Fig. 9.

Model for developmental relationships between tissues in the young caudal fin. Upper row, wild-type (WT). (A) At the beginning of caudal fin development, the epidermis (as grids) first establishes the fin ray pattern (only two fin rays at midline are shown). The ray epidermis can be distinguished by the Zn8 antibody (orange grid). (B) Then, blood vessels (green) grow into the caudal fin and form the ray pattern which apparently follows the ray pattern established by the epidermis. At this stage, only two vessels are found in each fin ray, with one located in the center and the other outside but adjacent to the fin ray. (C) Soon after the blood vessels establish the ray pattern, osteoblasts form rays which are as wide as the future fin ray (red boxes) associated with the blood vessels. The epidermis is not shown. (D) Osteoblasts then begin to deposit the ray matrix (gray boxes). (E) Mature fin rays form, and within each one, three blood vessels can be found. Both the epidermis and osteoblasts were omitted for simplicity. Lower row, prp mutant. (A) The early epidermis development seems normal. (B) Soon after blood vessels grow into the caudal fin, they form plexuses. (C) Osteoblasts follow the blood vessel pattern and are often misconnected or fused (D). (E) The fin rays eventually become wavy and/or fused.