GUTIERREZ, A*; SHIMOIDE, A; EBANKS, T; SALMON, A; YOON , I; FUSE, M; San Francisco State Univ., San Francisco: VIDEOGRAPHIC AND ELECTROPHYSIOLOGICAL ANALYSIS OF ECDYSIS BEHAVIORS IN THE LARVAE AND PUPAE OF THE HORNWORM, MANDUCA SEXTA

Ecdysis, or the shedding of old cuticle, is crucial to arthropod growth, revealing a new cuticle to accommodate a larger or different body form. The hornworm, Manduca sexta, undergoes several larval molts before transforming into a pupa and then an adult moth. The ecdysis behaviors consist of asynchronous contractions of each segment of the body wall, which propel the cuticle posteriorly. While M. sexta has become a model for peptidergic regulation of ecdysis behaviors, the in vivo behaviors have not been fully characterized. We have developed a video tracking program that monitors the movement of the spiracles on the body wall as a gauge of segmental muscle contraction. We have determined the frequency and amplitude of these contractions during larval and pupal ecdysis under natural conditions and when precociously induced by injection of Ecdysis-Triggering-Hormone (ETH). This data is compared with frequencies of fictive ecdysis motor patterns recorded electrophysiologically from the isolated CNS. The frequencies of ecdysis contractions in vivo are significantly faster than the associated fictive burst frequencies. Moreover, timing of some ecdysis behaviors are significantly altered in ETH-induced animals compared to naturally ecdysing animals. This data suggest that (i) peripheral inputs may modulate the basic ecdysis motor program, and are lost in vitro, and that (ii) precocious ecdysis may differ from naturally-occurring ecdysis. This method of data analysis will be very useful for analysis of in vivo ecdysis behaviors, and should improve our understanding of its hormonal regulation. This analysis is also imperative if we are to continue artificially inducing ecdysis in experimental animals.