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Philosophical Transactions of the Royal... Feb 2017One of the most amazing transitions and innovations during the evolution of mammals was the formation of a novel jaw joint and the incorporation of the original jaw... (Review)
Review
One of the most amazing transitions and innovations during the evolution of mammals was the formation of a novel jaw joint and the incorporation of the original jaw joint into the middle ear to create the unique mammalian three bone/ossicle ear. In this review, we look at the key steps that led to this change and other unusual features of the middle ear and how developmental biology has been providing an understanding of the mechanisms involved. This starts with an overview of the tympanic (air-filled) middle ear, and how the ear drum (tympanic membrane) and the cavity itself form during development in amniotes. This is followed by an investigation of how the ear is connected to the pharynx and the relationship of the ear to the bony bulla in which it sits. Finally, the novel mammalian jaw joint and versatile dentary bone will be discussed with respect to evolution of the mammalian middle ear.This article is part of the themed issue 'Evo-devo in the genomics era, and the origins of morphological diversity'.
Topics: Animals; Biological Evolution; Birds; Ear, Middle; Mammals; Reptiles
PubMed: 27994124
DOI: 10.1098/rstb.2015.0483 -
American Journal of Physiology.... Jan 2015The diving physiology of aquatic animals at sea began 50 years ago with studies of the Weddell seal. Even today with the advancements in marine recording and tracking... (Review)
Review
The diving physiology of aquatic animals at sea began 50 years ago with studies of the Weddell seal. Even today with the advancements in marine recording and tracking technology, only a few species are suitable for investigation. The first experiments were in McMurdo Sound, Antarctica. In this paper are examples of what was learned in Antarctica and elsewhere. Some methods employed relied on willingness of Weddell seals and emperor penguins to dive under sea ice. Diving depth and duration were obtained with a time depth recorder. Some dives were longer than an hour and as deep as 600 m. From arterial blood samples, lactate and nitrogen concentrations were obtained. These results showed how Weddell seals manage their oxygen stores, that they become reliant on a positive contribution of anaerobic metabolism during a dive duration of more than 20 min, and that nitrogen blood gases remain so low that lung collapse must occur at about 25 to 50 m. This nitrogen level was similar to that determined in elephant seals during forcible submersion with compression to depths greater than 100 m. These results led to further questions about diving mammal's terminal airway structure in the lungs. Much of the strengthening of the airways is not for avoiding the "bends," by enhancing lung collapse at depth, but for reducing the resistance to high flow rates during expiration. The most exceptional examples are the small whales that maintain high expiratory flow rates throughout the entire vital capacity, which represents about 90% of their total lung capacity.
Topics: Animals; Diving; Dolphins; Humans; Lung; Oxygen; Seals, Earless; Spheniscidae; Whales
PubMed: 25411360
DOI: 10.1152/ajpregu.00264.2014 -
Current Biology : CB Jun 2023Within mammals, different reproductive strategies (e.g., egg laying, live birth of extremely underdeveloped young, and live birth of well-developed young) have been...
Within mammals, different reproductive strategies (e.g., egg laying, live birth of extremely underdeveloped young, and live birth of well-developed young) have been linked to divergent evolutionary histories. How and when developmental variation across mammals arose is unclear. While egg laying is unquestionably considered the ancestral state for all mammals, many long-standing biases treat the extreme underdeveloped state of marsupial young as the ancestral state for therian mammals (clade including both marsupials and placentals), with the well-developed young of placentals often considered the derived mode of development. Here, we quantify mammalian cranial morphological development and estimate ancestral patterns of cranial shape development using geometric morphometric analysis of the largest comparative ontogenetic dataset of mammals to date (165 specimens, 22 species). We identify a conserved region of cranial morphospace for fetal specimens, after which cranial morphology diversified through ontogeny in a cone-shaped pattern. This cone-shaped pattern of development distinctively reflected the upper half of the developmental hourglass model. Moreover, cranial morphological variation was found to be significantly associated with the level of development (position on the altricial-precocial spectrum) exhibited at birth. Estimation of ancestral state allometry (size-related shape change) reconstructs marsupials as pedomorphic relative to the ancestral therian mammal. In contrast, the estimated allometries for the ancestral placental and ancestral therian were indistinguishable. Thus, from our results, we hypothesize that placental mammal cranial development most closely reflects that of the ancestral therian mammal, while marsupial cranial development represents a more derived mode of mammalian development, in stark contrast to many interpretations of mammalian evolution.
Topics: Pregnancy; Animals; Female; Marsupialia; Biological Evolution; Placenta; Mammals; Skull
PubMed: 37119816
DOI: 10.1016/j.cub.2023.04.009 -
ELife Sep 2017Many developmental functions in marsupials and eutherian mammals are accomplished by different tissues, but similar genes.
Many developmental functions in marsupials and eutherian mammals are accomplished by different tissues, but similar genes.
