Reversible plasticity in brain size, behaviour and physiology characterizes caste transitions in a socially flexible ant (Harpegnathos saltator)
Clint A. Penick, Majid Ghaninia, Kevin L. Haight, Comzit Opachaloemphan, Hua Yan, Danny Reinberg and Jürgen Liebig
科学家发现，蚂蚁拥有繁殖能力后脑容量骤降，但随着生育能力的下降，其脑容量会再次上升。
表型可塑性可以让生物在一生中对不断变化的环境做出反应，但这些变化很少是可逆的。一些相对长寿的脊椎动物的大脑表现出季节性的可塑性，不过在寿命较短的物种（如昆虫）中，尚未发现类似变化。
蚂蚁可能很小，但它们拥有超人的能力，比如能举起比自己重很多倍的物体。现在，研究人员发现，一些蚂蚁的大脑甚至可以收缩和再生。
美国佐治亚州肯尼索州立大学的Clint Penic和同事研究了印度跳蚁的繁殖工蚁的大脑可塑性。与大多数蚂蚁不同，跳蚁工蚁能够进行有性繁殖，它们会通过竞争建立一组生殖工蚁，研究人员将其称为“玩家”。他们发现，与觅食工蚁相比，“玩家”跳蚁的脑容量会大幅减少。
当蚁后去世后，印度跳蚁的雌性工蚁会进行长达数周的战斗，以建立新的领导层。经历“玩家”的赢家开始繁衍后代。根据近日发表于英国《皇家学会学报B》的一项研究，这些雌性跳蚁的卵巢变得更加活跃，但它们的大脑萎缩了约20%。
为了确定其中一些变化是否可逆，科学家抑制了这些跳蚁的生育能力。作为回应，大多数“玩家”雌蚁开始寻找食物——这是专注于觅食的工蚁的典型行为，它们的大脑随之扩张到与觅食蚂蚁的大脑大致相当的大小。因为觅食需要高级的认知能力，大脑的再扩张可以帮助工蚁在繁殖战失败后回到觅食状态。
研究人员说，这是第一次在昆虫的大脑中观察到可逆变化。
来源：中国科学报 晋楠
Abstract
Phenotypic plasticity allows organisms to respond to changing environments throughout their lifetime, but these changes are rarely reversible. Exceptions occur in relatively long-lived vertebrate species that exhibit seasonal plasticity in brain size, although similar changes have not been identified in short-lived species, such as insects. Here, we investigate brain plasticity in reproductive workers of the ant Harpegnathos saltator. Unlike most ant species, workers of H. saltator are capable of sexual reproduction, and they compete in a dominance tournament to establish a group of reproductive workers, termed ‘gamergates'. We demonstrated that, compared to foragers, gamergates exhibited a 19% reduction in brain volume in addition to significant differences in behaviour, ovarian status, venom production, cuticular hydrocarbon profile, and expression profiles of related genes. In experimentally manipulated gamergates, 6–8 weeks after being reverted back to non-reproductive status their phenotypes shifted to the forager phenotype across all traits we measured, including brain volume, a trait in which changes were previously shown to be irreversible in honeybees and Drosophila. Brain plasticity in H. saltator is therefore more similar to that found in some long-lived vertebrates that display reversible changes in brain volume throughout their lifetimes.
