Orconectes difficilis (Faxon, 1898)

Morehouse, Reid L. & Tobler, Michael, 2013, Crayfishes (Decapoda: Cambaridae) of Oklahoma: identification, distributions, and natural history, Zootaxa 3717 (2), pp. 101-157 : 128

Orconectes difficilis (Faxon, 1898) : Painted Crayfish

General charateristics. Adults rarely exceed 80 mm in total length. The carapace is robust, depressed, and the areola is closed. The rostrum has prominent lateral spines and a pointed acumen that is shorter than the basal portion. Chelae are triangular and flattened, often as long as the carapace in form I males. In form I males, gonopods are short, stout with central and mesial processes that are short and blunt. In females, the annulus ventralis is diamond shaped (Faxon, 1898).

Life coloration. The background color is olive brown to grayish tan. There is black speckling on the chelae and occasional speckling on the carapace and abdomen ( Figure 49 ). Fingers may have strong tints of blue to green, especially in form I males, and often have cream to yellow tips. Ventral side is cream to white.

Similar species. In Oklahoma, O. difficilis closely resembles O. deanae and O. palmeri longimanus . It can be differentiated from O. palmeri longimanus by the shape of the gonopods in form I males. In O. difficilis , the central projection and mesial process are short and less than 1/4 of the total length, while O. palmeri longimanus ’ central projection and mesial process are long, slender, and more than 1/4 of the total gonopod length. Orconectes difficilis differs from O. deanae by the curvature in the mesial process (90° angle to the shaft in O. deanae ).

Distribution and habitat. Orconectes difficilis is a tertiary burrower and occurs in streams of southeastern Oklahoma, southwestern Arkansas, northeastern Texas, and northwestern Louisiana. In Oklahoma, O. difficilis has been found in rocky, clear streams of Pittsburgh, Latimer, and McCurtain Counties. Our ecological niche model indicates that the southeastern quarter of the state provides suitable environmental conditions for O. difficilis ( Figure 50 ).

Life history. Information regarding the life history of O. difficilis comes from a study conducted by Walls (1985), where he reported form I males from June through February, with the majority collected in September and October, and suggests most reproductive activity occurs in September and October. We have collected form II males and females in October in southeast Oklahoma.

Syntopic species. Orconectes palmeri longimanus .

Conservation status. AFS: Currently Stable; Heritage Rank: Vulnerable (G3); IUCN: Least Concern; ODWC: Not Listed.

Additional resources. Johnson (2010); Walls (1985).

Figures

FIGURES 45 – 52. 45. Orconectes causeyi 46. Potential distribution of Orconectes causeyi 47. Orconectes deanae 48. Potential distribution of Orconectes deanae 49. Orconectes difficilis 50. Potential distribution of Orconectes difficilis 51. Orconectes lancifer 52. Potential distribution of Orconectes lancifer.