R. D. Ward

Reproductive isolation between different forms of Lutzomyia longipalpis (Lutz & Neiva), (Diptera: Psychodidae), the vector of Leishmania donovani chagasi Cunha & Chagas and its significance to kala-azar distribution in South America

The males of the sandfly Lutzomyia longipalpis occur in two forms, one which bears a single pair of pale spots on tergite 4 and another in which an additional pair of spots characterizes tergite 3. In crosses between laboratory reared stocks of the two forms originating from allopatric and sympatric sites in Brazil nearly all males of one form fail to inseminate females of the other. In addition, insemination failure between some allopatric populaytions of Lu. longipalpis with similar tergal spot patterns is recorded, indicating the existence of additional forms in an apparent species complex. The possibility that Lu. longipalpis sensu latu represents more than a single taxon is discussed and the relevance of these findings to future epidemiological studies on kala-azar is considered.

Laboratory response of female Lutzomyia longipalpis sandflies to a host and male pheromone source over distance.

ABSTRACT. A nylon net cage (260×40×40 cm) provided with unidirectional air flow was used to demonstrate the response of female sandflies, Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae) to a host and extract of male pheromone glands over a distance of 240 cm. Females responded more rapidly and in greater numbers to the host if male pheromone was present. Results suggest that one function of the pheromone may be to attract females from some distance to a common mating site, on or near the host.

Some methods for membrane feeding of laboratory reared, neotropical sandflies (Diptera: Psychodidae)

A brief introduction to the history and applications of membrane feeding is given, together with its use to feed and infect sandflies with Leishmania. The present paper describes methods for feeding Lutzomyia longipalpis and Lu. flaviscutellata through membranes. Of the membranes tested, chick skins and bat wings gave the best results. Membranes stored at -20 degrees C for over a year were found to be less effective than fresh ones. Blood meals were maintained at temperatures between 24 degrees C and 37 degrees C and it is concluded that although temperatures as high as 37 degrees C are unnecessary for successful membrane feeding of sandflies, fewer flies feed in most instances at temperatures below 27 degrees C. The influence on feeding of individual skins, different lots of blood and the addition of leishmanial cultures to offered blood are discussed.

Sex pheromone activity in a single component of tergal gland extract ofLutzomyia longipalpis (Diptera: Psychodidae) from Jacobina, Northeastern Brazil

The sex pheromone component of maleLutzomyia longipalpis tergal gland extract was isolated and its activity confirmed by bioassay. Whole tergal gland extract was analyzed by HPLC and fractions were collected as they eluted from the detector. Each fraction was tested in an attraction bioassay with virgin unfed femaleLutzomyia longipalpis. HPLC analysis showed that whole extract contained several peaks; one large peak, one small peak and several minor peaks. Purity of the HPLC fractions was determined by GC analysis. The bioassays revealed that the large peak was responsible for most of the observed female behavior. The addition of the small peak to the large peak improved the response although by itself the small peak failed to elicit any significant behavior. Minor peaks failed to elicit any response. Chemical analysis revealed the large peak to be a relatively nonpolar hydrocarbon.

Response of the sandfly Lutzomyia longipalpis to an oviposition pheromone associated with conspecific eggs

Abstract. Response of female Lutzomyia longipalpis Lutz & Neiva (Diptera: Psychodidae) to an oviposition attractant and/or stimulant associated with conspecific eggs was investigated in the laboratory. Females of two populations laid significantly higher mean number of eggs on sites with 160 eggs already present than on bare control sites. This response was lost when eggs placed on test sites were previously washed in organic solvents and distilled water. Age of eggs placed on test sites, 1–6 days after being laid, did not seem to affect the oviposition response of the females. Comparing effects of different numbers of eggs, positive responses were obtained when 80, 160 or 320 eggs were placed on test sites. No significant differences between mean egg numbers laid on test sites and controls were detected when batches of only 20 or 40 eggs were used.

