Introduction

A groundbreaking study reveals that one of the hottest periods in Earth's history, the Cretaceous period, may have driven lampreys apart on a genetic level. This fascinating discovery could hold key insights into how today’s aquatic species might react to our rapidly changing climate. The findings have been published in the esteemed journal, *Proceedings of the Royal Society B: Biological Sciences*.

The Importance of Lampreys

Lampreys, often viewed as bizarre fish due to their unique appearance, are more than just curious creatures with a circle of teeth. Lily Hughes, a research assistant professor at North Carolina State University and the lead author of the study, emphasizes their significance. "Lampreys are ancient and remarkable species, crucial for filtering nutrients and maintaining water quality in stream beds. Despite their ecological importance, we know surprisingly little about their evolutionary lineage,” Hughes stated.

Current Species Distribution

Currently, only 48 species of lampreys are recognized globally, classified into three families—one residing in the Northern Hemisphere and two in the Southern Hemisphere, with none inhabiting the tropical regions near the equator. Hughes, along with study co-first author Devin Bloom from Western Michigan University, and their research team aimed to pinpoint when these groups diverged from a common ancestor.

The Cretaceous Split

Utilizing a blend of DNA samples from existing lamprey species and fossil evidence, the researchers constructed phylogenomic trees that indicated a significant split between Northern and Southern Hemisphere lampreys around 93 million years ago, amidst the sweltering conditions of the Cretaceous period. "At this time, average global temperatures soared to around 82°F (28.1°C), with tropical regions hitting a scorching 93.5°F (34.2°C)," Hughes explained. “Since lamprey larvae prefer cooler environments, these extreme temperatures likely drove them away from tropical habitats they couldn’t survive in.”

Possible Extinction or Migration

The study posits two possible scenarios: either tropical lampreys faced extinction due to these high temperatures, erasing a genetic link, or they migrated away from the equator toward more temperate zones. While the exact distribution of lampreys during this period remains unclear, the evidence strongly indicates this divergence event.

Reevaluating Historical Distribution

This research also puts forth a novel hypothesis regarding the historical distribution of lampreys. "Previously, the distribution was attributed to the ancient supercontinent Pangea, which might have separated these groups physically," Bloom mentioned. "However, our findings suggest that the split between the Northern and Southern Hemisphere lampreys occurred long after Pangea had fragmented."

Implications for Modern Aquatic Species

The study's implications extend beyond lampreys themselves; understanding how this ancient species adapted to climate fluctuations can shed light on the resilience of modern aquatic creatures facing today’s environmental changes. As the planet warms and ecosystems evolve, knowing such evolutionary paths can be vital for conservation efforts.

Contributors to the Research

Researchers Kyle Piller, Nicholas Lang, and Richard Mayden also contributed to this pivotal work, potentially changing our understanding of aquatic biodiversity and its evolutionary history. As this research unfolds, it raises pressing questions: How will today’s aquatic life fare in the face of escalating temperatures? Can we expect more species to follow the path of lampreys and diverge in unexpected ways? Only time will tell.