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, dorsal and dorsolateral portions of carapace punctuate, lateral surface granulate; cephalic section laterally armed with small to moderate tubercles, gastric region with scattered small punctuations. Rostrum with moderately elevated and slightly thickened margins converging acutely to base, latter having small marginal tubercle; margins more strongly converging and moderately concave to dorsally directed apical tubercle, tip of which extends slightly beyond cephalic to distal margin of penultimate podomere of antennular peduncle; acumen comprising 21.7% of TCL; floor (dorsal surface) of rostrum with small punctuations on caudal half; ventral keel of rostrum lacking setae, tubercle, or spine; median carina absent.Postorbital ridge moderately developed dorsally, dorsolateral groove present; caudal end inflated, cephalic margin with acute spine.
The Marmorkrebs is characterized by its marble pattern on the carapace, and they are only parthenogenetic decapod crustacean known to date (Scholtz et al., 2003).While this manuscript was being prepared, Jones et al.(2008) published an account of a molecular study identifying crayfish specimens collected in Madagascar as Marmorkrebs.As this is a worrisome finding, the public should be alerted so that spread on the island can be prevented before it affects the vulnerable native crayfish biodiversity and the rice field business in Madagascar. This enigmatic crayfish is already widespread and sold in markets in and around Antananarivo, the capital of Madagascar.A preliminary examination of morphological characters suggested that the introduced Malagasy crayfish might be the so far undescribed Marmorkrebs (marbled crayfish) (Scholtz et al., 2003).The Marmorkrebs is the only parthenogenetic decapod crustacean known to date (Scholtz et al., 2003).
However, its taxonomic status and origin are not yet clarified.
Morphological and molecular data have suggested its close affinity to two species of (Faxon, 1884), (Scholtz et al., 2003; Vogt, 2008).
Due to its potential to colonize rivers and lakes by building up a population starting from just one individual, its high rate of reproduction, and the potential to transmit the crayfish plague and other diseases, it has been considered a menace to the endangered European species of crayfish.
Scale bars denote Alien crayfish (Marmorkrebs) collected in Madagascar: A, lateral view of carapace; B, dorsal view of carapace; C, dorsal view of antennal scale; D, ventral view of third maxilliped; E, dorsal view of distal podomere of cheliped; F, ventral view of basis of cheliped; G, epistome and base of antennae; H, annulus ventralis. Chela 2.0 times wider than deep; dorsal surface of palm punctuate, all area with tufted setal punctuations; medial surface with medial-most row of usually 8 tubercles, sometimes 7 or 10; lateral surface of palm moderately rounded, with tufted setal punctuations; ventral surface of palm with fewer and smaller tufted setal punctuations than those of dorsal surface. Pleon with median longitudinal broad brown stripe, flanked laterally by series of dark, oblique splotches situated anteriorly, each on first through fifth terga; pleura of second through sixth pleomeres delimited basally by ventrally convex black marks forming scalloped line. Chelipeds olive to brown mottled with dark brown tubercles. All specimens showed the characteristic opening of oviduct (female gonopore) at the coxae of the third pereiopods, and none displayed any male characters.
Scale bars denote times as long as broad, widest at mid-length, reaching or slightly extending to distal margin of ultimate podomere of antennular peduncle; lateral margin thickened and terminating in small spine; lamella approximately 2 times as wide as thickened lateral portion, mesial margin rounded. Dactyl of chelae 1.3 times as long as palm as measured along medial margin; dorsal surface with low, rounded ridge flanked by row of spaced, tufted setal punctuations. We dissected 10 specimens (mean POCL ) to analyze the gut contents.
Invasion of an alien freshwater crayfish is newly confirmed in Madagascar.