Cytological and isoenzyme analysis of the Bucay and Quevedo cytotypes of the onchocerciasis vector Simulium exiguum (Diptera: Simuliidae) in Ecuador

Four cytotypes of Simulium exiguum occur in Ecuador, where this morphospecies is the primary vector of onchocerciasis. In this paper, we give the first full description of the banding pattern of the larval polytene chromosomes of the Quevedo cytotypes differ from the chromosomal standard sequence (of the Cayapa cytotype) by the fixed inversions IIL-5 and IIL-6. The Quevedo cytotype additionally differs from the standard and Bucay cytotypes by processing a differentiated X chromosome, wich is indicated by the inversion IIS-A. As the degree of reproductive isolation between the Bucay and Quevedo cytotypes has not yet been estabilished, they must be regarded as intraspecific variants of the same species. In fact, isoenzyme characterizations showed that the Bucay and Quevedo cytotypes are differentiated only to the extent expected of incipient species or geographical populations. Moreover, the sibiling species status previously given to the Bucay cytotype needs be reassessed, there being inadequate analysis from areas in Ecuador where Bucay occurs in sympatry with the standard Cayapa cytotype. No isoenzyme electromorphs were discovered that identified all or mostadult females of any one (cytotype-pure) collection

Bioamines and proteins in the saliva and salivary glands of Palaearctic blackflies (Diptera: Simuliidae).

To elucidate the mechanisms of skin-reactions to blackfly bites, components in the saliva and salivary glands of Simulium lineatum and S. equinum females were studied. Histamine, putrescine, spermine, N1-monoacetyl-spermine, and spermidine were detected in both the saliva and salivary gland extract through high-performance liquid chromatography (HPLC), the content of histamine being much higher than that of the other amines. Whereas histamine concentration was increased by food stimulation and actual feeding, the content of the other amines did not differ from that of non-stimulated flies. S. lineatum and S. equinum females differed significantly in their spermine and spermidine contents, autumn and spring generation females did not differ from each other. The dispersion of histamine in the salivary glands of male and female S. lineatum and S. equinum was demonstrated through histochemical staining. The globular proteins of the salivary glands were fractionated by chromatography and electrophoresis, the molecular weight of proteins and the enzymatic activity of esterase were also determined.

Visual detection of microencapsulated insecticides with selective staining and scanning electron microscopy.

Selective staining with Sudan IV and methylene blue for light microscopy and scanning electron microscopy (SEM) were investigated to determine their potential for detecting and quantifying microencapsulated insecticides. Penncap-M (microencapsulated methyl parathion), Penncapthrin (microencapsulated permethrin), and Dyfonate (microencapsulated fonofos) were selectively stained with Sudan IV but not with methylene blue. Selective staining was not possible for Altosid SF-10 or SR-20 (microencapsulated methoprene) with either stain. Sudan IV enabled detection of some microencapsulated formulations in the digestive content of selected aquatic invertebrates and prepared contaminated pollen samples. Staining intensity with Sudan IV was greatest with acetone but capsular damage was high. A solvent ratio of 50:50 and 20:80 acetone/xylene minimized capsular collapse and maintained good staining intensity. The use of SEM for capsule identification and quantification depended upon the method of sample preparation: the slide smear method was superior to samples prepared by incision or microtomy. SEM was most suitable for investigation of formulations such as methoprene, for which selective staining was not possible. The chemical basis of staining with Sudan IV and potential application of both identification techniques are discussed.

Quantitating histamine in the saliva and salivary glands of two Palaearctic blackfly species (Diptera: Simuliidae).

Saliva was collected from females of Boophthora erythrocephala (Simulium erythrocephalum) and Wilhelmia lineata (S. lineatum) as they were feeding on a saline-ATP solution through an artificial silicone membrane. The histamine content of the saliva was measured by high-performance liquid chromatography (HPLC). The amount of histamine salivated by B. erythrocephala (2.9 ng/individual when feeding to repletion) was more than four times that released by W. lineata (0.7 ng/individual). For both species, the quantity of histamine salivated increased with duration of feeding and partially with the age of females. The proportion of histamine retaines by in vitro fed W. lineata averaged 36.1% W. lineata females engorged on saline-ATP solution, or stimulated for feeding with the same medium, produced significantly more hist-amine than died unstimulated flies.

Identification of adults of the Simulium damnosum complex using hydrocarbon analysis.

Using advanced gas liquid chromatography in association with multivariate statistical analysis, a study of four members of the S. damnosum complex - S. sirbanum, S. damnosum s.str., S. yahense and S. sanctipauli, revealed that both adult male and female flies could be distinguished by quantitative analysis of the cuticular hydrocarbon peaks. Adult flies were obtained from sites which were known to contain a very high proportion of pure cytospecies. The females of the complex were more readily separated from each other than were the males. On the basis of preliminary results, the technique provides for the first time, a reliable method for distinguishing S. sirbanum and S. damnosum s.str., the most important vectors of onchocerciasis in the savanna areas of West Africa, as well as an additional method for identification of adult S. sanctipauli and S. yahense. Analysis of the hydrocarbons by GC/MS showed them to be straight chain and branched saturated hydrocarbons ranging from C22-C35. The technique is simple in respect of field methods of collection, and thus holds considerable promise as a means of identifying S. damnosum complex flies throughout the area of onchocerciasis transmission in Africa.

Vectores de Onchocerca volvulus y Mansonella ozzardi en Colombia / Onchocerca volvulus and Mansonella ozzardi vectors in Colombia

Los estudios en el foco colombiano de oncocercosis del Rio Micay demostraron que el desarrollo de las microfilarias de Onchocerca volvulus hasta el estadio infectivo tuvo lugar en ejemplares de Simulium Exiguum que se habian alimentado en voluntarios con infecciones naturales. Sin embargo, fue comun observar un desarrollo demorado del parasito y aproximadamente 25% de las larvas tenian una apariencia anormal. Se considera a S. Exiguum, el unico Simulium que se colecto picando al hombre durante 6 visitas al area, como el unico vector de oncocercosis en el Rio Micay aun cuando su eficiencia sea algo reducida. Algunas especies de Simulium de los grupos S. amazonicum y S. sanguineum sirven como huespedes intermediarios y probables vectores de Mansonella ozzardi en 3 regiones endemicas de Colombia. En Puerto Palacios (Rio Arquia, Antioquia), el desarrollo de la microfilaria de M. Ozzardi hasta el estadio infectivo ocurrio en S. sanguineum que habia comido sobre voluntarios con infecciones naturales. El desarrollo en S. Exiguum, la especie que se capturo mas comunmente, no paso del primer estadio en mas de 400 ejemplares de la misma area. En Santa Marta (cerca a Mitu, Vaupes), una especie aparentemente no descrita del grupo S. sanguineum demostro ser un buen huesped intermediario para M. ozzardi y fue el unico Simulido que se obtuvo picando al hombre durante la estacion seca..