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Symmetry of priapulids (Priapulida). 2. Symmetry of larvae
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<111::aid-jmor1006>3.0.co;2-c
Subject(s) - symmetry (geometry) , biology , symmetry in biology , bilateral symmetry , anatomy , excretory system , physics , geometry , paleontology , mathematics , mechanical engineering , engineering
Larvae of priapulids are characterized by radial symmetry evident from both external and internal characters of the introvert and lorica. The bilaterality appears as a result of a combination of several radial symmetries: pentaradial symmetry of the teeth, octaradial symmetry of the primary scalids, 25‐radial symmetry of scalids, biradial symmetry of the neck, and biradial and decaradial symmetry of the trunk. Internal radiality is exhibited by musculature and the circumpharyngeal nerve ring. Internal bilaterality is evident from the position of the ventral nerve cord and excretory elements. Externally, the bilaterality is determined by the position of the anal tubulus and two shortened midventral rows of scalids bordering the ventral nerve cord. The lorical elements define the biradial symmetry that is missing in adult priapulids. The radial symmetry of larvae is a secondary appearance considered an evolutionary adaptation to a lifestyle within the three‐dimensional environment of the benthic sediment. J. Morphol. 247:111–121, 2001. © 2001 Wiley‐Liss, Inc.