The "Grouping Effect" in cockroaches: Which sensory cues are involved in the social facilitation of reproductive maturation in Blattella germanica females?

Social interactions are critical for various adaptive behaviors including foraging, food handling, and reproduction. In some animal species, social interactions can lead to physiological changes, resulting in faster development, sexual maturation, or reproduction. This phenomenon is called “social facilitation” or a “grouping effect”. Social facilitation of nymphal development has been shown in many cockroach species, where grouped nymphs reach adulthood faster than isolated or solitary nymphs. At the adult stage, so far, the German cockroach appears to be the only cockroach species in which females respond to social facilitation of reproduction. In an earlier study in our lab, it was shown that grouped females develop their oocytes faster and earlier than isolated females and that sexual maturation and oocyte growth are significantly delayed in isolated females. The sensory pathways, responsible for social facilitation of reproduction, include visual, tactile, acoustical or chemosensory signals. Social interactions stimulate the brain through certain sensory cues to accelerate reproduction, which can be measured by measuring the length of the basal oocytes. However the sensory modalities and pathways that mediate this physiological change are not understood yet. In my project, I investigate which sensory cues mediate the “grouping effect”, if this phenomenon is phase-dependent, how much time females need to be grouped to exhibit the full “grouping effect”, and if the sensory cues are species- and sex-specific.