Agnese Lanzetti

Species within the genus Cuterebra Clark, 1815 (Diptera: Oestridae: Cuterebrinae) are obligate parasites of rodents and other mammals during the larval stage, causing cutaneous myiasis. The internal larval anatomy of Cuterebra species remains unstudied, despite its potential utility for understanding their parasitic adaptations and for comparative studies with other Oestridae. The present study describes the internal larval anatomy of the species Cuterebra fontinella Clark, 1827 and Cuterebra americana (Fabricius, 1775), using micro-computed tomography-based virtual histological sections and 3-dimensional reconstructions. Both species show a broadly similar organization of the internal organs and tissues, with the digestive system being the main system within the hemocoel. The alimentary canal lacks gastric ceca and a crop; a condition shared with other Oestridae subfamilies, but which differs from the larvae of other Oestroidea families. The salivary glands are long and tubular, appearing morphologically distinct from those described in other Oestridae subfamilies thus far. The Malpighian tubules are uniformly thin and lack mineralized concretions, differing from the excretory organs of the oestrid species within the subfamily Oestrinae. The respiratory system shows little variation in relation to the basic tracheal scheme observed in the larvae of other cyclorrhaphous Diptera. Similarities and differences with the larvae of other Oestridae subfamilies and other Oestroidea families are discussed from a functional perspective, highlighting the value of nondestructive imaging techniques in comparative anatomical studies for contributing to a better understanding of the biology, evolution, and pathology of myiasis‑causing Diptera.

The Eurasian otter (Lutra lutra) exhibits the widest range among the Lutrinae, encompassing 11 extant subspecies across Eurasia and North Africa. However, recent mitochondrial DNA analyses have revealed distinct lineages that do not correspond to current subspecies classifications. To evaluate the degree of morphological divergence and identify populations potentially representing evolutionarily significant units, we used three-dimensional geometric morphometrics to examine 207 crania sampled across the species range. We digitized 30 anatomical landmarks along with nine curves using sliding semi-landmarks on three-dimensional models of crania. The morphometric analysis demonstrated significant differences in cranial size and shape between sexes and subspecies. Specifically, L. l. nair exhibited the most divergent cranial morphology and should be recognized as an evolutionarily significant unit. The Asian subspecies L. l. chinensis, L. l. barang, and L. l. nair displayed morphological affinities and were characterized by diverging traits from the nominal subspecies. Of the three subspecies described for the Transhimalaya, only L. l. aurobrunnea was clearly distinct from L. l. lutra. These patterns are likely to reflect evolutionary responses to ecological adaptation and geographical isolation, highlighting the need to explore the genetic structure of the Eurasian otter and reassess subspecies boundaries.

The Eurasian otter is a wide-ranging semi-aquatic mammal that underwent a significant population decline in the last century, leading to local extinctions, reduction and fragmentation of populations. The individuals of populations exposed to both external and internal stress may present the inability to produce a specific developmental outcome, generating developmental ‘noise’ (developmental instability (DI)). Factors contributing to DI include inbreeding depression, population bottlenecks, habitat loss and exposure to pollution. We analysed fluctuating asymmetry (FA) as a proxy of DI in two European otter populations that experienced a major decline in the 1990s. Using three-dimensional geometric morphometrics methods on skull samples of otters from the UK and Sweden, we compared the degree of FA both between populations before, during and after the decline. We found a higher FA in the UK populations compared with Sweden. The level of asymmetry differed significantly over time only in the UK population, where it was higher during the decline phase. FA in the UK populations can be attributed to the specific impact of polychlorinated biphenyls pollution that caused a bottleneck. More generally, our study suggests that habitat loss, pollution and limited gene flow may contribute to DI in declining otter populations, highlighting the need for continued investigation to identify and quantify the specific stressors behind this trend in local populations.

Intraspecific variation in cetacean vertebral anatomy as a result of ageing, growth, and sexual dimorphism is poorly understood. Using 3D geometric morphometrics, we investigated allometric patterns, sexual dimorphism, and ontogenetic trajectories in the vertebral column of false killer whale (Pseudorca crassidens). Our data set includes thoracic, lumbar, and caudal vertebrae of 30 specimens, including neonates, juveniles, and adults of both sexes. Vertebral shape was significantly correlated with size within each region. Neonatal vertebral shape differed significantly from juveniles and adults, displaying ontogenetic shape change. Allometric and growth patterns of the vertebral regions, particularly of the lumbar region with the thoracic and caudal regions, differed significantly, which may influence the function and mobility patterns of the vertebral regions during different life stages. Using quantitative methods, we could not conclude that the Pseudorca vertebrae are sexually dimorphic. This study describes for the first time intraspecific vertebral patterns in a cetacean species across ontogenetic stages. Pseudorca individuals live in large pods and swim together, sharing the same swimming mode. The neonates have a more flexible column and swim less efficiently following their mothers to nurse.

