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Symmetry of priapulids (Priapulida). 1. Symmetry of adults
Author(s) -
Adrianov Andrey V.,
Malakhov Vladimir V.
Publication year - 2001
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/1097-4687(200102)247:2<99::aid-jmor1005>3.0.co;2-0
Subject(s) - symmetry (geometry) , bilateral symmetry , symmetry in biology , sagittal plane , homogeneous space , biology , symmetry operation , rotational symmetry , physics , anatomy , geometry , mathematics , paleontology , mechanics , mechanical engineering , engineering
Priapulids possess a radial symmetry that is remarkably reflected in both external morphology and internal anatomy. It results in the appearance of 25‐radial (a number divisible by five) symmetry summarized as a combination of nonaradial, octaradial, and octaradial (9+8+8) symmetries of scalids. The radial symmetry is a secondary appearance considered as an evolutionary adaptation to a lifestyle within the three‐dimensional environment of bottom sediment. The eight anteriormost, or primary, scalids retain their particular position because of their innervation directly from the circumpharyngeal brain. As a result of a combination of the octaradial symmetry of primary scalids, pentaradial symmetry of teeth, and the 25‐radial symmetry of scalids, the initial bilateral symmetry remains characterized by the single sagittal plane. J. Morphol. 247:99–110, 2001. © 2001 Wiley‐Liss, Inc.