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The phylogeography of the Placozoa suggests a taxon-rich phylum in tropical and subtropical waters
M. Eitel and B. Schierwater


Phylum Placozoa
This phylum is composed of one species Trichoplax adhaerens
Largest taxonomic group to be comprised of only one species Species is broken down into Clades and then to Haplotypes Clades are groups that consist of an ancestor and all of its descendants Haplotypes are specific DNA sequences that are located at adjacent locations on chromosomes and are inherited together


· · ·

Up to 2mm in diameter Simplest Metazoan body plan

·

Gland cells excrete enzymes for extra cellular digestion -algae & biofilm

· Scale like protection layer faces water

Interconnected fiber cells provide fast movement and shape changes

·

Nutritional layer faces bottom
-Ciliated for slow movement · Asexual budding, binary fission, some sexual reproduction in lab setting


Habitat
-Mostly unknown -Conclusions: Warm tropic & Sub-tropic waters

-30°N-30°S Latitude
-Mangrove roots, reefs, boat docks, stony beaches, eulittoral, and littoral zones -Never on sandy beaches, where there is high wave activity, or freshwater input -Unknown population density


The experiment:
Sample 39 tropical and subtropical locations
Depths of 1-20 meters

By collecting stones, coral, and mussel shells. Dropping glass slides in racks hung by ropes in boat docks and coral reefs.
Molecular analyses done with samples in lab (genome sequencing)


-Of the total 39 sites, 23 were positive sites for Placozoans -Using the 16s sequence on the ribosomal subunit there were 6 known clades and 11 haplotypes before the study -After sampling and analyses were finished the clades were increased to 7 and the haplotypes to 16


Distribution:
-Some clades had cosmopolitan distributions and some endemic


Differences in DNA sequences:
-Out of 536 nucleotide positions the analysis resulted in making 7 clades in 2 groups, A and B. -A is separated into A1 and A2


Analyzing the mean pairwise nucleotide distances between and within clades:

The distances within clades was between 1.6%-2.1% The distances between clades was between 3.8%-21.5%


Comparisons to Porifera and Cnidaria Phyla:
The distances between haplotypes were at the same order of magnitude as the distance between families or genera in Porifera and Cnidaria So? The mean distance between clades reflects a number that separates taxonomic categories in Porifera and Cnidaria


Summary: Phylogeography, unexpected high biodiversity
· Never more than a single haplotype, in a single sample, from a single site: -niches and competition

· Clades have individual niches and cover different amounts of areas
· Clade ranges: II
· Haplotypes are euryoecious and stenoecious

· Evidence concludes that there could be several dozen to 100s of species, with complicated diversity and distribution
· More research should be considered given then amount of haplotypes found per number of locations sampled · Researching a basal organism may help us understand other benthic organisms in general


Citation:
· Eitel, M., and B. Schierwater. "The Phylogeography of the Placozoa Suggests a Taxonrich Phylum in Tropical and Subtropical Waters." Molecular Ecology 19.11 (2010): 2315327. Print. · "Trichoplax Pictures." Trichoplax Pictures. N.p., n.d. Web. 26 Feb. 2014. · Scientific Classification. N.p., n.d. Web. 26 Feb. 2014. · http://chandra.harvard.edu/xray_astro/navigation3.htmlGalactic Navigation. N.p., n.d. Web. 26 Feb. 2014.