The mechanism of puparium formation in flies

Abstract

The mechanism of puparium formation in the fleshfly Sarcophaga bullata Parker was studied. Several distinct morphological events take place during the hour prior to the completion of the white puparium. 1. The anterior three larval segments are irreversibly retracted. 2. The body contracts by muscular action to about two-thirds of its original length. 3. Simultaneously a longitudinal shrinkage occurs in the cuticle, giving it a smooth surface. 4. Finally the cuticle becomes stabilized in the sense that it can no longer be stretched, and no longer collapses upon release of internal pressure by bleeding. 5. Tanning starts almost as soon as the smooth barrel shape of the puparium is completed. The following observations demonstrate the largely independent nature of these processes: 1 . Paralyzing the musculature, by ligation, tetrodotoxin, or bee venom, leads to tanned puparia in the shape of the larva. 2. Disabling the shrinkage system (e.g., by ryanodine or eserine) leads to puparia with a deeply folded surface. 3. Injecting smaller doses of tetrodotoxin or bee venom leads to elongated puparia with a shrunken (smooth) surface. 4. Injecting a certain ecdysone analogue leads to a puparium which is normal except for the failure of the anterior end to retract. 5. Release of internal pressure by bleeding leads to puparia which are supercontracted and folded. 6. Injection of a tanning inhibitor (a-MDH) leads to a .white puparium of normal shape which fails to tan. The transformation of the larval cuticle into the tanned puparium is accompanied by a spectacular water loss i n the cuticle which is particularly rapid during the brief period between completion of the white puparium and start of tanning. This water loss is almost certainly correlated with the above mentioned stabilization of the puparium.

Évolution pondérale du parasitoïdeLixophaga diatraeae [Dip.: Tachinidae] de la sortie de l'hôte a l'émergence. Estimations des poids par mensurations de la pupe

“…La formation du puparium correspond au tannage de la cuticule du dernier stade larvaire et s'accompagne d'un changement de couleur (Zdarek & Fraenkel, 1972). Au moment pr6cis de la formation du tonnelet, la teinte est celle de la larve, blanche, ensuite il y a un brunissement progressif dans les heures qui suivent.…”

STUDIES ON THE DIFFERENTIATION AND GROWTH OF THE PRETARSUS IN TRICHOLIOPROCTIA IMPATIENS (WALKER) (DIPTERA: SARCOPHAGIDAE)

“…During the last hour or so of the post feeding larval stage, the larvae gradually contract to form the white prepupae. This stage lasts for only a few minutes and thus is a very convenient and accurate time to mark for ensuing developmental events (Zdarek and Fraenkel 1972). In this investigation all times are given in hours after formation of the white prepupa.…”

Cuticle: Biochemistry

“…When sclerotization of the fly puparium is inhibited, by injecting larvae with the dopadecarboxylase inhibitor DMH, a white puparium is formed. Cuticular stabilization occurs rapidly and does not involve dehydration (Zdarek and Fraenkel 1972). A theory of sclerotization based solely on dehydration discounts the presence of a very active phenoloxidase system in cuticles.…”

“…Formation of the fly puparium involves loss of water from the larval cuticle (Fraenkel and Ruddall 1940;Zdarek and Fraenkel 1972) and loss of water probably occurs during sclerotization of all arthropod cuticles (e.g. Andersen 1981).…”