Department of Entomology, North Carolina State University, Raleigh, NC 27695-7613, USA.
Evol Dev. 2010 Jan-Feb;12(1):95-105. doi: 10.1111/j.1525-142X.2009.00394.x.
Basal termites possess two developmental features that eusocial Hymenoptera lack: the majority of colony members are juveniles whose somatic and reproductive development is temporarily or permanently suspended, and individual development is characterized by extreme phenotypic plasticity. An examination of the literature indicates that the basis for these unique ontogenetic characters is not the prolongation of a pronymphal stage into postembryonic development, as recently suggested. Like other hemimetabolous insects, termites have three embryonic cuticles, and the pronymphal (EC3) cuticle is shed during or shortly after hatch. Nonetheless, a different developmental landmark, dorsal closure, occurs later during embryogenesis in termites than it does in their cockroach relatives, clearly indicating ontogenetic repatterning from an ancestral state. An alternate hypothesis for the origin of isopteran phenotypic plasticity becomes apparent if we remain focused on the phylogenetic and social context of termite evolution. Altricial development occurs in both vertebrate and invertebrate taxa, evolves in response to the parental environment, and is displayed by two distantly related, biparental, wood-feeding cockroaches, including Cryptocercus, the sister-group to termites. It is therefore likely the condition was present in subsocial termite ancestors, and played a complex, multidimensional role in the transition to eusociality. Most relevant to current arguments is that a shift in responsibility for the care of altricial dependents, from parents to the first nutritionally independent nymphs in the family (alloparents), resulted in the developmental stasis of alloparents at a relatively young age. Because early instar cockroaches are not metamorphically competent, these young alloparents would have provided a novel developmental template on which selection could act.
大多数群体成员是处于幼体阶段的个体，它们的躯体和生殖发育会被暂时或永久地抑制，而且个体发育具有极强的表型可塑性。对文献的研究表明，这些独特的个体发育特征的基础不是延长原头幼虫阶段进入胚胎后发育，正如最近所提出的那样。与其他半变态昆虫一样，白蚁有三个胚胎外皮，原头幼虫（EC3）外皮在孵化期间或孵化后不久脱落。尽管如此，在胚胎发生过程中，与它们的蟑螂亲缘相比，白蚁的背侧闭合发生在更晚的阶段，这清楚地表明了从祖先状态发生的个体发育重排。如果我们仍然关注白蚁进化的系统发育和社会背景，那么对于等翅目表型可塑性起源的另一种假说就变得明显了。晚成性发育发生在脊椎动物和无脊椎动物类群中，是对亲代环境的响应，并且由两种亲缘关系较远、双亲的、以木材为食的蟑螂展示，包括Cryptocercus，是白蚁的姐妹群。因此，这种情况很可能存在于亚社会性白蚁的祖先中，并在向社会性的过渡中发挥了复杂的、多维的作用。与当前论点最相关的是，照顾幼体后代的责任从父母转移到了家庭中第一个营养上独立的若虫（异亲代），这导致了异亲代在相对年轻的时候发育停滞。因为早期的蟑螂若虫没有变态能力，这些年轻的异亲代将提供一个新的发育模板，供选择作用。
