The thyroid gland has several functions,some of which are related to the growth of sea turtles.The gland structure and thyroxine levels appear to vary cyclically throughout a year in many vertebrate species.For two years,we observed the microstructure and ultrastructure of the thyroid in juvenile green turtles(Chelonia mydas) (N =20).The structure of the green turtle thyroid was similar to that of other reptiles,and the microstructure and ultrastructure of thyroid cells in juveniles showed significant annual changes.To observe the response of thyroid secretions to turtle growth,we used the chemiluminescence method to determine the levels of serums triiodothyronine (T3) and tetraiodothyronine (thyroxine or T4) in 8-to 20-month-old captive green turtles (N =60).We found that serum T3 concentration peaked in July,and juvenile growth peaked two months later in September.The highest serum T4 level was recorded in October.Air and water temperatures coincided positively with the annual change in T3 and T4 concentrations.The findings of this study infer an annual pattern in monthly growth rate,thyroid structural changes and concentrations of thyroid hormone.Monitoring of thyroid hormones may be useful for triage,monitoring of recovery,and assessing readiness for release.%观察了绿海龟甲状腺显微和超微结构特点,不仅说明绿海龟甲状腺具有和其他爬行动物相似的组织结构,而且幼体绿海龟甲状腺的组织结构和细胞超微形态特点也表现出明显的年周变化特点.通过化学发光法测定了人工养殖的8～20月龄绿海龟血清甲状腺激素的含量,结果表明:绿海龟血清T3(三碘甲状腺氨酸)浓度最高峰出现在7月,而生长速度最快的月份却是9月,滞后2个月;血清T4(四碘甲腺原氨酸)最高值出现在10月;全年环境温度(气温、水温)与绿海龟血清中T3、T4浓度变化皆成近似平行的单峰曲线.结论:绿海龟全年生长速度、甲状腺细胞形态结构和甲状腺激素分泌水平具有一定的节律性.监测甲状腺激素可以对分诊、监测健康恢复和评估放生海龟的准备工作有用.
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