Fig. 7

Remodeling of the pectoral girdle and endoskeletal disc during the larva-to-juvenile transition. a Developmental stages of the mudskipper Ps. modestus. Pink, blue, yellow, and brown bars indicate embryonic, planktonic larval, benthic juvenile, and amphibious juvenile stages, respectively. The shaded region indicates the larva-to-juvenile transition. b–d Morphological changes observed during the larva-to-juvenile transition. Indicative metamorphic changes are observed during 7.9 mm to 18.6 mm TL, including differentiation of the median fin and initiation of pelvic fin bud formation during 7.9 mm TL (b); formation of 14 fin rays during 14.5 mm TL and their ossification, as well as individualization of proximal radials and their ossification during 18.6 mm TL (c); and the dorsal shift in eye position and dispersion of melanophores throughout the body during 18.6 mm TL (d). e–g Morphological changes in the endoskeletal disc at each stage indicated in (a). Blue dots indicate the region where active cell divisions are observed. ed., endoskeletal disc: ff, fin fold. h-j The shape and oriented division of chondrogenic cells of the endoskeletal disc within the pectoral fin. h At the beginning of the planktonic larval stage, round-shaped cells are found proximally, whereas cylindrical cells are aligned along the proximal-distal axis. i At the beginning of the larva-to-juvenile transition [10], cells are actively dividing in the proximal region, whereas in the distal region they are cylindrical in shape, only infrequently dividing, and aligned along the proximal-distal axis. j At the end of the larva-to-juvenile transition, the distal cylindrical cells are dividing actively along the proximal-distal axis. See text for details