Unique Anatomy and Appearance
Gigantocypris stands out in the deep sea due to its size for an ostracod. While most of its relatives are microscopic, species of Gigantocypris can grow up to 3.2 cm in diameter, roughly the size of a small plum. Their body is enclosed within a spherical, bivalved carapace, a shell-like structure hinged like a clam. This protective orb is often semi-transparent and reddish-orange.
The animal’s body is suspended inside this watery, globular carapace, which consists of up to 95% water. From a small opening in the shell, it extends feathery antennae to propel itself through the water column with a smooth, rowing motion. This swimming is supported by a heart that is large for an ostracod.
A primary feature of Gigantocypris is its pair of large, forward-facing eyes. Instead of using lenses to focus light, these are complex mirror eyes. Each eye contains a large, concave parabolic mirror that collects and focuses the faint glimmers of bioluminescence present in the deep sea to spot potential prey.
Habitat and Deep-Sea Adaptations
The genus Gigantocypris is found in oceans worldwide, inhabiting the cold, dark waters of the deep sea. These ostracods live in the bathyal and abyssal zones, at depths ranging from a few hundred meters to over 3,000 meters below the surface. Most are found between 600 and 2,300 meters, an environment with immense pressure and near-total darkness.
The creature’s reddish-orange coloration makes it effectively invisible in its habitat. In the deep sea, long-wavelength red light does not penetrate, so without red light to reflect, the animal appears black. Its body has a near-neutral buoyancy, allowing it to swim efficiently without expending excessive energy to maintain its position in the water column.
The mirror eyes are adapted to detect the flashes of bioluminescent organisms, allowing Gigantocypris to locate food from a distance. Recent studies indicate that the mirrors within the eyes may flex or pulse. This mechanism could help the ostracod distinguish between the small, nearby lights of prey and the larger, more distant lights of potential predators.
Feeding and Lifestyle
Gigantocypris is an active carnivorous predator, a lifestyle that sets it apart from many smaller, filter-feeding ostracods. It hunts in the midwater column, using its vision to scan for the glow of bioluminescent creatures. Its diet consists of other small pelagic animals that share its deep-sea habitat.
Gigantocypris preys on a variety of organisms, including small crustaceans like copepods, arrow worms, and small fish or their larvae. Once prey is detected, the ostracod uses its oar-like antennae to swim towards and capture it.
Females use their large carapace as a protective brood chamber. They retain their eggs within the shell until they hatch into miniature versions of the adults. This gives the young a safe start in a challenging environment.