Date of Award:

5-1-1993

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Department name when degree awarded

Biology

Committee Chair(s)

Kimberly A. Sullivan

Committee

Kimberly A. Sullivan

Committee

Todd A. Crowl

Committee

Wilford J. Hanson

Abstract

I investigated the effects of ectoparasitism by hematophagous larvae of the blow flies Protocalliphora interrupta Whitworth and Protocalliphora (Trypocalliphora) braueri (Hendel) on nestling marsh wrens (Cistothorus palustris) over two years in northern Utah, USA. Despite random nest fumigations with synthetic pyrethrin, approximately 91 percent of wren nests contained P. interrupta and 1.2 percent contained P. braueri. Nestling mass, tarsus length, and hematocrit measured prior to fledging did not differ significantly with P. interrupta parasite load: No relationship was seen between parasite load and percent of young starved or percent of young with bacterial infections. In a year of cold, wet weather, broods of nestlings estimated to have had greater than 1.00 g of blood removed by larvae during the 10-day nestling period had significantly lighter fledging masses than those estimated to have had less blood removed; serum total protein and number of heterophil granulocytes also differed significantly between these broods. Differences in these parameters were not seen when nestlings were reassessed as independent juveniles, however, suggesting that the negative physiological effects of P. interrupta are of short tenure. Young wrens that were parasitized by P. braueri larvae had significant differences in pre- and post-infestation hematocrit and all died within 72 hr of infestation: The mechanism of pathogenicity was found to be Pseudomonas spp. Infection of myiasis-induced lesions and subsequent sepsis. Scanning electron micrographs of both Protocalliphora species were produced to compare the morphological characteristics of visible feeding structures. The mean length of visible pharyngeal sclerites of P. braueri was significantly less than those of P. interrupta and appeared to be better suited for a burrowing habit than one of intermittent hematophagy.

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