Researchers studying the North Pacific Subtropical Gyre have identified an extraordinary virus with the longest tail ever recorded. Named PelV-1, it infects a plankton species called Pelagodinium and features a tail measuring 2.3 micrometers—about 19 times the length of the coronavirus that caused COVID-19. The virus’s capsid, at 200 nanometers, is significantly smaller than its remarkable appendage, which scientists believe aids in attaching to and penetrating host cells. Unlike most viruses, which have either no tails or very short ones, PelV-1 is structurally unique. Time-lapse imaging reveals its tail binds to plankton during infection, yet newly formed viruses inside host cells lack this appendage.
The groundbreaking discovery occurred at Station ALOHA, a long-term ocean research site situated north of Hawaii. Scientists collected seawater samples from 25 meters below the surface, isolating Pelagodinium plankton and unexpectedly uncovering the giant-tailed virus. Viruses capable of infecting dinoflagellates, such as Pelagodinium, are exceedingly uncommon—only two other large DNA viruses are known to target this group. Studying such rare viruses could provide valuable insight into marine ecosystem processes, including energy transfer, nutrient cycling, and the formation of harmful algal blooms. The research highlights the untapped diversity of oceanic viruses and their potential role in regulating microscopic marine life.
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PelV-1 possesses an unusually large genome for a virus, containing 467 genes spread over 459,000 base pairs. Some of these genes are typically present only in living organisms, including components of energy production pathways, light-harvesting proteins, and rhodopsins—light-sensitive molecules that may allow the virus to harness sunlight. The study also uncovered another virus in the same culture, named co-PelV, which lacks a tail but carries metabolic genes that could influence the host’s energy usage and behavior. Future investigations aim to determine how PelV-1 constructs its massive tail, its exact function in infection, and whether similar long-tailed viruses inhabit other ocean regions.