Date of Award:

5-1-1984

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology

Committee Chair(s)

Nabil N. Youssef

Committee

Nabil N. Youssef

Committee

John R. Simmons

Committee

William A. Brindley

Abstract

The respiratory chamber of the dragonfly nymph, Aeshna multicolor, was studied by means of scanning and transmission electron microscopy. Transmission electron micrographs enable several cellular types, includig two epithelial types, to be distinguished within the individual gill fold. Epithelial cells located basally on the gill fold show features of an osmoregulatory tissue. Cuticle limiting these cells is thinner than-that of typical epithelium, the plasmalemmae are infolded enclosing numerous mitochondria, and a system of extracellular channels is located basally with mitochondria and glycogen seen in the basal cellular outfoldings. Tracheoles are rare. Epithelial cells more distally placed are typical of a cuticle-producing epidermal cell and are heavily tracheolated. A pressure sensillum is located between the two epithelial tissues just below the cuticle. The cuticle is extremely thin above the neural processes which adhere to each other by means of extensive septate desmosomes as well as apically placed maculae adherentes. The interior of a gill fold, sandwiched between cuticular-epithelial layers, contains hemolymph, hemocytes, trophocytes and large tracheae. At the extreme distal tips of the gill fold, cellular integrity is lacking, although pockets of organelles are seen. Between two layers of very thin cuticle, two kinds of large, dark, spherical vesicles are seen, as well as much cellular debris. One type of electron-dense vesicle is homogeneously textured and seems to contain pigment. A second type is heterogeneous, containing numerous spheroids and may contain metabolic endproducts. Possible physiological correlates of these ultrastructural observations are also discussed.

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