It is fascinating that the amnion and serosa/chorion, two extraembryonic (EE) tissues that are characteristic of the amniote vertebrates (mammals, birds and reptiles), have also independently... Show moreIt is fascinating that the amnion and serosa/chorion, two extraembryonic (EE) tissues that are characteristic of the amniote vertebrates (mammals, birds and reptiles), have also independently evolved in insects. In this review, we offer the first detailed, macroevolutionary comparison of EE development and tissue biology across these animal groups. Some commonalities represent independent solutions to shared challenges for protecting the embryo (environmental assaults, risk of pathogens) and supporting its development, including clear links between cellular properties (e.g. polyploidy) and physiological function. Further parallels encompass developmental features such as the early segregation of the serosa/chorion compared to later, progressive differentiation of the amnion and formation of the amniotic cavity from serosal-amniotic folds as a widespread morphogenetic mode across species. We also discuss common developmental roles for orthologous transcription factors and BMP signalling in EE tissues of amniotes and insects, and between EE and cardiac tissues, supported by our exploration of new resources for global and tissue-specific gene expression. This highlights the degree to which general developmental principles and protective tissue features can be deduced from each of these animal groups, emphasizing the value of broad comparative studies to reveal subtle developmental strategies and answer questions that are common across species.This article is part of the theme issue 'Extraembryonic tissues: exploring concepts, definitions and functions across the animal kingdom'. Show less
Archaeologists encounter cultural deposits on a daily basis. One possible method for demonstrating formation processes, and potential contextual re-positioning of particular deposits is by looking... Show moreArchaeologists encounter cultural deposits on a daily basis. One possible method for demonstrating formation processes, and potential contextual re-positioning of particular deposits is by looking at arthropod remains. Many members of this phylum are likely to be preserved in the archaeological record due to their sturdy chitinous exoskeletons. They are highly abundant in practically any habitat, which makes them very suitable for formational reconstructions. This article proposes a conceptual model to link arthropod assemblages to cultural formation processes. By defining the systemic contexts as domestic, peridomestic and natural, and the archaeological context as an urban archaeological pit containing waste, the movement of deposits can be traced through the ecological implications of the present arthropod remains. The distance between the original systemic context and the archaeological context defines four different sub-assemblages. These are then further divided into groups that show the relationship with human activities to separate the natural from the cultural formation process and indicate the type of deposit based on synanthropicity. Furthermore, a number of niche groups are distinguished to indicate the material contents and characteristics of a deposit. Reconstructing the origins and characteristics of these deposits allow for a better understanding of site formations and the functions of pits. Especially when there is no visible stratigraphic succession at the time of excavation, high resolution ecological information can shed light on the stratigraphy of a pit. Show less
