The larval arms of echinoid plutei are used for locomotion and feeding. They are composed of internal calcite skeletal rods covered by an ectoderm layer bearing a ciliary band. Skeletogenesis includes an autonomous molecular differentiation program in primary mesenchyme cells (PMCs), initiated when PMCs leave the vegetal plate for the blastocoel, and a patterning of the differentiated skeletal units that requires molecular cues from the overlaying ectoderm. The arms represent a larval feature that arose in the echinoid lineage during the (...) Paleozoic and offers a subject for the study of gene co-option in the evolution of novel larval features. We isolated new molecular markers in two closely related but differently developing species, Heliocidaris tuberculata and Heliocidaris erythrogramma. We report the expression of a larval arm-associated ectoderm gene tetraspanin, as well as two new PMC markers, advillin and carbonic anhydrase. Tetraspanin localizes to the animal half of blastula stage H. tuberculata and then undergoes a restriction into the putative oral ectoderm and future location of the postoral arms, where it continues to be expressed at the leading edge of both the postoral and anterolateral arms. In H. erythrogramma, its expression initiates in the animal half of blastulae and expands over the entire ectoderm from gastrulation onward. Advillin and carbonic anhydrase are upregulated in the PMCs postgastrulation and localized to the leading edge of the growing larval arms of H. tuberculata but do not exhibit coordinated expression in H. erythrogramma larvae. The tight spatiotemporal regulation of these genes in H. tuberculata along with other ontogenetic and phylogenetic evidence suggest that pluteus arms are novel larval organs, distinguishable from the processes of skeletogenesis per se. The dissociation of expression control in H. erythrogramma suggest that coordinate gene expression in H. tuberculata evolved as part of the evolution of pluteus arms, and is not required for larval or adult development. (shrink)

The debate over the genetic testing of minors has developed into a major bioethical topic. Although several controversial questions remain unanswered, a degree of consensus has been reached regarding the policies on genetic testing of minors. Recently, several commentators have suggested that these policies are overly restrictive, too narrow in focus, and even in conflict with the limited empirical evidence that exists on this issue. We respond to these arguments in this paper, by first offering a clarification of three key (...) concepts—autonomy of the minor, future autonomy, and parental authority—which must be disentangled. We then respond to the arguments by noting the uncertainty of the value of predictive genetic information, and by assessing the psychosocial risks still involved in genetic testing of minors, which are also largely unknown. We conclude that the current consensus position is justified at this stage, in light of the predictions of harm resulting from genetic testing of minors that have not been adequately proved to be unwarranted. (shrink)

R. A. Sharpe; VIII*—Art and Expertise, Proceedings of the Aristotelian Society, Volume 85, Issue 1, 1 June 1985, Pages 133–148, https://doi.org/10.1093/aristote.