Biology Reference
In-Depth Information
of elongated fi n rays (Fig. 4-a), induction of settling behavior on the bottom
of the aquarium (Fig. 4-b) and migration of the right eye to the left of the
head. Thus, exogenous T4 produced miniatures of naturally metamorphosed
juvenile fl ounder (Fig. 5-b). On the other hand, administration of thiourea
(TU), an inhibitor of thyroid hormone synthesis, arrested the metamorphic
process and produced unnaturally large-sized larvae (Fig. 5-c). When T4 or T3
was administered to fl ounder larvae that were in metamorphic stasis by TU
Figure 5.
Effects of T
4
and TU on metamorphosis of the Japanese fl ounder. (a) Flounder
larvae kept in normal seawater, 30ppm TU, 0.05ppm T
4
, and 0.1ppm T
4
for 6 days. (b) A
subnormal-sized juvenile (lower) precociously metamorphosed by T
4
treatment and a naturally
metamorphosing larva (upper) at metamorphic climax. (c) A giant pelagic larva in metamorphic
stasis induced by TU (upper) and naturally metamorphosing larva (lower), after 27 days of
treatment. Each scale line represent 5mm. [From Inui and Miwa, 1985, wtih permission].
