Nematostella Vectensis : The Starlet Anemone
We Discussed so many times on this blog about the need of appropriate model system to under take the challenge provided by the genomic era and expansion of integrative disciplines like evo devo,which requires researchers to adopt a more integrative approach while choosing model organisms.Another important point which should be considered in choosing model systems is their phylogenic position ,so that they might serve as a complement to existing model systems in reconstructing evolutionary history.
The starlet anemone “Nematostella Vectensis” is becoming an increasingly important model system for the study of development, evolution, genomics, reproductive biology, and ecology.The emergence of Nematostella as a model system owes much to the pioneering work of Cadet Hand.
The starlet sea anemone Nematostella vectensis finds a place among a number of informative cnidarian model systems, including Acropora,Eleutheria, Hydra, Hydractinia and Podocoryne, which have already unraveled significant puzzles of early metazoan evolution.Nematostella proving to be a very important model organism owing to the following characteristics:
1) Ease of culture
2) Reproductive and Developmental plasticity
3) Phylogenetic position
4) Now the entire genome is sequenced(allow the first genome-wide comparisons between Bilaterian and non-Bilaterian animals)
5) Availabilty of molecular,genomic and genetic tools l(ike RNAi for knocking down gene function ,tracking of gene expression by tagging to reporter constructs)
In spite of common thing one will come across in all text books that Cnidarians are radially symmetrical organisms but some cnidarians including Sea anemones exhibit Bilateral symmetry.The expression of Hox genes(along AP or Primary axis) and dpp expression along Dorso ventral axis ( Secondary axis) provides significant evidence of development of bilateral symmetry.The comparable Hox and dpp expression seen in Nematostella and Bilateria supports the hypothesis that bilateral symmetry evolved before the divergence of Cnidaria and Bilateria.
Nematostella is a diploblastic animal exhibiting only two germ layers in Endomerm and Ectoderm.But it possess many genes like orthologs of forkhead, snail, twist,tinman and brachyury,which play pivotal roles in specification and patterning of mesoderm in bilaterians.In Nematostella, these ‘‘mesodermal genes’’ are expressed predominantly in the endoderm or presumptive endoderm,which indicats a role in germ-layer specification and supports the hypothesis that both the mesoderm and endoderm of Bilaterians are derived from the endoderm of a diploblastic ancestor.
Finally in order to study and understand the complexity of developmental process which results in complex bilaterians one need to understand the appropriate animals who have branched off(out groups) before bilateral organisms evolved.This is reflected by the interest of any researchers in directing more towards basal organisms ,which forms the out groups to bilateria and Nematostella is contributing immensely as a model organism in trying to understand origin of Bilaterians.
For more details on Nematostella read the following review by Finnerty JR and others.
Darling JA, Reitzel AR, Burton PM, Mazza ME, Ryan JF, Sullivan JC, Finnerty JR.
Rising starlet: the starlet sea anemone, Nematostella vectensis.
Bioessays. 2005 Feb;27(2):211-21. Review
Website dedicated to Nematostella vectensis research: www.Nematostella.org
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Kingdom: Animalia
Phylum: Cnidaria
Class: Anthozoa
Order: Actiniaria
Family: Edwardsiidae
Genus: Nematostella
Species: vectensis
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