Our laboratory is mainly interested in the molecular aspects of vitellogenesis in the Phylum Nematoda. Vitellogenesis is the process of reserve accumulation in oocytes of oviparous animals, mediated by lipoprotein carriers, called vitellogenins. We have focused our efforts during the last 20 years on the molecular characterization of vitellogenins of nematode species belonging to the order Rhabditida. Members of this order are microbiovores (animals that feed on microorganisms, mainly bacteria) free-living, zooparasites or phytoparasites. The two main models with free-living habits, which we use for our studies, are Caenorhabditis elegans and Oscheius tipulae belonging to the suborder Rhabditina. Analysis of the sequence of vitellogenins and elongation factor 1A of protein synthesis (eEF1A) showed that O. tipulae and C. elegans differ much more at the molecular than the morphological level. In collaboration with researchers from UENF (Universidade Estadual do Norte Fluminense) we have characterized two species of entomopathogenic nematodes isolated in the Amazon Rainforest, also belonging to the suborder Rhabditina, identified as members of the genus Heterorhabditis: H. baujardi and H. indica. Vitellogenins isolated from these nematodes have a polypeptide composition similar to that found in the two other Rhabditina analyzed. These nematodes have symbiotic enterobacteria of the genus Photorhabdus that are extremely pathogenic to insects. Presently we are characterizing the genome and secondary metabolites of a Photorhabdus strain isolated from one of those entomopathogenic nematodes. Recently we have extended our studies to a nematode of the genus Panagrolaimus (order Rhabditida, suborder Tylenchina), isolated from the banks of the Madeira River in Rondônia. Its vitellogenin polypeptides are different from that found in the Rhabditina previously studied by us. This strain of Panagrolaimus sp. is also able to survive under anhydrobiotic conditions, being the first with these features isolated in the Neotropical region