Architecture of a nanocrystalline biomineralised shell

<p>Marginopora sp. is an eukaryotic large benthic foraminifera that biomineralises a high magnesium calcitic test (shell) in which dinoflagellate symbionts are stored. The discoidal test has a complex architecture; a very large cellular organism expends considerable energy to assemble and maintain a complex shell. What does the organism realise from this architecture? What are the elemental features of the architecture? Researchers have studied the test’s microstructures and chemical composition; its functional value has been suggested but an endeavour to pinpoint any particular value can be extremely complicated in a biological structure, i.e. an intractable problem is presented. Form is related to and often determines the adaptive functional value of biological structures; an enhanced understanding of form precedes and informs an understanding of function. This work increases an understanding of the form and functional value of the complex architecture of the test. Particularly, it adds to existing knowledge by: extending to a nanoscale a detailed characterization of the microstructures of the test, revealing calcium carbonate nanostructures and their associations to form crystals; conceptualising and applying a hierarchical arrangement of the microstructures across nano-macro dimensions of scale; visualising in three dimensions (3D) the microstructures of the test through ontogeny to reveal anisotropy and symmetry in the morphology of microstructures and in the test; and discovering and interpreting structural patterns that were previously not visible. Based upon these findings, the architecture and microstructures of the test; properties of biomineralised structures such as bone and echinoderm skeletons; structural arrangement of adequate models; and predominantly the mechanical adaptive value of the test are correlated. This thesis advances ideas and suggestions for research, design and practical applications of the structural principles abstracted from these findings and interpretations towards a biomimetic design of structures and processes. A combination of advanced microscopy techniques at higher resolutions and magnifications than previously used in the research of the test were used to evaluate pristine specimens of the test of Marginopora sp. Data and images obtained by the use of high resolution and cryo-scanning electron microscopy, transmission electron microscopy, polarising microscopy and, X-ray micro computed tomography (X-ray MCT) of several specimens representing different ontogenic stages were analysed. Especially, the applicability of X-ray MCT as a technique was tested for the quantitative and qualitative analysis of 3D features of the test. Visualisation and statistical techniques used in network analysis were applied to the data obtained by X-ray MCT. A materials sciences approach was adopted towards interpreting the nano-macro scale structural features of the test. In lieu of a protracted and difficult experimental approach a method used in the field of artificial intelligence was adopted to find models that could adequately point to the adaptive value of the architecture of the test. Results obtained using this approach indicated that the adaptive values are self-assembly in a phyllotactic pattern that allows an effective mechanical flexural response using a minimum of materials; close-packing of a particular pore volume; and that enables large surface areas and transmission of light through a 3D biconcave disc.</p>

