Environmentally responsive reproduction: neuroendocrine signalling and the evolution of eusociality

Abstract

Eusociality is a rare but successful life-history strategy that is defined by the reproductive division of labour. In eusocial species, most females forgo their own reproduction to support that of a dominant female or queen. In many eusocial insects, worker reproduction is inhibited via dominance hierarchies or by pheromones produced by the queen and her brood. Here, we consider whether these cues may act as generic 'environmental signals', similar to temperature or nutrition stress, which induce a state of reproductive dormancy in some solitary insects. We review the recent findings regarding the mechanisms of reproductive dormancy in insects and highlight key gaps in our understanding of how environmental cues inhibit reproduction.

Figure 1

Oogenesis and neuroendocrine control of reproduction and reproductive dormancy in D. melanogaster.(a) Stages of oogenesis in D. melanogaster and the ovarian checkpoints that result in cell death in response to environmental cues , . (b) Major neuroendocrine signalling systems that are known to respond to environmental signals and mediate reproduction in D. melanogaster, , , , , .

Figure 2

Environmental cues and reproductive dormancy in insects. (a) A diverse range of environmental cues impact neuroendocrine signalling in insects. However, there are key gaps in our knowledge regarding a) how different species are responding to environmental cues and stressors and b) how these diverse stressors are read and interpreted to result in reproductive dormancy. (b) In the honeybee, reproduction in workers is repressed, at least in part, by QMP. This is arguably the best-studied example of reproductive constraint in a eusocial inset, yet there are key gaps in our understanding of how QMP is detected and how this signal is transmitted to the ovary to repress oogenesis , .