The most basal animal group is the phylum Porifera, the sponges (Srivastava et al., 2010) . Sponges lack the complex tissue and organ structure found in other animal phyla, and lack cells specialized for protection from parasites. Although sponge immunobiology is in its infancy, one of the best-known sponges, Suberites domuncula, possesses membrane-spanning molecules that contain an intracellular Toll-interleukin 1 receptor (TIR) domain, though it lacks an external leucine-rich repeat pattern recognition receptor more typical of TLRs. On the basis of having a MyD88 homolog, S. domuncula has at least the rudiments of an NF-κB signaling pathway. Sponges also have molecules for attacking bacterial membranes, presumptive antiviral responses (Schroder et al., 2008) , and diversified scavenger receptor cysteine-rich molecules of unknown function (Wiens et al., 2007) .