Larval stages of a living sea lily (stalked crinoid echinoderm)

Nakano, Hiroaki; Hibino, Taku; Oji, Tatsuo; Hara, Yuko; Amemiya, Shonan

doi:10.1038/nature01236

Cited by 110 publications

(105 citation statements)

References 3 publications

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“…This hypothesis would be further supported if one could show, for example, an ontogenetic transformation of a single circum-blastoporal ciliary band into two transverse ciliary bands of the pilidium nielseni. Ontogenetic re-arrangement of a single larval ciliary band or a uniform ciliary field into several transverse rings has been shown in holothuroid and crinoid echinoderms (Lacalli andWest 1986, 2000;Nakano et al, 2003). Perhaps, spiralians are not immune to such developmental or evolutionary transformations either.…”

Section: B C D a 590 Sa Maslakova And Tc Hiebertmentioning

confidence: 99%

From trochophore to pilidium and back again - a larva’s journey

Maslakova¹,

Hiebert²

2014

Int. J. Dev. Biol.

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Nemerteans, a phylum of marine lophotrochozoan worms, have a biphasic life history with benthic adults and planktonic larvae. Nemertean larval development is traditionally categorized into direct and indirect. Indirect development via a long-lived planktotrophic pilidium larva is thought to have evolved in one clade of nemerteans, the Pilidiophora, from an ancestor with a uniformly ciliated planuliform larva. Planuliform larvae in a member of a basal nemertean group, the Palaeonemertea, have been previously shown to possess a vestigial prototroch, homologous to the primary larval ciliated band in the trochophores of other spiralian phyla, such as annelids and mollusks. We review literature on nemertean larval development, and include our own unpublished observations. We highlight recent discoveries of numerous pilidiophoran species with lecithotrophic larvae. Some of these larvae superficially resemble uniformly ciliated planuliform larvae of other nemerteans. Others possess one or two transverse ciliary bands, which superficially resemble the prototroch and telotroch of some spiralian trochophores. We also summarize accumulating evidence for planktotrophic feeding by larvae of the order Hoplonemertea, which until now were considered to be lecithotrophic. We suggest that 1) non-feeding pilidiophoran larval forms are derived from a feeding pilidium; 2) such forms have likely evolved many times independently within the Pilidiophora; 3) any resemblance of such larvae to the trochophores of other spiralians is a result of convergence and that 4) the possibility of planktotrophy in hoplonemertean larvae may influence estimates of pelagic larval duration, dispersal, and population connectivity in this group.

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Section: B C D a 590 Sa Maslakova And Tc Hiebertmentioning

confidence: 99%

From trochophore to pilidium and back again - a larva’s journey

Maslakova¹,

Hiebert²

2014

Int. J. Dev. Biol.

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“…In ophiuroid and echinoid echinoderms, a pluteus larva develops that has an oral-aboral axis, but the second axis is not exactly anteriorposterior and so is referred to as the A-V (Angerer et al 2001). However, in other echinoderm larvae, including basal crinoid larvae, it is clear that the egg A-V axis becomes the larval A-P axis (Nakano et al 2003). In hemichordates, the adult A-P axis is clearly identical to the larval A-P axis and the D-V axis is still being debated (Gerhart, 2001;Henry et al, 2001).…”

Section: Deuterostome Gastrulationmentioning

confidence: 99%

Nodal signaling and the evolution of deuterostome gastrulation

Chea

Wright

Swalla

2005

Developmental Dynamics

101

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Chordates, including vertebrates, evolved within a group of animals called the deuterostomes. All holoblastic deuterostomes gastrulate at the vegetal pole and the blastopore becomes the anus, while a mouth is formed at the anterior or to the oral side. Nodal is a member of the TGF-␤ superfamily of signaling molecules that are important in signaling between cells during many embryonic processes in vertebrate embryos. Nodal has also been found in other invertebrate deuterostomes, such as ascidians and sea urchins, but, so far, is missing in protostomes. Nodal has been shown to be particularly important in determining left-right asymmetries in vertebrate embryos, but less information is available for its developmental role in the invertebrate deuterostomes. We review gastrulation in the deuterostomes, then examine nodal expression early during mesoderm formation and later during the establishment of asymmetries in both vertebrates and invertebrates. Nodal is expressed asymmetrically on the left side in chordates and on the presumptive oral side of the embryo in echinoid echinoderms. The expression of nodal is in different germ layers in embryos of different phyla. Expression is in the ectoderm in most of the invertebrate deuterostomes, and in the mesoderm in vertebrates. We summarize the work that has been published to date, especially nodal expression in the invertebrate deuterostomes, and suggest future experiments to better understand the evolution of nodal signaling and deuterostome gastrulation. Developmental Dynamics 234:269 -278, 2005.

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“…They showed that the gene expression domains of hemichordates and chordates are surprisingly conserved, an observation that shed new light on the evolution of the central nervous system and the phyletic placement of chordates. In echinoderms, Nakano et al (2003) described the development of the sea lily, Metacrinus rotundus , and reported that this most basal echinoderm develops via a dipleurula-type larva. This observation strongly suggests that the latest common ancestor of echinoderms and hemichordates may be an indirect developer with dipleurula-type larvae, and Nakano et al (2003) have suggested that the common ancestor of deuterostomes (including chordates) may be an indirect developer.…”

Section: B Misakiensis As a Model Organismmentioning

confidence: 99%

The Development of the Enteropneust Hemichordate Balanoglossus misakiensis Kuwano

Urata

Yamaguchi

2004

Zoological Science

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-We describe development from fertilization to metamorphosis of the enteropneust hemichordate Balanoglossus misakiensis . This is the first report to describe the complete development of an indirect-developing hemichordate under laboratory conditions. Mature adults were induced to spawn by shifting the temperature of seawater from 23 to 28 ∞ C. Eggs (200 m m diameter) were enclosed within a nonmucilaginous membrane, and dispersed readily in seawater. After artificial insemination, a fertilization envelope was elevated from the egg surface beneath the egg membrane; this was followed by the formation of the first and second polar bodies within the envelope. Zygotes cleaved at 20-min intervals to form blastulae, and gastrulation started 9 h after fertilization. Embryos hatched 1 day after fertilization to become typical feeding tornaria larvae. The larvae metamorphosed 7-10 days after fertilization without undergoing the first (Müller) or forth (Krohn) stage of indirect-developing hemichordate development. Larvae that were not fed failed to metamorphose. Juveniles completed adult body formation within a week of settling in sand at the bottom of the culture tube. We discuss heterochronical modifications of B. misakiensis development, and make the case for this species as a potential model organism for the investigation of indirect-developing hemichordates.

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Larval stages of a living sea lily (stalked crinoid echinoderm)

Cited by 110 publications

References 3 publications

From trochophore to pilidium and back again - a larva’s journey

From trochophore to pilidium and back again - a larva’s journey

Nodal signaling and the evolution of deuterostome gastrulation

The Development of the Enteropneust Hemichordate Balanoglossus misakiensis Kuwano

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