Pterotrachea coronata, also known as the Sea Elephant, is the largest member of the pterotracheids, reaching up to 330 mm in length. This pelagic gastropod is noted for its streamlined, elongated, and cylindrical body. It has a long, pointed proboscis that ends in a small buccal mass. The trunk is slender with ventro-lateral folds forming a concave bib, while the large, laterally flattened tail aids in burst swimming. The eyes are rectangular with a retinal base wider than the lens. Males have a small fin sucker on the swimming fin, and females possess a long egg string extending below the visceral nucleus.
Pterotrachea coronata is cosmopolitan, found in tropical to subtropical waters worldwide. This species thrives in pelagic zones, often swimming with its ventral side directed upward during the day and downward at night. Its habitat includes open ocean waters, where it remains neutrally buoyant, either actively swimming in pursuit of prey or floating curled into a loose ball.
Larval Shell: The shell of Pterotrachea coronata is present only during the larval stage and is lost after metamorphosis.
Burst Swimming: The large, laterally flattened tail and the streamlined body allow for strong side-to-side flexion, facilitating quick burst swimming to escape predators or catch prey.
Diurnal Behavior: During the day, the Sea Elephant swims with its ventral side upward to locate prey against the lighted surface waters. At night, it reorients itself with the ventral side downward, potentially to spot bioluminescent prey beneath it.
Neutrally Buoyant: It remains neutrally buoyant most of the time, either actively swimming or floating passively.
Rarely Seen: Despite its widespread distribution, Pterotrachea coronata is rarely encountered by divers. The author’s encounter with this species during a dive around the Maltese Islands was a unique and first-time experience in over 20 years of regular diving.
Due to its elusive nature, Pterotrachea coronata is a rare and highly prized sighting for divers. Around Malta, Gozo, and Comino, this fascinating species can be encountered in deeper pelagic zones. Notable dive sites where the Sea Elephant might be spotted include:
For the best chances of seeing Pterotrachea coronata, dive in Gozo with us 😉
