Developmental biology of pterobranch hemichordates: History and perspectives

Sato, Atsuko; Bishop, John D. D.; Holland, Peter W.H.

doi:10.1002/dvg.20395

Cited by 34 publications

(20 citation statements)

References 28 publications

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“…The development and structural features (including tubarium ultrastructure) are better known in R. compacta colonies (e.g. Stebbing 1968; Dilly 1971, 1973, 1975, 1985a, 1986; Stebbing & Dilly 1972; Cavers 2005; Urbanek & Dilly 2000; Mierzejewski & Kulicki 2003; Sato et al. 2008a,b) than in the other commonly reported Rhabdopleura species, R. normani Allman (1869), and for our purposes, the differences between them are of no importance.…”

Section: Phylogenetic Analysismentioning

confidence: 67%

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Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite

Mitchell

Melchin

Cameron

et al. 2013

LET

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A phylogenetic analysis of morphological data from modern pterobranch hemichordates (Cephalodiscus, Rhabdopleura) and representatives of each of the major graptolite orders reveals that Rhabdopleura nests among the benthic, encrusting graptolite taxa as it shares all of the synapomorphies that unite the graptolites. Therefore, rhabdopleurids can be regarded as extant members of the Subclass Graptolithina (Class Pterobranchia). Combined with the results of previous molecular phylogenetic studies of extant deuterostomes, these results also suggest that the Graptolithina is a sister taxon to the Subclass Cephalodiscida. The Graptolithina, as an important component of Early–Middle Palaeozoic biotas, provide data critical to our understanding of early deuterostome phylogeny. This result allows one to infer the zooid morphology, mechanics of colony growth and palaeobiology of fossil graptolites in direct relation to the living members of the clade. The Subdivision Graptoloida (nom. transl.), which are all planktic graptolites, is well supported in this analysis. In addition, we recognize the clade Eugraptolithina (nov.). This clade comprises the Graptoloida and all of the other common and well‐known graptolites of the distinctive Palaeozoic fauna. Most of the graptolites traditionally regarded as tuboids and dendroids appear to be paraphyletic groups within the Eugraptolithina; however, Epigraptus is probably not a member of this clade. The Eugraptolithina appear to be derived from an encrusting, Rhabdopleura‐like species, but the available information is insufficient to resolve the phylogeny of basal graptolites. The phylogenetic position of Mastigograptus and the status of the Dithecoidea and Mastigograptida also remain unresolved. □ Biodiversity, Cambrian, Hemichordata, Deuterostomia, Ordovician.

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Section: Phylogenetic Analysismentioning

confidence: 67%

“…0 – absent; 1 – resorption; 2 – primary. The vesicular prosicula in Rhabdopleura is secreted initially as a closed vesicle, through which a pore is resorbed for growth of the metasicula (Dilly 1986; Sato et al. 2008a).…”

Section: Phylogenetic Analysismentioning

confidence: 99%

Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite

Mitchell

Melchin

Cameron

et al. 2013

LET

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“…Nonetheless, this does not obviate the possibility that certain aspects of pterobranch biology, like the possession of feeding tentacles, is primitive for hemichordates given the similarities between the tentacles of pterobranchs and crinoid echinoderms. Therefore, detailed work on pterobranchs (Sato et al, ) now must accompany our rapidly growing understanding of enteropneust (Brown et al, ; Röttinger and Lowe, ) and echinoderm (McClay, ) development, in conjunction with our growing knowledge of the fossil record of these groups (Swalla and Smith, ), in order to assess potential homologies and to polarize characters across the Ambulacraria, and ultimately Deuterostomia.…”

