Life history and physical observations of primary burrowing crayfish (Decapoda: Cambaridae) Cambarus (Lacunicambarus) diogenes and Cambarus (Tubericambarus) polychromatus

Abstract

Primary burrowing crayfish make up 15% of total crayfish species, but account for 32% of those imperiled. Primary burrowers are also much less studied as compared to secondary and tertiary burrowers. The purpose of this study was to observe the annual life cycles, and morphometric and morphological characteristics of two primary burrowing crayfish species: Cambarus (Lacunicambarus) diogenes Girard, 1852 and C. (Tubericambarus) polychromatus Thoma et al., 2005. Sampling occurred adjacent to two streams near Troy, AL, using hand excavation at one-month intervals from February 2011 to March 2012. A total of 195 C. diogenes (sex ratio = 1.3) and 194 C. polychromatus (sex ratio = 0.85) were collected. For a given size, C. diogenes had a broader carapace than C. polychromatus ( p< 0.001), and males had larger chelae than females for both species (p = 0.01 and p = 0.001, respectively). Minimum carapace length at sexual maturity (smallest form I) was 32.7 mm for C. diogenes males, 41.2 mm for C. diogenes females, 27.4 mm for C. polychromatus males, and 32.2 for C. polychromatus females. The proportion of form I males for both species increased in summer and remained at an increased level through winter, though C. polychromatus males remained reproductively active longer than C. diogenes. Females of both species were reproductively active only in winter except for one form I C. polychromatus female. Four ovigerous C. diogenes and three ovigerous C. polychromatus were collected in March, and five young of the year of C. polychromatus were found in burrows in June, July, and September.