Architecture of a nanocrystalline biomineralised shell

<p>Marginopora sp. is an eukaryotic large benthic foraminifera that biomineralises a high magnesium calcitic test (shell) in which dinoflagellate symbionts are stored. The discoidal test has a complex architecture; a very large cellular organism expends considerable energy to assemble and maintain a complex shell. What does the organism realise from this architecture? What are the elemental features of the architecture? Researchers have studied the test’s microstructures and chemical composition; its functional value has been suggested but an endeavour to pinpoint any particular value can be extremely complicated in a biological structure, i.e. an intractable problem is presented. Form is related to and often determines the adaptive functional value of biological structures; an enhanced understanding of form precedes and informs an understanding of function. This work increases an understanding of the form and functional value of the complex architecture of the test. Particularly, it adds to existing knowledge by: extending to a nanoscale a detailed characterization of the microstructures of the test, revealing calcium carbonate nanostructures and their associations to form crystals; conceptualising and applying a hierarchical arrangement of the microstructures across nano-macro dimensions of scale; visualising in three dimensions (3D) the microstructures of the test through ontogeny to reveal anisotropy and symmetry in the morphology of microstructures and in the test; and discovering and interpreting structural patterns that were previously not visible. Based upon these findings, the architecture and microstructures of the test; properties of biomineralised structures such as bone and echinoderm skeletons; structural arrangement of adequate models; and predominantly the mechanical adaptive value of the test are correlated. This thesis advances ideas and suggestions for research, design and practical applications of the structural principles abstracted from these findings and interpretations towards a biomimetic design of structures and processes. A combination of advanced microscopy techniques at higher resolutions and magnifications than previously used in the research of the test were used to evaluate pristine specimens of the test of Marginopora sp. Data and images obtained by the use of high resolution and cryo-scanning electron microscopy, transmission electron microscopy, polarising microscopy and, X-ray micro computed tomography (X-ray MCT) of several specimens representing different ontogenic stages were analysed. Especially, the applicability of X-ray MCT as a technique was tested for the quantitative and qualitative analysis of 3D features of the test. Visualisation and statistical techniques used in network analysis were applied to the data obtained by X-ray MCT. A materials sciences approach was adopted towards interpreting the nano-macro scale structural features of the test. In lieu of a protracted and difficult experimental approach a method used in the field of artificial intelligence was adopted to find models that could adequately point to the adaptive value of the architecture of the test. Results obtained using this approach indicated that the adaptive values are self-assembly in a phyllotactic pattern that allows an effective mechanical flexural response using a minimum of materials; close-packing of a particular pore volume; and that enables large surface areas and transmission of light through a 3D biconcave disc.</p>

Tricking Parents: A Review of Mechanisms and Signals of Host Manipulation by Brood-Parasitic Young

Obligate avian brood parasites depend entirely on heterospecific hosts for rearing their offspring. From hatching until independence, the young parasites must deal with the challenge of obtaining sufficient parental care from foster parents that are attuned to provisioning their own offspring. Parent-offspring communication is mediated by complex begging displays in which nestlings and fledglings exhibit visual (e.g., gaping and postures) and vocal (e.g., begging calls) traits that serve as signals to parents to adjust and allocate parental effort. Parasites can manipulate host parental behavior by exploiting these stable parent-offspring communication systems in their favor. During the past 30 years, the study of host exploitation by parasitic chicks has yielded important insights into the function and evolution of manipulative signals in brood parasites. However, despite these major advances, there are still important gaps in our knowledge about how parasitic nestling and fledglings tune into the host’s communication channels and the adaptive value of the visual and acoustic signals they exhibit. Here we review the literature pertaining to host manipulation by parasitic young, focusing on four non-mutually exclusive mechanisms (i.e., host chick mimicry, begging exaggeration, host-attuned begging calls, and sensory exploitation) and the function and evolution of the signals involved, with the aim to summarize and discuss putative adaptations for stimulating parental feeding and escaping host discrimination. Finally, we bring some concluding remarks and suggest directions for future research on the ways in which brood parasites adapt to the communication systems of other birds to exploit the necessary parental care.

Recursion: What is it, who has it, and how did it evolve?

Recursion is a topic of considerable controversy in linguistics, which stems from its varying definitions and its key features, such as its universality, uniqueness to human language, and evolution. Currently, there appear to be at least two common senses of recursion: (1) embeddedness of phrases within other phrases, which entails keeping track of long-distance dependencies among phrases and (2) the specification of the computed output string itself, including meta-recursion, where recursion is both the recipe for an utterance and the overarching process that creates and executes the recipes. There are also at least two evolutionary scenarios for the adaptive value of recursion in human language. The gradualist position posits precursors, such as animal communication and protolanguages, and holds that the selective purpose of recursion was for communication. The saltationist position assumes no gradual development of recursion and posits that it evolved for reasons other than communication. In the latter view, some heritable event associated with a cognitive prerequisite of language, such as Theory of Mind or working memory capacity, allowed recursive utterances. Evolutionary adaptive reasons for recursive thoughts were also proffered, including diplomatic speech, perlocutionary acts, and prospective cognitions.

