The aardvark is the last living Tubulidentata, an order of afrotherian mammals. Afrotheria is supported strongly by molecular analyses, yet sparingly by morphological characters. Moreover, the ...biology of the aardvark remains incompletely known. The inner ear, and its ontogeny in particular, has not been studied in details yet, though it bears key ecomorphological characters and phylogenetical signal. The aim of this study is to decipher and discuss the ontogenetic development of the different areas of the inner ear of Orycteropus afer. We focused in particular on their relative size and morphological rates of development. Specimens were scanned with 3D imaging techniques. 3D and 2D geometric morphometrics coupled with qualitative descriptions of the petrosal ossification allowed us to evidence several stages through development. Based on our sample, the cochlea is the first structure of the inner ear to reach adult size, but it is the last one to acquire its adult morphology close to parturition. In contrast, after a delayed growth spurt, the semicircular canals reach their mature morphology before the cochlea, concomitantly with the increase of petrosal ossification. The ontogeny of the aardvark inner ear shows similarities with that of other species, but the apex of the cochlea presents some autapomorphies.
This work constitutes a first step in the study of the ontogeny of this sensorial organ in Afrotheria.
X ray Micro Tomography coupled with Magnetic Resonance Imaging allowed us to explore the modalities of the acquisition of the mature shape of the inner ear of Orycteropus afer as well as to consider for the first time inter‐individual inner ear variability among adult aardvarks. The developmental steps for O. afer inner ear were compared with that of other vertebrates and we showed that it presents similarities with the inner ear ontogeny of other mammals but also peculiarities.
Rapid phenotypic evolution is observed in response to rapid environmental changes. These phenotypic variations can occur at different scales, from the population to the community. We intended to ...characterize these multiscale phenotypic responses in rodents from the archaeological site El Harhoura 2 (Rabat, Morocco), dated from the Late Pleistocene to the Holocene, and relate them to paleoenvironmental variations. Upper and lower first molars were used as proxies for phenotype. Their shape was quantified using a landmark-free method. To account for both intra- and interspecific variations, we used morpho-groups as phenotypic units. Those morpho-groups were identified using unsupervised clustering. Three shape indicators were computed: number of morpho-groups, morpho-group disparity and changes in morpho-group mean shape over time. To evaluate this little-used approach on small mammals, we compared it to three widely used biodiversity indices: number of taxa, Shannon index, and Simpson index. Phenotypic evolution between and within species was highlighted. Morpho-groups seemed to be phenotypic response units representing ecological groups that transversed species. Variations in the morpho-group mean shapes were partly related to paleoenvironmental changes; however, variations in disparity were not. Thus, environmental changes deduced from fossil microvertebrate communities did not seem to be the main determinants of the characterized phenotypic variations.
Lateralization of hand use in primates has been extensively studied in a variety of contexts, and starts to be investigated in other species and organs in order to understand the evolution of the ...laterality according to different tasks. In elephants, the orientation of the movements of the trunk has been observed mainly in feeding and social contexts, in free conditions. However, little is known about the influence of task complexity on trunk laterality. In this study, we compared the lateralization of the trunk in two conditions: standardized and free. We offered granules to six African elephants on each side of an opened trapdoor to create a constraining environment and reported the different behaviours employed and their orientation. In addition, we observed the same individuals in free conditions and noted the lateralization of the use of their trunk. We revealed a common right side preference in all our elephants, both in standardized and free conditions. This side bias was stronger in our constraining task, adding evidence for the task complexity theory. We finally described laterality in new behaviours in the literature on elephants, such as pinching, gathering or exploration with the trunk.
Modularity of the Neck in Birds (Aves) Terray, Léa; Plateau, Olivia; Abourachid, Anick ...
Evolutionary biology,
06/2020, Letnik:
47, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The neck connects the head and the trunk and is the key structure allowing all movements of the head. The neck morphology of birds is the most variable among living tetrapods, including significant ...differences in the number and shape of the cervical vertebrae. Despite these differences, according to the literature, three morphofunctional regions (i.e., modules) have been identified along the neck. However, this regionalization has not been quantitatively tested through a geometric morphometric approach applied to the cervical vertebrae. Based on the examination of 187 cervical vertebrae belonging to 16 species with various ecologies, we revealed a common modular structure of the neck using 3D surface geometric morphometrics. We adopted an approach without a priori clustering to identify modules along the neck. The phylogenetic influence on each module was tested. Then, each module was digitally reconstructed as a 3D vertebral model, and postural characteristics were studied. We characterized 9 modules: 7 are transpecific, being shared by at least 2 and up to 15 species. Two modules are specific to species with particularly long necks. The modularity pattern appears to be tightly linked to morphofunctional aspects and partially to phylogeny. In contrast, feeding ecology seems to be more closely related to the chaining of modules (the neck) than to the modules themselves. A study of postural properties revealed that each modular unit exhibits a characteristic curvature. Overall, the modular structure of the neck corresponds to the three traditional functional regions. However, the results also revealed unexpected pattern complexity, including subdivisions within these regions. The study of the patterns of modularity is therefore a relevant approach for challenging the three-functional-region hypothesis and allowed us to identify the structure of the diversity of the necks of birds.
