MARTINEZ.G.M: Muscle Development in the Long-finned Squid using Phalloidin Staining Methods.

Whole mounts and serial sections of embryonic and paralarval Loligo peali squids were prepared and stained with phalloidin�rhodamine flourescent stain which binds to F-actin filaments. Staining revealed a network of actin filaments at different densities at different stages. Muscles of the mantle, arms, tentacles and buccal mass were traced from Stage 17 to post hatching (staging according to Arnold, 1965). Particularly striking was the formation of the chromatophore musculature system, which appears as a circular array around individual chromatophores. Extensive work on the functional morphology of cephalopod muscles has been carried out by Kier et al., although the actual ontogeny of major muscle systems has not been followed. I here present a new method for investigating muscle development. This technique will also be useful for comparative studies, and in providing phylogenetically useful characters.