Variations in the gonostyle of Nyssomyia intermedia (Lutz & Neiva) (Diptera: Psychodidae)

SYSTEMATICS, MORPHOLOGY AND PHYSIOLOGY

Variations in the gonostyle of Nyssomyia intermedia (Lutz & Neiva) (Diptera: Psychodidae)

Israel S Pinto^{I, II}; Claudiney B Santos^{I, III}; Adelson L Ferreira^I; Aloísio Falqueto^{I, II}

^IUnidade de Medicina Tropical, Depto de Patologia

^IIPrograma de Pós-Graduação em Biologia Animal, Depto de Ciências Biológicas. Univ Federal do Espírito Santo, Av Marechal Campos 1468, 29043-900 Vitória, ES, Brasil

^IIINúcleo de Entomologia da Secretaria de Estado da Saúde do Espírito Santo, Av Marechal Campos 1468, 29043-900 Vitória, ES, Brasil; [e-mail]

ABSTRACT

This paper describes sand flies similar to Nyssomyia intermedia (Lutz & Neiva) with variations in the number of spines at the gonostyle and tests the hypothesis whether these specimens belong or not to N. intermedia species. Using Principal Component Analysis and Neighbour Joining, the measurements of 15 structures of the phlebotomine with variations in number of spines were compared with measurements of 30 sand flies of N. intermedia species. Both analyses didn't cluster the specimens with variation in spines number in one group and provided evidence to the hypothesis that those sand flies belong to N. intermedia.

Key words: Anomaly, morphological variation, sand fly, taxonomy

Among Neotropical sand flies species, Nyssomyia intermedia (Lutz & Neiva) is pointed as the principal vector of Leishmania (Viannia) braziliensis, the etiologic agent of american tegumentary leishmaniasis (ATL), in modified environments in the Southeastern region of Brazil (Tolezano et al 1980, Falqueto et al 2003).

Although males of N. intermedia present high morphological similarities with Nyssomyia neivai (Pinto) males, they can be distinguished by the form of the tip of the ejaculatory ducts: "deep spoon" form in N. intermedia and "shallow" form in N. neivai (Andrade Filho et al 2003). In the Southeastern region the two species occur in sympatry only in the states of Minas Gerais and São Paulo (Andrade Filho et al 2007).

The right taxonomic identification of N. intermedia is fundamental in the elaboration of ATL prevention measures based on the geographic distribution of this vector. However, the occurrence of morphological variations might cause confusion resulting in failure in the taxonomic position of a particular specimen, as it occurred with Martinsmyia alphabetica (Fonseca) male (Coutinho & Barretto 1940).

Some authors have reported variations in the genitalia of sand flies (Sherlock et al 1958, Ximenes et al 2002, Andrade Filho et al 2004), including N. intermedia (Marcondes 1999). However, most of these variations are not symmetrical and can occur in the antennae, palps, cibarium, female spermathecae, and male terminalia. As these structures are bilateral, the comparisons between the two sides of the body allow the correct specific identification (Andrade Filho et al 2004). However, with the occurrence of bilateral variations, such comparisons are often not precise being necessary the inclusion of comparisons between other structures for the correct species identification.

Material and Methods

During studies in the locality of Belém (20º47'29''S; 41º00'06''W), municipality of Vargem Alta, Espírito Santo state, 12 sand fly specimens with five spines in each gonostyle (Fig 1b) and two sand flies with three spines in each gonostyle (Fig 1c) were captured. Although the specimens were similar to N. intermedia and N. neivai on external morphology, based on the "deep spoon" form of the final portion of the ejaculatory ducts, all these individuals would be included in the N. intermedia species. However, N. intermedia (Fig 1a) has four spines in each gonostyle, so these aberrant specimens do not fit well into the normal morphology of N. intermedia. Thus, in the present work, these 14 specimens are described and the hypothesis whether these individuals belong to N. intermedia is tested.

The specimens with five and with three spines in each gonostyle were examined and measured with a microscope calibrated for morphometric exams. Following the Andrade Filho et al (2004) proposal, the three first flagellomeres, palpomeres, head, clypeus, ejaculatory pump, genital filaments, lateral lobe, gonocoxite and gonostyle were measured. Measurements of these structures were compared with those from 30 specimens of N. intermedia collected in the same locality. The nomenclature and the terminology of the characters followed Galati (2003).

Comparison among the measurements of sand flies with five and with three spines in each gonostyle and the measures of the 30 specimens of N. intermedia was done by multivariate analysis of Principal Components (PCA) and by Neighbour Joining (NJ) analysis. The analyses were performed using the PAST program (Hammer et al 2001). A sand fly sample with five spines in the gonostyle was not used in the analyses due to the absence of some structures that could have been lost during collection and/or handling for identification.

The voucher specimens of sand flies with variations in the number of spines in the gonostyle are deposited in the Phlebotomine Collection of the Instituto de Pesquisas René Rachou-Fiocruz, Belo Horizonte, Minas Gerais, Brazil.

Results and Discussion

The relation of the measured structures, their mean and their standard deviations for the sand fly samples with five and three spines in the gonostyle and for the samples of N. intermedia are plotted in the Table 1. The measurements of the structures of the sand flies with five and with three spines in each gonostyle do not show significant difference in relation to the measurements of the specimens of N. intermedia studied (Fig 2) and neither with distinct groups (Fig 3).

