The possibilities outlined above are especially pertinent to the question of whether
osteoblasts and their microtubules are involved in the formation and positioning of
growth annuli on the scales of certain teleosts. Growth annuli are zones that are
interpolated in the pattern of circuli where the spacing and/or arrangement of circuli
differs distinctly from that of circuli in the intervening regions (Tesch, 1968). The
number and spacing of a scale’s growth annuli are sometimes used, rather like treerings,
to estimate the ages and growth rates of their owners (Van Oosten, 1957;
Tesch, 1968).