A genetic and biochemical analysis of the temperature sensitive, normal-winged alleles of the rudimentary locus of Drosophila melanogaster.

The genetic and biochemical characteristics of a particular class of mutants at the rudimentary locus are described. The mutants are pyrimidine auxotrophs, like classical rudimentary alleles, but they are unique in that they do not alter the size or shape of the wing (Falk and Nash 1974b). Aspartate transcarbamylase and dihydroorotase activities have been measured in seven different normal-winged mutants, and the results indicate that these strains are enzymologically "leaky" mutants. Previous studies have shown that three genetic functions (corresponding to the first three enzymes of pyrimidine synthesis) are associated with the rudimentary locus. Four of the seven mutants appear to affect all three of these functions. Each of the four is temperature sensitive, and a biochemical analysis of the temperature sensitivity of one of these mutants, (r)pyr1-3, suggests that a process affecting the synthesis or assembly of these enzymes is altered at high temperatures.

Warble development by the rodent bot Cuterebra fontinella (Diptera: Cuterebridae) in the deer mouse.

Warbles induced by the rodent bot fly larvae, Cuterebra fontinella, developed over a period of 3.5-4 weeks in the deer mouse Peromyscus maniculatus. Warble location, structure and dynamics were examined. Clustering of warbles occurred primarily within the inguinal region of the deer mouse with a significant number favoring the area between the anus and genital organ. No differences in warble production were found in hosts of either sex. On two occasions, a warble was encountered forming directly in the genitals. Warble structure consisted of a pore, cavity and capsule, all of which changed in shape and size as the larvae grew. A new pore was formed during the first larval molt and was commonly bordered by a yellowish precipitate. A bi-layered warble capsule surrounded the cavity as a thin layer and a thick diffuse outer layer. The growing warble expanded into the subcutaneous tissue of the inguinal area and stretched the hide caudally. Subcutaneous tissue surrounding developing warbles became relegated to small areas, leaving only a thin muscle to separate the warble from the peritoneum. Widening of the pore at the time of larval emergence is described. Linear relationships are given describing warble growth and pore enlargement as a factor of time. The location of warbles and the morphology of the pore are discussed in relationship to larval protection. Damage to the host due to warble formation is also addressed.

Effects of migrating Gasterophilus intestinalis larvae (Diptera: Gasterophilidae) on the mouth of the horse.

Lesions were formed in the mouth of the horse by first- and second-stage Gasterophilus intestinalis larvae. The lesions resulted as larvae burrowed through the top millimeter of the tongue and then became embedded in the interdental gingiva. Appearance of the lesion was dependent on the degree of larval burrowing activity and healing that had taken place. Active tunneling production occurred at the posterior end of the lesion. Extensive change in configuration and color was apparent along the longer lesions with active larvae. Virtually all tissue in the path of the larvae was removed while forming a tunnel. Tissue destroyed included tops of the lamina propria mucosae evaginations and the deeper portions of the lamina epithelialis mucosae. Histopathologic findings showed that the tissue removed included the nerve and blood supply of the proprial evaginations. Hemorrhage and exocytosis into the tunnels included erythrocytes mixed with some macrophages, lymphocytes and scant numbers of eosinophils. Air shafts excavated in the tongue by larvae enabled bacteria to enter into the tunnels. Bacteria became adhered to larvae and initiated microabscesses. Microabscesses were composed of clotted erythrocytes, bacteria, disintegrating epithelial cells, and large numbers of neutrophils. Cells surrounding the tunnel exhibited pyknosis, epithelial hydropic degeneration and became separated from each other. Healing of tongue lesions occurred as epithelial cell growth below raised the tunnel upward and affected tissue desquamated. Interdental gingiva invaded by larvae were hyperemic and denuded of epithelia. Recession and ulceration of the gingiva produced periodontal pockets. Extensive invasion by larvae led to compound periodontal pockets. Larval mouth hooks were embedded in the submucosa of the pockets and tore at engorged capillaries. The cephalic portion of embedded larvae became surrounded by a cellular exudate containing erythrocytes and mononuclear cells. Attachment of second-stage larvae at the root of the tongue did not produce observable damage.

Field observations of the host-parasite relationship associated with the common horse bot fly, Gasterophilus intestinalis.

Behavior of Gasterophilus intestinalis (Diptera: Gasterophilidae) was observed in the laboratory and field over a period of 10 years. Mating occurred in a frenzied manner as flies emerged from pupae. Males attempted to copulate with females that had not fully emerged from the pupal case. Mating was never observed in the field or near the horse. Observations suggest that fecal piles of the horse are used as the mating site for the newly hatched flies. Activation of host-seeking behavior was found to occur early and remain throughout the life span of the adult as it sought multiple hosts for oviposition. Evidence is presented supporting the use of olfaction and vision in finding the host. Interest by flies in shadows and linear high-contrast objects was observed. Methods used by the flies to maintain close proximity with the host are discussed including flight with the host and avoidance of host defenses. Recapture methods were successful in determining the time taken to reestablish at the host, and extent of travel to the host. The presence of kairomone(s) within horse secretions is suspected.

