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Understanding the processes leading to fossilization

Modern death assemblages provide insights about the early stages of fossilization and useful ecological information about the species inhabiting the ecosystem. The results of taphonomic monitoring of modern vertebrate carcasses and bones from Doñana National Park, a Mediterranean coastal ecosystem in Andalusia, Spain, are presented. Ten different habitats were surveyed. Half of them occur in active depositional environments (marshland, lake margin, river margin, beach and dunes). Most of the skeletal remains belong to land mammals larger than 5 kg in body weight (mainly wild and feral ungulates). Overall, the Doñana bone assemblage shows good preservation with little damage to the bones, partly as a consequence of the low predator pressure on large vertebrates. Assemblages from active depositional habitats differ significantly from other habitats in terms of the higher incidence of breakage and chewing marks on bones in the latter, which result from scavenging, mainly by wild boar and red fox. The lake-margin and river-margin death assemblages have high concentrations of well preserved bones that are undergoing burial and offer the greatest potential to produce fossil assemblages. The spatial distribution of species in the Doñana death assemblage generally reflects the preferred habitats of the species in life. Meadows seem to be a preferred winter habitat for male deer, given the high number of shed antlers recorded there. This study is further proof that taphonomy can provide powerful insights to better understand the ecology of modern species and to infer past and future scenarios for the fossil record. informacion[at] Domingo et al (2020) Taphonomic information from the modern vertebrate death assemblage of Doñana National Park, Spain. PLOS ONE 15(11): e0242082. DOI 10.1371/journal.pone.0242082
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Epigenetics, human malaria, and mosquitoes

Epigenetics, human malaria, and mosquitoes

Plasmodium falciparum phenotypic plasticity is linked to the variant expression of clonal multigene families such as the var genes. This study examined changes in transcription and histones modifications that occur during sporogonic development of P. falciparum in the mosquito host. All var genes are silenced or transcribed at low levels in blood stages (gametocyte/rings) of the parasite in the human host. After infection of mosquitoes, a single var gene is selected for expression in the oocyst, and transcription of this gene increases dramatically in the sporozoite. The same PF3D7_1255200 var gene was activated in 4 different experimental infections. Transcription of this var gene during parasite development in the mosquito correlates with the presence of low levels of H3K9me3 at the binding site for the PF3D7_1466400 AP2 transcription factor. This chromatin state in the sporozoite also correlates with the expression of an antisense long non-coding RNA (lncRNA) that has previously been shown to promote var gene transcription during the intraerythrocytic cycle in vitro. Expression of both the sense protein coding transcript and the antisense lncRNA increase dramatically in sporozoites. The findings suggest a complex process for the activation of a single particular var gene that involves AP2 transcription factors and lncRNAs. informacion[at] Gómez-Díaz et al (2017) Epigenetic regulation of Plasmodium falciparum clonally variant gene expression during development in Anopheles gambiae. Sci Rep doi:10.1038/srep40655