The influence of thyroid hormone on development and settlement of spottybelly greenling (Hexagrammos agrammus; pisces)
Titel:
The influence of thyroid hormone on development and settlement of spottybelly greenling (Hexagrammos agrammus; pisces)
Auteur:
Matsumoto, Shigeki Tanaka, Masaru
Verschenen in:
Marine & freshwater behaviour & physiology
Paginering:
Jaargang 28 (1996) nr. 1-2 pagina's 33-44
Jaar:
1996-07
Inhoud:
Spottybelly greenling (Hexagrammos agrammus; Pisces) grow from a newly hatched larva to dorsal-bluish and ventral-silvery pelagic juvenile. During the juvenile period a habitat shift occurs from offshore neustonic to nearshore benthic life and the body color becomes brown. Two experiments were conducted to investigate the importance of thyroid hormones to these morphological and behavioral changes. In the first experiment, developmental changes in tissue thyroid hormone concentrations were measured. Both thyroxine (T4) and triiodothyronine (T3) concentrations were low in the pre-metamorphic phase (T4, 1.04 ng/g; T3, 0.10 ng/g) increased significantly at the early and late metamorphosing phases (T4, 13.20-21.25 ng/g; T3, 0.30-0.60 ng/g), then declined during the post-metamorphic phase (T4, 5.97 ng/g; T3, 0.38 ng/g). In the second experiment, 0.1 ppm T4 and 30 ppm of thiourea (TU, antithyroidal agent) were added to the rearing water of pre-metamorphic juveniles. The body color of T4-treated fish transformed and these fish settled to the bottom significantly earlier than control fish. In contrast, TU inhibited both the morphological and behavioral changes. These findings suggest that thyroid hormones play an important role in morphological and behavioral transformations associated with the habitat shift in spottybelly greenling.
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