Orconectes nais (Faxon, 1885)

Morehouse, Reid L. & Tobler, Michael, 2013, Crayfishes (Decapoda: Cambaridae) of Oklahoma: identification, distributions, and natural history, Zootaxa 3717 (2), pp. 101-157 : 131-132

Orconectes nais (Faxon, 1885) : Water Nymph Crayfish

General charateristics. Adults rarely exceed 130 mm in total length. The carapace is smooth, lightly punctate dorsally, granulate laterally, and the areola is open. The abdomen is nearly the same length as the carapace. The rostrum is long, centrally depressed, and has lateral margins converging into small but distinct spines. Chelae are broad, flattened, and long. The fingers are long with tubercles along the mesial margins of palm and dactyl. Tubercles also line the inner margin on the non-movable finger, and long setae are present at the base of the fingers. In form I males, gonopods terminate in two slender processes, and the mesial process curves the entire length of the gonopod. In females, the annulus ventralis is triangular with a median longitudinal fissure (Faxon, 1885).

Life coloration. The background color is greenish brown to brown with cream stripes running along the bottom halves of the carapace. The abdomen has two rows of black blotches running longitudinally ( Figure 61 ). Chelae have a bluish-green tint, with yellow to off-white tubercles along the inner margin of the palm and fingers. Fingers usually tipped with orange. Ventral side is white in color.

Similar species. In Oklahoma, O. nais closely resembles O. virilis and O. causeyi . Orconectes virilis differs from O. nais in the shape of the gonopods of the form I males. In O. nais , the mesial process curves the entire length, while it only curves at the tip in O. virilis . See O. causeyi for differences between these two species.

Distribution and habitat. Orconectes nais occurs in the Great Plains of Kansas, Oklahoma, and Texas. It likely also occurs in the southwestern corner of Missouri and northwestern corner of Arkansas, but has not been reported to date. In Oklahoma, O. nais is found state wide, usually in larger rivers and streams with sand or silt as substrate. Additionally, we have excavated O. nais from burrows in roadside ditches that previously held standing water as it is a tertiary burrower. Our ecological niche model confirms the current distribution of O. nais , as much of the state is considered as having suitable environmental conditions ( Figure 62 ).

Life history. The majority of specimens of O. nais have been collected from April through October. Ovigerous females have been collected from October and April, and females ready to spawn were also collected in April, suggesting reproduction may occur multiple times a year (Armitage et al., 1972).

Syntopic species. Orconectes deanae , Orconectes neglectus neglectus , Orconectes virilis , and Procambarus acutus .

Conservation status. AFS: Currently Stable; Heritage Rank: Widespread (G5); IUCN: Least Concern; ODWC: Not Listed.

Additional resources. Armitage & Topping (1962); Armitage & Wall (1982); Evans-White et al. (2001); Evans-White et al. (2003); Johnson (2010); Mathews et al. (2008); Pippitt (1977).

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.