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reared fl atfi shes. Concentrations of fatty acids, particularly DHA and EPA
or DHA/EPA ratio, in the diet are considered to be important factors for the
healthy development and normal pigmentation of fl atfi sh larvae (Kanazawa,
1993; Estevez and Kanazawa, 1995; Naess and Lie, 1998). On the other
hand, Vitamin A seems to be rather specifi cally related to pigmentation of
cultured fl atfi sh. Vitamin A supplementation to rotifer or Artemia distinctly
reduced albinism in the Japanese fl ounder (Miki et al., 1990; Takeuchi et al.,
1995) and in turbot, Scophthalmus maximus (Estevez and Kanazawa, 1995),
though administration of too much Vitamin A induced skeletal deformity at
a high rate (Estevez and Kanazawa, 1995; Takeuchi et al., 1995). Miwa and
Yamano (1999) found that administration of 9-cis-retinoic acid, biologically
active retinoid normally synthesized from vitamin A, in the rearing seawater
at premetamorphosis or prometamorphosis induced the development of
adult type chromatophores not only on the ocular side but also on the blind
side, resulting in reduction of albinism and induction of ambicoloration. To
enhance larval nutrition and normal pigmentation, proper enrichment of
zooplankton with fatty acids and vitamin A compounds have been proposed
and is now commonly used in rearing fl atfi shes (Takeuchi et al., 1995; Dedi
et al., 1995; Bolker and Hill, 2000).
One of the most important fi ndings shared by above mentioned studies
may be that the period responsible for the modulation of pigmentation
anomalies by nutrition is early developmental stage, or more specifi cally,
the period from premetamorphosis to prometamorphosis. This period
coincides with the timing of chromatoblast differentiation to adult type
chromatophores (see Development of asymmetrical pigmentation in this
chapter). Seikai et al. (1987) found that albinistic skins totally lack adult-
type melanophores, having exclusively a small number of large-sized
larval melanophores. Miwa and Yamano (1999) reported that the sensitive
stage of the fl ounder to retinoic acid was earlier than the time when the
adult chromatophores actually appear, suggesting that retinoic acid only
stimulates the determination of the developmental fate of neural crest cells to
adult chromatophores but does not stimulate chromatophore development
itself. Seikai et al. (1987) also reported that albinism in fl ounder juveniles
fed on Brazilian Artemia was caused, at least in part, by the blockage of
melanoblast development into adult-type melanophores. Collectively, these
studies indicate that dietary imbalance, especially that of vitamin A or its
precursors induces most of albino and some ambicoloration in hatchery-
reared fl ounder juveniles, by disturbing the differentiation of chlomatoblast
to adult type chromatophores during early metamorphosis.
Administration of a high dose of thyroid hormone to the Japanese
fl ounder, especially at prometamorphosis, induced albinism at a very
high rate (Yoo et al., 2000). As thyroid hormone primarily regulate
metamorphosis, it is quite conceivable that the pigmentation during
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