The classic economic dilemma of balancing quality with quantity finds relevance in biology as described by a team of British, American, and Japanese researchers. Their study reveals that this trade-off has likely shaped the evolution of ants, one of the planet's most successful organisms.
The research indicates that, as ant societies became more complex and populous, they reduced the size of their workers and made them more cost-efficient.
The Cost of Armor
In insects, the cuticle, an exoskeleton, provides protection against predators, pathogens, and desiccation and supports muscle attachment. This protective layer requires considerable amounts of nitrogen and rare minerals like zinc and manganese. While insufficient armor might mean death for a solitary insect, ants have evolved to balance these costs differently.
According to Evan Economo, an entomologist at the University of Maryland and study co-author, "There’s a question in biology about what happens to individuals as the societies they belong to become more complex. The individuals themselves may become simpler, as tasks needed for survival by a solitary organism are managed collectively."
The researchers hypothesized that social insects like ants might favor the colony's benefit over individual needs, as losing a few individuals may not significantly impact a large colony, making heavy investments in individual defenses inefficient. To explore this, they studied whether ant species with massive, specialized workforces were investing less in their workers' exoskeletons.
Scanning Superorganisms
Testing this hypothesis required a large-scale comparative study of ant anatomy. "We collaborated with partners to scan ant specimens and species globally to capture the diversity of ants," says Economo. The team leveraged the Antscan database, a comprehensive repository of three-dimensional X-ray microtomography images of ants from around the world.