Topics: Animals; Eutheria; Evolution, Molecular; Female; Gene Expression Regulation, Developmental; Humans; Lactation; Mammals; Mammary Glands, Human; Marsupialia; Placentation; Pregnancy
PubMed: 28895533
DOI: 10.7554/eLife.30994 -
Proceedings. Biological Sciences Feb 2019Dung beetles are increasingly used as a study taxon-both as bioindicators of environmental change, and as a model system for exploring ecosystem functioning. The... (Review)
Review
Dung beetles are increasingly used as a study taxon-both as bioindicators of environmental change, and as a model system for exploring ecosystem functioning. The advantages of this focal taxon approach are many; dung beetles are abundant in a wide range of terrestrial ecosystems, speciose, straightforward to sample, respond to environmental gradients and can be easily manipulated to explore species-functioning relationships. However, there remain large gaps in our understanding of the relationship between dung beetles and the mammals they rely on for dung. Here we review the literature, showing that despite an increase in the study of dung beetles linked to ecosystem functioning and to habitat and land use change, there has been little research into their associations with mammals. We summarize the methods and findings from dung beetle-mammal association studies to date, revealing that although empirical field studies of dung beetles rarely include mammal data, those that do, indicate mammal species presence and composition has a large impact on dung beetle species richness and abundance. We then review the methods used to carry out diet preference and ecosystem functioning studies, finding that despite the assumption that dung beetles are generalist feeders, there are few quantitative studies that directly address this. Together this suggests that conclusions about the effects of habitat change on dung beetles are based on incomplete knowledge. We provide recommendations for future work to identify the importance of considering mammal data for dung beetle distributions, composition and their contributions to ecosystem functioning; a critical step if dung beetles are to be used as a reliable bioindicator taxon.
Topics: Animals; Biodiversity; Coleoptera; Ecosystem; Feces; Food Chain; Mammals
PubMed: 30963853
DOI: 10.1098/rspb.2018.2002 -
PeerJ 2023Southern Mexico's tropical forests are home to the country's highest richness of mammal species; La Chinantla region is situated within this area, its name from the...
Southern Mexico's tropical forests are home to the country's highest richness of mammal species; La Chinantla region is situated within this area, its name from the indigenous group residing in the area and holding territorial ownership, namely the Chinantecos. In La Chinantla, there are no Protected Areas; instead, there are Areas Destined Voluntarily for Conservation (ADVC) and "Voluntary Conservation Areas" (VCA), that are managed by local inhabitants through social consensus. These ADVC may function as an archipelago reserve, which represents regional diversity, including the social context, through complementarity. To verify its biodiversity, we analyzed the richness, composition, distribution, and conservation of wild mammals in the region. Records were obtained from four sources-primary data collection, databases, scientific literature, and community monitoring-and were organized into four zones based on altitudinal and vegetation gradients. We compared the diversity between zones for three categories of mammals: small (<100 gr.), bats, and medium and large (>100 gr.). 134 species were identified comprising 11 orders, 26 families and 86 genera. The zone with highest elevation presented the greatest species richness for the assemblage of mammals and terrestrial mammals, while the zone with the lowest elevation had the highest richness of bats. For each mammal category, the zone with the most species also registered the highest number of exclusive species. For the assemblage of mammals and for medium and large mammals, the similarity index was highest between the two intermediate zones, while for small mammals and bats, the greatest similarity occurred between the areas of higher altitude. The study region was found to have the second highest richness of mammals in Mexico. Finally, we suggest that the conservation proposals by indigenous people could function as a set of "islands" that promote the conservation of biodiversity, possibly as an Archipelago Reserve.
Topics: Humans; Animals; Chiroptera; Mexico; Biodiversity; Mammals; Forests
PubMed: 37953770
DOI: 10.7717/peerj.16345 -
Ecological Applications : a Publication... Jan 2023Landscape-scale deforestation poses a major threat to global biodiversity, not only because it limits habitat availability, but also because it can drive the degradation...
Landscape-scale deforestation poses a major threat to global biodiversity, not only because it limits habitat availability, but also because it can drive the degradation of the remaining habitat. However, the multiple pathways by which deforestation directly and indirectly affects wildlife remain poorly understood, especially for elusive forest-dependent species such as arboreal mammals. Using structural equation models, we assessed the direct and indirect effects of landscape forest loss on arboreal mammal assemblages in the Lacandona rainforest, Mexico. We placed camera traps in 100 canopy trees, and assessed the direct effect of forest cover and their indirect effects via changes in tree basal area and canopy openness on the abundance and diversity (i.e., species richness and exponential of Shannon entropy) of arboreal mammals. We found that forest loss had negative indirect effects on mammal richness through the increase of tree canopy openness. This could be related to the fact that canopy openness is usually inversely related to resource availability and canopy connectivity for arboreal mammals. Furthermore, independently of forest loss, the abundance and richness of arboreal mammals was positively related to tree basal area, which is typically higher in old-growth forests. Thus, our findings suggest that arboreal mammals generally prefer old-growth vegetation with relatively low canopy openness and high tree basal area. However, unexpectedly, forest loss was directly and positively related to the abundance and richness of mammals, probably due to a crowding effect, a reasonable possibility given the relatively short history (~40 years) of deforestation in the study region. Conversely, the Shannon diversity was not affected by the predictors we evaluated, suggesting that rare mammals (not the common species) are the ones most affected by these changes. All in all, our findings emphasize that conservation measures ought to focus on increasing forest cover in the landscape, and preventing the loss of large trees in the remaining forest patches.
