RESUMEN

Melanaphis sorghi (Hemiptera: Aphididae), are an economically important pest to sorghum in the Americas. Previous studies have found that a super-clone that belongs to multilocus lineage (MLL)-F predominated in the U.S. from 2013 to 2018 and uses multiple hosts besides sorghum. In contrast, previous studies found that aphids in South America belong to MLL-C, but these studies only examined aphids collected from sugarcane. In this study we sought to determine if the superclone persisted in the U.S. in 2019-2020 and to determine the MLL of aphids found on sorghum in the largest country in South America, Brazil. Melanaphis spp. samples (121) were collected from the U.S. in 2019-2020 and Brazil in 2020 and were genotyped with 8-9 Melanaphis spp. microsatellite markers. Genotyping results showed that all samples from the U.S. in 2019 and Brazil in 2020 had alleles identical to the predominant superclone. Of the 52 samples collected in the U.S. in 2020, 50 samples were identical to the predominant super-clone (multilocus lineage-F; M. sorghi), while two samples from Texas differed from the super-clone by a single allele. The results demonstrated that the super-clone remains in the U.S. on sorghum, Johnsongrass, and giant miscanthus and is also present on sorghum within Brazil.

RESUMEN

The swine-origin influenza A (H1N1) virus that appeared in 2009 and was first found in human beings in Mexico, is a reassortant with at least three parents. Six of the genes are closest in sequence to those of H1N2 'triple-reassortant' influenza viruses isolated from pigs in North America around 1999-2000. Its other two genes are from different Eurasian 'avian-like' viruses of pigs; the NA gene is closest to H1N1 viruses isolated in Europe in 1991-1993, and the MP gene is closest to H3N2 viruses isolated in Asia in 1999-2000. The sequences of these genes do not directly reveal the immediate source of the virus as the closest were from isolates collected more than a decade before the human pandemic started. The three parents of the virus may have been assembled in one place by natural means, such as by migrating birds, however the consistent link with pig viruses suggests that human activity was involved. We discuss a published suggestion that unsampled pig herds, the intercontinental live pig trade, together with porous quarantine barriers, generated the reassortant. We contrast that suggestion with the possibility that laboratory errors involving the sharing of virus isolates and cultured cells, or perhaps vaccine production, may have been involved. Gene sequences from isolates that bridge the time and phylogenetic gap between the new virus and its parents will distinguish between these possibilities, and we suggest where they should be sought. It is important that the source of the new virus be found if we wish to avoid future pandemics rather than just trying to minimize the consequences after they have emerged. Influenza virus is a very significant zoonotic pathogen. Public confidence in influenza research, and the agribusinesses that are based on influenza's many hosts, has been eroded by several recent events involving the virus. Measures that might restore confidence include establishing a unified international administrative framework coordinating surveillance, research and commercial work with this virus, and maintaining a registry of all influenza isolates.

Asunto(s)

Evolución Molecular , Subtipo H1N1 del Virus de la Influenza A/genética , Gripe Humana/virología , Virus Reordenados/genética , Animales , Asia , Aves , Europa (Continente) , Humanos , Subtipo H1N1 del Virus de la Influenza A/aislamiento & purificación , Gripe Aviar/virología , México , América del Norte , Infecciones por Orthomyxoviridae/virología , Virus Reordenados/aislamiento & purificación , Porcinos , Enfermedades de los Porcinos/virología

RESUMEN

We have examined the embryonic development of the major neuromast lines of the lateral-line system in the urodele Ambystoma mexicanum both in vivo (using microsurgical techniques to transplant placodes) and in preserved embryos using scanning electron microscopy (SEM). We have compared this to SEM observations of embryos of the anuran Rana pipiens. We have determined the approximate locations of the lateral-line placodes in A. mexicanum and the approximate timing of both the migration of the lateral line primordia and the neuromast eruption in both species. We find that, at hatching, all primary neuromasts are present and fully formed in Ambystoma, while migration of the primordia is just beginning in Rana. The neuromast systems in both species are fully formed by the time feeding begins. If neuromast eruption is considered in relation to developmental events other than hatching, fewer differences are found between species, suggesting that hatching is precocious in Rana. We find no evidence of heterochrony to account for the morphological differences observed in these lateral-line systems. Orthogonal neuromasts on the head, a derived feature of urodeles, appears to be the result of lateral neuromast movement subsequent to the rostral migration of the primordia. This process was not observed in the anuran. In addition, we observe that ciliated epidermal cells disappear from the area immediately around each of the lines and suggest that neuromasts cause the regression of cilia in their immediate vicinity.

RESUMEN

In the Mexican axolotl (Ambystoma mexicanum), the pronephros begins to form at the four-somite stage. It is initially continuous with the posterior-lateral region of somite 2 and the lateral margin of somites 3 and 4. By the seven-somite stage, the pronephros has become compacted, and the cells are now morphologically distinct from the somitic cells. At this stage, a mass of loosely connected cells, apparently originating from the lateral mesoderm, is seen below somites 4 and 5. By the eight-somite stage, these presumptive duct cells have migrated dorsally to the duct path and are found below somites 5-7. By the nine-somite stage they have begun to migrate caudally.