Histology of the alimentary canal during the metamorphosis of Hyalophora cecropia (L.)

Abstract

The histology of the alimentary canal is described for the last instar larva, pupa, and adult Hyalopkora cecropia ( L . ) . Particular attention is given to the changes occurring in the midgut during the larval-pupal transformation and in the hindgut during the pupal-adult transformation. Descriptions are made as to the nature of the imaginal rings at each end of the midgut and a new structure is described in the larval ileum. The formation of adult rectal pads is followed in detail.Although the last few years have brought US a clearer understanding of the chemical nature of insect growth hormones (cf. Gilbert, '69) and recent studies have been concerned with the biochemical inechanisms involved in the action of these humoral agents, little is known regarding the morphological effects of insect hormones on internal organ systems. This is particularly surprising in the case of

Morphological study of the hindgut in larvae of Anticarsia gemmatalis Hübner(Lepidoptera: Noctuidae)

“…2A and 2C) are similar to those described in other insets (Judy & Gilbert 1970, Gonçalves 1980. The colon epithelium is composed by a simple squamous epithelial cells, and the thicker cuticular intima is thrown into longitudinal folds; because of this folding, the lumen is very restricted and has a compound tubular appearance (Fig.…”

“…1D). Similar spinner cuticle lining the pyloric posterior region was also observed in H. cecropia (Judy & Gilbert 1970), Heliothis zea Boddie, Heliothis virescens Fabricius and Spodoptera frugiperda Smith (Chi et al 1975). According to Barth (1972), the presence of this chitinous structure can be correlated with the insects feeding habits: if they feed with fluid material, like the phytophagous and hematophagous insects, the internal wall is smooth; in solid feeding species, the cuticular layer showed chitinous microspines that helps in the undigested material transport toward the other portions of the hindgut.…”

“…The outer circular muscles are more developed than the inner longitudinal fibers (Figs. 2A and 2B); similar aspects were observed in Lepidoptera species (Mathur 1966, Judy & Gilbert 1970, Chi et al 1975 and in some Coleoptera (Areekul 1957). However, Vasques (1988) described a different muscular arrangement in Pyrearinus termitilluminans Costa, with inner circular and outer longitudinal muscular layer.…”

“…Two distinct pyloric portions were recognized in A. gemmatalis (Fig. 1B), as described for Hyalophora cecropia L. (Judy & Gilbert 1970). The anterior pyloric portion is lined with a simple basophilic squamous epithelium and the chitinous intima has no spines; the muscle layer presents inner circular and outer longitudinal fibers (Figs.…”

“…The undigested material goes straight to the hindgut where the water absorption and feces formation and elimination occur. The hindgut of most Lepidoptera larvae may be morphologically subdivided in pylorus, ileum, colon and rectum (Drecktrah et al 1966, Judy & Gilbert 1970, Chi et al 1975. The Malpighian tubules open into the pylorus; their distal ends are associated with the rectal wall and form the Lepidopteran characteristic cryptonephric excretory system (Wigglesworth 1984) that conserves water by absorbing it actively from the feces either to the hemolymph or to the lumen of the Malpighian tubules (Maddrell & O´Donnell 1992).…”