Evolution of Maternal Provisioning and Development in the Ophiuroidea: Egg Size, Larval Form, and Parental Care.

The Ophiuroidea is the most speciose class of echinoderms and has the greatest diversity of larval forms, but we know less about the evolution of development (evo-devo) in this group than for the other echinoderm classes. As is typical of echinoderms, evo-devo in the Ophiuroidea resulted in the switch from production of small eggs and feeding (planktotrophic) larvae to large eggs and non-feeding (lecithotrophic) larvae. Parental care (ovoviviparity or viviparity/matrotrophy) is the most derived life history.

[Strategies and recommendations to face respiratory syncytial virus disease in 2024].

During the winter of 2023, Chile faced a complex situation related to the respiratory syncytial virus (RSV). After experiencing a decline in RSV circulation during the years of the SARS-CoV-2 pandemic, a late outbreak was observed in the spring of 2022 and an early onset of the outbreak in 2023, with a significant increase in the number of serious cases. The ineffectiveness of strategic planning and risk communication contributed to the complexity of the situation.

Recent reconfiguration of an ancient developmental gene regulatory network in Heliocidaris sea urchins.

Changes in developmental gene regulatory networks (dGRNs) underlie much of the diversity of life, but the evolutionary mechanisms that operate on regulatory interactions remain poorly understood. Closely related species with extreme phenotypic divergence provide a valuable window into the genetic and molecular basis for changes in dGRNs and their relationship to adaptive changes in organismal traits. Here we analyse genomes, epigenomes and transcriptomes during early development in two Heliocidaris sea urchin species that exhibit highly divergent life histories and in an outgroup species.

Transcriptomic analysis of Nodal - and BMP- associated genes during development to the juvenile seastar in Parvulastra exigua (Asterinidae).

The molecular mechanisms underlying development of the pentameral body of adult echinoderms are poorly understood but are important to solve with respect to evolution of a unique body plan that contrasts with the bilateral body plan of other deuterostomes. As Nodal and BMP2/4 signalling is involved in axis formation in larvae and development of the echinoderm body plan, we used the developmental transcriptome generated for the asterinid seastar Parvulastra exigua to investigate the temporal expression patterns of Nodal and BMP2/4 genes from the embryo and across metamorphosis to the juvenile. For echinoderms, the Asteroidea represents the basal-type body architecture with a distinct (separated) ray structure.

Culturing echinoderm larvae through metamorphosis.

Echinoderms are favored study organisms not only in cell and developmental biology, but also physiology, larval biology, benthic ecology, population biology and paleontology, among other fields. However, many echinoderm embryology labs are not well-equipped to continue to rear the post-embryonic stages that result. This is unfortunate, as such labs are thus unable to address many intriguing biological phenomena, related to their own cell and developmental biology studies, that emerge during larval and juvenile stages.

Early development of the feeding larva of the sea urchin Heliocidaris tuberculata: role of the small micromeres.

The two modes of development in sea urchins are direct development, in which the adult develops directly from the gastrula to the adult and does not feed, and indirect development, in which the adult develops indirectly through a feeding larva. In this account of the indirect, feeding larva of Heliocidaris tuberculata, the question raised is whether an evolutionary difference of unequal cell divisions contributes to the development of feeding structures in the indirect larva. In indirect development, the cell divisions at the fourth and fifth cell cycles of the zygote are unequal, with four small micromeres formed at the vegetal pole at the fifth cell division.

Phylogenomics, life history and morphological evolution of ophiocomid brittlestars.

Brittlestars in the family Ophiocomidae are large and colourful inhabitants of tropical shallow water habitats across the globe. Here we use targeted capture and next-generation sequencing to generate robust phylogenomic trees for 39 of the 43 species in order to test the monophyly of existing genera. The large genus Ophiocoma, as currently constituted, is paraphyletic on our trees and required revision.

Expression of genes and proteins of the pax-six-eya-dach network in the metamorphic sea urchin: Insights into development of the enigmatic echinoderm body plan and sensory structures.

Background: Photoreception-associated genes of the Pax-Six-Eya-Dach network (PSEDN) are deployed for many roles in addition to photoreception development. In this first study of PSEDN genes during development of the pentameral body in sea urchins, we investigated their spatial expression in Heliocidaris erythrogramma.

