How marine snails switched from laying eggs to giving live births

like the emergence of flight, vision, or live offspring, don't occur in sudden leaps but evolve gradually, say biologists led by the University of Sheffield. In a study using new methodologies, they've unraveled the mysteries behind these transformative shifts. We used to only imagine understanding the process that turned egg laying marine snails into live bearing ones.

Now that it is within reach, it's like uncovering a blueprint for the major game changers in evolution. The team's findings are pivotal; they shed light on the fundamental question of how these innovations fundamentally reshaped the course of life on Earth. For years, scientists debated whether these transformations occurred through dramatic, giant steps or via a series of small, incremental changes favored by natural selection.

But now, by examining the whole genome sequences of marine snails that recently switched birthing styles, researchers from the University of Sheffield, alongside collaborators from the University of Gothenburg and the Institute of Science and Technology Austria, have provided compelling evidence. The research zeroed in on the seaside marine snail Littorina saxatilis, known for its multitude of shell variations and habitats, causing centuries of misidentification by scientists.

Beyond its exterior diversity, this snail holds a unique reproductive strategy—while its habitat mates lay eggs, evolved live bearing, making it an anomaly in the snail kingdom. Stankowski's investigation, unveiling the evolutionary family tree of and its egg laying relatives through whole genome sequences, highlighted a surprising revelation.

Live bearing wasn't aligned with a distinct evolutionary group within s, enabling researchers to isolate the genetic underpinnings of this reproductive shift from other genomic alterations. "We identified around 50 genomic regions crucial in determining egg laying versus live bearing," Stankowski explains.

"While the exact functions of these regions remain unclear, comparing gene expression patterns in both types of snails linked many of these regions to reproductive differences." The study uncovers that live bearing endowed these snails with the ability to inhabit and thrive in environments inaccessible to egg layers.

However, the precise advantages of this reproductive strategy remain veiled. Stankowski speculates that natural selection possibly favored increased egg retention time, ensuring better offspring survival by protecting them from drying out, damage, and predators—an advantage that live bearing offspring inherently enjoy.

Professor Roger Butlin, leading the research at the University of Sheffield's School of Biosciences, emphasized the significance: "Understanding the origins of these innovations is crucial because they shape evolution's trajectory, like how live bearing triggered mammalian diversification or feathers paved the way for avian flight." The team's next steps The breakthrough doesn't stop there.

This methodology holds promise for studying other adaptations crucial for species survival in a changing world— we think traits like thermal tolerance are necessary for coping with climate change. This study not only redefines how biologists perceive but also equips them with tools to explore and comprehend the genetic and historical underpinnings of various adaptive traits.

It's a game changer in decoding the mechanisms driving life's most significant transformations. The team's next steps involve delving deeper into understanding these identified genes' functions and applying their methodology to unravel other adaptive mechanisms essential for species survival.

Their work might just hold the key to understanding and potentially mitigating the impacts of a rapidly changing world on diverse species. The was published in the journal on January 4..