Morphological aspects of immature stages of Migonemyia migonei (Diptera: Psychodidae, Phlebotominae), an important vector of Leishmaniosis in South America, described by scanning electron microscopy

Correction: Morphological aspects of immature stages of Migonemyia migonei (Diptera: Psychodidae, Phlebotominae), an important vector of Leishmaniosis in South America, described by scanning electron microscopy

[This corrects the article DOI: 10.1371/journal.pone.0242163.].

Chaetotaxy of the fourth larval stage of Pintomyia longiflocosa, a primary vector of cutaneous leishmaniasis in Colombia

INTRODUCTION

Pintomyia (Pifanomyia) longiflocosa is an endemic species from Colombia, found between the central and eastern Andes, and reported as one of the primary vectors of cutaneous leishmaniasis in coffee-growing zones of the country. This species is classified in the Townsendi series and can only be identified by the morphology of the male adults.

OBJECTIVE

To determine the potential use of the fourth larval stage of the vector Pi. longiflocosa in morphological taxonomy based on the description of its chaetotaxy.

MATERIALS AND METHODS

Pintomyia longiflocosa adults were captured in Campoalegre, Huila, and reared in the Entomology Laboratory at the Colombian Instituto Nacional de Salud. To identify the setae found in each corporal segment, 15 fourth-instar larvae were mounted on microscope slides using Canadian balm after being cleared with 10 % potassium hydroxide and saturated phenol. Additionally, five specimens were prepared for their observation by scanning electron microscopy.

RESULTS

Based on the description of Pi. longiflocosa, we established that all species of the subgenus Pifanomyia so far described have the same antennal morphology and clavate setae along their body. However, various setae present in Pi. longiflocosa are absent in Pi. youngi, suggesting differences among the larvae of the Townsendi series.

CONCLUSIONS

These results support the potential importance of morphological characters from the fourth larval instar, such as antennal morphology and chaetotaxy, specifically in closely related species that are cryptic in their adult stages.

Sand Fly larvae are capable of positive chemotaxis: a proof of concept study using Phlebotomus papatasi (Diptera: Psychodidae) as a model species

Phlebotomine sand flies are important vectors of medical and veterinary importance, transmitting pathogens, such as the Leishmania parasites, responsible for 700,000 to 1 million new cases of leishmaniasis every year. The vast majority of the current sand fly surveillance and control tools are tailored against the adult stages, due to the limited knowledge on the ecology of the larval stages. Since vector control is primarily an ecological problem, an in-depth understanding of the behavior of the target insect pests across all the different life stages of their development is required prior to the development of effective control strategies. It is well known that chemical cues play an important role in insect behavior. While there are numerous studies investigating the behavior of adult sand flies in response to chemical sources, there is currently no information available on the response of their larval stages. In this study, novel bioassays were constructed to investigate the effect of chemical cues (gustatory and olfactory) on the behavior of Phlebotomus papatasi (Scopoli) sand fly larvae. The larvae exhibited a clear food preference within a few hours of exposure in a 2-choice bioassay, while, also, demonstrated positive chemotaxis in response to volatile stimuli emitted from their preferred food source. Identification of the specific chemical compounds (or the combination thereof) eliciting attractance response to sand fly immature stages could lead to the development of innovative, and targeted (larval-specific) tools for the surveillance, and management of these important public health pests.

A Review of Historical Phlebotominae Taxonomy (Diptera: Psychodidae)

Psychodidae is a group constituted by ca. 3400 species distributed in six existing and one extinct subfamily. Among them, Phlebotominae is of relevant medical and veterinary interest as vectors of pathogens, such as viruses, bacteria, and trypanosomatides, to vertebrates. The taxonomy of Phlebotominae, begun in 1786, received a great boost at the beginning of the twentieth century, when some of its species began to be implicated as vectors of leishmaniasis agents. Currently, the group consists of 1060 species/subspecies described for both hemispheres. Its taxonomy and systematics have been largely based on the morphological characters of adults in view of the limited number of species known in their immature forms, as well as by molecular approaches. This review focuses on the evolution of the phlebotomine systematics, with information regarding when the descriptions of the sand fly species/subspecies occurred, where their type localities are, the number of authors involved in their descriptions, and the researchers who have most contributed to the description of these taxa and their respective institutions. The morphological characters of adult forms used in the taxonomy of groups, in an evolutionary approach, and the current state of knowledge based on immature forms is also presented.

Significance of eggshell morphology as an additional tool to distinguish species of sand flies (Diptera: Psychodidae: Phlebotominae)

Morphological characteristics of eggshells are important in sand fly ootaxonomy. In this study, eggshells from Phlebotomus stantoni Newstead, Sergentomyia khawi (Raynal), and Grassomyia indica (Theodor) sand flies collected in Chiang Mai province, Thailand were examined and characterized using light microscopy (LM) and scanning electron microscopy (SEM). Then, eggshell morphology of these three species was described for the first time. Each gravid female was forced to lay eggs by decapitation and the eggs were collected for SEM analysis. Egg laying females were identified by morphological examination and molecular typing using cytochrome b (Cytb) as a molecular marker. The chorionic sculpturing of Ph. stantoni eggs combines two patterns on the same egg: unconnected parallel ridges and reticular patterns. Sergentomyia khawi and Gr. indica have similar chorionic polygonal patterns, but their exochorionic morphology and aeropylar area are different. Results indicate that eggshell morphological characteristics such as chorionic pattern, exochorionic morphology, inter-ridge/boundary area, aeropylar area (including the number of aeropyles) and basal layer, can be useful to develop morphological identification keys of eggs. These can serve as an additional tool to distinguish species of sand flies. In addition, the chorionic sculpturing of the eggs of the three species of sand flies observed by LM is useful for species identification in gravid females with spermathecae obscured by eggs.