scholarly journals Characterizing the body morphology of the first metacarpal in the Homininae using 3D geometric morphometrics

Author(s):  
Jonathan Morley ◽  
Ana Bucchi ◽  
Carlos Lorenzo ◽  
Thomas A. Püschel
2020 ◽  
Author(s):  
Jonathan Morley ◽  
Ana Bucchi ◽  
Carlos Lorenzo ◽  
Thomas A. Püschel

AbstractObjectivesExtinct hominins can provide key insights into the development of tool use, with the morphological characteristics of the thumb of particular interest due to its fundamental role in enhanced manipulation. This study quantifies the shape of the first metacarpal’s body in the extant Homininae and some fossil hominins to provide insights about the possible anatomical correlates of manipulative capabilities.Materials and methodsThe extant sample includes MC1s of modern humans (n=42), gorillas (n=27) and chimpanzees (n=30), whilst the fossil sample included Homo neanderthalensis, Homo naledi and Australopithecus sediba. 3D geometric morphometrics were used to characterize the overall shape of MC1’s body.ResultsHumans differ significantly from extant great apes when comparing overall shape. H. neanderthalensis mostly falls within the modern human range of variation although also showing a more robust morphology. H. naledi varies from modern human slightly, whereas A. sediba varies from humans to an even greater extent. When classified using a linear discriminant analysis, the three fossils are categorized within the Homo group.DiscussionThe results are in general agreement with previous studies on the morphology of the MC1. This study found that the modern human MC1 is characterized by a distinct suite of traits, not present to the same extent in the great apes, that are consistent with an ability to use forceful precision grip. This morphology was also found to align very closely with that of H. neanderthalensis. H. naledi shows a number of human-like adaptations consistent with an ability to employ enhanced manipulation, whilst A. sediba apparently presents a mix of both derived and more primitive traits.


2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Renan Rodrigues Rocha ◽  
Rosana de Mesquita Alves ◽  
Rubens Pasa ◽  
Karine Frehner Kavalco

The Astyanax scabripinnis complex is composed of a large number of almost morphological indistinguishable species, including Astyanax paranae and Astyanax rivularis, which exist in the Paraná and São Francisco Basins, respectively, and sometimes are considered subspecies of the A. scabripinnis group or even are cited just as A. scabripinnis. The two river basins are separated by the Upper Paranaíba Arc, likely the main cause of the isolation of these species. We used geometric morphometric tools and DNA analyses of populations of both species to identify the differences between them. Geometric morphometrics separated the two species into distinct groups, whose main difference was the body depth. This is generally related to the speed of the water flow in the river basins. The maximum likelihood phylogram based on mitochondrial DNA sequences formed two main clades: one composed of the population of A. rivularis and the other, of A. paranae. In the haplotype network, the species were similarly separated into two groups from the same ancestral haplotype, with A. rivularis dispersing into two lineages in the São Francisco River Basin. The distribution of A. paranae is a consequence of a secondary dispersion event in the Paraná River Basin. It forms two lineages from a haplotype derived from the ancestor. The vicariant effect of separate basins, through the elevation of the Upper Paranaíba Arc, led to the allopatric speciation of the populations originating the present species. The results of geometric morphometrics and molecular data of the fish show the importance of this geological event in the biogeography and evolutionary history of the ichthyofauna of the region and indicate that the isolation of these species seems to be effective.


2015 ◽  
Vol 80 ◽  
pp. 83-95 ◽  
Author(s):  
Julia Arias-Martorell ◽  
David M. Alba ◽  
Josep M. Potau ◽  
Gaëlle Bello-Hellegouarch ◽  
Alejandro Pérez-Pérez

2019 ◽  
Vol 2 ◽  
Author(s):  
Francesco Simone Mensa ◽  
Federica Spani ◽  
Andrea Di Giulio

The genus Paussus is a highly specialized, charismatic group of ground beetles (Carabidae) classified in the subfamily Paussinae. All species of Paussus are obligate myrmecophiles (associates of ants). As with many other myrmecophilous or termitophilous beetles, Paussus have undergone extreme phenotypic adaptations for life with ants, at the level of head, antennae, and prothorax. Host data suggest that Paussus species are likely to be species-specific ant parasites, and the structural modifications of antennae and other body parts are likely under selection by their host ants. Investigating anatomical structures have been fundamental to better understand living organisms, and their interplay with the surrounding environment, which could induce significant morphological variation. In the last few years, bio-imaging techniques paired with geometric morphometrics (GM) overcame the limits of traditional anatomical studies, becoming widely non-invasive and highly informative for both internal and external characters. The use of Computed Tomography (CT) scanners definitively allowed to advance in the knowledge of either known or neglected biological structures. For this project, we used X-ray micro-computed tomography, in order to acquire 2D serial, cross-sections of various paussines samples, with a resolution between 0.954 and 2.44 micrometers. The 2D images in high resolution are then processed using a high-performance computer system and Thermo Scientific™ Amira™ Software and Thermo Scientific™ Avizo™ Software for the reconstruction of 3D models. With these models, we will be able to conduct a morphological study of the most variable parts in the body of the genus Paussus using 3D geometric morphometrics (3D GM), as these integrative techniques allows to describe in a quantitative way even subtle differences between structures, so as to determine whether the striking diversity of phenotypes is caused by the host or by other factors, overlapping the results obtained with the molecular part of phylogeny. These innovative practices help to deepen the meaning of shape in insect biology, from both structural and evolutionary views. They will allow, in particular, to describe the relationship between phylogeny and functional morphology in the extremely variable species of the subfamily Paussinae.


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