Use of detomidine hydrochloride as an adjunct for studying first-stage Gasterophilus intestinalis (Diptera: Gasterophilidae) in the tongue of the horse.

A synthetic alpha-2 adrenergic agonist, detomidine hydrochloride, was used in the study of in vivo activity of Gasterophilus intestinalis (Diptera: Gasterophilidae) during migration in the tongue of the horse. Use of the drug allowed the investigator to manipulate the tongue and closely observe the movement patterns and tissue disturbance caused by burrowing first-stage larvae. Detomidine hydrochloride should be utilized in studies of drug efficacy and larval biology, whenever possible, to avoid the need to sacrifice the horse.

Inter-relationship between Gasterophilus larvae and the horse's gastric and duodenal wall with special reference to penetration.

The degree of penetration into the stomach and duodenum of the horse by bot fly larvae, Gasterophilus intestinalis (De Geer) and G. nasalis (Linnaeus) (Diptera : Gasterophilidae) was evaluated. Evidence of larval perforation of the stomach or duodenum was not found on gross inspection. Palpation of the intact stomach and duodenum was not effective in establishing the existence of Gasterophilus larvae within the organs. Findings suggest that larvae of both species produce an ulcer of similar depth within the gastrointestinal wall. The ulcer depth produced by larvae did not correlate with the normal, unaffected thickness of the particular stomach or duodenum. Tissue proliferation beneath ulcers of the stomach and duodenum was not correlated with the depth of the ulcer. Proliferation of the tissue beneath the ulcers of the stomach generally exceeded that found under duodenal ulcers. Gastric wall beneath the G. intestinalis ulcer frequently attained a thickness equal to or greater than the normal stomach wall. Histopathological examinations below the ulcer revealed intense fibrosis. Duodenal thickness below the G. nasalis ulcer was typically less than normal and resulted in an attenuated wall. Histopathological analysis of the affected duodenum revealed severe loss of submucosal glands in a sharply demarcated area below and surrounding the lesion. Fibrosis of the underlying lamina propria mucosae and tunica submucosa was appreciable but failed to restore the original thickness of the duodenal wall. Host tissue response and moderation of the parasite' s behavior reduce the chances of direct perforation of the gastrointestinal tissue.

Effects of Cephenemyia spp. (Diptera: Oestridae) on the nasopharynx of black-tailed deer (Odocoileus hemionus columbianus).

A study was conducted to determine gross and microscopic tissue changes in the nasopharynx of black-tailed deer (Odocoileus hemionus columbianus) infected with nasal bot fly larvae (Cephenemyia spp.). Paired retropharyngeal recesses were the preferred sites for the growing second and third stage larvae of two species of Cephenemyia (C. apicata and C. jellisoni). Retropharyngeal recesses distended into "pouches" that harbored up to 30 larvae. Pouches were oriented caudal-laterally toward the basisphenoid bone of the cranium. Lateral support of the pouch mass was provided by the stylohyoid bone. The laryngeal orifice was never occluded by the enlarged recesses. The distal pouch wall was relatively thin and remained uniform in thickness as expansion progressed. Occasionally, aberrant larvae were found protruding through the distal wall of the pouch. Disruption of the epithelium and submucosa by larval mouth hooks and integumentary spines were examined by scanning electron microscopy. Histological examination of infected recesses revealed substantial loss of epithelium and mucous glands. Enlargement of recesses into pouches resulted from fibrosis. Healing occurred after larvae egressed from the pouches. Degenerating mucous glands, epithelial metaplasia, epithelial desquamation, and intense inflammation were found near larvae. An eosinophilic exudate with a mixture of macrophages and erythrocytes was present in the lumen of the pouch. The presence of larvae within the pouch inhibited secondary bacterial infection and suppuration. Infection by larvae caused severe local trauma and intense tissue response.

Morphology of a newly discovered sensory array on the mouthhooks of Gasterophilus larvae.

The distal mouthhooks of Gasterophilus intestinalis (DeGeer) (Diptera: Gasterophilidae) and G. nasalis (Linnaeus) (Diptera: Gasterophilidae) larvae were studied with scanning electron microscopy to determine the morphology of a previously unknown sensory array. The design of the 3rd stage G. intestinalis sensory array was used as the model for comparison to the 2nd stage of this species and the 2nd and 3rd stadia of G. nasalis. Some components forming the sensory array of the 3rd stage G. intestinalis mouthhook were found in 3rd stage G. nasalis. A major difference between these species was the replacement of shallow pits with sensilla-laden troughs in G. nasalis. Second-stage G. intestinalis has a distal mouthhook that varies considerably from the model type, lacking shallow pits and associated peg-like sensilla. By contrast, the sensory array of the 2nd stage G. nasalis larva is the most elaborate yet encountered, with extensive sensilla and troughs. The existence of other types of sensilla on the mouthhook is proposed, as well as a sensory role for the unsculptured surface. Possible uses of the sensory array by the parasite are discussed.