Geometric Morphometrics of Bilateral Asymmetry in Eunotia bilunaris (Eunotiales, Bacillariophyceae) as a Tool for the Quantitative Assessment of Teratogenic Deviations in Frustule Shapes

A number of pennate diatom genera typically have teratogenic deformations of their siliceous frustules due to the effects of environmental stress, such as high concentrations of heavy metals and low pH. However, the quantitative assessment of these deformations has rarely been applied. One species in which aberrations have frequently been reported is Eunotia bilunaris, which typically has bilaterally symmetric frustules with dorso-ventral differentiation. In this study, we aimed to illustrate the geometric morphometric analysis of symmetry as a tool for assessing the severity of teratogenic deformations. These were quantified by Procrustes superimposition of equidistant points placed along the valvar outlines in pairs of configurations based on their bilateral reflection symmetry. The shape deformations were mostly confined to central parts of the ventral outlines and were captured both by the symmetric and asymmetric subspaces of the variation. The amount of bilateral asymmetry in individual cells was negatively related to frustule size via the allometric power law relationship, illustrating that asymmetry increased in the asexual diminution series. The presented analysis provides a framework for the quantitative assessment of frustule deformations in eunotioid diatoms that can be used for the comparative scoring of teratogenic deviations among cells, populations, or species.

hox gene expression predicts tetrapod-like axial regionalization in the skate, Leucoraja erinacea

The axial skeleton of tetrapods is organized into distinct anteroposterior regions of the vertebral column (cervical, trunk, sacral, and caudal), and transitions between these regions are determined by colinear anterior expression boundaries of Hox5/6, -9, -10, and -11 paralogy group genes within embryonic paraxial mesoderm. Fishes, conversely, exhibit little in the way of discrete axial regionalization, and this has led to scenarios of an origin of Hox-mediated axial skeletal complexity with the evolutionary transition to land in tetrapods. Here, combining geometric morphometric analysis of vertebral column morphology with cell lineage tracing of hox gene expression boundaries in developing embryos, we recover evidence of at least five distinct regions in the vertebral skeleton of a cartilaginous fish, the little skate (Leucoraja erinacea). We find that skate embryos exhibit tetrapod-like anteroposterior nesting of hox gene expression in their paraxial mesoderm, and we show that anterior expression boundaries of hox5/6, hox9, hox10, and hox11 paralogy group genes predict regional transitions in the differentiated skate axial skeleton. Our findings suggest that hox-based axial skeletal regionalization did not originate with tetrapods but rather has a much deeper evolutionary history than was previously appreciated.

Padrões morfológicos na venação alar de espécies de Tetragona Lepeletier & Serville, 1828 do grupo clavipes (Hymenoptera: Apidae: Meliponini)

Tetragona Lepeletier & Serville, 1828 (Hymenoptera: Apidae) is a genus of stingless bees widely distributed in Brazil. It has 15 species distributed in the Neotropics, from Mexico to Uruguay, nine of which are found in Brazil. However, Tetragona elongata (Lepeletier & Serville, 1828), a species known only from the Southeast region and which had been synonymized with Tetragona clavipes (Fabricius, 1804), was revalidated without any justification. The aim of this study was to test whether the morphometrics analysis of the wings is efficient in the diagnosis of the species of this genus, in addition to testing the validity of the revalidation mentioned above. This technique was applied by accessing the right forewings of 660 workers of T. clavipes, T. elongata e T. quadrangula (Lepeletier, 1836), from five Brazilian collections. For the geometric morphometric analysis, 12 landmarks were selected. The software MorphoJ version 1.6 was used to do Discriminant Function analysis (1000 replications) and Canonical Variation Analysis (CVA). Between T. clavipes and T. elongata, there was a 100% variance between species (canonical variation analysis), suggesting that it may be an indication of speciation. Even though T. elongata has been revalidated, it still has overlapped with T. clavipes, which indicates to be the same species. Taxonomic studies are needed to synonymize them.

Perdiz arrow points from Caddo burial contexts aid in defining discrete behavioral regions

Recent research in the ancestral Caddo area yielded evidence for distinct _behavioral regions_, across which material culture from Caddo burials—bottles and Gahagan bifaces—has been found to express significant morphological differences. This inquiry assesses whether Perdiz arrow points from Caddo burials, assumed to reflect design intent, may differ across the same geography, and extend the pattern of shape differences to a third category of Caddo material culture. Perdiz arrow points collected from the geographies of the northern and southern Caddo _behavioral regions_ defined in a recent social network analysis were employed to test the hypothesis that morphological attributes differ, and are predictable, between the two communities. Results indicate significant between-community differences in maximum length, width, stem length, and stem width, but not thickness. Using the same traditional metrics combined with the tools of machine learning, a predictive model---support vector machine---was designed to assess the degree to which community differences could be predicted, achieving a receiver operator curve score of 97 percent, and an accuracy score of 94 percent. The subsequent geometric morphometric analysis identified significant differences in Perdiz arrow point shape, size, and allometry, coupled with significant results for modularity and morphological integration. These findings bolster recent arguments that established two discrete _behavioral regions_ in the ancestral Caddo area defined on the basis of discernible morphological differences across three categories of Caddo material culture.