periproct


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periproct

[′per·ə‚präkt]
(invertebrate zoology)
The area surrounding the anus of echinoids.
References in periodicals archive ?
excentricus, the periproct is normally adjacent to the third pair of post-basicoronal plates (Gordon 1929; Durham 1955).
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.
But in modern forms, the periproct always moves from the posterior margin onto the oral surface, into an area with a high density of food grooves (fig.
The dendrasterid periproct also undergoes retrodisplacement.
Second, there is no obvious explanation for the retrodisplacement of the periproct.
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.