Three-Spined Stickleback Fish
(Gasterosteus aculatus)
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| Japanese Three-spined Stickleback Fish (Taken by Hooper from The Japan Times, 2006) |
A. Morphology and Morphometry
1. Morphology
The Three-spined stickleback have a laterally compressed body. The base of the tail is slender. In front of the
dorsal fin is three spines, a characteristic that give the fish its name (although,
some individuals may have two or four spines). The third spine (the closest one
to the dorsal fin) is shorter than the other two. Each spine is joined to the
body by a thin membrane on the back. The anal fin is preceded by a short spine,
and the pelvic fins consist of one spine each. All spines can be locked in
erect position, making the fish extremely hard to swallow by a predator. This
fish has large pectoral fins. The body has no scales, but is protected by bony
plates (scutes) on the back, flanks, and ventral.
