Bilaterian Origins: Significance of New Experimental Observations

Peterson, Kevin J.; Cameron, R. Andrew; Davidson, Eric H.

doi:10.1006/dbio.1999.9475

Cited by 120 publications

(102 citation statements)

References 116 publications

(128 reference statements)

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“…These polarities reestablish the traditional view that heteronomous polychaetes are derived in relation to those with a largely homonomous pattern of segmentation (FAUVEL 1923). With Owenia positioned as the sister group of Enterocoela, several genetic patterns of tagmosis found in basal groups of deuterostomes (PETERSON et al 2000a) are also seen to be found in polychaetes, providing further empirical support for the present hypothesis.…”

Section: Mollusk-like Cleavagesupporting

confidence: 68%

Polychaeta, Annelida, and Articulata are not monophyletic: articulating the Metameria (Metazoa, Coelomata)

et al. 2003

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Polychaetes are metameric worms recognized for having parapodia, chaetae, and nuchal organs. Some authors have extended the Annelida to include Pogonophora, Echiura, and Clitellata. These suggestions are insufficient to generate a monophyletic group. They do not take into account two very large and important clades that in a cladistic analysis at a higher level are shown to be nested within the Annelida: the Ecdysozoa (arthropods and related taxa) and Enterocoela (deuterostomes and related taxa). Evolutionary histories of most characters across metazoan phyla are still very poorly known. Metameres and coeloms have been considered homoplastic in the literature, and yet the homeobox genes responsible for the expression of metamerism and of paired appendages, at least, are very largely distributed among the Metazoa. A phylogenetic analysis was performed for the ingroups of Polychaeta, including Clitellata, Enterocoela, and Ecdysozoa as terminal taxa. The remaining non-metameric phyla Platyhelminthes, Nemertea, Mollusca, and Sipuncula were included to root the tree within the Bilateria. Empirical data was obtained from the literature and run with the software Hennig86 with two comparative interpretations of a priori hypotheses of primary homology: one with negative characters (coding losses) and another considering only positive characters (without assumptions about losses). The most relevant conclusions are: (1) Annelida and Polychaeta are non-monophyletic, even when including Echiura, Clitellata, and Pogonophora; (2) Articulata, as traditionally circumscribed for Annelida and Arthropoda, is also not monophyletic; (3) Metameria becomes monophyletic only when Ecdysozoa and Enterocoela are included in addition to the traditional annelid taxa; (4) Ecdysozoa are the sister group of Aphrodita; (5) Clitellata are related to deposit-feeding sedentary polychaetes (scolecids), and Questidae represent their sister group; (6) Owenia plus Enterocoela form a monophyletic group related to the tubicolous polychaetes

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Section: Mollusk-like Cleavagesupporting

confidence: 68%

Polychaeta, Annelida, and Articulata are not monophyletic: articulating the Metameria (Metazoa, Coelomata)

et al. 2003

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“…Most directly developing marine bilaterians use much larger eggs that are able to produce embryos consisting of relatively large numbers of cells without feeding. Many lines of evidence show that for deuterostomes and lophotrochozoans maximal indirect development is primitive, and direct development is derived (36)(37)(38). A palentological argument against this view has been cited (39) based on some large eggs of Cambrian origin (40).…”

Section: Discussionmentioning

confidence: 99%

Precambrian animal diversity: Putative phosphatized embryos from the Doushantuo Formation of China

Chen

Oliveri

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

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172

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Putative fossil embryos and larvae from the Precambrian phosphorite rocks of the Doushantuo Formation in Southwest China have been examined in thin section by bright field and polarized light microscopy. Although we cannot completely exclude a nonbiological or nonmetazoan origin, we identified what appear to be modern cnidarian developmental stages, including both anthozoan planula larvae and hydrozoan embryos. Most importantly, the sections contain a variety of small (<200 m) structures that greatly resemble gastrula stage embryos of modern bilaterian forms.

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“…1). The Triploblastica encompasses the vast majority of animal phyla and species, and a great deal of research has been conducted in an attempt to explain the remarkable evolutionary radiation of this group (e.g., Peterson et al, 2000). Many human developmental regulatory genes and disease-related genes have clear orthologs in Nematostella, indicating that they must have originated prior to the cnidarian-triploblast split (Putnam et al, 2007;.…”

Section: Early Evolution Of Animal Stress-response Pathwaysmentioning

confidence: 99%

Genomic Survey of Candidate Stress-Response Genes in the Estuarine AnemoneNematostella vectensis

Reitzel

Sullivan

Traylor-Knowles

et al. 2008

The Biological Bulletin

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Abstract. Salt marshes are challenging habitats due to natural variability in key environmental parameters including temperature, salinity, ultraviolet light, oxygen, sulfides, and reactive oxygen species. Compounding this natural variation, salt marshes are often heavily impacted by anthropogenic insults including eutrophication, toxic contamination, and coastal development that alter tidal and freshwater inputs. Commensurate with this environmental variability, estuarine animals generally exhibit broader physiological tolerances than freshwater, marine, or terrestrial species. One factor that determines an organism's physiological tolerance is its ability to upregulate "stressresponse genes" in reaction to particular stressors. Comparative studies on diverse organisms have identified a number of evolutionarily conserved genes involved in responding to abiotic and biotic stressors. We used homologybased scans to survey the sequenced genome of Nematostella vectensis, the starlet sea anemone, an estuarine specialist, to identify genes involved in the response to three kinds of insult-physiochemical insults, pathogens, and injury. Many components of the stress-response networks identified in triploblastic animals have clear orthologs in the sea anemone, meaning that they must predate the cnidariantriploblast split (e.g., xenobiotic receptors, biotransformative genes, ATP-dependent transporters, and genes involved in responding to reactive oxygen species, toxic metals, osmotic shock, thermal stress, pathogen exposure, and wounding). However, in some instances, stress-response genes known from triploblasts appear to be absent from the Nematostella genome (e.g., many metal-complexing genes). This is the first comprehensive examination of the genomic stress-response repertoire of an estuarine animal and a member of the phylum Cnidaria. The molecular markers of stress response identified in Nematostella may prove useful in monitoring estuary health and evaluating coastal conservation efforts. These data may also inform conservation efforts on other cnidarians, such as the reef-building corals.

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Bilaterian Origins: Significance of New Experimental Observations

Cited by 120 publications

References 116 publications

Polychaeta, Annelida, and Articulata are not monophyletic: articulating the Metameria (Metazoa, Coelomata)

Polychaeta, Annelida, and Articulata are not monophyletic: articulating the Metameria (Metazoa, Coelomata)

Precambrian animal diversity: Putative phosphatized embryos from the Doushantuo Formation of China

Genomic Survey of Candidate Stress-Response Genes in the Estuarine AnemoneNematostella vectensis

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