Yellow crazy ants are known for their frenzied movements following disturbances. While this interesting feature is what gave them their name, a groundbreaking international study points to another quality that makes them unique in the animal world. Research published in Science revealed that male yellow crazy ants are the first known animal species that have both maternal and paternal genomes in different cells of their body and are thus chimeras. That is, they develop from fertilized eggs in which the maternal and paternal nuclei divide separately within the same egg. Chimeras occur in other species, but not in this unique way. “It’s a piece of biology that’s unparalleled as far as we know,” says Daniel Kronauer, a biologist at the Rockefeller University in New York City.
The Invasive Yellow Crazy Ants
Yellow crazy ants (Anoplolepis gracilipes) are one of the world’s worst invasive species. They pose a threat to invertebrates and even some small mammals across southeast Asia and Oceania. For example, the red crab — which is considered a keystone species on Christmas Island, an Australian territory south of Java — has experienced significant population loss due to yellow crazy ants since the 1990s.
Genetic Markers Unveil Puzzling Biology
Researchers have long recognized that there was something highly unusual about how yellow crazy ants reproduce. “The results of previous genetic analyses of the yellow crazy ant have shown that the males of this species have two copies of each chromosome. This was highly unexpected, as males usually develop from unfertilized eggs in ants, bees, and wasps — and thus should only have one maternal copy of each chromosome,” explained Hugo Darras, an evolutionary biologist at Johannes Gutenberg University Mainz in Germany, and lead author of the research. “With this in view, we decided to investigate this puzzling phenomenon with subsequent experiments.”
Unraveling Chimerism in Males
Darras and his colleagues found that each cell in the male ants contained a single version of the ant’s genome. However, these genomes differed between cells, with some cells carrying the lineage present in queens (defined by an ‘R’ chromosome) while others had a copy of a distinct genome, characterized by a ‘W’ chromosome.
The Role of Chimerism in the Ants’ Caste System
The team’s research further demonstrated that the chimerism observed in male yellow crazy ants plays a vital role in their caste system. Queen ants’ eggs carry one copy of the R genome. If fertilized by a R-carrying sperm, a queen develops. If fertilized by a W sperm, two outcomes are possible. The cell nuclei can fuse, resulting in a sterile female worker ant. Alternatively, chimerism in male ants can occur when the parental nuclei divide separately within one egg. In these chimeric males, some cells carry the R genome and others carry the W genome. The R cells are mostly present in the ants’ body cells and sperm cells are mostly W cells. These chimeric male ants play a variety of roles in the colony, including soldier ants that defend the hive.
Implications and Opportunities
The discovery of yellow crazy ants’ chimerism opens a world of possibilities for understanding their invasive capabilities. Queen ants’ specialized organs can store sperm from multiple males, enabling a single queen carrying R and W sperm to initiate a new ant colony. This has led researchers to question whether their unique reproductive characteristics could be leveraged to control ant populations.
Unanswered Questions and Future Explorations
While the breakthrough sheds light on the chimerism phenomenon, it also raises numerous questions. The reasons behind the failure of some sperm nuclei to fuse with the egg nucleus, resulting in chimeric males, remain unclear. Darras suggests that genes in W lineage cells, which are disproportionately represented in sperm, might be involved. “There’s so much we don’t know,” he concluded.
QPS is a GLP- and GCP-compliant contract research organization (CRO) delivering the highest grade of discovery, preclinical and clinical drug research development services. Since 1995, it has grown from a tiny bioanalysis shop to a full-service CRO with 1,200+ employees in the U.S., Europe and Asia. Today, QPS offers expanded pharmaceutical contract R&D services with special expertise in neuropharmacology, DMPK, toxicology, bioanalysis, translational medicine and clinical development. An award-winning leader focused on bioanalytics and clinical trials, QPS is known for proven quality standards, technical expertise, a flexible approach to research, client satisfaction and turnkey laboratories and facilities. Through continual enhancements in capacities and resources, QPS stands tall in its commitment to delivering superior quality, skilled performance and trusted service to its valued customers. For more information, visit www.qps.com or email [email protected].