Effect of Water Velocity on the Timing of Skeletogenesis in the Arctic Charr, Salvelinus alpinus (Salmoniformes: Teleostei): An Empirical Case of Developmental Plasticity

Table 3

Direction of chondrification and ossification for the serially repeated elements of the median fins of Salvelinus alpinus reared under two treatments of water velocity (treatments S and F). Three conditions of direction have been interpreted: antero-posterior (A to P), bidirectional, and simultaneous (all elements forming simultaneously). (?) refers to ambiguous directionality (see text). NA is for not applicable. Bold-face indicates difference between treatments.

	Chondrification		Ossification
	Treatment S	Treatment F	Treatment S	Treatment F
Caudal fin
Epurals	A to P	simultaneous	simultaneous	A to P
Uroneurals	A to P	A to P	A to P	A to P
Hypurals	A to P	A to P	A to P	A to P
Ural chordocentra	NA	NA	bidirectional	bidirectional
Dorsal fin
Proximal radials	bidirectional	bidirectional	bidirectional	bidirectional (?)
Distal radials	bidirectional (?)	bidirectional	NA	NA
Anal fin
Proximal radials	bidirectional (?)	bidirectional	bidirectional	bidirectional
Distal radials	bidirectional (?)	A to P	NA	NA