Comb jellies, or ctenophores, captivate scientists with their ethereal glow and prehistoric roots. A Pristine Seas expedition in 2022 spotlighted these elusive plankton in Colombian waters, revealing species diversity through stunning underwater photography.
Origins and Evolutionary Secrets of Ctenophores
Comb jellies trace their lineage to over 500 million years ago, emerging before dinosaurs roamed Earth. Recent genomic studies position ctenophores as a "sibling group" to all other animals, diverging early from the common ancestor shared by sponges and more complex life forms. This placement challenges traditional views of animal evolution, suggesting ctenophores evolved key traits like nervous systems independently.
Fossil evidence from Utah's Cambrian rocks further illuminates their ancient history. Specimens like Thalassostaphylos elegans and Ctenorhabdotus campanelliformis reveal early nervous and sensory structures, including apical organs and ciliated furrows linked to nerve rings. These soft-bodied predators left rare traces despite their gelatinous nature, highlighting adaptations that persisted through eons. Ctenophores' unique biology—lacking true muscles yet coordinating via epithelial cells—sets them apart, fueling debates on how animal organ systems first arose.
Their shimmering appearance stems from eight rows of cilia, tiny hair-like structures that beat rhythmically for locomotion. Light diffracts off these combs, producing iridescent rainbows that pulse across translucent bodies. Sizes vary dramatically: some span mere centimeters, while others like the Venus's girdle (Cestum veneris) stretch over a meter, resembling living ribbons in the water column.
The Pristine Seas Expedition in Colombian Waters
The Pristine Seas expedition, led by National Geographic explorers, ventured into Colombia's remote Caribbean and Pacific regions in 2022. Researchers documented 15 ctenophore species, six appearing for the first time in national records: Beroe forskalii, Ocyropsis maculata, Ocyropsis maculata immaculata, Cestum veneris, Leucothea pulchra, and Thalassocalyce inconstans. Traditional nets failed against these 95% water organisms, which disintegrate upon capture, so the team turned to non-invasive methods.
Underwater photography proved revolutionary. Divers and remotely operated vehicles snapped gallery-quality images of comb jellies drifting like alien spacecraft or inflated balloons. Juan Mayorga, a Pristine Seas marine scientist, emphasized how these visuals enabled precise taxonomy without harming specimens. Citizen scientists supplemented the data, submitting photos from local dives and filling historical gaps in Colombia's gelatinous plankton records. Lead author Cristina Cedeño-Posso from INVEMAR hailed the approach as a model for studying fragile marine life in hard-to-reach areas.
This effort underscores ctenophores' global distribution—they inhabit every ocean from surface waters to abyssal depths. In Colombian seas, they thrive amid diverse currents, contributing to biodiversity hotspots. The expedition's findings, published in peer-reviewed journals, demonstrate how collaborative science uncovers hidden ecosystems.
Feeding Strategies and Ecological Impact
Comb jellies sustain oceanic food webs as voracious carnivores. They target fish eggs, larvae, and smaller plankton, deploying tentacles lined with colloblasts—specialized cells that eject sticky spirals on contact, ensnaring prey without venom. Unlike jellyfish nematocysts, colloblasts release adhesive glue, allowing ctenophores to reel in meals efficiently. Some species, like Haeckelia rubra, even repurpose stolen nematocysts from consumed hydrozoans for defense and hunting.
Feeding varies by form: lobate comb jellies use flattened lobes to generate currents that funnel plankton into waiting mouths, while tentaculate types cast out sticky lines like living lassos. This opportunism makes them ecosystem influencers—blooms can crash fisheries by devouring eggs, yet they serve as prey for turtles, fish, and crustaceans. In turn, ctenophores regulate smaller plankton populations, maintaining balance in marine chains.
Recent research reveals even stranger traits. A 2024 study on Mnemiopsis leidyi showed ctenophores capable of reverse development, reverting adult forms to youthful states—a flexibility hinting at ancient regenerative powers. Fused specimens observed at the Marine Biological Laboratory displayed integrated nervous systems, suggesting potential for tissue compatibility unseen in other animals. These discoveries position comb jellies as models for studying aging, regeneration, and neural evolution.
Challenges in Studying Comb Jellies and Future Directions
Ctenophores evade easy study due to their delicacy. Preservation biases their fossil record, leaving mostly impressions of comb rows or internal skeletons. Modern techniques like genomics and high-resolution imaging bridge these gaps, as seen in chromosome linkage analyses confirming their basal position. Synteny patterns—conserved gene arrangements—reveal ctenophores branched off before key animal innovations like centralized brains.
The Pristine Seas expedition exemplifies how photography merges art and science. Images not only document diversity but enable species identification through subtle morphological cues, like cilia arrangement or tentacle branching. Such methods scale globally, aiding surveys in under-explored regions. Climate change and ocean acidification threaten these plankton, potentially disrupting gelatinous communities and the predators dependent on them.
Ongoing work expands ctenophore knowledge. Cambrian fossils suggest sensory complexity rivaling modern forms, with nerve nets coordinating hunting and navigation. Behavioral studies highlight bioluminescence in some species, used for communication or startling prey. As tools improve, from DNA barcoding to AI-enhanced imaging, comb jellies yield more secrets about life's deep history.
Key Takeaways on Ctenophores from Recent Expeditions
Pristine Seas expedition revelations in Colombia highlight comb jellies' enduring allure and scientific value. These ancient ctenophores bridge past and present oceans, their biology informing evolution, ecology, and conservation. Explorations like these propel discoveries, inviting deeper dives into marine mysteries.
Frequently Asked Questions
1. What are comb jellies?
Comb jellies, or ctenophores, are gelatinous marine plankton with rows of cilia that create iridescent rainbow patterns through light refraction. They're ancient, predating dinosaurs by over 500 million years, and unrelated to jellyfish.
2. How do comb jellies move and glow?
They propel via eight rows of comb-like cilia (ctenes) that beat in waves for gliding motion. The shimmering colors come from light diffraction off these cilia, not bioluminescence—though some species also produce blue-green light.
3. What do comb jellies eat?
Ctenophores are carnivores targeting fish eggs, larvae, and plankton. Tentacles feature colloblasts that release sticky glue (not venom) to trap prey, which they reel to their mouths; some recycle nematocysts from other jellies.
4. Are comb jellies found in Colombian waters?
Yes, a 2022 Pristine Seas expedition documented 15 species there, including six new records like Cestum veneris and Beroe forskalii, using non-invasive photos since they dissolve in nets.
5. Why are comb jellies hard to study?
Their 95% water bodies disintegrate in traditional sampling, so researchers rely on underwater imaging and direct observation, as in the Colombian discovery.
6. What is the ecological role of ctenophores?
They regulate plankton and larvae populations as predators but serve as prey for fish, turtles, and crustaceans, influencing ocean food webs and nutrient cycling.
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