Term of Award

Summer 1993

Degree Name

Master of Science in Biology

Document Type and Release Option

Thesis (restricted to Georgia Southern)

Committee Chair

James H. Oliver, Jr.

Committee Member 1

Sara N. Bennett

Committee Member 2

William S. Irby

Abstract

H. H. Davis, E. M. Dotson and J. H. Oliver, Jr. Localization of an insulin-like peptide in the synganglion of nymphal and adult Dermacentor variabilis (Acari: Ixodidae). Experimental and Applied Acarology

Abstract:

Immunocytochemical staining based on a peroxidase-antiperoxidase method showed neurosecretory cells (NSC) reactive to bovine insulin in five of 18 paraldehyde fuchsin-positive neurosecretory regions (NSR) in the synganglion of unfed adult Dermacentor variabilis. The insulin-specific immunoreactive cells included the posterior medial group of the protocerebral center, posterior group of dorsal opisthosomal center, anterior lateral group of the dorso-lateral cheliceral center, dorsal group of the frontal stomodeal center, and anterior group of the ventral palpal center. After feeding and mating, females no longer had immunoreactive cells in three of five NSR found in virgin, unfed females. However, two cells of the posterior group in the dorsal opisthosomal center and anterior lateral group of the dorso-lateral cheliceral center remained immunoreactive throughout feeding. Fed, mated males continued to display immunoreactive cells in four of five NSR found in the virgin, unfed males. All developmental stages of nymphs examined had insulin-specific immunoreactive cells in two of the five NSR found in unfed adults, including two positively stained cells of the posterior group in the dorsal opisthosomal center and anterior group of the ventral palpal neurosecretory center.

H. H. Davis, H. J. Hutcheson and J. H. Oliver, Jr. Morphometrics of insulinpositive neurosecretory cells in the synganglion of nymphal and adult Dermacentor variabilis (Acari: Ixodidae). Experimental and Applied Acarology

Abstract:

Neurosecretory cells stained with antibodies to bovine insulin indicate the presence of insulin-like neuropeptide(s) in the synganglion of nymphal and adult Dermacentor variabilis. Depending on developmental stage of the tick, neurosecretory cells (NSCs) from 2 - 5 neurosecretory regions (NSRs) showed positive immunoreactivity. Insulin-positive NSCs in the synganglion of nymphs, males, and females through several developmental stages were measured with an image analysis system. Cellular dimensions (cellular and nuclear area, cellular length and width, nuclear length and width) were statistically analyzed using univariate ANOVA and Student-Newman-Keuls multiple comparison tests to compare means. Significant differences (P < 0.01) in the six cell dimensions were found across neurosecretory regions and within developmental stages. Cellular and nuclear area revealed more variation than the other dimensions and were used to describe cell size. Significant changes in insulin-positive NSC size occurred after feeding and after ecdysis in nymphs, and after feeding and mating in adults. Cell dimensions of insulin-positive neurosecretory cells were also compared to those of paraldehyde fuchsin-positive NSCs from previous studies of acarines.

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