Cytogenetics analysis and testis morphology of aquatic species of the families Belostomatidae, Gelastocoridae, Gerridae, Notonectidae, and Veliidae (Heteroptera).

The Heteroptera have holocentric chromosomes with kinetic activity restricted to the end of chromosomes. The first meiotic division is reductional for the autosomes and equational for the sexual. Only a few species of this suborder have been analyzed. In this study, we observed the morphologies of the testes of the Heteroptera species Belostoma anurum (Herrich-Schäffer, 1948), Belostoma micantulum (Stal, 1858), Gelastocoris angulatus (Melin, 1929), Gelastocoris flavus flavus (Guérin-Méneville, 1844), Rheumatobates crassifemur crassifemur (Esaki, 1926), Buenoa amnigenus (White, 1879), Buenoa unguis (Truxal, 1953), Martarega brasiliensis (Truxal, 1949), Martarega membranácea (White, 1879), Martarega uruguayensis (Berg, 1883), Rhagovelia tenuipes (Champion, 1898) and Rhagovelia zela (Drake, 1959). We found that the testes of these species can be round, round/spiral, or elongated/spiral. The size of the prophase I cells was found to vary, with the smallest ones being detected in B. micantulum and Rha. zela, the largest in G. f. flavus, and ones of intermediate size in R. c. crassifemur and M. brasiliensis. With respect to the chromosome complement, we verified the presence of 2n = 16: (14A+XY, B. micantulum and G. angulatus), 21: (20A+X0, R. c. crassifemur), 23: (22A+X0, Rha. zela and Rha. tenuipes), 25: (24A+X0, Bu. amnigenus and Bu. unguis; 22A+2m+X0, M. membranacea), 27: (24A+2m+X0, M. brasiliensis and M. uruguayensis), 29: (26A+X1X2Y, B. anurum), and 35: (30A+X1X2X3X4Y, G. f. flavus). We found that the features of spermatogenesis in these species are similar to those of other previously described Heteroptera species, differing only in testicular morphology, chromosome number, and sex chromosome system.

Triatoma brasiliensis species complex: characterization of the external female genitalia.

The Triatoma brasiliensis complex is composed of six species (Triatoma bahiensis, T. juazerensis, T. lenti, T. melanica, T. petrocchiae, and T. sherlocki) and two subspecies (T. brasiliensis brasiliensis and T. b. macromelasoma). Phylogenetic studies have shown that it is a monophyletic group, but the morphological relationships among the members can be better understood. We applied a tool of high resolution based on morphology to identify details that characterize the female genitals for each member of this group. The external genital structures of five to fifteen females of each taxon were analyzed. Insects had their abdomen transversely cut to separate the last abdominal segments, and representative illustrations obtained via scanning electron microscopy (SEM) are shown. Observations were performed in the dorsal and the ventral views. The morphological characterization of female external genitalia allowed a differentiation of each species/subspecies. The subspecies T. b. brasiliensis and T. b. macromelasoma were the most similar. On the other hand, dorsal view of structures evidenced some unique characteristics for T. petrocchiae and T. sherlocki. Regarding these structures for T. petrocchiae, the differentiation was in accordance with molecular studies, since this species exhibits the highest genetic distances in relation to other species of T. brasiliensis complex.

Karyotype Evolution of Chagas Disease Vectors (Hemiptera, Triatominae).

The Triatominae subfamily is composed of 153 hematophagous species that are potential vectors of Trypanosoma cruzi, the etiological agent of Chagas disease. Karyotypic studies in triatomines were initiated in 1909. There are 92 karyotypes described, all grouped into the tribes Rhodniini and Triatomini. Recently, a phylogenetic study of the triatomines that combines molecular data with geological changes was performed. We now discuss how the karyotype evolved with the diversification of the triatomines.

Hybrid Collapse Confirms the Specific Status of Triatoma bahiensis Sherlock and Serafim, 1967 (Hemiptera, Triatominae), an Endemic Species in Brazil.

Six to seven million people worldwide are estimated to be infected with Trypanosoma cruzi, the etiologic agent of Chagas disease transmitted mainly by triatomines. Triatoma bahiensis was recently collected in the Brazilian state of Bahia and revalidated using different approaches. The main criterion used to define a "good" biological species is reproductive isolation, so we evaluated the cytogenetics of first-generation (F1) hybrids resulting from the experimental cross between T. bahiensis females and Triatoma lenti males to possibly characterize the postzygotic isolation associated with the hybrid breakdown. All cells analyzed presented a karyotype of 2n = 22 and a pair of univalent autosomes. This chromosome behavior represents hybrid collapse and underscores the specific status of T. bahiensis. Thus, we have characterized the presence of the hybrid collapse phenomenon in an experimental cross, and we confirm the specific status of T. bahiensis, thus contributing to the Triatominae taxonomy.