Attempts to explain the origin and diversification of vertebrates have commonly invoked the evolution of feeding ecology, contrasting the passive suspension feeding of invertebrate chordates and larval lampreys with active predation in living jawed vertebrates. Of the extinct jawless vertebrates that phylogenetically intercalate these living groups, the feeding apparatus is well-preserved only in the early diverging stem-gnathostome heterostracans. However, its anatomy remains poorly understood. Here, we use X-ray microtomography to characterize the feeding apparatus of the pteraspid heterostracan Rhinopteraspis dunensis (Roemer, 1855). The apparatus is composed of 13 plates arranged approximately bilaterally, most of which articulate from the postoral plate. Our reconstruction shows that the oral plates were capable of rotating around the transverse axis, but likely with limited movement. It also suggests the nasohypophyseal organs opened internally, into the pharynx. The functional morphology of the apparatus in Rhinopteraspis precludes all proposed interpretations of feeding except for suspension/deposit feeding and we interpret the apparatus as having served primarily to moderate the oral gape. This is consistent with evidence that at least some early jawless gnathostomes were suspension feeders and runs contrary to macroecological scenarios that envisage early vertebrate evolution as characterized by a directional trend towards increasingly active food acquisition.

Synopsis: Artificial intelligence (AI) is poised to revolutionize many aspects of science, including the study of evolutionary morphology. While classical AI methods such as principal component analysis and cluster analysis have been commonplace in the study of evolutionary morphology for decades, recent years have seen increasing application of deep learning to ecology and evolutionary biology. As digitized specimen databases become increasingly prevalent and openly available, AI is offering vast new potential to circumvent long-standing barriers to rapid, big data analysis of phenotypes. Here, we review the current state of AI methods available for the study of evolutionary morphology, which are most developed in the area of data acquisition and processing. We introduce the main available AI techniques, categorizing them into 3 stages based on their order of appearance: (1) machine learning, (2) deep learning, and (3) the most recent advancements in large-scale models and multimodal learning. Next, we present case studies of existing approaches using AI for evolutionary morphology, including image capture and segmentation, feature recognition, morphometrics, and phylogenetics. We then discuss the prospectus for near-term advances in specific areas of inquiry within this field, including the potential of new AI methods that have not yet been applied to the study of morphological evolution. In particular, we note key areas where AI remains underutilized and could be used to enhance studies of evolutionary morphology. This combination of current methods and potential developments has the capacity to transform the evolutionary analysis of the organismal phenotype into evolutionary phenomics, leading to an era of “big data” that aligns the study of phenotypes with genomics and other areas of bioinformatics.

The neurocranium is an integral part of the vertebrate head, itself a major evolutionary innovation^1,2. However, its early history remains poorly understood, with great dissimilarity in form between the two living vertebrate groups: gnathostomes (jawed vertebrates) and cyclostomes (hagfishes and lampreys)^2,3. The 100 Myr gap separating the Cambrian appearance of vertebrates^4–6from the earliest three-dimensionally preserved vertebrate neurocrania⁷further obscures the origins of modern states. Here we use computed tomography to describe the cranial anatomy of an Ordovician stem-group gnathostome:Eriptychius americanusfrom the Harding Sandstone of Colorado, USA⁸. A fossilized head ofEriptychiuspreserves a symmetrical set of cartilages that we interpret as the preorbital neurocranium, enclosing the fronts of laterally placed orbits, terminally located mouth, olfactory bulbs and pineal organ. This suggests that, in the earliest gnathostomes, the neurocranium filled out the space between the dermal skeleton and brain, like in galeaspids, osteostracans and placoderms and unlike in cyclostomes². However, these cartilages are not fused into a single neurocranial unit, suggesting that this is a derived gnathostome trait.Eriptychiusfills a major temporal and phylogenetic gap in our understanding of the evolution of the gnathostome head, revealing a neurocranium with an anatomy unlike that of any previously described vertebrate.

Attempts to explain the origin and diversification of vertebrates have commonly invoked the evolution of feeding ecology, contrasting the passive suspension feeding of invertebrate chordates and larval lampreys with active predation in living jawed vertebrates. Of the extinct jawless vertebrates that phylogenetically intercalate these living groups, the feeding apparatus is preserved only in the early diverging stem-gnathostome heterostracans and its anatomy remains poorly understood. Here we use X-ray microtomography to characterise the feeding apparatus of the pteraspid heterostracan Rhinopteraspis dunensis (Roemer, 1855). We show that the apparatus is composed of thirteen plates arranged approximately bilaterally, the majority of which articulate from the postoral plate. Our reconstruction of the apparatus shows that the oral plates would have been capable of movement within the dorso-ventral plane, but their degree of movement was limited. The functional morphology of the apparatus in Rhinopteraspis precludes all proposed interpretations of feeding except for suspension/deposit feeding and we interpret the apparatus as having served primarily to moderate the oral gape. This is consistent with evidence that at least some early jawless gnathostomes were suspension feeders and runs contrary to macroecological scenarios that envisage early vertebrate evolution as characterised by a directional trend towards increasingly active food acquisition.