GENETICS OF THE RED SWAMP CRAWFISH, Procambarus clarkii (GIRARD): STATE‐OF‐THE‐ART

Abstract

ABSTRACTThe inheritance patterns of three mutants (light blue body color, dark [French] blue body color, and white eye color) of Procambarus clarkii were determined. All were initially discovered in specimens in nature which were subsequently inbred for six to eight generations in the laboratory to determine inheritance patterns. The light blue body color allele, in which specimens appear powder blue and have reduced numbers of chromatophores, was found to transmit as a simple recessive allele to normal body color. The allele for French blue body color is recessive to its normal allele also, but is known only in females. Homozygosity for the French blue allele is apparently lethal to males. Male carriers for the allele have normal pigmentation. The body color of both alleles is partially due to a carotenoid pigment conjugated with protein. The pigment is tentaively identified as crustacyanin which partially replaces the normal astaxanthin in the exoskeleton which retains its blue color when shed in molting. The white eye phenotype results from the absence of distal and retinular screening pigments. The accessory pigments around the bases of the rhabdoms are still present and appear white in reflected light and pinkish brown in transmitted light. The white eye allele is inherited as a simple recessive mutant allele. Specimens with this allele do not see well in bright light but function normally in dim light. Reciprocal dihybrid crosses of these three mutants showed no evidence of linkage. Field records of mutants and estimates of frequency (white eye color) in natural populations are discussed.