ABSTRACT
The toxicity of the secretion has been attributed to a single protein of a molecular weight of 14,000 daltons. Named pardaxin, this toxin is constructed of a monomeric chain, with a helical structure and four disulfide bridges. Investigators using a chamber apparatus that separated the fish anterior from the rest of its body found that toxicity to F.heteroclitus occurred when flatfish secretion and pardaxin were administered to the head part of the chamber. The action of the secretion on transmitter release and muscle contraction was studied in the frog's cutaneouspectoris nerve-muscle preparation and the ileum smooth-muscle preparation. The planar lipid membranes served as a model system to study the nature of the interaction between the P.marmoratus secretion and lipid bilayers. In the 19th century ichthyologists noted that soles of the genus Pardachirus possess a series of more than 200 pores along their dorsal and anal fins. Pressing this area would release a milky fluid from the fish.
