Search for: All records

Abstract Flat hydrodynamic shells likely represent an evolutionary trade-off between adaptation to an aquatic lifestyle and the instability of more rounded shells, thought beneficial for self-righting. Trade-offs often result in compromises, this is particularly true when freshwater turtles, with flatter shells, must self-right to avoid the negative effects of inverting. These turtles, theoretically, invest more biomechanical effort to achieve successful and timely self-righting when compared to turtles with rounded carapaces. This increase in effort places these hatchlings in a precarious position; prone to inversion and predation and with shells seemingly maladapted to the act of self-righting. Here, we examine hatchling self-righting performance in three morphologically distinct freshwater turtle species (Apalone spinifera,Chelydra serpentinaandTrachemys scripta scripta) that inhabit similar environmental niches. We demonstrate that these hatchlings were capable of rapid self-righting and used considerably less biomechanical effort relative to adult turtles. Despite differences in shell morphology the energetic efficiency of self-righting remained remarkably low and uniform between the three species. Our results confound theoretical predictions of self-righting ability based on shell shape metrics and indicate that other morphological characteristics like neck or tail morphology and shell material properties must be considered to better understand the biomechanical nuances of Testudine self-righting. 

1. Silica is crucial to terrestrial plant life and geochemical cycling on Earth. It is also implicated in the evolution of mammalian teeth, but there is debate over which type of siliceous particle has exerted the strongest selective pressure on tooth morphology. 2. Debate revolves around the amorphous silica bodies (phytoliths) present in plants and the various forms of siliceous grit—that is, crystalline quartz (sand, soil, dust)—on plant surfaces. The problem is that conventional measures of silica often quantify both particle types simultaneously. 3. Here we describe a protocol that relies on heavy-liquid flotation to separate and quantify siliceous particulate matter in the diets of herbivores. The method is reproducible and well suited to detecting species- or population-level differences in silica ingestion. In addition, we detected meaningful variation within the digestive tracts of cows, an outcome that supports the premise of ruminal fluid ‘washing’ of siliceous grit. 4. We used bootstrap resampling to estimate the sample sizes needed to compare species, populations or individuals in space and time. We found that a minimum sample of 12 individuals is necessary if the species is a browser or as many as 55 if the species is a grazer, which are more variable. But a sample size of 20 is adequate for detecting statistical differences. We conclude by suggesting that our protocol for differentiating and quantifying silica holds promise for testing competing hypotheses on the evolution of dental traits. 

Abstract Bone surface modifications are crucial for understanding human subsistence and dietary behaviour, and can inform about the techniques employed in the production and use of bone tools. Permission to destructively sample such unique artefacts is not always granted. The recent development of non-destructive proteomic extraction techniques has provided some alternatives for the analysis of rare and culturally significant artefacts, including bone tools and personal ornaments. The Eraser Extraction Method (EEM), first developed for ZooMS analysis of parchment, has recently been applied to bone and ivory specimens. To test the potential impact of the EEM on ancient bone surfaces, we analyse six anthropogenically modified Palaeolithic bone specimens from Bacho Kiro Cave (Bulgaria) through a controlled sampling experiment using qualitative and 3D quantitative microscopy. Although the overall bone topography is generally preserved, our findings demonstrate a slight flattening of the microtopography alongside the formation of micro-striations associated with the use of the eraser for all bone specimens. Such modifications are similar to ancient use-wear traces. We therefore consider the EEM a destructive sampling approach for Palaeolithic bone surfaces. Together with low ZooMS success rates in some of the reported studies, the EEM might not be a suitable approach to taxonomically identify Pleistocene bone specimens.