Graduate School of Environmental Science, Hokkaido University, Sapporo, Japan.
PLoS One. 2012;7(9):e44527. doi: 10.1371/journal.pone.0044527. Epub 2012 Sep 17.
Ergonomic efficiency is in termites maximized by task partitioning among specialized castes. The isopteran caste systems can be classified as either (i) linear, when tasks are performed by pluripotent immatures (pseudergates), retaining the ability to develop into winged imagoes or (ii) bifurcated, with the presence of a true worker caste, which diverges early and permanently from the sexual (nymph/alate) line.
Here, we report on the ontogenetic potentialities of the highly polymorphic sand termite Psammotermes hybostoma. Beside numerous pluripotent pseudergates, constituting the main work force, some larger non-feeding apterous immatures, also occur. These individuals are unable to proceed to the winged imago stage, but store large amounts of fat and also give rise to large soldiers. Soldiers therefore originate from a wide range of apterous instars, consequently being highly polymorphic.
The caste system of P. hybostoma is essentially linear, as in other basal Rhinotermitidae, but is distinguished by the late bifurcation leading to large apterous immatures. Because these large worker-like individuals deviate late and do not perform worker tasks, they cannot be considered homologous to the true workers of Termitidae and advanced Rhinotermitidae, but they provide a novel example of the evolution of sterile immatures in termites.
通过专门分工，白蚁的任务分配可实现最佳的工效学效率。等翅目昆虫的等级制度可分为以下两种类型：（i）线性，此时多能未成熟个体（拟成虫）执行任务，保留发育成有翅成虫的能力；（ii）分支，存在真正的工蚁等级，该等级从性（若虫/有翅芽）线早期和永久分化。
本文报道了高度多态沙白蚁 Psammotermes hybostoma 的个体发生潜力。除了大量构成主要劳动力的多能拟成虫外，还存在一些较大的不取食无翅未成熟个体。这些个体无法进入有翅成虫阶段，但能储存大量脂肪，也能产生大型兵蚁。因此，兵蚁起源于广泛的无翅龄期，因此具有高度多态性。
P. hybostoma 的等级制度本质上是线性的，与其他基础等翅目昆虫一样，但具有导致大型无翅未成熟个体的后期分支。由于这些大型类似工蚁的个体后期偏离，并且不执行工蚁任务，因此不能将它们视为与 Termitidae 和高级 Rhinotermitidae 的真正工蚁同源，但它们提供了白蚁中不育若虫进化的新范例。
