Development of Genital Plates in Nymphs of Triatoma pallidipennis, Stål 1872, (Hemiptera: Reduviidae) and its Application as Sexing Method

Vol. 98(6): 777-782, September 2003

Milton Rodríguez-Sánchez, Ricardo Alejandre-Aguilar, Benjamín Nogueda-Torres/⁺, Alejandro D Camacho*, Eliézer Martín-Frías

Laboratorio de Entomología Médica, Depto. de Parasitología *Laboratorio de Entomología, Depto. de Zoología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Prol. Carpio y Plan de Ayala s/n, Col. Casco de Santo Tomás, C.P. 11340, México D. F., México

Searching for morphometric differences between sexes in immature forms, the development of genital plates in the exuviae of Triatoma pallidipennis Stål 1872 nymphs was studied. Differences were found in the form and size of the 9th genital urosternite, it is larger and wider in males as compared to females. This difference is reported in several South American Triatoma species. From our results it is possible to sex early stages from microscopic observation of genital plates in whole insects.

Key words: Triatoma pallidipennis - sexing methods - genital plates - urosternites

The interest on the studies of development of genital plates in immature forms in triatomines has increased due to its application for sexing and taxonomic value (Perlowagora-Szumlewics & Nigri da Cruz 1972, Da Rosa et al. 1992, Jurberg et al. 1998). Galliard (1935) was first to report morphological evidence from genital plates as useful for sexing 5th nymphal stage in Triatoma protracta (Uhler 1894), T. dimidiata (Latreille 1811) and Rhodnius prolixus, Stål 1872. Further research conducted by Corrêa (1954), Corrêa et al. (1964), Espínola (1966), Ramírez Pérez (1969), Lent and Jurberg (1969), Salgado et al. (1979), Martín and Dávila (1981), Gonçalvez et al. (1985), Jurberg et al. (1986), and Galindez-Giron et al. (1999), include the use of optic and scanning electronic microscopy (SEM).

Most studies were conducted on South American species such as T. maculata (Erichson 1848), T. pseu-domaculata Corrêa and Espínola 1964, T. brasiliensis Neiva 1911, T. infestans (Klug 1834), Psammolestes coreodes Bergroth 1911, and Panstrongylus megistus (Burmeister 1835). Previous works by Galliard (1935), Ryckman (1962) and Martin and Dávila (1981) were done on Mexican Triatoma species, yet further research is required on the subject. The present work was conducted on T. pallidipenis, a species of the "phyllosoma complex", widely distributed in México. Because of its peridomestic behavior in some regions, it is an interesting species for epidemiology (Lent & Wygodzinsky 1979, Zárate & Zárate 1985, Beltrán & Carcavallo 1985, Velasco-Castrejón 1991, Martínez-Ibarra & Katthain-Duchateau 1999). We studied the development of genital plates through the life cycle and looked for morphological differences that could allow for sexing on 1st to 5th instar nymphs.

MATERIALS AND METHODS

RESULTS

DISCUSSION

REFERENCES

Fig. 1 | Fig. 2 | Fig. 3 | Fig. 4 | Fig. 5 | Fig. 6 | Fig. 7 | Fig. 8 | Table

⁺Corresponding author. Fax: +52-55-5729.6300 ext. 62399. E-mail: bnogueda@yahoo.com

Received 26 August 2002

Accepted 9 July 2003