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A new record of Anopheles (Stethomyia) kompi Edwards from Sergipe, northeastern Brazil

2018; Wiley; Volume: 43; Issue: 1 Linguagem: Inglês

10.1111/jvec.12301

1948-7134

Sirlei Antunes de Morais, David Andrade, Roseli La Corte,

Vector-borne infectious diseases

Sergipe is the smallest Brazilian state, located in the country's northeastern region. Despite its size, Sergipe encompasses two major terrestrial biomes, the Caatinga and the Atlantic Forest, as well as transitional ecotones. The mosquito fauna of this state is still poorly known, with the most comprehensive sampling effort being conducted recently in the Caatinga biome where three species of the genus Anopheles were recorded (Marteis et al. 2015). The genus Anopheles (Diptera: Culicidae) includes many species of mosquito vectors that can transmit malaria, one of the most widespread infectious diseases in the world. The different species of this genus are dispersed throughout the world and have different levels of importance in the transmission cycle (Sinka et al. 2010). The species reported here belongs to the subgenus Stethomyia, described by Theobald in 1902, which includes four other species: An. (Stethomyia) acanthotorynus Komp, An. (Ste.) canorii Floch and Abonnenc, An. (Ste.) nimbus (Theobald), and An. (Ste.) thomasi Shannon. The mosquitoes of this subgenus are darkly colored, lack white scales on the wings, legs, and palps, and have a silvery, longitudinal band that runs along the whole median mesonotum. Stethomyia is found in the New World, including Central America and a number of countries of South America (WRBU 2017). While the medical importance of the subgenus is still unclear, Stethomyia mosquitoes are known to be hematophagous and are considered to be anthropophilic (Camargo et al. 1993, Harbach 2017). Mosquitoes of the subgenus Stethomyia have mainly been recorded from South American countries of the equatorial zone. In Brazil, larvae of Stethomyia sp. were collected in the municipality of Lábrea, in the southern extreme of the state of Amazonas, near the border with Bolivia (Rufalco-Moutinho et al. 2016). An. (Ste.) acanthotorhynus has been recorded in Porto Almendras, Iquitos, Peru (Sallum et al. 2002). An. (Ste.) nimbus has been registered in the municipality of Gran Sabana, Bolívar state, Venezuela (Berti et al. 2014), in Colombia (Ahumada et al. 2016), and in the Brazilian city of Goiânia (Camargo et al. 1993). These species have not been recorded in northeastern Brazil in recent years, but in the late 1940s, when the country established an audacious program for the eradication of malaria, An (Ste.) kompi was recorded in 14 Brazilian states, including the northeastern states of Alagoas, Ceará, Bahia, Maranhão, and Paraíba (Ferreira 1964). This note registers the first record of the species An. (Ste.) kompi Edwards 1930 from the Brazilian state of Sergipe (Figure 1). Specimens were collected in the Mata do Junco State Wildlife Refuge (RVS Mata do Junco), a conservation unit with a total area of 9 km2 of strictly protected Atlantic Forest (Morato et al. 2011). This area is adjacent to the urban zone and is visited frequently by researchers and local residents, often for cultural practices. The RVS Mata do Junco is located in the municipality of Capela (10°30’12” S, 37°03’10” W), 67 km from the Sergipe state capital, Aracaju, at an altitude of 162 m above sea level. The local climate is dry and sub-humid megathermal, with a mean temperature of 24° C and mean annual rainfall of 1,372 mm. The refuge is a small patch of Atlantic rain forest under regeneration that has been compromised to some extent by human activity. While many exotic species are present, it also harbors a considerable diversity of fauna and flora, including approximately 100 tree species, 134 species of birds, and 23 mammalian and 20 amphibian species. The symbol of the refuge is the endangered titi monkey, Callicebus coimbrai Kobayashi & Langguth 1999 (AGS 2017). The refuge also protects important hydrological resources, such as the headwaters of the Lagartixo River, which supplies Capela with drinking water. The rainy season normally lasts from March to August. The collection site (Bica do Estreito) was 3.5 km from the center of the town of Capela (10°32’17” S, 37°03’39” W). The larvae were encountered in a small stream, at a shaded location with running water. The water was clean with a pH of 5.5 and temperature of approximately 26° C. The larvae were collected using an entomological dipper, a 350 ml container with a long handle. The dipper