Metamorphosis of Flatfish (Pleuronectiformes) - Metamorphosis in Fish - page 107

CHAPTER 4
Metamorphosis of Flatfi sh
(Pleuronectiformes)
Yasuo Inui 1 and Satoshi Miwa 2, *
4.1 General Aspects of Flatfi sh Metamorphosis
Flatfi sh (Pleuronectiformes) are a group of teleosts. They have the most
extremely asymmetrical body of all vertebrates: both eyes lie either one
side of the head (Kyle, 1923; Norman, 1934; Hubbs and Hubbs, 1945;
Policansky, 1982a; Ahlstrom et al., 1984). In the same species, usually the
eyes are always either on the right side of the head (dextral) or on the left
side (sinistral). The two species of very primitive genus Psettodes are the
only fl atfi sh in which the eyed-side is indiscriminately determined in each
individual, and hence, there are both dextral and sinistral fi sh within the
same species. (Hubbs and Hubbs, 1945; Ahlstrom et al., 1984). In the starry
fl ounder, Platichthys stellatus , there are also both dextral and sinistral fi sh.
However, the eyed-side is not randomized as Psettodes but depends on the
location where the fi sh lives. Off the US coast they are nearly half sinistral
and half dextral. In the middle of the US and Japan, off Alaska, about 70
percent of them are sinistral, and in Japanese waters nearly 100 percent are
sinistral (Policansky, 1982a).
The asymmetry of the fl atfi sh appears during the development. When
the fl atfi sh hatch from eggs, they have symmetrical bodies like many other
fi shes, and they keep the symmetry and upright swimming position during
the pelagic, larval period. Toward the end of the larval stage, however, the
one eye migrates across the top of the head to the contralateral side of the
1 Tamaki, Mie, 519-0414, Japan.
E-mail: [e-mail]
2 Inland Station, National Research Institute of Aquaculture, Tamaki, Mie 519-0423, Japan.
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*Corresponding author