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The Role of Ligaments in Arm Extension in Feather Stars (Echinodermata: Crinoidea)
Author(s) -
Grimmer John C.,
Holland Nicholas D.
Publication year - 1987
Publication title -
acta zoologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.414
H-Index - 37
eISSN - 1463-6395
pISSN - 0001-7272
DOI - 10.1111/j.1463-6395.1987.tb00879.x
Subject(s) - coelom , feather , anatomy , biology , stars , physics , zoology , astrophysics
It has long been thought that feather star arms flex due to muscular contraction and extend due to an opposing elastic force supplied by the ligaments, however, in 1985, Candia Carnivali and Saita ( J. Morph. 185 , 59–74) proposed that extension was due not to elastic ligaments, but to hydraulic pressure within the coelomic canals of the arm. We tested this new proposal experimentally by destroying the coelomic canals along the proximal halves of all ten arms of a feather star and then inducing it to swim. The wave form of the swimming arms was recorded on cine film for frame analysis. While the animal was swimming even the arm regions without coelomic canals were able to extend vigorously. Therefore, hydraulic pressure in the coeloms is not required for arm extension in feather stars. Our results are consistent with the classical idea that elastic ligaments extend the arms of crinoids.