Pituitary–thyroid axis development during the larval–juvenile transition in the pejerrey Odontesthes bonariensis

Abstract

The morphological development of the thyroid gland of pejerrey Odontesthes bonariensis during larval-juvenile transition was studied and related to whole-body concentrations of thyroxine (T ) and tri-iodothyronine (T ). A complementary (c)DNA fragment of the thyroid-stimulating hormone β-subunit (tshb) was sequenced and transcript levels quantified during this period. Follicles with eosinophilic and T -immunoreactive colloids were detected at hatching together with tshb transcript levels and whole-body concentrations of T and T hormones. Thyroid follicles were located in the subpharyngeal region associated with the ventral aorta below the hyoid bone. Follicle structure switched from the rounded form at hatching to oval in juveniles. Significant increase of follicle number per larva, mean colloidal area and total colloidal area was observed throughout development with maximum values at the end of the larval-juvenile transition. A significant decrease of tshb expression together with a significant increase in T and T whole-body concentrations was observed prior to achieving the juvenile phenotype. These results are in accordance with a negative feedback regulation of tshb expression by thyroid hormones and a possible association between thyroid hormone levels and the acceleration of metabolic processes necessary to complete metamorphosis.

Ontogenetic changes in the body structure of the Arctic fish Leptoclinus maculatus

“…Most follicles are discrete; however, some of them are conjoined, doubled, or organized in chains. The similar chains of follicles were present in Odontesthes bonariensis 30 , Rachycentron canadum 31 . This organization most probably indicates the continued folliculogenesis 32 .…”

Involvement of thyroid hormone in the intestine and liver development of the common sole (Solea solea L.) larvae

“…Dissimilar to other vertebrates, most teleosts do not have an organized compact thyroid gland; instead, they have dispersed thyroid follicles found individually or in clusters around the basibranchial region (Brown et al, 2004;Ortiz Delgado et al, 2006;Geven et al, 2007;Kawakami et al,2008;Hsu et al, 2014;Chalde and Miranda, 2017). For fish larvae, a few small follicles appear at the first stage of larval development, and then the follicles increase gradually in size and number (Miwa and Inui, 1987).…”