Utilize este identificador para referenciar este registo: http://hdl.handle.net/10400.1/5480
Título: Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut
Autor: Einarsdóttir, Ingibjörg E.
Silva, Nadia
Power, Deborah
Smaàradóttir, Heiddis
Björnsson, Björn Thrandur
Palavras-chave: Flatfish
Pituitary
Thyroid
Metamorphosis
Hippoglossus hippoglossus
Data: 2006
Editora: Springer Verlag
Citação: Ingibjörg Eir Einarsdóttir Æ Nadia Silva Deborah M. Power Æ Heiddis Smáradóttir Björn Thrandur Bjornsson, "Thyroid and pituitary gland development from hatching through metamorphosis of a teleost flatfish, the Atlantic halibut" in Anat Embryol (2006) 211: 47–60.
Resumo: Fish larval development, not least the spectacular process of flatfish metamorphosis, appears to be under complex endocrine control, many aspects of which are still not fully elucidated. In order to obtain data on the functional development of two major endocrine glands, the pituitary and the thyroid, during flatfish metamorphosis, histology, immunohistochemistry and in situ hybridization techniques were applied on larvae of the Atlantic halibut (Hippoglossus hippoglossus), a large, marine flatfish species, from hatching through metamorphosis. The material was obtained from a commercial hatchery. Larval age is defined as day-degrees (D =accumulated daily temperature from hatching). Sporadic thyroid follicles are first detected in larvae at 142 D (27 days post-hatch), prior to the completion of yolk sack absorption. Both the number and activity of the follicles increase markedly after yolk sack absorption and continue to do so during subsequent development. The larval triiodothyronine (T3) and thyroxine (T4) content increases, subsequent to yolk absorption, and coincides with the proliferation of thyroid follicles. A second increase of both T3 and T4 occurs around the start of metamorphosis and the T3 content further increases at the metamorphic climax. Overall, the T3 content is lower than T4. The pituitary gland can first be distinguished as a separate organ at the yolk sack stage. During subsequent development, the gland becomes more elongated and differentiates into neurohypophysis (NH), pars distalis (PD) and pars intermedia (PI). The first sporadic endocrine pituitary cells are observed at the yolk sack stage, somatotrophs (growth hormone producing cells) and somatolactotrophs (somatolactin producing cells) are first observed at 121 D (23 days post-hatch), and lactotrophs (prolactin producing cells) at 134 D (25 days post-hatch). Scarce thyrotrophs are evident after detection of the first thyroid follicles (142 D ), but coincident with a phase in which follicle number and activity increase (260 D ). The somatotrophs are clustered in the medium ventral region of the PD, lactotrophs in the anterior part of the PD and somatolactotrophs are scattered in the mid and posterior region of the pituitary. At around 600 D , coinciding with the start of metamorphosis, somatolactotrophs are restricted to the interdigitating tissue of the NH. During larval development, the pituitary endocrine cells become more numerous. The present data on thyroid development support the notion that thyroid hormones may play a significant role in Atlantic halibut metamorphosis. The time of appearance and the subsequent proliferation of pituitary somatotrophs, lactotrophs, somatolactotrophs and thyrotrophs indicate at which stages of larval development and metamorphosis these endocrine cells may start to play active regulatory roles.
Peer review: yes
URI: http://hdl.handle.net/10400.1/5480
DOI: http://dx.doi.org/10.1007/s00429-005-0055-z
ISSN: 0340-2061
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