Face Your Fears: Cleaning Gobies Inspect Predators despite Being Stressed by Them

social stressors typically elicit two distinct behavioural responses in vertebrates: an active response (i.e., "fight or flight") or behavioural inhibition (i.e., freezing). Here, we report an interesting exception to this dichotomy in a Caribbean cleaner fish, which interacts with a wide variety of reef fish clients, including predatory species. Cleaning gobies appraise predatory clients as potential threat and become stressed in their presence, as evidenced by their higher cortisol levels when exposed to predatory rather than to non-predatory clients. Nevertheless, cleaning gobies neither flee nor freeze in response to dangerous clients but instead approach predators faster (both in captivity and in the wild), and interact longer with these clients than with non-predatory clients (in the wild). We hypothesise that cleaners interrupt the potentially harmful physiological consequences elicited by predatory clients by becoming increasingly proactive and by reducing the time elapsed between client approach and the start of the interaction process. The activation of a stress response may therefore also be responsible for the longer cleaning service provided by these cleaners to predatory clients in the wild. Future experimental studies may reveal similar patterns in other social vertebrate species when, for instance, individuals approach an opponent for reconciliation after a conflict.

Evolutionarily conserved mechanisms of male germline development in flowering plants and animals

Sexual reproduction is the main reproductive strategy of the overwhelming majority of eukaryotes. This suggests that the last eukaryotic common ancestor was able to reproduce sexually. Sexual reproduction reflects the ability to perform meiosis, and ultimately generating gametes, which are cells that carry recombined half sets of the parental genome and are able to fertilize. These functions have been allocated to a highly specialized cell lineage: the germline. Given its significant evolutionary conservation, it is to be expected that the germline programme shares common molecular bases across extremely divergent eukaryotic species. In the present review, we aim to identify the unifying principles of male germline establishment and development by comparing two very disparate kingdoms: plants and animals. We argue that male meiosis defines two temporally regulated gene expression programmes: the first is required for meiotic commitment, and the second is required for the acquisition of fertilizing ability. Small RNA pathways are a further key communality, ultimately ensuring the epigenetic stability of the information conveyed by the male germline.