A phylogenetic analysis of hundreds of arthropod species, published August 6, 2026, in Nature Communications, concludes that sperm cooperation has evolved independently many times across insects, spiders, crabs and centipedes — and that the common ancestor of all insects itself carried conjugated sperm.

The finding challenges the textbook model of fertilization as a race won by the fastest individual cell. In many arthropods, reproductive success depends on sperm that assemble into organized groups or shared structures before reaching the egg, a phenomenon called sperm conjugation.

"Fertilization is often viewed as a competition among individual sperm, but in many species we see cells working together in ways that can influence reproductive success," says Steve Dorus, professor of biology at Syracuse University's College of Arts and Sciences and co-author of the study.

Researchers from Syracuse University, the University of Siena in Italy and the University of Szeged in Hungary conducted the work. They compiled sperm characteristics from hundreds of species, drawing on decades of previously published research, and mapped those traits onto an evolutionary family tree. The resulting timeline tracks sperm conjugation and sperm-associated material (SAM) across major animal lineages over the past 600 million years.

A strategy gained and lost repeatedly

Scientists first documented sperm conjugation more than 100 years ago but treated it as a curiosity. The new analysis shows it is widespread and evolutionarily labile. The strategy appeared, disappeared, and re-emerged many times across different arthropod lineages.

"Evolution has effectively run the same experiment over and over again across different groups of arthropods," says R. Antonio Gomez, a postdoctoral scholar in Syracuse's Department of Biology and lead author. "That allows us to see not only when sperm cooperation emerges, but also when it disappears and reappears under different evolutionary conditions."

In many species, cooperation involves sperm-associated material — a membrane-enclosed substance that attaches sperm to one another or builds structures arranging them into groups. The authors suggest SAM may have originated as a packaging or protective mechanism and later enabled conjugation to arise.

Grouped sperm may gain advantages in mobility, organization or performance while traversing the female reproductive tract, a physically complex environment a single cell must otherwise negotiate alone. Scott Pitnick, Weeden Professor of Biology and senior author, notes that sperm are the most rapidly evolving cell type, shaped by the challenge of operating outside the body.

Implications split by discipline

Companion-animal and human fertility research. The study is basic evolutionary biology, but its logic extends to clinical reproductive work. Pitnick describes fertilization as an obstacle course rather than a straightforward race. If group behavior and shared biological structures influence reproductive outcomes, fertility investigations that score only individual sperm motility and morphology may miss functional contributors. Understanding how sperm cooperate could eventually inform how researchers approach human reproductive difficulties.

Pest control. The more immediate applied target is agricultural. The invasive spotted lanternfly, a growing agricultural concern in New York and other eastern states, has highly unusual sperm: no conjugation at all, but every individual cell completely embedded in a thick layer of SAM. "Their sperm are highly unusual," Pitnick says. "They do not have conjugation, but each individual sperm is completely embedded in this material, and we do not even know how they are motile."

That gap in knowledge is also an opening. If SAM proves essential for lanternfly reproduction, disrupting the material could yield a species-specific control method that spares non-target arthropods — an approach that would require regulatory evaluation before any field deployment.

Open questions

Why sperm cooperation evolves remains unresolved. Grouped cells may move through the reproductive tract more effectively, or they may transport key molecules to specific locations. Testing these hypotheses is difficult because sperm on glass slides behave differently from sperm inside the female body. Future studies plan to observe sperm groups within actual reproductive systems and to quantify the benefits and costs of the behavior.

The broader lesson, Dorus argues, is that cooperation and competition are not opposing forces — even at the cellular level. "Evolution keeps arriving at similar cooperative solutions in very different groups and across vast expanses of time," he says. "These examples remind us that cooperation can be just as important as competition in shaping biological success."

The full citation: R. Antonio Gomez, Romano Dallai, David Mercati, Rita Sinka, Steve Dorus, Scott Pitnick, "Pervasive convergent evolution of sperm conjugation across the Arthropoda tree of life," Nature Communications, 2026; 17(1), DOI: 10.1038/s41467-026-73950-z. Next steps include direct observation of sperm groups inside reproductive tracts, which should clarify whether the cooperative strategy pays off — and whether SAM can be turned against pests like the spotted lanternfly.