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Ultrastructure of prothoracic glands during larval‐pupal development of the tobacco hornworm, Manduca sexta : A reappraisal
Author(s) -
Hanton Wilma K.,
Watson R. Douglas,
Bollenbacher Walter E.
Publication year - 1993
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1052160110
Subject(s) - manduca sexta , prothoracic gland , biology , manduca , ultrastructure , sphingidae , endoplasmic reticulum , microbiology and biotechnology , corpus allatum , endocrinology , medicine , context (archaeology) , ecdysone , anatomy , hormone , larva , botany , juvenile hormone , paleontology
The structure of Manduca sexta prothoracic glands was investigated using a protocol that preserves membranes. During the last larval stadium, prothoracic gland cells increase in diameter, volume, protein content, and perhaps number, enhancing their capacity to produce ecdysteroids. The glands' strand‐of‐cells morphology, their in situ location, the presence of gap junctions between cells, and junctional foot‐like structures within cells support previous findings that prothoracicotropic hormone stimulates ecdysteroidogenesis via Ca 2+ ‐induced Ca 2+ release. A different method of tissue fixation from that previously used to investigate the ultrastructure of Manduca sexta prothoracic glands has revealed a significantly different ultrastructure. These new findings begin to define roles for endoplasmic reticulum and mitochondria in ecdysteroid synthesis and support the hypothesis that the glands secrete the steroid hormone via exocytosis. The structural dynamics of the glands are discussed in the context of the glands' function during Manduca sexta larvalpupal development. © 1993 Wiley‐Liss, Inc.