Nyssomyia intermedia shows four spines in the gonostyle, being one apical, one external subapical, one external proximal and one internal proximal. The proximal spines are implanted at the same level (Fig 1a). In the sand flies specimens with five spines in each gonostyle, except for the presence of a spine between the apical and the external subapical (Fig 1b), the implantation of the spines follows the same pattern as in N. intermedia. In the same way, the specimens with three spines in each gonostyle also present the same pattern of implantation of spines in the gonostyles as N. intermedia, except for the absence of the subterminal external spine (Fig 1c). This corroborates the hypothesis that we are dealing with individuals with intraspecific variation.

The analysis of Principal Components grouped individuals with and without variation in the number of gonostyle spines, offering evidence that favors the hypothesis that all the analyzed sand flies belong to the species N. intermedia (Fig 2). This hypothesis was also corroborated by the Neighbour Joining analysis that did not group in the same cluster all the individuals with the same number of spines in each gonostyle (Fig 3).

Therefore, the association between the morphological similarity and the evidences obtained by PCA and NJ similarity support the hypothesis that the examined sand fly samples with symmetric bilateral variations in the number of gonostyle spines belong to N. intermedia species. Furthermore, adding molecular data could explain the significance of the variation in number of spines, as could examination of females of N. intermedia from the same geographic region.

Finally, the present study reports the finding of variations in the gonostyle of N. intermedia, and given the rarity of this occurrence in sand flies, the above observations are important to avoid taxonomic misidentification and erroneous descriptions of new species.

Acknowledgments

To Gustavo Rocha Leite for statistical help provided. To Dr Yuri Luiz Reis Leite for useful suggestions. To CAPES for the fellowship granted to Israel de Souza Pinto. Thanks also to anonymous reviewers for their comments and suggestions.

Received 27/II/09.

Accepted 21/V/09.

Edited by Takumasa Kondo - CORPOICA

• Andrade Filho J D, Carvalho G M L, Saraiva L, Falcão A L (2004) Bilateral anomaly in the style of Micropygomyia schreiberi (Martins, Falcão & Silva) (Diptera, Psychodidae). Rev Bras Entomol 48: 583-585.
• Andrade Filho J D, Galati E A B, Falcão A L (2003) Redescription of Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) (Diptera: Psychodidae). Mem Inst Oswaldo Cruz 98: 1059-1065.
• Andrade Filho J D, Galati E A B, Falcão A L (2007) Nyssomyia intermedia (Lutz & Neiva, 1912) and Nyssomyia neivai (Pinto, 1926) (Diptera: Psychodidae: Phlebotominae) geographical distribution and epidemiological importance. Mem Inst Oswaldo Cruz 102: 481-487.
• Coutinho J O, Barretto M P (1940) Contribuição para o conhecimento dos flebótomos do estado de São Paulo. III. Descrição do macho de Phlebotomus alphabeticus Fonseca, 1936 e de Phlebotomus pascalei n. sp. (Diptera: Psychodidae). An Fac Med Univ São Paulo 16: 193-206.
• Falqueto A, Sessa P A, Ferreira A L, Vieira V P, Santos C B, Varejão J B M, Cupolillo E, Porrozzi R, Carvalho-Paes L E, Grimaldi Jr G (2003) Epidemiological and clinical features of Leishmania (Viannia) braziliensis american cutaneous and mucocutaneous leishmaniasis in the state of Espírito Santo, Brazil. Mem Inst Oswaldo Cruz 98: 1003-1010.
• Galati E A B (2003) Morfologia, terminologia de adultos e identificação dos táxons da América, p.53-175. In Rangel E F, Lainson R (eds) Flebotomíneos do Brasil. Rio de Janeiro, Fiocruz, 367p.
• Hammer Ø, Harper D A T, Ryan P D (2001) PAST: Palaeontological statistics software package for education and data analysis. Palaent Electron 4: 9p. http://folk.uio.no/ohammer/past/
• Marcondes C B (1999) Anomalies of Lutzomyia intermedia (Lutz & Neiva, 1912) (Diptera, Psychodidae, Phlebotominae). Mem Inst Oswaldo Cruz 94: 365-366.
• Sherlock I A (1958) Anomalias de Phlebotomus longipalpis Lutz & Neiva, 1912 (Diptera: Psychodidae). Rev Bras Biol 18: 433-437.
• Tolezano J E, Macoris S A G, Dinis J M P (1980) Modificação na epidemiologia da leishmaniose tegumentar americana no Vale do Ribeira, estado de São Paulo, Brasil. Rev Inst Adolfo Lutz 40: 49-54.
• Ximenes M F F M, Bermudez E G C, Freitas R A (2002) Morphological genitalic anomaly in Lutzomyia longipalpis sensu lato (Lutz & Neiva, 1912) collected in the State of Rio Grande do Norte, Brazil. Entomotrópica 17: 183-184.

Publication Dates

• Publication in this collection
  19 Nov 2010
• Date of issue
  Oct 2010

History

• Received
  27 Feb 2009
• Accepted
  21 May 2009