''Chaceon bicolor'' is a species of
crab
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" (abdomen) ( el, βραχύς , translit=brachys = short, / = tail), usually hidden entirely under the thorax. They live in all the ...
.
[Manning, Raymond B., and L. B. Holthuis. "Two new genera and nine new species of geryonid crabs (Crustacea, Decapoda, Geryonidae)." Proceedings of the Biological Society of Washington 102.1 (1989): 50-77.] ''Chaceon bicolor'' differs from all species of the genus in color pattern, with the anterior part of the body purplish rather than reddish. In addition to color pattern, ''C. bicolor'' also differs from ''
C. granulatus'' in having compressed rather than depressed
dactyli on the walking legs; also, the hepatic region of the
carapace
A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...
in ''C. granulatus'' is coarsely granular, whereas it is smooth in ''C. bicolor''. Juvenile specimens differ from adults in many features: the teeth of the carapace are much larger and sharper, there is a sharp spine on the
carpus of the
cheliped and a distal spine on the
merus of each walking leg, plus the legs are longer and slenderer. Adult females differ from males in having much sharper anterolateral teeth on the carapace, sharper suborbital spines, and much shorter legs, with less trace of a distal dorsal projection on the merus. The carapace of females is more strongly arched from front to back and the protogastric regions are noticeably more inflated. The species is named as such because of its colour patter, purple an tan.
Description
It is a large ''Chaceon'', its size varying from to , with small anterolateral teeth on the carapace and laterally-compressed dactyli on the walking legs.
Its median pair of frontal teeth is narrower than the laterals, separated by a U-shaped emargination. The carapace has a distinct granulation medial to the fifth tooth and on protogastric, cardiac, and branchial regions; its hepatic region is smooth; protogastric region inflated in large specimens, especially in females.
Its cheliped is lightly tuberculate dorsally; upper margin of merus with a sharp subdistal spine; the
carpus lacking an outer spine in adults;
propodus unarmed distally.
Meri of its posterior walking legs has a distinct distal dorsal angled projection, spined in juveniles. The dactyli of walking legs are laterally compressed.
The anterior part of the carapace is predominantly purple, its branchial regions tan and its legs yellowish.
Distribution
It has a wide distribution in the central
Pacific, from the
Emperor Seamount Chain to eastern Australia, off Sydney, in depths between .
References
External links
*
ADW entryWORMS entry
Portunoidea
Crustaceans described in 1989
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