Senescence as a trade-off between successful land colonisation and longevity: critical review and analysis of a hypothesis

Background Most common terrestrial animal clades exhibit senescence, suggesting strong adaptive value of this trait. However, there is little support for senescence correlated with specific adaptations. Nevertheless, insects, mammals, and birds, which are the most common terrestrial animal clades that show symptoms of senescence, evolved from clades that predominantly did not show symptoms of senescence. Thus, we aimed to examine senescence in the context of the ecology and life histories of the main clades of animals, including humans, and to formulate hypotheses to explain the causes and origin of senescence in the major clades of terrestrial animals. Methodology We reviewed literature from 1950 to 2020 concerning life expectancy, the existence of senescence, and the adaptive characteristics of the major groups of animals. We then proposed a relationship between senescence and environmental factors, considering the biology of these groups of animals. We constructed a model showing the phylogenetic relationships between animal clades in the context of the major stages of evolution, distinguishing between senescent and biologically ‘immortal’ clades of animals. Finally, we synthesised current data on senescence with the most important concepts and theories explaining the origin and mechanisms of senescence. Although this categorisation into different senescent phenotypes may be simplistic, we used this to propose a framework for understanding senescence. Results We found that terrestrial mammals, insects, and birds show senescence, even though they likely evolved from non-senescent ancestors. Moreover, secondarily aquatic animals show lower rate of senescence than their terrestrial counterparts. Based on the possible life histories of these groups and the analysis of the most important factors affecting the transition from a non-senescent to senescent phenotype, we conclude that aging has evolved, not as a direct effect, but as a correlated response of selection on developmental strategies, and that this occurred separately within each clade. Adoption of specific life history strategies could thus have far-reaching effects in terms of senescence and lifespan. Conclusions Our analysis strongly suggests that senescence may have emerged as a side effect of the evolution of adaptive features that allowed the colonisation of land. Senescence in mammals may be a compromise between land colonisation and longevity. This hypothesis, is supported by palaeobiological and ecological evidence. We hope that the development of new research methodologies and the availability of more data could be used to test this hypothesis and shed greater light on the evolution of senescence.

Testing olfaction in equids: Age and gestational stage affects olfactory interest

In spite of the highly developed olfactory apparatus of horses, implying a high adaptive value, research on equine olfaction is sparse. Our limited knowledge poses a risk that horse behaviour does not match human expectations. The benefit of acquiring more knowledge of equine olfaction is therefore twofold; 1) it can aid the understanding of horse behaviour and hence reduce the risk of dangerous situations, and 2) there may be unexploited potential of using odours in several practical situations where humans interact with horses. This study investigated olfactory abilities of, 35 Icelandic, horses who were presented to four odours: peppermint, orange, lavender and cedarwood. The response variables were sniffing duration per presentation and behavioural reaction (licking, biting, snorting, and backing). Results showed horses were able to detect and distinguish between all four odours and showed increased interest (significantly longer sniffing duration) for peppermint. More horses expressed licking behaviour when presented to peppermint compared to cedarwood and lavender. Young horses sniffed cedarwood for longer than old horses, and pregnant mares sniffed lavender less than non-pregnant mares. In conclusion, the test paradigm seemed meaningful for horses, and olfactory interest of horses varied with age and gestational status but not sex.

Initial developmental rate delay in modern highly productive cultivars of winter bread wheat from West Europe

Aim. To evaluate the vernalization requirement duration and sensitivity to photoperiod in the set of modern high yielding winter bread wheat cultivars from West Europe which are proposed for production in Ukraine. Methods. Planting in natural and shortened photoperiods followed by artificial vernalizing variants of 5-days green seedlings have been used for heading dates registration. Results. Many foreign cultivars revealed the durable vernalization requirement and strong photosensitivity. Few stocks were characterized by the week analogous physiological reactions, which are typical in most modern Ukrainian cultivars and breeding lines. Conclusions. Reveled data confirmed the adaptive value of discussed properties for specific environment which are similar to Ukrainian one in many zones of winter wheat cultivation. And they refute the assertion that strong photosensitivity and durable vernalization requirement limit the improvement of yield potential by selection. Keywords: winter bread wheat, vernalization requirement, photosensitivity, modern cultivars from West Europe.