Leishmania in Phlebotomid Sandflies: VI. Importance of Hindgut Development in Distinguishing between Parasites of the Leishmania mexicana and L. braziliensis Complexes

In addition to their growth in the midgut and foregut of the sandfly vectors, parasites of the Leishmania braziliensis complex undergo development in the hindgut, where they are predominantly attached to the wall of the pylorus and, to a lesser extent, the ileum. Such development is absent in the life-cycle of members of the Leishmania mexicana complex, which develop only in the midgut and foregut. This difference was maintained in the sandfly Lutzomyia longipalpis experimentally infected with a variety of leishmaniae, some of which have also been studied in their natural vectors. Development in this laboratory-bred insect therefore serves as a quick means of distinguishing between isolates of the mexicana and braziliensis complexes. Subspecies of Leishmania hertigi, from neotropical porcupines, were not found to develop in the hindgut of Lu. longipalpis: for this and other reasons they are removed from the L. braziliensis complex and placed in a group of their own. Leishmania enriettii, of the guinea-pig, similarly failed to develop in the hindgut: this, with additional features of the parasite, supports its continued inclusion in the L. mexicana complex. The significance of hindgut development of certain leishmaniae is discussed, particularly with regard to the evolution of the genus Leishmania.

The application of random amplified polymorphic DNA for sandfly species identification

Abstract. We have applied the recently developed Random Amplified Polymorphic DNA (RAPD) method to produce species‐specific, DNA profiles for two sympatric, Venezuelan sandfly species, thought to be the vectors responsible for recent outbreaks of cutaneous and mucocutaneous leishmaniasis in the Andean State of Tachira. Moreover, within the profile, it was possible to identify a diagnostic DNA band for Lu.youngi of 0.32 kb. Results showed that the size of this diagnostic DNA band remained constant and did not vary with sex or geographical distribution.

Isolation of oviposition pheromone from the eggs of the sandfly Lutzomyia longipalpis

Abstract. Semiochemical components of eggs of the sandfly Lutzomyia longipalpis (Diptera: Psychodidae) were separated by high performance liquid chromatography. HPLC fractions were examined quantitatively and qualitatively by gas chromatography (GC). A bioassay was used to determine the oviposition attraction of gravid L. longipalpis to each of the fractions separately and a peak responsible for the semiochemical activity was identified. Gravid flies were placed in individual oviposition tubes to determine if the peak of interest was an oviposition stimulant. The active semiochemical fraction attracted gravid flies for oviposition. Furthermore, egg laying was enhanced: gravid flies exposed to the pheromone oviposited earlier and laid more eggs than control flies. GC analysis indicated that 1200 eggs (2 days old) gave a yield of 12.75 ug of active pheromone. This fraction had similar HPLC and GC retention times to caryophyllene oxide, suggesting comparable polarity and molecular weight.

Evidence for the accessory glands as the site of production of the oviposition attractant and/or stimulant ofLutzomyia longipalpis (Diptera: Psychodidae)

The phlebotomine sandflyLutzomyia longipalpis Lutz and Neiva, the vector of visceral leishmaniasis in South America, has recently been shown to produce an oviposition semiochemical. In the present study it was found that a nonpolar extract of eggs was attractive and/or stimulatory to ovipositing females. A Chromatographic investigation indicated the presence of similar compounds in accessory glands and egg extracts. Extract of accessory gland was also found to elicit a positive oviposition response. It is concluded that the pheromone is produced in the accessory glands and is secreted onto the eggs during oviposition.

The effect of male sandfly pheromone and host factors as attractants for female Lutzomyia longipalpis (Diptera: Psychodidae)

Abstract Male Lutzomyia longipalpis (Lutz & Neiva) pheromone extracted from tergal glands combined with heat, carbon dioxide gas and hamster urine was found to be attractive to virgin female sandflies. The host factors if offered in the absence of pheromone or a heat source were, however, unattractive to female flies. Pheromone stored for 6 days and then combined with the same host components remained attractive to female flies but storage failed to enhance its attractiveness. The effects of carbon dioxide gas, hamster urine, chicken uropygial gland extract and octenol plus acetone on the responses of females were inconsistent. A ceramic battery powered heat source was tested with pheromone and host attractants and showed potential for field application in developing a pheromone trap.