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Spongilla lacustris Trinity transcriptome
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Sponges (Porifera) are among the earliest evolving metazoans. Their filter-feeding body plan based on choanocyte
chambers organized into a complex aquiferous system is so unique among metazoans that it either reflects an early
divergence from other animals prior to the evolution of features such as muscles and nerves, or that sponges lost these
characters. Analyses of the Amphimedon and Oscarella genomes support this view of uniqueness—many key metazoan
genes are absent in these sponges—but whether this is generally true of other sponges remains unknown.We studied the
transcriptomes of eight sponge species in four classes (Hexactinellida, Demospongiae, Homoscleromorpha, and Calcarea)
specifically seeking genes and pathways considered to be involved in animal complexity. For reference, we also sought
these genes in transcriptomes and genomes of three unicellular opisthokonts, two sponges (A. queenslandica and O.
carmela), and two bilaterian taxa. Our analyses showed that all sponge classes share an unexpectedly large complement of
genes with other metazoans. Interestingly, hexactinellid, calcareous, and homoscleromorph sponges share more genes
with bilaterians than with nonbilaterian metazoans. We were surprised to find representatives ofmostmolecules involved
in cell–cell communication, signaling, complex epithelia, immune recognition, and germ-lineage/sex, with only a few, but
potentially key, absences. A noteworthy finding was that some important genes were absent from all demosponges
(transcriptomes and the Amphimedon genome), which might reflect divergence from main-stem lineages including
hexactinellids, calcareous sponges, and homoscleromorphs. Our results suggest that genetic complexity arose early in
evolution as shown by the presence of these genes in most of the animal lineages, which suggests sponges either possess
cryptic physiological and morphological complexity and/or have lost ancestral cell types or physiological processes. -
- Date created
- 2014-02-27
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