Carlos Brisola Marcondes; Ueslei Paterno
Laboratório de Entomologia Médica, Departamento de Microbiologia e Parasitologia do Centro de Ciências Biológicas da Universidade Federal de Santa Catarina, Florianópolis, SC, Brasil
A positive coefficient of association (affinity) between Runchomyia reversa and Anopheles cruzii and high (0.38) index were observed, probably due to the similar breeding places (bromeliads) and to landing habits. Furthermore, a high (0.92) index of association between Oc. scapularis and Wyeomyia incaudata, with low coefficient of association was observed.
Key-words: Culicidae. Interspecific association. Runchomyia reversa. Anopheles cruzii. Bromeliad.
Foi observado coeficiente de associação positivo (afinidade) entre Runchomyia reversa and Anopheles cruzii e alto (0,38) índice de associação, provavelmente devido a similaridade entre os criadouros (bromélias) e aos hábitos de pouso, e alto (0,92) índice de associação entre Oc. scapularis e Wyeomyia incaudata, com baixo coeficiente de associação.
Palavras-chaves: Culicidae. Associação interespecífica. Runchomyia reversa. Anopheles cruzii. Bromélia.
The study of association between species of mosquitoes can provide clues to an understanding of their biology and role in the transmission of pathogens. Associations can be due to the sharing of the same breeding places or to the flying and feeding behaviour of adults. For example, the coefficients and indices of association between Culex pipiens and Culex torrentium in containers and in ground pools were studied, with somewhat different values for each habitat5. Methods for the study of association were revised6, citing several studies on mosquitoes, though none done in South America.
Mosquitoes were collected weekly from September to December 2001 in a trail at a secondary forest at Unidade de Conservação Ambiental Desterro (27º31’51” S 48º30’44” W, 50-150m a.s.l., Florianópolis, Santa Catarina, southern Brazil). Mosquitoes landing on two collectors in the morning, in ten points in the trail, were collected.
Three hundred fifty eight mosquitoes, belonging to 22 species, 14 of them new for the fauna of the state, were obtained4. Runchomyia reversa Lane & Cerqueira, Ochlerotatus scapularis Rondani, Wyeomyia incaudata (Root) and Anopheles cruzii Dyar & Knab were the predominant species, constituting 62.9% of the total. Samples from below and from above the waist were separated, and 136 samples were analyzed.
Coefficients of interspecific association1 and indices of association7 8 were calculated to clarify the relationship between pairs of the four species above. The coefficient (CAB) considers only the numbers of occurrences in which both species are together or separated, while the index of association (I) considers also the numbers of mosquitoes in the collections in which they occur together. The values of the coefficients of association and of the indices of association can vary from +1 (complete association) to —1 (complete dissociation).
The coefficients of association, shown in the Table 1, between the species indicate at a first glance some association between Runchomyia reversa and Wyeomyia incaudata (0.22±0.12) and between that species and Anopheles cruzii (0.83±0.04). However, except for the high value of X2(15.02) for the coefficient of association1 6 7 between R. reversa and A. cruzii, all the others were lower than the X2 for the 2 x 2 analysis (3.84). Therefore, most coefficients of association were not significant. In the association between R. reversa and A. cruzii, the product of the number of samples in which both species are absent and that in which both are present is greater than the product of the numbers of samples in which one of them is absent; therefore, this association is positive (affinity)7.
The indices of association for two pairs (O. scapularis vs W. incaudata and R. reversa vs A. cruzii) were respectively 0.92 and 0.38. This result should be added to the high coefficient of association for R. reversa vs An. cruzii. The habitats of immature insects of the first pair are quite different. Immature forms of O. scapularis live in temporary pools in the ground, and sometimes in artificial containers, while those of Wyeomyia (Phoniomyia) spp and R. reversa2 are in bromeliads. So, any association is probably related to the flying and landing habits of the species, or possibly in the shelters. A. cruzii has its immature forms in bromeliads2, like R. reversa, and this association can have had some influence on the above results.
Only I, and not CAB, was high for the pair O. scapularis/ W. incaudata. This could indicate that they are not frequently associated, but that there are specific conditions, such as temperature, humidity, luminosity, pressure, hour, which stimulate several mosquitoes of both species to bite. The landing habits of the mosquitoes were studied (CB Marcondes, U Paterno: dados não publicados) and it is probable that these habits of the species constituting the pairs are much more important than the habitats of the immature forms.
Since samples from below and from above the waist were separated, this association could be related to a similar distribution of landing on the body. In fact, all W. incaudata were collected below the waist, a significantly greater quantity of R. reversa was collected below, and there is a non-significant indication of preference of O. scapularis to land on this part of the body (CB Marcondes, U Paterno: dados não publicados), which should be further investigated. This is additional evidence for the influence of biting habits on the results.
This preliminary evidence of association between mosquito species in the Atlantic forest should be further studied, if possible associated to careful observation of meteorological conditions in the sites of breeding and collection of the insects.
To Drs. Oswaldo Paulo Forattini and Iná Kakitani, and to Mr. Aristides Fernandes, of Faculdade de Saúde Pública of Universidade de São Paulo, for the useful comments, for the checking of identification of some mosquitoes and for training one of the authors (UP). To Dr. Maike Hering Queiroz, of Departamento de Botânica of Universidade Federal de Santa Catarina, for authorization to develop the work in UCAD, and to Mr. Silvânio Guilherme da Costa, for assistance in the field work.
1. Cole LC. Measurement of interspecific association. Ecology 30: 411-424, 1949. [ Links ]
2. Forattini OP. Culicidologia médica. Editora Universidade de São Paulo, São Paulo, 2002. [ Links ]
3. Lane J, Cerqueira NL. Os sabetíneos da América (Diptera, Culicidae). Arquivos de Zoologia do Estado de São Paulo 3: 473-849, 1942. [ Links ]
4. Paterno U, Marcondes CB. Mosquitos antropofílicos de atividade matutina em trilha em Mata Atlântica em Florianópolis, Santa Catarina, Brasil (Diptera, Culicidae). Revista de Saúde Pública 38: 133-135, 2004. [ Links ]
5. Service MW. The taxonomy and biology of two sympatric sibling species of Culex, C. pipiens and C. torrentium (Diptera: Culicidae). Journal of Zoology 156: 313-326, 1968. [ Links ]
6. Service MW. Mosquito ecology: field sampling methods. Chapman & Hall, London, 1993. [ Links ]
7. Southwood TRE. Ecological methods. Chapman & Hall, London, 1978. [ Links ]
8. Whittaker RH, Fairbanks CW. A study of plankton copepod communities in the Colombian basin, south eastern Washington. Ecology 39: 49-65, 1958. [ Links ]
prof. Carlos Brisola Marcondes
Depto de Microbiologia e Parasitologia/CCB/UFSC
Campus Trindade, 88040-900 Florianópolis, SC
Tel: 55 48 331-5208, Fax: 55 48 331-9258
Recebido em: 9/7/2004
Aceito em 13/9/2004
Partially financed by CNPq (Proc.-690143/01-0).