Section: Discussionmentioning

confidence: 99%

MicroRNAs support the monophyly of enteropneust hemichordates

Peterson

Arnone

et al. 2013

J Exp Zool Pt B

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Understanding the evolutionary history of deuterostomes requires elucidating the phylogenetic interrelationships amongst the constituent taxa. Although the monophyly and interrelationships among the three principal groups-the chordates, the echinoderms, and the hemichordates-are well established, as are the internal relationships among the echinoderm and chordate taxa, the interrelationships among the principal groups of hemichordates-the harrimaniid enteropneusts, the ptychoderid enteropneusts, and the pterobranchs-remain unresolved. Depending on the study some find enteropneusts paraphyletic with pterobranchs (e.g., Cephalodiscus) more closely related to the harrimaniid enteropneusts (e.g., Saccoglossus) than either are to the ptychoderid enteropneusts (e.g., Ptychodera), whereas other studies support a monophyletic Enteropneusta. To try and resolve between these two competing hypotheses, we turned to microRNAs, small ∼22 nt non-coding RNA genes that have been shown to shed insight into particularly difficult phylogenetic questions. Using deep sequencing we characterized the small RNA repertoires of two hemichordate species, Cephalodiscus hodgsoni and Ptychodera flava, and the crinoid echinoderm Antedon mediterranea, and combined our results with the described complements of the hemichordate Saccoglossus kowalevskii, the sea urchin Strongylocentrotus purpuratus, and the starfish Patiria miniata. Our data unambiguously support the monophyly of Enteropneusts as S. kowalevskii shares 12 miRNA sequences with P. flava that are not present in the C. hodgsoni or A. mediterranea libraries, and have never been reported from another metazoan taxon. Thus, these data resolve the phylogenetic position of pterobranchs, ultimately allowing for a better understanding of body plan evolution throughout the deuterostomes.

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“…There is, however, an earlier report of internal brooding in an enteropneust by Gilchrist (1925), who published a drawing of a single advanced larva within the trunk coelom of an adult female of Xenopleura vivipara (family Harrimaniidae). Some enteropneust species, like Saccoglossus pusillus (Davis, 1908) as well as pterobranch hemichordates in the genera Cephalodiscus (Sciaparelli et al, 2004) and Rhabdopleura (Lester, 1988;Sato et al, 2008), retain early developmental stages in the maternal burrow or tube.…”

Section: Reproductive Biologymentioning

confidence: 99%

An Externally Brooding Acorn Worm (Hemichordata, Enteropneusta, Torquaratoridae) from the Russian Arctic

Osborn

Gebruk

Rogacheva

et al. 2013

The Biological Bulletin

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Abstract.A single specimen of a previously undescribed acorn worm in the family Torquaratoridae was trawled from a bottom depth of about 350 m in the Kara Sea (Russian Arctic). The new species is the shallowest of the exclusively deep-sea torquaratorids found to date, possibly an example of high-latitude emergence. On the basis of ribosomal DNA sequences and morphology, the worm is described here as the holotype of Coleodesmium karaensis n. gen., n. sp. It is most similar in overall body shape to the previously described enteropneust genus Allapasus, but is uniquely characterized by a tubular component of the proboscis skeleton ensheathing the collar nerve cord. Additionally, within the proboscis, the sparseness of the musculature of C. karaensis clearly distinguishes it from the much more muscular members of Allapasus. The holotype is a female bearing about a dozen embryos on the surface of her pharyngeal region, each recessed within a shallow depression in the dorsal epidermis. The embryos, ranging from late gastrula to an early stage of coelom formation, are a little more than 1 mm in diameter and surrounded by a thin membrane. Each embryo comprises an external ectoderm of monociliated cells (not arranged in obvious ciliated bands) and an internal endo-mesoderm; the blastopore is closed. In the most advanced embryos, the anterior coelom is starting to constrict off from the archenteron. Coleodesmium karaensis is the first enteropneust (and indeed the first hemichordate) found brooding embryos on the surface of the mother's body.

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Developmental biology of pterobranch hemichordates: History and perspectives

Cited by 34 publications

References 28 publications

Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite

Phylogenetic analysis reveals that Rhabdopleura is an extant graptolite

MicroRNAs support the monophyly of enteropneust hemichordates

An Externally Brooding Acorn Worm (Hemichordata, Enteropneusta, Torquaratoridae) from the Russian Arctic

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