Thyroid gland development in Rachycentron canadum during early life stages

Abstract

The aim of this study was to describe the ontogeny of thyroid follicles in cobia Rachycentron canadum. Larvae were sampled daily (n=15 -20) from hatching until 15 dah (days after hatching). Following, larvae were sampled every two days by 28 dah; a new sample was taken at 53 dah. The samples were dehydrated, embedded in Paraplast, and sections of 3 µm were dewaxed, rehydrated and stained with HE and PAS. A single follicle was already present 1 dah and three follicles were found 8 dah. The number of follicles increased up to 19 on 53 dah. The diameter of follicles and follicular cell height were lower 1 dah (6.83 ± 1.00 and 4.6 ± 0.01 µm), but increased from 8 dah (24.03 ± 0.46 μm e 6.43 ± 0.46 μm). From 8 dah, the presence of reabsorption vesicles was observed in the colloid and from the 19 dah some follicles did not present colloid. The early thyroid follicle appearance in cobia larvae as well as the high quantity of follicles without colloid and/or with vesicles even after the metamorphosis, might be the explanation of the fast growth of the cobia.

Effect of triiodothyronine (T3) in the larval development of the barber gobyElacatinus figaro

“…Delgado et al (2006) noticed that after the metamorphosis of Solea senegalensis, the number of follicles remained constant and the size of the follicle cells decreased. The same pattern was noticed with cobia Rachycentron canadum, where individuals of 23-28 DAH, showed 18 follicles, and this number remained constant until 53 DAH (Otero et al, 2014).…”

“…In fish and amphibious, thyroid follicles do not compose a single organ as in mammals, and are microscopically found spread all over the entire afferent artery (Yamano, ). In E. figaro , thyroid follicles were found in the branchial region along the afferent artery and ventral aorta, as seen in most teleosts (Delgado, Ruane, & Pousão‐Ferreira, ; Einarsdóttir, Silva, Power, Smáradóttir, & Björnsson, ; Otero et al, ; Yamano, ).…”

“…Different letters are significantly different from each other by Tukey's test (p < 0.5. TCcontrol, no addition of the T 3 ; T01concentration of 0.01 mg/L T 3 ; 025concentration of 0.025 mg/L T 3 ; T05concentration of 0.05 mg/L T 3 ) & Pousão-Ferreira, 2006;Einarsdóttir, Silva, Power, Smáradóttir, & Björnsson, 2006;Otero et al, 2014;Yamano, 2005).…”

“…Slides with sections of 5 µm were prepared with the assistance of a semi-automatic microtome (LUPE-TEC MRPO3; Lupetec) and then stained with periodic acid-Schiff.The slides were observed in an optical microscope (Primo Star Gmbh; Carl Zeiss, Germany) attached to a digital camera (Axiocam ERc 5s; Carl Zeiss). The thyroid follicles were quantified and then measured for their area and diameter, and the presence of resorption vacuoles was verified according toOtero, Rodrigues, Sampaio, Romano, and Tesser (2014).…”

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 .…”