Title page for ETD etd-11072008-063358


Type of Document Master's Thesis
Author Hamilton, Robert Lewis
URN etd-11072008-063358
Title Cold-acclimation of the wood cockroach Crytocercus punctulatus (Scudder) (Dictyoptera: Cryptocercidae)
Degree Master of Science
Department Entomology
Advisory Committee
Advisor Name Title
Mullins, Donald E. Committee Chair
Orcutt, David M. Committee Chair
Cochran, Donald G. Committee Member
Keywords
  • Cryptocercidae
Date of Defense 1985-07-05
Availability restricted
Abstract
The general overwintering strategy employed by the woodroach, Cryptocerclls punctulatus (Scudder) appears to be fairly typical among freeze-tolerant insects. In this species, as well as others, heat-labile hemolymph ice nucleating factors induce extracellular ice formation at a high subzero temperature (around -6°C), there is a seasonal accumulation of a cryoprotective substance (polyol) and internal ice is tolerated only during the winter. In addition, body water content does not fluctuate seasonally.

Hemolymph Ice Nucleating Factors (INF's) have been previously described from members of the following orders of insects: Diptera, Coleoptera, and Hymenoptera. This study documents the occurrence of INF's in a fourth order: Dictyoptera.

Cryptocercus punctulatus contains hemolymph ice nucleating factors through out the year. In this species, hemolymph serum freezes at -5.5°C all year long and appears to be initiated by a heat-labile proteinacious nucleating factor. These proteins may function primarily as nucleators in the winter, and perform other function (s) during the other seasons of the year.

A sugar alcohol (ribitol), contained in the hemolymph of Cryptocercus punctulatus was found to fluctuate seasonally. Ribitol levels were highest in the winter months, and declined to undetectable levels in the summer. To date, five polyols have been reported as occurring in insect hemolymph. They are: glycerol, sorbitol, mannitol, erythritol, and threitol. There is one report of the occurrence of an unidentified 5-carbon polyol, possibly either arabitol or ribitol from whole body extracts of winter-acclimated collembolans. This thesis documents the occurrence of ribitol in insect hemolymph. It is assumed that ribitol, like other polyols acts as a cryoprotectant to stabilize protein structure, membrane integrity, and reduce osmotic fluctuations in freezing tissues.

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