Life in the deep ocean unfolds in mysterious zones, influenced by temperature, saltiness, and currents. Many creatures, like the Botrynema jellyfish, prefer to stay in specific conditions, almost like having a home base. So, when one drifts far from its usual spot, it raises eyebrows about the animal and its environment.
A Unique Discovery
Researchers from The University of Western Australia recently stumbled upon a Botrynema jellyfish far south of its typical icy Arctic waters, swimming in warmer subtropical depths near Florida. This finding suggests there might be a hidden biogeographic barrier in the North Atlantic that influences where these jellyfish can live.
The Life of Botrynema Jellyfish
Most jellyfish transition between a floating medusa stage and a stationary polyp stage. However, Botrynema, part of the Trachymedusae group, skips the polyp phase. Instead, the jellyfish floats throughout its life. The focus has been on a subspecies, Botrynema brucei ellinorae, which scientists believed lived in polar regions and deep oceans. Over the years, researchers noticed two body types – one with a tiny top bump (apical knob) and one smooth-topped.
Mapping Distribution
The study aimed to explore three key questions: Where is Botrynema found worldwide? How are the two body shapes connected genetically? And how did an Arctic jellyfish end up in warm waters? To tackle this, the team studied physical traits, DNA, and documentation spanning over a century of sightings, along with global biodiversity records.
Fresh Insights from Norway
Historical research played a role, but modern findings were crucial too. In the Norwegian Arctic, researchers captured numerous Botrynema brucei ellinorae jellyfish using plankton nets. They documented their features and preserved samples for genetic analysis, creating a fresh comparison point for the resting jellyfish.
A Curious Species in New Waters
During a North Atlantic study, a remote vehicle filmed a jellyfish drifting at about 3,280 feet, confirming it as a Botrynema. This specimen had the apical knob and pale pink gonads, becoming central to the exploration of why this Arctic species was so far south.
Genetic Surprises
In the lab, scientists analyzed DNA from both the southern jellyfish and Arctic samples. To their surprise, the DNA from the specimen matched closely with its Arctic relatives, indicating it’s not a new species—just an Arctic jellyfish that found its way south.
Patterns in Distribution
Examining global distribution revealed an interesting trend. The knobbed forms of the jellyfish were widespread, thriving across various climates. In contrast, the knobless versions were confined largely to the Arctic and a narrow section of the North Atlantic Drift. The researchers speculated that deep-sea currents might explain how the jellyfish reached Florida.
The Role of Ocean Currents
Cold, dense water near Greenland flows southward, forming what’s known as the Deep Western Boundary Current. This underwater pathway may enable Botrynema brucei ellinorae to drift south without swimming actively, connecting Arctic deep-sea communities to warmer waters.
Understanding Soft Barriers
Interestingly, the study referenced a “soft barrier” in the North Atlantic Drift, where conditions like temperature, prey, and predators shift. North of this zone, both morphs of Jellyfish coexist peacefully. South of it, only the knobbed version seems to thrive. The researchers propose that perhaps the knob provides a slight edge against predators in warmer waters.
Conclusion
This exploration of the Botrynema jellyfish highlights how ocean currents and environmental conditions shape marine life. Despite drifting thousands of kilometers south, jellyfish can only live in certain areas due to these “soft barriers.” The findings remind us how oceans can influence survival, revealing a deeper understanding of our planet’s biodiversity.
For more on this fascinating topic, you can read the full study published in Deep Sea Research.
