For nearly a century, marine scientists have been puzzled by an unusual phenomenon in thorny skates (Amblyraja radiata) found in the North Atlantic. In certain parts of their range, these fish exist in two distinct sizes, regardless of sex. Despite numerous studies, the reason behind this size variation remained unknown—until now.
Breakthrough Discovery Solves Longstanding Skate Mystery
Jeff Kneebone, a marine scientist at the Anderson Cabot Center for Ocean Life at the New England Aquarium, first encountered this enigma during his college research in 2002. After decades of uncertainty, a team led by Kneebone and researchers from the Florida Museum of Natural History has finally uncovered the answer. Their findings, published in Nature Communications, shed light on the genetics behind this peculiar size discrepancy.
The Urgent Need for Answers
Scientists have observed this size variation for decades, but the issue gained critical importance in the 1970s when thorny skate populations plummeted due to overfishing. To prevent further decline, the U.S. government implemented a strict fishing ban in 2003 for thorny skates and the barndoor skate (Dipturus laevis), another species in distress. While the barndoor skate population has since rebounded, thorny skates have not recovered despite 20 years of protection. According to the National Oceanic and Atmospheric Administration (NOAA), thorny skate numbers have dropped by 80% to 95% in some areas, particularly in the Gulf of Maine.
A Unique Distribution and a Puzzling Genetic Code
Thorny skates are widely distributed, spanning from South Carolina to the Arctic Circle and across the Atlantic to Scotland, Norway, and Russia. However, the size discrepancy is unique to North American waters—elsewhere, only one size variety exists.
Previous genetic studies failed to identify differences between large and small skates, deepening the mystery. The larger skates take 11 years to mature, while the smaller ones reach adulthood in just six years. Scientists suspected genetic differences must be at play but couldn’t pinpoint them—until now.
Gene Inversion Unlocks the Mystery
To solve this puzzle, the research team adopted a gene capture approach, sequencing DNA from hundreds of thorny skates across the Northern Hemisphere. However, the COVID-19 pandemic disrupted lab work, forcing them to take an alternative route—whole-genome sequencing of a few specimens.
This high-risk strategy paid off. As researcher Pierre Lesturgie analyzed the data, he identified an unusual segment on chromosome two. Initially thought to be an error, it turned out to be a gene inversion—a flipped DNA sequence—found exclusively in large thorny skates. This breakthrough confirmed that the size difference was genetically driven, solving a mystery that had baffled scientists for generations.
What This Means for Conservation Efforts
Now that researchers understand the genetic basis of the size variation, they can refine conservation strategies. Previously, stock assessments treated all thorny skates as a single population, which may have contributed to ineffective recovery efforts. Identifying and monitoring the two size morphs separately could be crucial for developing targeted conservation plans.
Climate Change and Future Research
Despite this genetic revelation, thorny skates continue to struggle in certain regions, particularly the Gulf of Maine. Scientists suspect that environmental factors, including climate change, may be exacerbating the problem. This region has experienced some of the fastest ocean warming globally, which has already led to the collapse of cod fisheries.
Understanding how climate change interacts with the genetic makeup of thorny skates will be key to their future survival. Kneebone and his team aim to gather more data to determine whether rising temperatures impact interbreeding between the two morphs, potentially threatening the species’ ability to sustain its population.
Conclusion: A Step Toward Effective Marine Conservation
This groundbreaking discovery not only solves a century-old marine biology mystery but also opens new avenues for species conservation. By integrating genetic insights into fisheries management, scientists can develop more effective strategies to protect thorny skates and other vulnerable marine species in the face of climate change.
For more details, refer to the study: Pierre Lesturgie et al, Short-term evolutionary implications of an introgressed size-determining supergene in a vulnerable population, Nature Communications (2025). DOI: 10.1038/s41467-025-56126-z.