The Life History of the Crayfish Orconectes kentuckiensis in Big Creek, Illinois

Abstract

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Morphological divergence between cave and surface populations of the digger crayfish, Fallicambarus fodiens (Cottle, 1863) (Decapoda, Cambaridae)

“…Most character variation was due to sexual dimorphism, evident in the significantly longer chelae for males and larger tails (abdomen and telson) for females. Similar sexual dimorphism has been observed for numerous species of crayfishes (Boyd & Page, 1978;Grandjean et al, 1997;Streissl & Hödl, 2002). Larger chela size in male crayfish has been linked to intrasexual fighting and for manipulating females during copulation (Stein, 1976;Grandjean et al, 1997;Schroeder & Huber, 2001).…”

“…We followed the PCA with a two-way multivariate analysis of variance (MANOVA) to determine whether the morphological variation captured by the principal components showed significant differences between cave and surface populations in morphometric space. We included habitat and sex as the two independent variables in the MANOVA model to account for morphological variation by habitat and by sex (Stein et al, 1977;Boyd & Page, 1978). We then used post-hoc analysis of variance (ANOVA with Tukey's honestly significant difference test) to assess whether the characters that accounted for the greatest amount of variation on the second and third principal component axes (PC 2 and PC 3, respectively) differed significantly between habitats or between sexes.…”

Differential Growth in Body and Chela Size Following Molts to Form I and Form II in the Crayfish, Orconectes Rusticus (Decapoda, Cambaridae)

“…A number of studies have examined natural cambarid crayfish populations and documented size at sexual maturity and growth following molting (Smart, 1962;Stein et al, 1977;Boyd & Page, 1978;Lowery, 1988;Norrocky, 1991;Muck et al, 2002). However, in most studies, molts to Form I or Form II were not distinguished and size was measured only by carapace length and/or weight.…”

“…As first reported by Hagen (1870), Form I animals are 1 ) e-mail: atierney@mail.colgate.edu able to reproduce whereas Form II animals are nonreproductive. In most species, adult males in a population molt from one form to another simultaneously (Creaser, 1933;Hobbs, 1942;Smart, 1962;Crocker & Barr, 1968;Boyd & Page, 1978;Corey, 1988;Muck et al, 2002), but in some species molting is asynchronous and adults of both forms can be found in the same population (Crocker, 1957;Norrocky, 1991;Guiaşu & Dunham, 1998). Form I males are easily distinguished from Form II by their external structure.…”

Behavioral Correlates of Alternate Male Forms (Form I and Form II) in the Crayfish Orconectes Rusticus

“…Hagen (1870), following an observation by Louis Agassiz, first noted that one of the forms (Form I) was able to reproduce while the other form (Form II) was apparently sterile. The two forms have since been described in numerous species of Cambaridae and the alternation of forms in individual males is well documented (Ortmann, 1906;Creaser, 1933;Hobbs, 1942;Smart, 1962;Crocker and Barr, 1968;Boyd and Page, 1978;Corey, 1988;Norrocky, 1991). Typically, all adult males in a population molt from one form to another simultaneously, but in some species molting is asynchronous and adults of both forms can be found in the same population (Crocker, 1957;Norrocky, 1991;Guiasu and Dunham, 1998).…”