Donald W. Hall

Significance of transovarial infections of Amblyospora sp. (Microspora: Thelohaniidae) in relation to parasite maintenance in the mosquito Culex salinarius☆

Abstract Adult females of Culex salinarius, transovarially infected with the microsporidium Amblyospora sp., showed no significant differences in overall fecundity, physiological longevity, and preoviposition periods when compared to healthy adults under laboratory conditions. Development times and survival rates for congenitally infected young to reproductive age were also indistinguishable from those of healthy controls. A significant reduction of 52% in egg hatch was observed for infected eggs when compared to healthy eggs. Prevalence rates of infection for progeny produced by infected females declined with each successive gonotrophic cycle and averaged 90%. Transovarial transmission is not sufficient for the maintenance of the microsporidium in a population of mosquitoes. An alternate host is suggested as a mechanism whereby the microsporidium can reenter a healthy mosquito population.

Intracolony morphometric variation and labral shape in Florida Reticulitermes (Isoptera: Rhinotermitidae) soldiers: significance for identification

Measurements of pronotal width, broadest gular width, and labral length of Reticulitermes soldiers collected in San Felasco State Preserve, Florida, showed considerable intracolony variation and interspecific overlap. The termites collected did not differ in size from termites collected state wide. The reported 0.81 mm pronotal width threshold failed to separate soldiers of R. flavipes from R. virginicus. An average pronotal width measurement (n or equal to 0.90 mm denotes R. flavipes, 5) separates R. flavipes from R. virginicus. A new character, labral shape, was found to be very reliable for separating the three species.

Life cycle of a new species of Amblyospora (Microspora: Amblyosporidae) in the mosquito Aedes taeniorhynchus☆☆☆

Abstract A new species of Microspora, Amblyospora polykarya , is described from the mosquito Aedes taeniorhynchus . The parasite is transovarially transmitted for one generation only. Spores in adult females extrude binucleate sporoplasms which infect developing eggs. Merogony occurs in larval oenocytes with diplokaryotic stages in early instars giving rise to plasmodia with many diplokarya. Plasmodia undergo cytokinesis to form diplokaryotic sporonts. In fat body cells, these sporonts secrete pansporoblastic membranes and undergo two nuclear divisions to form octonucleate sporonts. Cytokinesis and differentiation result in uninucleate spores in packets of eight. These spores are not transmissible per os and are of different morphotype from those in adult females. Infected larvae die in the fourth stadium.

Pathology of a mosquito iridescent virus (MIV) infecting Aedes taeniorhynchus

Abstract An investigation was initiated to study the pathology and biology of the regular mosquito iridescent virus (RMIV) in the black salt marsh mosquito, Aedes taeniorhynchus. RMIV was capable of infecting a variety of tissues within its host. Cells of the fat body, tracheal epithelium, imaginal discs, and epidermis were the primary sites of viral replication. Extensive destruction of the fat body by this virus resulted in the death of most infected mosquitoes before they reached the adult stage. Other tissues which were involved to a lesser extent were hemocytes, esophagus, nerve, muscle, and both larval and adult ovaries. The transovarial transmission of RMIV was confirmed, and when transovarial transmission occurred, either all or none of the progeny of a given female were infected. The presence of virus in the ovaries was taken as evidence that RMIV is transmitted within the egg.

Sporulation of Amblyospora californica (Microspora: Amblyosporidae) in autogenous female Culex tarsalis

Sporulation of Amblyospora parasites in adult female mosquitoes is usually synchronized with the hosts ovarian development which is initiated after a blood meal. The high percentage of sporulation in non-blood-fed autogenous Culex tarsalis supports the hypothesis that sporulation is stimulated by some host reproductive event (possibly hormonal) rather than by blood meal components.

Physical and serological comparisons of “R” and “T” strains of mosquito iridescent virus from Aedes taeniorhynchu

Abstract The relationship between the regular mosquito iridescent virus (RMIV) and the turquoise mosquito iridescent virus (TMIV) was studied by comparing serological and physical properties of the viruses. Gel diffusion studies with alkaline degraded virus preparations exhibited four antigens common to both viruses, but no unique antigens were detected for either virus. Electron micrographs of infected tissue sections showed tubular structures associated with both RMIV and TMIV. These structures were slightly smaller in diameter than the respective virus with which they were associated and their possible significance is discussed. RMIV and TMIV sedimented at different rates in sucrose density gradients, and RMIV was found to be slightly more dense than TMIV by equilibrium ultracentrifugation in cesium chloride. Also, RMIV was found to be larger than TMIV on the basis of measurements from electron micrographs of tissue sections.

Characterization and biological activity of a Brazilian isolate of Bacillus sphaericus (Neide) highly toxic to mosquito larvae.

Primary powders of Bacillus sphaericus strain S2 isolated from soil samples in Brazil, and strain 2362 were produced in a 14 liter fermentor. Growth patterns and sporulation observed in three trials with strains S2 and 2362 in the fermentor were similar. Second-instar larvae of Culex quinquefasciatus, Anopheles albimanus, Anopheles quadrimaculatus, and Aedes aegypti exposed for 48 hr to strain S2 responded with LC50 values of 0.25, 5.95, 12.28 and 140.0 ppb of lyophilized primary powder, respectively. Under the same conditions, strain 2362 resulted in LC50 values of 0.39, 7.16, 16.93 and 307.0 ppb of lyophilized primary powder, respectively, in those mosquito larvae. Statistical analysis of the bioassay data did not show significant differences among LC50 values observed in B. sphaericus strains S2 and 2362, at the 0.05 level. Toxins of strains S2 and 2362 were extracted at pH 12 with NaOH. Electrophoresis of the extracts in polyacrylamide gel under denaturing conditions revealed the 51 and 42 kDa toxins in both S2 and 2362 B. sphaericus strains. The presence of the 42 kDa peptide in the extracts was confirmed by Western blot and Elisa, with anti-42 kDa IgG previously prepared from strain 2362.

Septate Gregarines From Reticulitermes Flavipes and Reticulitermes Virginicus (Isoptera: Rhinotermitidae)

ABSTRACT. The gregarine parasites of Reticulitermes virginicus and Reticulitermes flavipes begin their development as trophozoites attached to the midgut epithelium by a small button‐shaped epimerite. the epimerite is lost when the parasite becomes free‐living in the gut lumen as a solitary gamont. Syzygy is late and was not observed. When full‐grown, gamonts enter the hemocoel and fuse in pairs to form large gametocysts that are attached to the midgut of the termite by a duct. Thousands of sporocysts are formed within the original gametocyst. the mature sporocysts are released into the lumen of the midgut through the connecting duct. They are then passed out with the feces. These gregarines are believed to be identical to Gregarina termitis Leidy which was described from a single gamont and later erroneously placed in the genus Hirmocystis by Henry.

A new microsporidian parasite of the mosquito Aedes taeniorhynchus

Abstract A new species of microsporidium is described from the mosquito Aedes taeniorhynchus . This microsporidium is vertically transmitted and exhibits dimorphic development with one sequence leading to formation of short pyriform, uninucleate spores in male fourth instar larvae, pupae, and adults, and the other sequence leading to formation of diplocaryotic stages and cylindrical spores in adult females. Vertical transmission is apparently limited to a single generation, and the uninucleate spores are not transmissible per os to larvae.