The analyses described above concluded that sponges are closest to the ancestors of all Metazoa, of all multi-celled animals including both sponges and more complex groups. However, another comparison in 2008 of 150genes in each of 21genera, ranging from fungi to humans but including only two species of sponge, suggested that comb jellies ( ctenophora) are the most basal lineage of the Metazoa included in the sample. [116] [117] [118] [119] If this is correct, either modern comb jellies developed their complex structures independently of other Metazoa, or sponges' ancestors were more complex and all known sponges are drastically simplified forms. The study recommended further analyses using a wider range of sponges and other simple Metazoa such as Placozoa. [116] These creatures do not have any form of digestive system. Regardless, they use their pore system to obtain nutrients in the form of food particles. The individual cells of the organism absorb food particles and digest them. This process occurs instead of the creature having a specialized set of cells that digests the food. Carnivorous Sponges

a b c Krautter M (1998). "Ecology of siliceous sponges: Application to the environmental interpretation of the Upper Jurassic sponge facies (Oxfordian) from Spain" (PDF). Cuadernos de Geología Ibérica. 24: 223–239. Archived from the original (PDF) on March 19, 2009 . Retrieved 2008-10-10. Sponges have three asexual methods of reproduction: after fragmentation, by budding, and by producing gemmules. Fragments of sponges may be detached by currents or waves. They use the mobility of their pinacocytes and choanocytes and reshaping of the mesohyl to re-attach themselves to a suitable surface and then rebuild themselves as small but functional sponges over the course of several days. The same capabilities enable sponges that have been squeezed through a fine cloth to regenerate. [44] A sponge fragment can only regenerate if it contains both collencytes to produce mesohyl and archeocytes to produce all the other cell types. [34] A very few species reproduce by budding. [45] Sponges". Cervical Barrier Advancement Society. 2004. Archived from the original on January 14, 2009 . Retrieved 2006-09-17. Medina M, Collins AG, Silberman JD, Sogin ML (August 2001). "Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA". Proceedings of the National Academy of Sciences of the United States of America. 98 (17): 9707–12. Bibcode: 2001PNAS...98.9707M. doi: 10.1073/pnas.171316998. PMC 55517. PMID 11504944. Even if a few sponges are able to produce mucus – which acts as a microbial barrier in all other animals – no sponge with the ability to secrete a functional mucus layer has been recorded. Without such a mucus layer their living tissue is covered by a layer of microbial symbionts, which can contribute up to 40–50% of the sponge wet mass. This inability to prevent microbes from penetrating their porous tissue could be a major reason why they have never evolved a more complex anatomy. [22]A sponge's body is hollow and is held in shape by the mesohyl, a jelly-like substance made mainly of collagen and reinforced by a dense network of fibers also made of collagen. The inner surface is covered with choanocytes, cells with cylindrical or conical collars surrounding one flagellum per choanocyte. The wave-like motion of the whip-like flagella drives water through the sponge's body. All sponges have ostia, channels leading to the interior through the mesohyl, and in most sponges these are controlled by tube-like porocytes that form closable inlet valves. Pinacocytes, plate-like cells, form a single-layered external skin over all other parts of the mesohyl that are not covered by choanocytes, and the pinacocytes also digest food particles that are too large to enter the ostia, [21] [23] while those at the base of the animal are responsible for anchoring it. [23]

One of these predators is the sponge fly. These opportunists have developed specialist skills to effectively target sea sponges. They will lay their eggs in the proximity of the sea sponges. Then once they are fertilized and hatched, they will be released to feed on the nearest sponges. They will utilize their long mouths to tear through the spongy outer flesh. They will sometimes settle within the sponge itself and feed from the inside.Other anatomical and biochemical evidence links the Eumetazoa with Homoscleromorpha, a sub-group of demosponges. A comparison in 2007 of nuclear DNA, excluding glass sponges and comb jellies, concluded that: Tanaka Y, Miyajima T, Umezawa Y, Hayashibara T, Ogawa H, Koike I (2009) Net release of dissolved organic matter by the scleractinian coral Acropora pulchra. J Exp Mar Biol Ecol 377: 101−106 Egan S, Thomas T (2015). "Editorial for: Microbial symbiosis of marine sessile hosts- diversity and function". Frontiers in Microbiology. 6: 585. doi: 10.3389/fmicb.2015.00585. PMC 4468920. PMID 26136729. The majority of sea sponge species retain their eggs until they have fully developed. However, some do release their sperm into the water column. They then float around and once fertilized, they turn into larvae. These larvae then hunt for the perfect conditions to grow.