Hartfelder K, Cnaani J, Hefetz A
Departamento de Biologia, FFCLRP-Universidade de São Paulo, 14040-901, Ribeirao Preto, SP, Brazil
J Insect Physiol. 2000 Nov 1;46(11):1433-1439. doi: 10.1016/s0022-1910(00)00067-6.
Mounting evidence implicates ecdysteroids in queen-worker differentiation during the last larval instars of highly social insects. In the present study, we analyzed ecdysteroid titers in queen and worker larvae of the bumblebee Bombus terrestris from the second to the early fourth instar. B. terrestris is of particular interest because caste is already determined in the second instar, presumably by a pheromonal signal emitted by the egg-laying queen. Caste differences in the adults, however, are only expressed at the physiological and not at the morphological level, except for the distinctly larger size of the queen. In the second and third instar, ecdysteroid titers in queen larvae were generally higher than those of workers. These early caste-specific differences, however, were abolished in the fourth instar. In the early fourth instar we could detect two small ecdysteroid peaks, with the one preceding the cocoon-spinning phase presenting the characteristics of a pupal commitment peak. The synchrony of caste differences in ecdysteroid and juvenile hormone titers suggests a synergistic action of these hormones in caste determination.
越来越多的证据表明，蜕皮类固醇在高度社会化昆虫的最后幼虫龄期的蜂王 - 工蜂分化过程中起作用。在本研究中，我们分析了从第二龄到第四龄早期的地熊蜂蜂王和工蜂幼虫体内的蜕皮类固醇滴度。地熊蜂特别引人关注，因为其在第二龄时就可能由产卵蜂王发出的信息素信号决定了级型。然而，成虫的级型差异仅在生理水平而非形态水平上表现出来，除了蜂王明显更大的体型。在第二龄和第三龄时，蜂王幼虫体内的蜕皮类固醇滴度通常高于工蜂幼虫。然而，这些早期的级型特异性差异在第四龄时消失了。在第四龄早期，我们可以检测到两个小的蜕皮类固醇峰值，其中在结茧阶段之前的那个峰值呈现出蛹期承诺峰值的特征。蜕皮类固醇和保幼激素滴度中级型差异的同步性表明这些激素在级型决定中具有协同作用。
