Indirect development with an intermediate larva exists in all major animal lineages, which
makes larvae central to most scenarios of animal evolution,,,,,,,,–. Yet how larvae evolved …

It is widely held that the bilaterian tubular gut with mouth and anus evolved from a simple gut
with one major gastric opening. However, there is no consensus on how this happened. Did …

The intestine consists of epithelial cells that secrete digestive enzymes and mucus (gland
cells), absorb food particles (enterocytes), and produce hormones (endocrine cells) …

Background The evolutionary origin of gastrulation—defined as a morphogenetic event that
leads to the establishment of germ layers—remains a vexing question. Central to this debate …

Hox genes define regional identities along the anterior–posterior axis in many animals. In a
number of species, Hox genes are clustered in the genome, and the relative order of genes …

Abstract Background The polychaete annelid Capitella teleta (formerly Capitella sp. I)
develops by spiral cleavage and has been the focus of several recent developmental …

Background Reconstructing the evolutionary history of nervous systems requires an
understanding of their architecture and development across diverse taxa. The spiralians …

The fate of the blastopore during development in the bilaterian ancestor is currently not well
understood. In deuterostomes, the blastopore forms the anus, but its fate in protostome …

Abstract Background The Fox gene family is a large family of transcription factors that arose
early in organismal evolution dating back to at least the common ancestor of metazoans and …

Electron microscopy (EM) provides a uniquely detailed view of cellular morphology,
including organelles and fine subcellular ultrastructure. While the acquisition and (semi-) …