Panopeus lacustris
Desbonne, 1867
knot-fingered mud crab
Panopeus lacustris, commonly known as the knot-fingered mud crab, is a small true crab (infraorder Brachyura) in the Panopeidae. It is distinguished by unequal-sized chelae, with the larger claw being exceptionally broad, knobbly, and bearing teeth in the molar area with an immobile finger. The exhibits in size, with males typically larger than females. It is native to the subtropical western Atlantic but has been introduced to Hawaii and the Pacific coast of California. The species serves as a for the parasitic barnacle Loxothylacus panopaei, which manipulates crab and causes functional castration.
Pronunciation
How to pronounce Panopeus lacustris: /pəˈnoʊpiˌəs ləˈkustrɪs/
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Identification
Distinguished from related by the exceptionally broad and knobbly main chela. in size aids identification: males average larger than females. Right-handed individuals (with larger right chela) significantly more common than left-handed.
Appearance
Small crab with unequal-sized chelae. The larger chela is exceptionally broad and knobbly, with teeth in the molar area and an immobile finger; this claw is often worn and coalesced. and upper side of limbs are dull mottled reddish; undersides of body and limbs are whitish. Individuals in caves are paler with antennules bearing white spots.
Habitat
Coastal marine environments; rocky areas with crevices and caves. Found in intertidal and shallow subtidal zones. Cave-dwelling occur in some areas.
Distribution
Native: subtropical western Atlantic Ocean including southern Florida, Bermuda, Caribbean Sea, West Indies, and South American coast to Cabo Frio, Brazil. Introduced: Hawaii (since 1950s) and Pacific coast of California (since 1980s or earlier).
Host Associations
- Loxothylacus panopaei - Parasitic barnacle that develops inside crab, manipulates to induce care of barnacle eggs, and causes functional castration of both male and female crabs. Type locality for this was Tampa, Florida, based on P. lacustris as host.
Behavior
Exhibits handedness: right-handed crabs (larger right chela) significantly more common than left-handed. When parasitized by Loxothylacus panopaei, manipulated to care for barnacle under as if own young.
Ecological Role
considered stable in studied environment. Serves as for parasitic barnacle Loxothylacus panopaei, which was first described from this host .
Human Relevance
Introduced to Hawaii and California, potentially impacting local . Subject of research in Brazil.
More Details
Sexual Maturity
Morphological sexual maturity at 12.32 mm width (males) and 12.00 mm (females); 50% physiological maturity at 11.35 mm CW (males) and 10.61 mm CW (females).
Reproduction
Reproductive period is continuous year-round. Sex ratio 1:1.15 (males:females).
Parasite Type Locality
Loxothylacus panopaei was first described in 1884 from P. lacustris collected at Tampa, Florida.