A cDNA library was established from the eyestalk ganglia of the blue crab Callinectes sapidus. Screening resulted in the isolation of a clone (497 bp excluding poly(A) tail) which encodes a beta-PDH previously found in several crustacean species. It displays high sequence similarity with a clone isolated from an eyestalk cDNA library of the shore crab Carcinus maenas, indicating the close phylogenetic relationship of both species. A second clone (414 bp exclusive of the poly(A) tail) encodes a novel beta-PDH analog which displays 400-fold less potency in crab bioassays. Both cDNAs encode open reading frames of 234 bp for the prepropeptides, consisting of signal peptides, PDH-precursor-related peptides, and PDH sequences.