Thelastoma vanwaerebekei n. sp. (Oxyurida: Thelastomatidae) a parasite of Gymnetis litigiosa (Coleoptera: Scarabaeidae) from Uruguay.

Thelastoma vanwaerebekei n. sp. was extracted from the hindgut of Gymnetis litigiosa. The new species is included in the group of species with females having the excretory pore at the same level as the pharyngeal basal bulb (or slightly anteriorly), long tail length (approximately 30% of total body length) and males without spicules. Females of T. vanwaerebekei n. sp. differ from those of T. madecassum in tail shape (filiform and conical, respectively). They differ from T. basiri, T. imphalensis and T. dessetae in the morphology of the anterior region. In females, pharyngeal length is shorter than in T. depressum. In males, T. vanwaerebekei n. sp. differs from T. blabericola in the tail length, and from T. raoi in the number of caudal papillae. The partial 18S SSU and 28S LSU rRNA gene regions were amplified.

Morphological and molecular characterisation of the entomoparasitic nematode Hammerschmidtiella diesingi (Nematoda, Oxyurida, Thelastomatidae).

A population of Hammerschmidtiella diesingi was detected in specimens of Periplaneta americana collected in Córdoba city (Argentina) was studied. Nematodes were characterized based on morphological, morphometric and genetic (D2-D3 expansion segment) analyses. New data are provided, especially on particular morphological characters that were a matter of controversy in previous studies. H. diesingi is reported in Argentina for the first time.

Structural organization of the mitochondrial DNA control region in Aedes aegypti.

The complete A+T - rich region of Aedes aegypti mitochondrial DNA has been cloned and sequenced. In Argentinean populations of the species, a polymorphism in the length of the amplified fragment was observed. Nucleotide sequence comparison of the shortest and longest A+T - rich amplified fragments detected revealed the presence of 2 types of tandemly repeated blocks. The size variation observed in natural populations is mainly due to the presence of a variable number of a 181 bp tandem repeat unit, located toward the 12S rRNA gene end. The size of the longest A+T - rich region was of 2070 bp, representing the largest control sequence reported for any mosquito species. Few relevant short blocks of primary-sequence similarity conserved in the control region of mosquitoes and other insects were detected scattered throughout the whole region. Five putative stem-loop secondary structures were found, one of them flanked by conserved sequences described in other insects. Our results suggest that there are no universal models of structure-function relations in the control region of insect mtDNA. In addition, we identified a short A+T - rich variable segment in the Ae. aegyti control region that would be suitable for population genetic studies.