Coming of age: Annual onset of coral reproduction is determined by age rather than size

Abstract

Constraints on organisms possessing a unitary body plan appear almost absent from colonial organisms. Like unitary organisms, however, coral colonies seemingly delay reproduction until reaching a critical size. Elucidating ontogenetic processes, such as puberty and aging are complicated by corals' modular design, where partial mortality and fragmentation lead to distortions in colony size-age relationships. We explored these enigmatic relations and their influence on reproduction by fragmenting sexually mature colonies of five coral species into sizes below the known size at first reproduction, nurturing them for prolonged periods, and examining their reproductive capacity and trade-offs between growth rates and reproductive investment. Most fragments were reproductive regardless of their size, and growth rates hardly affected reproduction. Our findings suggest that once the ontogenetic milestone of puberty is reached, corals retain reproductive capacity irrespective of colony size, highlighting the key role that aging may have in colonial animals, which are commonly considered non-aging.