Trichoplax was discovered in 1883 by the German zoologist Franz Eilhard Schulze, in a seawater aquarium at the Zoological Institute in Graz, Austria.

The specific epithet adhaerens is Latin meaning "adherent", reflecting its propensity to stick to the glass slides and pipettes used in its examination.

One hypothesis is that the larger a motile animal lacking a nervous system is, the less coordinated its locomotion becomes, placing an upper limit on their possible size.

Trichoplax lacks tissues and organs; there is also no manifest body symmetry, so it is not possible to distinguish anterior from posterior or left from right.

The absence of this structure, which is otherwise to be found in all animals except the sponges, can be explained in terms of function: a rigid separating layer would make the amoeboid changes in the shape of Trichoplax adhaerens impossible.

Striking accumulations of calcium ions, which may have a function related to the propagation of stimuli, likewise suggest a possible role as protosynapses.

This view is supported by the fact that fluorescent antibodies against cnidarian neurotransmitters, i.e. precisely those signal carriers that are transferred in synapses, bind in high concentrations in certain cells of Trichoplax adhaerens, and thus indicate the existence of comparable substances in the Placozoa.

The genetic complement of Trichoplax adhaerens has not yet been very well researched; it has, however, already been possible to identify several genes, such as Brachyury and TBX2/TBX3, which are homologous to corresponding base-pair sequences in eumetazoans.

Antibody studies have been able to show that the gene's product occurs only in the transition zones of the dorsal and ventral sides, perhaps in a fifth cell type that has not yet been characterized.

Initially, molecular-biology methods were applied unsuccessfully to test the various theories regarding Placozoa's position in the Metazoa system.

Nevertheless, this negative result supported the suspicion that Trichoplax might represent an extremely primitive lineage of metazoans, since a very long period of time had to be assumed for the accumulation of so many mutations.

This contrasts to other model systems such as fruit flies and soil nematodes that have experienced a paring down of non-coding regions and a loss of the ancestral genome organizations.

[17] Trichoplax has been collected, among other places, in the Red Sea, the Mediterranean, and the Caribbean, off Hawaii, Guam, Samoa, Japan, Vietnam, Brazil, and Papua New Guinea, and on the Great Barrier Reef off the east coast of Australia.

[18] Field specimens tend to be found in the coastal tidal zones of tropical and subtropical seas, on such substrates as the trunks and roots of mangroves, shells of molluscs, fragments of stony corals or simply on pieces of rock.

In feeding, one or several small pockets form around particles of nutrients on the ventral side, into which digestive enzymes are released by the gland cells; the organisms thus develop a temporary "external stomach", so to speak.

This mode of feeding could be unique in the animal kingdom: the particles, collected in a slime layer, are drawn through the intercellular gaps (cellular interstices) of the epitheloid by the fibre cells and then digested by phagocytosis ("cell-eating").

Such "collecting" of nutrient particles through an intact tegument is only possible because some "insulating" elements (specifically, a basal lamina under the epitheloid and certain types of cell-cell junctions) are not present in the Placozoa.

[21] Placozoa can move in two different ways on solid surfaces: first, their ciliated crawling sole lets them glide slowly across the substrate; second, they can change location by modifying their body shape, as an amoeba does.

[22] It has been possible to demonstrate a close connection between body shape and the speed of locomotion, which is also a function of available food: Since the transition is not smooth but happens abruptly, the two modes of extension can be very clearly separated from one another.

The following is a qualitative explanation of the animal's behavior: The actual direction in which Trichoplax moves each time is random: if we measure how fast an individual animal moves away from an arbitrary starting point, we find a linear relationship between elapsed time and mean square distance between starting point and present location.

Using T. adhaerens as a model, 0.02–0.002 Hz oscillations in locomotory and feeding patterns were observed, and taken as evidence of complex multicellular integration, dependent on endogenous secretion of signal molecules.

Evolutionarily conserved low-molecular-weight transmitters (glutamate, aspartate, glycine, GABA, and ATP) acted as coordinators of distinct locomotory and feeding patterns.

It is also possible to rub Trichoplax adhaerens through a strainer in such a manner that individual cells are not destroyed but are separated from one another to a large extent.

[14] Trichoplax lack a homologue of the Boule protein that appears to be ubiquitous and conserved in males of all species of other animals tested.

[24] If its absence implies the species has no males, then perhaps its "sexual" reproduction may be a case of the above-described process of regeneration, combining cells from two separate organisms into one.

Due to the possibility of its cloning itself by asexual propagation without limit, the life span of Placozoa is infinite; in the laboratory, several lines descended from a single organism have been maintained in culture for an average of 20 years without the occurrence of sexual processes.

At the genetic level, the way in which Trichoplax adhaerens protects against damage to its genome needs to be studied, particularly with regard to the existence of special DNA-repair processes.

[citation needed] Significant genetic differences have been observed between collected specimens matching the morphological description of T. adhaerens, leading scientists to suggest in 2004 that it may be a cryptic species complex.

[30] A later study defined Trichoplax more restrictively as only clade I (haplotypes H1, H2 and H17), with H3 being suggested to belong to a separate undescribed genus in the family Trichoplacidae.

H2 have suggested that their genetic similarity might be due to an interbreeding event having happened in the wild at least several decades ago, with one of them being the result of hybridization between the other and a third unknown strain.