Desmodium raymundoramirezii L. Torres-Colín y A. Delgado is here described and illustrated. Plants of this taxon were found growing in oak-pine, and pine forests and in transitional areas of both with montane cloud forest of Sierra Madre del Sur in the Mexican states of Guerrero and Oaxaca. This species is morphologically similar to D. cordistipulum Hemsl. forma cordistipulum, both with lanceolate leaflets and amplexicaul stipules, but differs from it by occasionally developing 5 leaflets per leaf (attribute not known in Mexican Desmodium species), rachis longer than petiole, flowers 3-5 per node, and loments usually flat with the margins alternately revolute and involute when immature. These differences were supported by molecular evidence.

Se describe e ilustra Desmodium raymundoramirezii L. Torres-Colín y A. Delgado. Las plantas de este taxón fueron recolectadas creciendo en bosque de Pinus-Quercus, bosque de Pinus y zonas de ecotonía con bosque mesófilo en la sierra Madre del Sur, en los estados de Guerrero y Oaxaca, México. Morfológicamente y en estado vegetativo es muy parecida a D. cordistipulum Hemsl. forma cordistipulum, por los folíolos lanceolados y las estípulas amplexicaules, pero se diferencia de esta por desarrollar en ocasiones 5 folíolos, atributo nunca antes visto en especies mexicanas del género, por el raquis más largo que el pecíolo, 3-5 flores por nudo y lomentos generalmente planos con los márgenes revolutos e involutos cuando inmaduros; diferencias también apoyadas por evidencia molecular.

Two allelic genomic fragments containing ribosomal protein S4 encoding genes (rpS4) from Trypanosoma cruzi (CL-Brener strain) were isolated and characterized. One allele comprises two complete tandem repeats of a sequence encoding an rpS4 gene. In the other, only one rpS4 gene is found. Sequence comparison to the accessed data in the genome project database reveals that our two-copy allele corresponds to a variant haplotype. However, the deduced aminoacid sequence of all the gene copies is identical. The rpS4 transcripts processing sites were determined by comparison of genomic sequences with published cDNA data. The obtained sequence data demonstrates that rpS4 genes are expressed in epimastigotes, amastigotes, and trypomastigotes. A recombinant version of rpS4 was found to be an antigenic: it was recognized by 62.5% of the individuals with positive serology for T. cruzi and by 93.3% of patients with proven chronic chagasic disease.