Embryonic, Larval, and Juvenile Development of the Sea Biscuit Clypeaster subdepressus (Echinodermata: Clypeasteroida)

Sea biscuits and sand dollars diverged from other irregular echinoids approximately 55 million years ago and rapidly dispersed to oceans worldwide. A series of morphological changes were associated with the occupation of sand beds such as flattening of the body, shortening of primary spines, multiplication of podia, and retention of the lantern of Aristotle into adulthood. To investigate the developmental basis of such morphological changes we documented the ontogeny of Clypeaster subdepressus. We obtained gametes from adult specimens by KCl injection and raised the embryos at 26C. Ciliated blastulae hatched 7.5 h after sperm entry. During gastrulation the archenteron elongated continuously while ectodermal red-pigmented cells migrated synchronously to the apical plate. Pluteus larvae began to feed in 3 d and were 20 d old at metamorphosis; starved larvae died 17 d after fertilization. Postlarval juveniles had neither mouth nor anus nor plates on the aboral side, except for the remnants of larval spicules, but their bilateral symmetry became evident after the resorption of larval tissues. Ossicles of the lantern were present and organized in 5 groups. Each group had 1 tooth, 2 demipyramids, and 2 epiphyses with a rotula in between. Early appendages consisted of 15 spines, 15 podia (2 types), and 5 sphaeridia. Podial types were distributed in accordance to Lovén's rule and the first podium of each ambulacrum was not encircled by the skeleton. Seven days after metamorphosis juveniles began to feed by rasping sand grains with the lantern. Juveniles survived in laboratory cultures for 9 months and died with wide, a single open sphaeridium per ambulacrum, aboral anus, and no differentiated food grooves or petaloids. Tracking the morphogenesis of early juveniles is a necessary step to elucidate the developmental mechanisms of echinoid growth and important groundwork to clarify homologies between irregular urchins

Embryonic chirality and the evolution of spiralian left-right asymmetries

This work has been funded by the Sars core budget to A.H

Clustered brachiopod Hox genes are not expressed collinearly and are associated with lophotrochozoan novelties

Temporal collinearity is often considered the main force preserving Hox gene clusters in animal genomes. Studies that combine genomic and gene expression data are scarce, however, particularly in invertebrates like the Lophotrochozoa. As a result, the temporal collinearity hypothesis is currently built on poorly supported foundations. Here we characterize the complement, cluster, and expression of Hox genes in two brachiopod species, Terebratalia transversa and Novocrania anomala. T. transversa has a split cluster with 10 genes (lab, pb, Hox3, Dfd, Scr, Lox5, Antp, Lox4, Post2, and Post1), whereas N. anomala has 9 genes (apparently missing Post1). Our in situ hybridization, real-time quantitative PCR, and stage-specific transcriptomic analyses show that brachiopod Hox genes are neither strictly temporally nor spatially collinear; only pb (in T. transversa), Hox3 (in both brachiopods), and Dfd (in both brachiopods) show staggered mesodermal expression. Thus, our findings support the idea that temporal collinearity might contribute to keeping Hox genes clustered. Remarkably, expression of the Hox genes in both brachiopod species demonstrates cooption of Hox genes in the chaetae and shell fields, two major lophotrochozoan morphological novelties. The shared and specific expression of Hox genes, together with Arx, Zic, and Notch pathway components in chaetae and shell fields in brachiopods, mollusks, and annelids provide molecular evidence supporting the conservation of the molecular basis for these lophotrochozoan hallmarks

Cleavage modification did not alter blastomere fates during bryozoan evolution

This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.The study was funded by the core budget of the Sars Centre and by The European Research Council Community’s Framework Program Horizon 2020 (2014–2020) ERC grant agreement 648861 to A

Development and reproductive cycle of the sea biscuit Clypeaster subdepressus (Echinodermata: Echinoidea) from São Sebastião, SP

<p>M.Sc. thesis on the development and reproduction of the sea biscuit <em>Clypeaster subdepressus</em>. Text is in portuguese.</p> <p>Original title: "Desenvolvimento e ciclo reprodutivo da bolacha-do-mar <em>Clypeaster subdepressus</em> (Echinodermata: Echinoidea) de São Sebastião, SP"</p> <p>Developmental chapter was published in PLOS ONE http://www.plosone.org/article/info:doi/10.1371/journal.pone.0009654</p

Topologically associating chromatin domains: Methods for their identification and their role in the development of mammals

Trial Lecture for my PhD given at the Department of Molecular Biology of the University of Bergen on February 17th 2016.<br><br>The topic cannot be directly related to your PhD. It is chosen by a committee and you have 10 days to make a presentation.<br

Gene orthology for the brachiopod segmentation project

<p>Orthology was assigned by aligning amino acid sequences of brachiopods against annotated genes using MAFFT 7.215, retaining only informative portions of the alignment with GBlocks 0.91b with relaxed parameters and running a Maximum Likelihood phylogenetic analysis with RAxML 8.1.17 using automatic model recognition and rapid bootstrap.</p

Sea biscuit life cycle

<p>This video shows the life cycle of Clypeaster subdepressus, an irregular echinoderm belonging to the Clypeasteroida (sand dollars and sea biscuits). Footage depicts all developmental stages: adults releasing gametes (eggs and sperm), fertilization of the egg, first embryonic cell divisions, gastrulation sequence, swimming blastulae and gastrulae, swimming pluteus larvae with 2/4/6/8 arms, developing juvenile rudiment inside larvae, settlement behavior of competent plutei, and complete metamorphosis into a juvenile.</p> <p>For the complete description and further details please consult the pulished article in the link below.</p

Cell lineages of Membranipora membranacea

SIMI°BioCell source files containing the cell lineages of four wild type embryos of the bryozoan <i>Membranipora membranacea</i>