A new scientific discovery has revealed that Alicella gigantea, a rare giant deep-sea amphipod previously believed to be elusive, is actually widespread across the world’s oceans. This shrimp-like crustacean, known to grow up to 34 cm long, has now been confirmed to inhabit more than 59% of global ocean areas, according to a recent study published in the journal Royal Society Open Science by researchers from the University of Western Australia.
What Is Alicella gigantea? Meet the Giant Deep-Sea Amphipod
Alicella gigantea is a type of amphipod—a group of small, shrimp-like crustaceans with narrow bodies and a distinct curled posture. While amphipods are commonly found in nearly all aquatic habitats on Earth, A. gigantea stands out due to its extraordinary size, earning it the nickname “supergiant amphipod.”
These creatures typically dwell in the deep ocean, including abyssal zones (3,000–6,000 meters deep) and hadal zones (deeper than 6,000 meters). The first photographic evidence of this giant amphipod came from a depth of 5,304 meters in the North Pacific, capturing a 28 cm specimen whose identity was later confirmed as A. gigantea.
Alicella gigantea: Once Thought Rare, Now Found in 3 Major Oceans
For decades, Alicella gigantea was considered an extremely rare species due to its infrequent sightings and the limited number of physical specimens. However, this latest global study challenges that assumption.
By analyzing 195 recorded sightings from 75 distinct locations across the Pacific, Atlantic, and Indian Oceans, the researchers found that A. gigantea has one of the broadest distributions among deep-sea amphipods. Its primary habitat includes deep-sea regions within the ideal depth range of 3,890 to 8,931 meters, with the Pacific Ocean being the largest potential habitat.
Genetic Insights Reveal a Single, Globally Distributed Species
To understand the species’ population structure and evolutionary history, the research team analyzed three genetic markers from newly collected specimens:
- Two mitochondrial genes: 16S and COI
- One nuclear gene: 28S
The genetic analysis revealed very low divergence among populations from different oceans. This suggests that Alicella gigantea is a single, globally distributed species, exhibiting strong genetic conservation despite its vast range.
Using haplotype networks to map genetic relationships, scientists found shared genetic patterns across regions, reinforcing the species’ genetic uniformity.
Why This Discovery Matters for Marine Biology and Biodiversity
The rediscovery and global mapping of Alicella gigantea have significant implications for our understanding of deep-sea biodiversity, species distribution, and evolutionary biology. This research:
- Offers the first comprehensive global dataset on A. gigantea
- Establishes a foundation for developing a global species hypothesis
- Highlights the importance of deep-sea exploration and conservation
Despite occupying more than half the world’s oceans, our understanding of this supergiant amphipod remains limited, particularly in areas like population dynamics, ecological roles, and adaptations to extreme environments.
Conclusion: The Giant Shrimp That Was Hiding in Plain Sight
Alicella gigantea, once considered a rare marvel of the deep sea, is now recognized as a widespread species with a global presence. This study redefines how scientists perceive deep-sea ecosystems and emphasizes the hidden biodiversity lurking in the unexplored depths of our oceans.
📚 Source
Paige J. Maroni et al. The supergiant amphipod Alicella gigantea may inhabit over half of the world’s oceans. Royal Society Open Science, 2025. DOI: 10.1098/rsos.241635