Vascular Adaptations for Blood Supply to Locomotory Muscles of Icefish
191
Fig. 4. Scanning electronmicrographs of vascular casts from Chionodraco hamatus
pectoral muscle. Scale bars included for each picture. a Feed arteriole (A) lying under a
mat of capillaries, some of which branch direct from the parent vessel. b The capillary bed
covers muscle fibers in an evenly spaced network, orientated with the long axis. T, terminal
arteriole; C capillary; V collecting venule. c Loops formed by convergence and divergence
of capillaries (C) provide maximal coverage of the fibre surface for diffusive exchange. d
Large drainage venules (V) have joining capillaries as well as terminal venules (T). Muscle
fibre axis lies in the horizontal direction
Capillaries from trout muscle are orientated along the longitudinal axis
of muscle fibres (unpublished data) with some tortuosity but little
branching (anisotropic orientation) adding only ca. 5% to capillary length
over that of a truly straight capillary network, as in other teleosts [8].