Species-Specificity in the Action of Big and Small Prothoracicotropic Hormones (PTTHs) of the Swallowtail Butterflies, Papilio xuthus, P. machaon, P. bianor and P. helenus

To investigate whether four Papilio species, Papilio xuthus, P. machaon, P. bianor and P. helenus, have two molecular forms of the prothoracicotropic hormones (PTTHs), referred to as big- and small-PTTHs, the PTTHs were extracted and fractionated from their pupal brains. The activating ability of big- and small-PTTH fractions was examined by the in vitro assay using the prothoracic glands (PGs) of 2-day-old 5th-instar larvae of their own and several other papilionid species. Big- and small-PTTH fractions activated the larval PGs of their own species to increase the ecdysteroid secretion in vitro. The doses of small-PTTH fractions for activating the larval PGs were 8- to 10-times larger than those of big-PTTH fractions. The big- and small-PTTH fractions as well as those of P. machaon activated the PGs of 2-day-old 5thinstar larvae of several heterogeneous papilionids, but the activating ability did not always decrease with the distance of the genetic (or phylogenetic) relationships. The results in...