periproct


Also found in: Dictionary, Wikipedia.

periproct

[′per·ə‚präkt]
(invertebrate zoology)
The area surrounding the anus of echinoids.
References in periodicals archive ?
Periproct Position.--In irregular echinoids, the periproct lies between the two plate columns of the posterior interambulacrum (area 5).
The dendrasterid periproct undergoes retrodisplacement late in ontogeny.
elsmerensis, has a true marginal periproct (Durham 1949).
As the dendrasterid periproct moves onto the oral surface, it is accompanied by the adjacent plates in the posterior interambulacrum.
The retrodisplacement of the periproct serves as a conspicuous marker of this plate migration.
Retrodisplacement of the Periproct.--Mio-Pliocene dendrasterids often have marginal or admarginal periprocts.
The dendrasterid periproct also undergoes retrodisplacement.
Second, there is no obvious explanation for the retrodisplacement of the periproct. In fact, it is easier to see the adaptive costs of this feature than any adaptive benefits.
It assumes that a heterochronic change in the Echinarachnius pattern could simultaneously affect many aspects of test morphology, including the apical system, peristome, periproct, ambulacra, and interambulacra.
Fourth, the plates at the posterior margin, along with the associated periproct, would be displaced onto the oral surface.
This model successfully accounts for the unusual features of the dendrasterid oral surface, including the retrodisplacement of the peristome and periproct. However, one important question remains: what adaptive benefits are conferred by this developmental change?