Biology Reference
In-Depth Information
A
C
d
d
r
l
r
l
v
v
B
l
d
r
l
d
v
v
r
Figure 6.1 The flatfish interocular and interaural axes reorient perpendicular to each
other during metamorphosis. The interocular and interaural axes are parallel to each
other in typical larval and adult “round” fish (A) and also in fish with dorsoventrally
compressed morphology (e.g., skates and rays, Superorder Batoidea; anglerfish,
Family Lophiidae) (B). The interocular and interaural axes in laterally compressed
premetamorphic larval flatfish (Order Pleuronectiformes) are initially parallel to each
other but reorient during metamorphosis as one eye migrates to the opposite side
of the head; by the postmetamorphic juvenile stage, the axes have become perpendic-
ular to each other (C). Dashed line denotes interocular axis, and dotted line denotes the
interaural axis. Dorsal, d; ventral, v; left, l; right, r. The dorsal-medial-localized curved lines
denote the semicircular canals.
2. GENETIC BASIS OF FLATFISH ASYMMETRY
Within the currently recognized 15 flatfish families, most species are
laterally monomorphic and, as adults, display either exclusively “dextral”
(both eyes are located on the right side after metamorphosis) or “sinistral”
(both eyes are located on the left side) morphology (
Munroe, 2005
).
However, of the approximately 715 known flatfish species, 7 display varying
proportions of dextral to sinistral polymorphism within geographically dis-
tinct populations (
Bergstrom, 2007; Hubbs & Hubbs, 1944; Munroe, 2005;
Policansky, 1982b
). For example, in starry flounder (
Platichthys stellatus
), the
proportion of sinistrality increases along a geographical gradient from 50% in
California to 100% in Japan (
Bergstrom, 2007; Hubbs & Kuronuma, 1942
),