Topics: Animals; Trees; Forests; Ecosystem; Biodiversity; Mammals
PubMed: 36106555
DOI: 10.1002/eap.2744 -
The Science of the Total Environment Jan 2023Invasive alien mammals cause huge adverse ecological impact on human society and natural ecosystems. Although studies have estimated economic costs of mammal invasions...
Invasive alien mammals cause huge adverse ecological impact on human society and natural ecosystems. Although studies have estimated economic costs of mammal invasions at regional scales, there is lacking the large-scale comprehensive assessment of currency costs for this taxon. Here, we estimated the economic cost of invasive alien mammals on a global scale using the most comprehensive global database compiling economic costs of invasive species (InvaCost). From 1960 to 2021, mammal invasions caused costs (summing damage costs and management costs) of US$ 462.49 billion to the global economy, while the total amount of robust costs reached US$ 52.49 billion. The majority of the total economic costs corresponded to damage costs (90.27 %), while only 7.43 % were related to management cost. Economic costs showed an increasing trend over time. The distribution of costs was uneven among taxonomic groups and regions, with the global total cost highly biasing toward to 5 species (European rabbit, Domestic cat, Black rat, Wild boar and Coypu), and North America reporting much higher costs (60.78 % of total economic costs) than other regions. The total costs were borne by agriculture, environment, authorities stakeholders and other sectors. Geographic and taxonomic biases suggested that total economic costs caused by invasive alien mammals were underestimated. Integrated research efforts are needed to fill in knowledge gaps in the economic costs generated by mammal invasions and to identify the drivers of the economic costs.
Topics: Animals; Cats; Rabbits; Agriculture; Ecosystem; Introduced Species; Mammals; North America
PubMed: 36265628
DOI: 10.1016/j.scitotenv.2022.159479 -
Proceedings. Biological Sciences Mar 2012Decompression sickness (DCS; 'the bends') is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers.... (Review)
Review
Decompression sickness (DCS; 'the bends') is a disease associated with gas uptake at pressure. The basic pathology and cause are relatively well known to human divers. Breath-hold diving marine mammals were thought to be relatively immune to DCS owing to multiple anatomical, physiological and behavioural adaptations that reduce nitrogen gas (N(2)) loading during dives. However, recent observations have shown that gas bubbles may form and tissue injury may occur in marine mammals under certain circumstances. Gas kinetic models based on measured time-depth profiles further suggest the potential occurrence of high blood and tissue N(2) tensions. We review evidence for gas-bubble incidence in marine mammal tissues and discuss the theory behind gas loading and bubble formation. We suggest that diving mammals vary their physiological responses according to multiple stressors, and that the perspective on marine mammal diving physiology should change from simply minimizing N(2) loading to management of the N(2) load. This suggests several avenues for further study, ranging from the effects of gas bubbles at molecular, cellular and organ function levels, to comparative studies relating the presence/absence of gas bubbles to diving behaviour. Technological advances in imaging and remote instrumentation are likely to advance this field in coming years.
Topics: Animals; Behavior, Animal; Decompression; Decompression Sickness; Diving; Humans; Hydrostatic Pressure; Kinetics; Mammals; Nitrogen; Stress, Physiological
PubMed: 22189402
DOI: 10.1098/rspb.2011.2088 -
Developmental Biology Aug 2017Adult stem cells self-renew and replenish differentiated cells in various organs and tissues throughout a mammal's life. Over the last 25 years an ever-growing body of... (Review)
Review
Adult stem cells self-renew and replenish differentiated cells in various organs and tissues throughout a mammal's life. Over the last 25 years an ever-growing body of knowledge has unraveled the essential regulation of adult mammalian epithelia by the canonical Wnt signaling with its key intracellular effector β-catenin. In this review, we discuss the principles of the signaling pathway and its role in adult epithelial stem cells of the intestine and skin during homeostasis and tumorigenesis. We further highlight the research that led to the identification of new stem cell markers and methods to study adult stem cells ex vivo.
Topics: Adult Stem Cells; Animals; Cell Self Renewal; Epidermal Cells; Epidermis; Epithelial Cells; Humans; Intestinal Mucosa; Models, Biological; Wnt Signaling Pathway; beta Catenin
PubMed: 28526587
DOI: 10.1016/j.ydbio.2017.05.015