Can sibling species of the Drosophila willistoni subgroup be recognized through combined microscopy techniques?

ABSTRACT In several arthropod groups, male genitalia is the most important feature for species identification, especially in cryptic species. Cryptic species are very common in the Drosophila genus, and the Neotropical Drosophila willistoni species group is a good example. This group currently includes 24 species divided into three subgroups: alagitans, bocainensis and willistoni. There are six sibling species in the willistoni subgroup – D. willistoni, D. insularis, D. tropicalis, D. equinoxialis, D. pavlovskiana and D. paulistorum, which is a species complex composed of six semispecies – Amazonian, Andean-Brazilian, Centroamerican, Interior, Orinocan and Transitional. The objective of this study was to characterize male genitalia of the willistoni subgroup, including the D. paulistorum species complex, using scanning electron microscopy and light microscopy. We also tried to contribute to the identification of these cryptic species and to add some comments about evolutionary history, based on male genitalia characters. Despite being cryptic species, some differences were found among the siblings, including the Drosophila paulistorum semispecies.

Over-activation of the Drosophila melanogaster hsp83 gene by selenium intoxication

Selenium is an important dietary micronutrient and an essential component of selenoproteins and the active sites of some enzymes, although at high concentrations it is toxic. We investigated diphenyl diselenide ((C6H5)2Se2 ) for its effects on the developmental stages of Drosophila melanogaster and found that in the larval and pupae stages the toxic threshold for this compound when added to the banana-agar medium on which the larva were fed was 350 µmol. In adult flies, fed on the same media, there were no observable toxic effects below 500 µmol but there were toxic effects above 600 µmol, indicating that adult flies were more resistant to selenium intoxication. In larvae, a when diphenyl diselenide was present above the toxic threshold there was increased activation of the hsp83 heat shock protein gene. Selenium promotes oxidation of sulfhydryl groups and affects the folding of proteins and this could explain the over-expression of hsp83 because the product of this gene is involved in protein folding and defense responses, including the response to heat shock.

The genus Zygothrica Wiedemann 1830 (Diptera, Drosophilidae) in Santa Catarina state, southern Brazil: distribution and ecological notes / O gênero Zygothrica Wiedemann 1830 (Diptera, Drosophilidae) no Estado de Santa Catarina, sul do Brasil: distribuição e notas ecológicas

The present paper brings together survey data from nine collection sites in Santa Catarina state, southern Brazil. Samples were obtained during about four years in forested, coastal and urban areas. Flies were attracted by fermented banana baits and captured in traps. Among the species of the genus Zygothrica Wiedemann 1830 collected, Zygothrica apopoeyi Burla 1956, Z. bilineata (Williston 1896), Z. dispar (Wiedemann 1830), Z./ lanceolata Burla 1956, Z. nigropleura Grimaldi 1987, and Z. poeyi (Sturtevant 1921) were recorded for the first time in Santa Catarina state and, except for Z. bilineata, also in southern Brazil. Apart from these species, we also collected Zygothrica hypandriata Burla 1956, Z. orbitalis (Sturtevant 1916) (as Z. parilis), Z. prodispar Duda 1925 and Z. vittimaculosa Burla 1956. Except for Z. bilineata and Z. hypandriata, these are the new southernmost records for the geographical distribution of these species. All the collected species were represented by few individuals, probably as a consequence of the collection method, and most of them was captured in winters and springs. Five species were restricted to the more preserved studied site, and most individuals were collected in forest sites. Nevertheless, four species were also captured in urban or xeric environments, indicating a higher tolerance and a wider ecological versatility in this genus as compared to what was previously thought, at least for some species.

O presente estudo reúne dados de pesquisa de nove locais de coleta no estado de Santa Catarina, sul do Brasil. Foram obtidas amostras durante aproximadamente quatro anos em áreas florestais, litorâneas e urbanas. As moscas foram atraídas através de isca de banana fermentada e capturadas em armadilhas. Dentre as espécies do gênero Zygothrica Wiedemann 1830 coletadas, Zygothrica apopoeyi Burla 1956, Z. bilineata (Williston 1896), Z. dispar (Wiedemann 1830), Z. lanceolata Burla 1956, Z. nigropleura Grimaldi 1987, e Z./poeyi (Sturtevant 1921) foram registradas pela primeira vez no estado de Santa Catarina e, com exceção de Z. bilineata, também no sul do Brasil. Além destas espécies, também foram coletadas Zygothrica hypandriata Burla 1956, Z. orbitalis (Sturtevant 1916) (como Z. parilis), Z. prodispar Duda 1925 e Z. vittimaculosa Burla 1956. Com exceção de Z. bilineata e Z. hypandriata, estes registros representam os novos limites de distribuição geográfica sul para estas espécies. Todas as espécies coletadas foram representadas por poucos indivíduos, provavelmente como conseqüência do método de coleta, e a maioria delas foi capturada em invernos e primaveras. Cinco/espécies foram restritas ao local estudado mais preservado e a maioria dos indivíduos foi coletada em áreas de floresta. Entretanto, quatro espécies também foram capturadas em ambientes urbanos ou xéricos, indicando uma tolerância mais alta e uma versatilidade ecológica mais ampla do que previamente era pensado para este gênero, pelo menos para algumas de suas espécies.

Transposable elements P and gypsy in natural populations of Drosophila willistoni

The presence and integrity of the P transposon and the gypsy retrotransposon in the genome of 18 samples of natural Drosophila willistoni populations collected from a large area of South America were Southern blot screened using Drosophila melanogaster probes. The aim of this screening was provide further knowledge-base on the geographical distribution of D. willistoni and to carry out an inter-population analysis of the P and gypsy elements present in the genomes of the populations analyzed. The fragment patterns obtained indicate that both the P and gypsy elements are ancient in the D. willistoni genome, but whereas the gypsy retroelement appears to be invariable and stable the P element varies between populations and appears to still have some capacity for mobilization.

Chromosomal polymorphism in Drosophila willistoni populations from Uruguay

Chromosomal polymorphism in natural populations of Drosophila willistoni from Uruguay and southern Brazil was investigated in order to understand the genetic characteristics and evolutionary potential of these almost geographically marginal populations. The level of chromosomal polymorphism in samples from Uruguay was higher than in those from the southernmost Brazilian state of Rio Grande do Sul. The increase in the polymorphism of these populations, in which the species almost reaches its southern limit, contradicts the low level of paracentric inversion polymorphism expected under the central-marginal chromosomal polymorphism cline previously reported. The high frequency of some inversions and the presence of unique inversions in samples from Uruguay indicate the uniqueness of these populations