Abstract
Acoustic communication is well-known in insects since the Mesozoic, but earlier evidence of this behavior is rare. Titanoptera, an ‘orthopteroid’ Permian-Triassic order, is one of the few ...candidates for Paleozoic intersex calling interactions: some specimens had highly specialized broadened zones on the forewings, which are currently considered—despite inconclusive evidence—as ‘resonators’ of a stridulatory apparatus. Here we argue that the stridulatory apparatus hypothesis is unlikely because the Titanoptera lack a stridulatory file on their bodies, legs or wings. Instead, comparing these broadened zones with similar structures in extant locusts, flies, and fossil damselflies, we find evidence that the Titanoptera used their wings to produce flashes of light and/or crepitated sounds. Moreover, we describe the first Carboniferous (~310 Mya) Titanoptera, which exhibits such specialized zones, thus corresponding to the oldest record of wing communication in insects. Whether these communication systems were used to attract sexual partners and/or escape predators remain to be demonstrated.
The jaw system in mammals is complex and different muscle morphotypes have been documented. Pigs are an interesting group of animals as they are omnivorous and have a bunodont crushing dentition. ...Moreover, they have interacted with humans for over 10,000 years and grow nearly two orders of magnitude in size. Despite being a model system for studies on cranial form and function, data on the growth of the jaw adductor muscles are scant. Moreover, whether captivity impacts the growth and architecture of the jaw adductors remains unknown. Based on dissection data of the jaw adductors of 45 animals ranging from less than 1 kg to almost 100 kg, we show that muscle masses, muscle fiber lengths, and cross‐sectional areas scale as predicted for geometrically similar systems or with slight negative allometry. Only the fiber length of the lateral pterygoid muscle grew with slight positive allometry. Animals raised in captivity in stalls or in an enclosure were overall very similar to wild animals. However, some muscles were larger in captive animals. Interestingly, variation in bite force in captive animals was well predicted by the variation in the size of the superficial masseter muscle relative to the overall jaw adductor mass.
We show that muscle masses, muscle fiber lengths, and cross‐sectional areas in wild boar scale as predicted for geometrically similar systems or with slight negative allometry. Animals raised in captivity in stalls or in an enclosure were overall very similar to wild animals.
The acquisition of habitual bipedal locomotion, which resulted in numerous modifications of the skeleton was a crucial step in hominid evolution. However, our understanding of the inherited skeletal ...modifications versus those acquired while learning to walk remains limited. We here present data derived from X‐rays and CT scans of quadrupedal adult humans and compare the morphology of the vertebral column, pelvis and femur to that of a bipedal brother. We show how a skeleton forged by natural selection for bipedal locomotion is modified when used to walk quadrupedally. The quadrupedal brother is characterised by the absence of femoral obliquity, a very high anteversion angle of the femoral neck, a very high collo‐diaphyseal angle and a very reduced lordosis. The differences in the pelvis are more subtle and complex, yet of functional importance. The modification of the ischial spines to an ischial ridge and the perfectly rounded shape of the sacral curvature are two unique features that can be directly attributed to a quadrupedal posture and locomotion. We propose a functional interpretation of these two exceptional modifications. Unexpectedly, the quadrupedal brother and sister show a greater angle of pelvic incidence compared to their bipedal brother, a trait previously shown to increase with learning to walk in bipedal subjects. Moreover, the evolution from an occasional towards a permanent bipedality has given rise to a functional association between the angle of pelvic incidence and the lumbar curvature, with high angles of incidence and greater lumbar curvature promoting stability during bipedal locomotion. The quadrupedal brother and sister with a high angle of incidence and a very reduced lordosis thus show a complete decoupling of this complex functional integration.
Three‐dimensional reconstruction of the pelvis and femur of the two brothers. (a) Frontal view of the bipedal brother. (b) Frontal view of the quadrupedal brother. The absence of femoral obliquity in the quadrupedal brother is clear.
Despite the considerable scientific interest in the variability and patterns of integration in the dog skull, how these patterns impact or are driven by function remains largely unexplored. Since the ...mandible is directly involved in mastication, it can be expected to be directly related to the development of the adductor and abductor muscles. Here, we explore whether variation in the architecture and size of the masticatory muscles is associated with the variation in mandibular shape in dogs. We obtained muscle data from the dissection of 48 dogs from different breeds and morphotypes to explore the architecture of the muscles and used 3D geometric morphometric approaches to quantify the shape of the mandible. Covariations between the masticatory muscles and mandibular shape were explored using two-block partial least square analyses (2B-PLS). Our results show there is a strong covariation between mandibular shape and masticatory muscles mass (rPLS from 0.70 to 0.74 for the first axis representing more than 90% of the total covariance) and physiological cross-sectional area (rPLS from 0.64 to 0.73 for the first axis representing more than 80% of the total covariance), irrespective of whether size is taken into account or not. These results suggest muscle size and thus attachment area requirements for individual muscles are likely drivers of mandibular shape. Moreover, mandible shape is likely to be a good predictor of muscle force. Finally, it appears that domestication of dogs has not resulted in a disuse phenotype characterized by a decoupling between form and function.
The Proboscideans, an order of mammals including elephants, are the largest of the Earth lands animals. One probable consequence of the rapid increase of their body size is the development of the ...trunk, a multitask highly sensitive organ used in a large repertoire of behaviours. The absence of bones in the trunk allows a substantial degree of freedom for movement in all directions, and this ability could underlie individual-level strategies. We hypothesised a stronger behavioural variability in simple tasks, and a correlation between the employed behaviours and the shape and size of the food. The observations of a captive group of African elephants allowed us to create a complete catalogue of trunk movements in feeding activities. We noted manipulative strategies and impact of food item properties on the performed behaviours. The results show that a given item is manipulated with a small panel of behaviours, and some behaviours are specific to a single shape of items. The study of the five main feeding behaviours emphasises a significant variability between the elephants. Each individual differed from every other individual in the proportion of at least one behaviour, and every behaviour was performed in different proportions by the elephants. Our findings suggest that during their lives elephants develop individual strategies adapted to the manipulated items, which increases their feeding efficiency.
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