Article Figures & Tables
Figures
- Fig. 1.
Temporal change in T3 content (N=5, open circles) and otolith growth (N=14, filled circles) of tilapia larvae and juveniles during the experimental period. T3 content was measured every 2 days but samples at 27 day post-hatching were lost. The data are given as means ± s.e.m. for clarity.
- Table 1.
Effects of thiourea treatment on tilapia juveniles
0 p.p.m. 300 p.p.m. 600 p.p.m. 900 p.p.m. Total length (mm) 13.7±1.1a 11.3±0.5b 10.7±0.4c 10.4±0.4c Wet mass (mg) 35.1±11.0a 16.4±2.6b 12.9±1.4bc 10.9±1.6c Mortality (%) 0 13.6 50.8 44.1 Otolith growth Core to TC (μm) 127.4±10.3a 127.8±8.5a 128.8±5.9a 127.1±7.2a TC to edge (μm) 80.5±27.2a 45.4±6.1b 34.8±6.9c 33.2±4.8c Newly deposited DGI 13.0±1.3a 11.0±0.9b 9.0±0.9c 9.2±1.1c -
Fish were immersed in different concentrations of thiourea (TU, p.p.m.) from 15 to 27 days post-hatching (d.p.h.) and were then killed for measurement on 28 d.p.h. Data are shown as means ± s.d. (N=15–18). TC, tetracycline mark; DGI, daily growth increment. Values with different superscript letters are significantly different (P<0.05)
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- Table 2.
Effects of thiourea, triiodothyronine or both on tilapia juveniles
0 p.p.m. 0.1 p.p.b. T3 10 p.p.b. T3 0.1 p.p.b. T3 + 300 p.p.m. TU 10 p.p.b. T3 + 300 p.p.m. TU Total length (mm) 18.4±1.0a 18.1±1.3a 19.2±1.2a 14.0±0.6b 13.9±0.5b Wet mass (mg) 80.1±16.4a 76.9±20.7a 88.9±21.4a 25.2±4.9b 24.5±5.1b Mortality (%) 0 0 3.7 0 7.4 Otolith growth Core to TC (μm) 191.3±5.6a 192.9±4.4a 192.2±4.8a 189.6±5.7a 189.9±5.2a TC to edge (μm) 111.6±20.5a 113.1±20.8a 129.9±16.5a 45.7±11.8b 62.9±10.7b Newly deposited DGI 13.2±0.4b 14.0±0.7ab 14.4±0.9a 9.0±1.6c 10.8±1.6c -
Fish were immersed in different treatments from 15 to 27 days post-hatching (d.p.h.) and samples were killed for measurement on 28 d.p.h. Data are shown as means ± s.d. (N=22–26). TU, thiourea; T3, triiodothyronine; TC, tetracycline mark; DGI, daily growth increment. Values with different superscript letters are significantly different (P<0.05)
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- Table 3.
Newly deposited daily growth increment of the tilapia juveniles receiving different treatments of thiourea and triiodothyronine
DGI 0 p.p.m. 0.1 p.p.b. T3 10 p.p.b. T3 0.1 p.p.b. T3 + 300 p.p.m. TU 10 p.p.b. T3 + 300 p.p.m. TU 6 – – – 2 (8%) – 7 – – – 2 (8%) – 8 – – – 4 (16%) – 9 – – – 8 (32%) 5 (22.73%) 10 – – – 6 (24%) 6 (27.27%) 11 – – – 2 (8%) 4 (18.18%) 12 – – – – 4 (18.18%) 13 21 (80.77%) 5 (20.83%) 5 (19.23%) 1 (4%) 1 (4.55%) 14 5 (19.23%) 14 (58.33%) 7 (26.92%) – 2 (9.09%) 15 – 5 (20.83%) 12 (46.15%) – – 16 – – 2 (7.69%) – – -
Fish were immersed in different treatments from 15 to 27 days post-hatching (d.p.h.). and samples were killed for measurement on 28 d.p.h. (N=22–26). DGI, daily growth increment; T3, triiodothyronine; TU, thiourea
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- Table 4.
Effects of thiourea, triiodothyronine, or both on tilapia larvae
Larvae 0 p.p.m. 25 p.p.b. T3 300 p.p.m. TU 25 p.p.b. T3 + 300 p.p.m. TU Total length (mm) 11.0±1.1a 11.0±0.9a 10.8±0.7a 10.9±0.6a Wet mass (mg) 14.5±4.1a 14.6±4.9a 12.4±2.9a 12.6±1.9a Mortality (%) 40 6.7 35.5 56.8 Otolith growth TC to edge (μm) 156.0±18.8b 171.7±18.8a 147.9±10.6b 156.1±13.5b Newly deposited DGI 14.4±1.3a 15.0±1.0a 13.8±0.5a – T3 content (ng g–1) 1.4±0.4b 4.8±0.9a 0.8±0.3b – -
Fish were immersed in different treatments from 4 to 16 days post-hatching (d.p.h.) and were killed for measurement on 17 d.p.h. Data are shown as means± s.d. (N=13–20). TU, thiourea; T3, triiodothyronine; TC, tetracycline mark; DGI, daily growth increment. Values with different superscript letters are significantly different (P<0.05)
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- Fig. 2.
Ontogenic expression of thyroid hormone receptor α (filled circles) and β (open circles) RNA during tilapia larval and juvenile stages (N=3). The mRNA expression was normalized in relation toβ -actin. The data are given as means ± s.e.m.
- Fig. 3.
Microstructure and morphology of otoliths from tilapia juveniles immersed in 300 p.p.m. thiourea (TU) from 15 to 27 days post-hatching (d.p.h.), followed by a recovery period in fresh water from 28 to 41 d.p.h. (C,D,F). Otoliths of normal fish are shown in A,B,E for comparison. The innermost fluorescent ring indicates the beginning of TU treatment. The outer three fluorescent rings were laid down on the second, fourth and sixth day after ending TU treatment. A–D are left sagittae; E and F are right sagittae. AR, antirostrum; PR, postrostrum; R, rostrum. Scale bars, 100 μm.
- Fig. 4.
Otolith growth rate during the 300 p.p.m. thiourea (TU) treatment from 15 to 27 d.p.h., followed by recovery in fresh water from 28–41 d.p.h. Filled circles indicate the control group without treatment; open circles indicate the experimental group (N=12 for each group). Data are shown as means ± s.e.m. for clarity. Arrows indicate the dates of treatment with tetracycline that produced the fluorescent rings as shown in Fig. 3.
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