Properties of Orange-Pupa-Inducing Factor (OPIF) in the swallowtail butterfly, Papilio xuthus L.

Abstract

Diapause pupae of the swallowtail butterfly Papilio xuthus L. exhibit diapause-green, orange and brownish-orange color polymorphism. Development of orange pupae involves a neuroendocrine factor inducing orange pupa (Orange-Pupa-Inducing Factor, OPIF), which is secreted from the head–thoracic region during late pharate pupal stages, in particular from the ganglia of short-day animals located posteriorly from the second thoracic ganglion 2 (TG 2). This report describes certain properties of OPIF using bioassays involving ligated abdomens of short-day pharate pupae. Localization of OPIF in the central nervous system of short-day larvae indicated that it was present predominantly in TG 2, thoracic ganglion 3 (TG 3) and abdominal ganglion 1 (AG 1) complexes. OPIF activity in TG 2,3–AG 1 complexes was over two times higher than in the more posteriorely located ganglia. The developmental profile of OPIF in last instar short-day larvae revealed that OPIF activity in larval ganglia posterior to TG 2 became gradually higher as larval growth proceeded, suggesting that OPIF might be accumulated in TG 2,3–AG 1–7 complexes as larvae prepare for pupal molting. Furthermore, ligated abdomens of short-day larvae developed into pupae of an orange type when a 2% NaCl extract containing OPIF prepared from TG 2,3–AG 1–7 complexes of long-day larvae was injected into ligated abdomens of short-day pharate pupae, indicating that OPIF is also present in long-day larvae. Additionally, a biochemical investigation using gel filtration chromatography showed that the molecular weight of OPIF was about 10 kDa.