Larva/adult transformation

The study of the nutrition and/or the metabolism of a larva in situ, within a vertebrate intermediate host, clearly raises difficult technical problems and apparently no direct studies have been made. Most information is based on in vitro studies, special attention being paid to the changes which take place when larval/adult transformation takes place. Since the larval metabolism is so intimately related to that of the adult, it is discussed, with the latter, in Chapters 4-6. 

An elegant demonstration that the larval/adult transformation, resulting in sexual differentiation, is, in fact, associated with a neurosecretory mechanism has been made by Gustafsson and co-workers (207, 278, 280, 281,283). They showed that a clear activation of the peptidergic neurones took place when plerocercoid larvae of Diphyllobothrium dendriticum were transferred from the poikilothermic intermediate fish host to the final homeothermic bird host. The effect could also be reproduced by cultivating... 

Our laboratory is concerned with targeting potential insecticides that disrupt normal development and metamorphosis in insects. Juvenile hormones (JHs), acting in concert with the steroid hormone ecdysone, are believed to control the timing of the larval-larval molts, larval-pupal and pupal-adult transformations of the insects. It has been demonstrated that the events leading to pupation are initiated by reduction of the JH titer in the hemolymph. In addition to a cessation of biosynthesis, this reduction in JH titer is controlled by degradative metabolism (16,17). Hydrolysis of the epoxide and ester functionalities present in active JH are two routes of degradation and subsequent inactivation of JH (18). The primary route of JH metabolism in the hemolymph of last stadium lepidopterous larvae is ester hydrolysis, and it is catalyzed by the enzyme juvenile hormone esterase (JHE). JHE has been shown to... 

Beetles pass a holometabolous development with several larval instars, pupae (often poorly known), and completely transformed adults. Larvae show biting mouth parts and often possess abdominal cerci-like structures which are absent in adults. The usually short heads of adults may be elongated to form a snout (as in weevils). Antennae and legs, especially the tarsomeres, may vary strongly with species and are taxonomically useful. 

The transformation from larva to adult that a butterfly undergoes during pupation is an example of metamorphosis. 

In the case of the red-spotted newt (Notophthalmus viridescens) of North America, the red eft is the stage that occurs after transformation of the aquatic larva. The red eft is bright red or orange, and is a pre-reproductive adult stage. The red eft wanders widely in forests, sometimes for several years, and is most common on moist nights. Eventually, the red eft migrates to an aquatic... 

During those early years, 1 joined a collaboration to help identify the structure of the insect juvenile hormone, one of three such hormones thought to be the substances that controlled the maturation of insects from pupae to larvae and finally adults [15-18]. By understanding their chemistry, a safer approach for control of populations of harmful insects was envisioned. We determined the structure of juvenile hormone as 1. In thinking about how such a compound might be derived biologically, we conjectured that maybe there existed an enzymatic process that transformed the common sesquiterpene... 

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