was immersed at the surface of the water at 1-m intervals around the perimeter of the aquatic environment, in order to sample the presence of larvae. The specimens collected were stored in plastic pots containing water from the stream for transportation to the Laboratory of Entomology and Tropical Parasitology of the Federal University of Sergipe (LEPAT) in Sao Cristovao. The larvae were transferred to breeding trays and fed with fry ration (Tretamin fish food®) until reaching the pupal phase, when they were separated into 50 ml individual disposable cups until the emergence of the adults. The two female specimens that emerged were euthanized at −5° C. The specimens were mounted with an entomological pin for the identification of their external morphology (Figure 2) based on a taxonomic key for the South American anophelines (Consoli and Lourenço-de-Oliveira 1994) and were deposited in the entomological collection at LEPaT. The morphological identification of the specimens was complemented by the analysis of two DNA barcoding markers, the Internal Transcribed Spacer 2 (ITS2) and Cytochrome Oxidase subunit I (COI). Both sequences contain diagnostic single nucleotide polymorphisms (SNPs), and the ITS2 also contains species-specific insertions/deletions (indels) that contribute to the accuracy of the identification of taxa. Samples of DNA were extracted from a leg of each specimen for preservation as voucher specimens. The COI fragment was amplified using the primer pair LCO1490 and HCO2198 (Folmer et al. 1994) and the ITS2 rRNA fragment using the primer pair 5.8S and 28S (Collins and Paskewitz 1996). The PCR reaction was run using the Phire Tissue Direct PCR Master Mix kit (Thermo Scientific™). The PCR products were verified by electrophoresis in 1.5% agarose gel. The sequencing of the COI gene produced a fragment of 528 bps, which was deposited in the GenBank database under accession number MF537257. The ITS2 fragment had 443 bps, and was deposited under accession number MF537254. In the present study, the comparison of the COI sequence with that of An. (Ste.) kompi available in GenBank (JF923715) confirmed the identity of the specimens collected in the RVS Mata do Junco. In the case of the ITS2 sequence, no samples of An. (Ste.) kompi were available in GenBank, so the sequence obtained here contributed to the expansion of the database available for the Stethomyia subgroup. An. (Ste.) kompi is rarely reported in inventories of mosquito faunas, which is probably due, in part, to the restriction of the species to areas of preserved habitat. While the species was known to have originally occurred within the region of the Amazonian city of Belém, for example, Silva et al. (2006) were unable to confirm the occurrence of An. (Ste.) kompi in their inventory. Overall, very few data are available on the distribution of the species in Brazil over the past 50 years (Hutchings et al. 2011). This reinforces the importance of protected areas of Atlantic rain forest, even relatively small fragments, such as the RVS Mata do Junco in Sergipe, for the preservation of the local fauna. The water sources found within the refuge probably contribute to the maintenance of this species, providing a continuous supply of clean water, which is fundamental to the development of the larvae. The characteristics of the biology of An. (Ste.) kompi were described 70 years ago by Deane et al. (1948), and the environments known to be inhabited by the larvae are consistent with the conditions found in the RVS Mata do Junco. Due to its intolerance of impacted environments, An. (Ste.) kompi can be considered to be an effective bioindicator of environmental quality. In this case, the lack of recent records of the species may reflect the increasing fragmentation of habitat and pollution of water resources occurring over recent decades. An aggravating factor is the lack of funding for inventories and taxonomic research on the mosquito fauna, given that the limited funds that are made available tend to be invested in vector control. The environment of northeastern Brazil has changed drastically since the malaria eradication campaign of the 1940s, which reinforces the need for a modern, systematic survey of the geographical distribution of anophelines in Brazil. We thank SEMARH for providing accommodation at the RVS Mata do Junco and for supporting this study. We are also grateful to the staff of the refuge, in particular Marcelo Guigó, for guiding us through the forest. We thank John Stolzle for the review of the English text. Financial support: CNPq-DCR-FAPITEC-SE N.351156/2013.