Definition of Term

annulus

(English) In ichthyology, a ring or rings on a fish scale or in a bony or cartilaginous structure corresponding to a year of growth. In a scale usually constists of closely arranged ridges (circuli). An accessory annulus is a ring caused by retarded or temporarily terminated growth that does not represent an annual cycle. In the tropics annuli may indicate spawning rather than growth. (See also: growth, ichthyology, cartilage)

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