THE NUCLEUS SIZE AND POSSIBLE PEDOMORPHOSIS OF THE PITUITARY IN THE GOBY, RHINOGOBIUS-FLUMINEUS

This study offers an example of the attempts to correlate the shape of an organ to the nucleus size. The pituitary glands of gobiid teleosts are partly embedded in the hypothalamus in contrast to those of non-g obiid teleosts. The pituitaries of the embryonic smelt, catfish, and g uppy are partly embedded in the hypothalamus as in the embryonic and a dult goby, Rhinogobius flumineus. The nucleus size of cerebellar granu lar cells, that may represent the genome size, is variable in gobies ( 16 species studied) as in non-gobiid perciforms (63 species studied). However, the ratio of the nucleus size of cerebellar Purkinje's cells to that of granular cells is consistently low in gobiids compared with non-gobiid perciforms. This ratio is a sort of peramorphic (morpholog ically advanced) index, and the low value may represent paedomorphosis (juvenile morphology). The gobiid pituitary gland partly embedded in the hypothalamus may be the result of paedomorphosis that could be ref lected in the relatively poor increase rate in the size of Purkinje's cells as against the genome size.