Results: Expression of PSEDN genes in the hydrocoele of early (Dach, Eya, Six1/2) and/or late (Pax6, Six3/6) larvae, and the five hydrocoele lobes, the first morphological expression of pentamery, supports a role in body plan development.

Nodal and BMP expression during the transition to pentamery in the sea urchin Heliocidaris erythrogramma: insights into patterning the enigmatic echinoderm body plan.

Background: The molecular mechanisms underlying the development of the unusual echinoderm pentameral body plan and their likeness to mechanisms underlying the development of the bilateral plans of other deuterostomes are of interest in tracing body plan evolution. In this first study of the spatial expression of genes associated with Nodal and BMP2/4 signalling during the transition to pentamery in sea urchins, we investigate Heliocidaris erythrogramma, a species that provides access to the developing adult rudiment within days of fertilization.

Results: BMP2/4, and the putative downstream genes, Six1/2, Eya, Tbx2/3 and Msx were expressed in the earliest morphological manifestation of pentamery during development, the five hydrocoele lobes.

Transcriptomic analysis of Nodal- and BMP-associated genes during juvenile development of the sea urchin Heliocidaris erythrogramma.

Understanding the unusual radial body plan of echinoderms and its relationship to the bilateral plan of other deuterostomes remains a challenge. The molecular processes of embryonic and early larval development in sea urchins are well characterised, but those giving rise to the adult and its radial body remain poorly studied. We used the developmental transcriptome generated for Heliocidaris erythrogramma, a species that forms the juvenile soon after gastrulation, to investigate changes in gene expression underlying radial body development.

Fixed, free, and fixed: the fickle phylogeny of extant Crinoidea (Echinodermata) and their Permian-Triassic origin.

Although the status of Crinoidea (sea lilies and featherstars) as sister group to all other living echinoderms is well-established, relationships among crinoids, particularly extant forms, are debated. All living species are currently placed in Articulata, which is generally accepted as the only crinoid group to survive the Permian-Triassic extinction event. Recent classifications have recognized five major extant taxa: Isocrinida, Hyocrinida, Bourgueticrinina, Comatulidina and Cyrtocrinida, plus several smaller groups with uncertain taxonomic status, e.

Characterization and expression of a sea star otx ortholog (Protxβ1/2) in the larva of Patiriella regularis.

A transcript of otx from the sea star Patiriella regularis (Protxβ1/2) was characterized and its expression in early bipinnaria larvae was documented by whole mount in situ hybridization (WMISH). The nucleotide sequence exhibited 94% identity with Amotxβ1/2 from the closely related species Patiria miniata. Protxβ1/2 was expressed strongly in the developing archenteron in the future fore and mid-gut regions.

Expression of Hox4 during development of the pentamerous juvenile sea star, Parvulastra exigua.

Expression of Hox4 during development of the bilateral larva and pentameral juvenile sea star was investigated in Parvulastra exigua. The role of Hox4, possibly the anterior-most gene in the echinoderm Hox cluster, in the formation of the echinoderm adult body plan has not been examined previously. In the larva of P.

Engrailed is expressed in larval development and in the radial nervous system of Patiriella sea stars.

We documented expression of the pan-metazoan neurogenic gene engrailed in larval and juvenile Patiriella sea stars to determine if this gene patterns bilateral and radial echinoderm nervous systems. Engrailed homologues, containing conserved En protein domains, were cloned from the radial nerve cord. During development, engrailed was expressed in ectodermal (nervous system) and mesodermal (coeloms) derivatives.

Reproduction and larval morphology of broadcasting and viviparous species in the Cryptasterina species complex.

The Cryptasterina group of asterinid sea stars in Australasia comprises cryptic species with derived life histories. C. pentagona and C.

Development and distribution of the peptidergic system in larval and adult Patiriella: comparison of sea star bilateral and radial nervous systems.

Development of the larval peptidergic system in the sea star Patiriella regularis and structure of the adult nervous system in Patiriella species were documented in an immunofluorescence investigation using antisera to the sea star neuropeptide GFNSALMFamide 1 (S1) and confocal microscopy. P. regularis has planktotrophic development through bipinnaria and brachiolaria larvae.