown, white, pink, and orange and have dorsal red stripes. The
are red. Carapace
width to 14 cm in males, 8.1 cm in females.
Chionoecetes bairdi Rathbun, 1893
Common name(s): Tanner crab, Southern tanner crab, snow crab, cobbler
opilio (those found south of
|Chionoecetes juvenile captured
at 250-300 foot depth in San Juan Channel. Carapace width 2.75 cm.
|(Photo by: Dave Cowles, July 2011)
How to Distinguish from Similar Species: Chionoecetes
tanneri (C. angulatus?)
has a rostrum
which turns dorsally. It is mainly found at depths below 1000 m.
style="font-style: italic;">C. opilio is an arctic species common near
the Aleutian Islands, with carapace
length and width nearly equal and less spines on the carapace.
Most other crabs from family Majidae, which look similar, have a carapace
longer than wide (except for Mimulus
foliatus, in which the carapace
margins are expanded into winglike flanges).
Geographical Range: Northern Alaska to
Depth Range: 6 to 475 m
Habitat: Subtidal, Sandy or muddy bottoms
Biology/Natural History: This crab is
harvested commercially in Alaska as the snow crab, although that harvest
is mostly of the relative C. opilio.
Predators include sea otters in Alaska. The egg masses of this species
may be parasitized by a tiny Nemertean worm Carcinonemertes
regicides. A leech, Notostomium
cyclostoma, which feeds off fishes lays its eggs on the crab carapace.
The leeches do not appear to feed on the crab. It may also be parasitized
by the dinoflagellate Hematodinium.
This crab has a terminal molt. Females reaching their terminal molt breed
for the first time while still soft from molting, but can breed again while
still hard. They store sperm (from male spermatophores)
in their spermatheca. Males first produce spermatophores
when about 45 mm carapace
width, but larger males produce more spermatophores.
Females may become sexually mature by about 55 mm carapace
width but may be as large as 85 mm carapace
width (Paul, 1992).
and Hanby, 2005
and O'Clair, 1998
Myers, T.C., T.M. Botelho, T.M. Koeneman,
S. Short, and K. Inamura, 1990. Distribution of bitter crab dinoflagellate
syndrome in southeast Alaskan Tanner Crabs Chionoecetes
bairdi. Dis. Aquat. Org. 9: pp. 37-43
Paul, A.J., 1992. A review of size a maturity of male tanner (Chionoecetes bairdi) and King (Paralithodes camtschaticus) crabs and the methods used to determine maturity. American Zoologist 32: pp. 534-540
General Notes and Observations: Locations,
abundances, unusual behaviors:
This closeup shows the rostrum,
the spines on the anterolateral
margins of the carapace,
and the eye pattern. Photo by Dave Cowles, July 2011.
A photo of another individual clearly shows the small spines lining
Captured by Kirt Onthank by SCUBA at about 20 m depth at night in Burrows
Bay. Photo by Dave Cowles, August 2015
|These images of the underside of a male show the shape
of the abdomen
and the specialized first pleopods
width on this individual is 3.5 cm. Photos by Dave Cowles, August
||Abdomen folded back to show pleopods
A dorsal view of the same individual.
And the ventral side
This closeup of the chelae
shows that the chelipeds
are relatively short but with small spines and granules. The base
(palm) of the propodus
is swollen and slightly elongated. The fingers of the chelae
are long and narrow and are serrated with sharp teeth.
A view of the mouth.
Authors and Editors of Page:
Dave Cowles (2011): Created original page
CSS coding for page developed by Jonathan Cowles (2007)