Spatial distribution of conspecific genotypes within chimeras of the branching coral Stylophora pistillata.

Chimerism is a coalescence of conspecific genotypes. Although common in nature, fundamental knowledge, such as the spatial distribution of the genotypes within chimeras, is lacking. Hence, we investigated the spatial distribution of conspecific genotypes within the brooding coral Stylophora pistillata, a common species throughout the Indo-Pacific and Red Sea. From eight gravid colonies, we collected planula larvae that settled in aggregates, forming 2-3 partner chimeras. Coral chimeras grew in situ for up to 25 months. Nine chimeras (8 kin, 1 non-related genotypes) were sectioned into 7-17 fragments (6-26 polyps/fragment), and genotyped using eight microsatellite loci. The discrimination power of each microsatellite-locus was evaluated with 330 'artificial chimeras,' made by mixing DNA from three different S. pistillata genotypes in pairwise combinations. In 68% of 'artificial chimeras,' the second genotype was detected if it constituted 5-30% of the chimera. Analyses of S. pistillata chimeras revealed that: (a) chimerism is a long-term state; (b) conspecifics were intermixed (not separate from one another); (c) disproportionate distribution of the conspecifics occurred; (d) cryptic chimerism (chimerism not detected via a given microsatellite) existed, alluding to the underestimation of chimerism in nature. Mixed chimerism may affect ecological/physiological outcomes for a chimera, especially in clonal organisms, and challenges the concept of individuality, affecting our understanding of the unit of selection.

Morphometric and allometric rules of polyp's landscape in regular and chimeric coral colonies of the branching species Stylophora pistillata.

BACKGROUND: Most studies on architectural rules in corals have focused on the branch and the colony level, unveiling a variety of allometric rules. Working on the branching coral Stylophora pistillata, here we further extend the astogenic directives of this species at the polyp level, to reveal allometric and morphometric rules dictating polyps' arrangement. RESULTS: We identified a basic morphometric landscape as a six-polyp circlet developed around a founder polyp, with established distances between polyps (six equilateral triangles), reflecting a strong genetic-based background vs high plasticity on the population level. Testing these rules in regular and chimeric S. pistillata colonies, we revealed similar morphometric/allometric rules developed via a single astogenic pathway. In regular colonies, this pathway was driven by the presence/absence of intra-circlet budding polyps, while in chimeras, by the distances between the two founder polyps. In addition, we identified the intra-circlet budding as the origin of first branching, if BPC distances are kept <1.09 ± 0.25 mm. CONCLUSIONS: The emerged allometric/morphometric rules indicate the existence of a positional information paradigm for polyps' landscape distribution, where each polyp creates its own positional field of morphogen gradients through six inductive sites, thus forming six positional fields for the development of the archetypal "six-polyp crown".

Dataset from the dynamic shake-table test of a full-scale unreinforced clay-masonry building with flexible timber diaphragms.

This paper provides information related to the sensor measurements obtained from an unreinforced masonry building subjected to incremental dynamic shake-table tests at the EUCENTRE facilities in Pavia, Italy. These tests provide a unique data set that captures at full scale the in-plane and out-of-plane behavior of unreinforced masonry walls, and the influence of flexible diaphragms on the dynamic global response of a complete building. The authors made this information available to assist in the development of analytical and numerical models, necessary to estimate the dynamic response and the engineering parameters for the performance-based seismic assessment of unreinforced masonry buildings. All recorded data (acceleration and displacement time histories) and the videos of the tests can be requested online on the EUCENTRE repository at the URL www.eucentre.it/nam-project referring to EUC-BUILD-2. For further interpretation of the sensor recordings, and for a detailed discussion on the seismic performance of the building specimen, the reader is referred to the article entitled "Experimental seismic performance of a full-scale unreinforced clay-masonry building with flexible timber diaphragms" (Kallioras et al., 2018) [1].