Orconectes nana Williams, 1952

Morehouse, Reid L. & Tobler, Michael, 2013, Crayfishes (Decapoda: Cambaridae) of Oklahoma: identification, distributions, and natural history, Zootaxa 3717 (2), pp. 101-157 : 132

Orconectes nana Williams, 1952 : Midget Crayfish

General charateristics. Adults rarely exceeds 50 mm in total length. The carapace is nearly equal in length to the abdomen. The rostrum is narrow with a well-developed trough-like depression. Chelae are short but broad and look oversized relative to body size. In form I males, gonopods have two long, slender, and slightly curved processes that reach the base of the second pair of pereiopods. In females, the annulus ventralis has a deep fossa (Williams, 1952).

Life coloration. The background color is uniform olive-tan to brown without any colorful markings. The cheeks exhibit a yellowish spot with a reddish edge. There is a dark brown to black saddle at the conjunction of the carapace and abdomen ( Figure 63 ). The ventral side is light yellow to white.

Similar species. In Oklahoma, O. nana closely resembles O. macrus and O. meeki brevis . See O. macrus and O. meeki brevis sections for differences.

Distribution and habitat. Orconectes nana occurs in the upper Illinois River in eastern Oklahoma and northwestern Arkansas. Our ecological niche model indicates that O. nana is likely confined to this region, as larger rivers do not provide suitable environmental conditions and habitat ( Figure 64 ). O. nana inhabits clear, permanently flowing Ozark streams with gravel substrate in fast shallow water. It usually digs under large rocks or digs short tunnels under smaller gravel and is a tertiary burrower.

Life history. Little is known about the life history of O. nana , but due the close relationship it is likely similar to O. macrus . We have collected form I males in September and October as well as form II males and females throughout the year. We collected one ovigerous female in October that carried 5 large eggs.

Snytopic species: Orconectes meeki brevis and Orconectes neglectus neglectus .

Conservation status. AFS: Vulnerable; Heritage Rank: Imperiled (G3); IUCN: Least Concern; ODWC: Tier 1.

Additional resources. Crandall (1998); Dillman et al. (2010); Taylor & Knouft (2006).

Figures

FIGURES 61 – 68. 61. Orconectes nais 62. Potential distribution of Orconectes nais 63. Orconectes nana 64. Potential distribution of Orconectes nana 65. Orconectes neglectus neglectus 66. Potential distribution of Orconectes neglectus neglectus 67. Orconectes palmeri longimanus 68. Potential distribution of Orconectes palmeri longimanus.