The Mottled Sea Hare

Sometimes referred to as the “Sooty Sea Hare”

The mottled sea hare has a scientific name, Aplysia fasciata. It falls under the Atlantic species of sea hare, or sea slug. Classed as a marine opisthobranch gastropod mollusk from the family Aplysiidae.


The mottled sea hare can be located in the Western Altantic from Brazil to New Jersey, also common in the Eastern Atlantic including the waters of the Mediterranean Sea and the West African coast. It is rarely located around the British Isles, and even less common in the southern waters of the British Isles. It lives on rocky ground, preferring regions where it can graze on algae


The length and size can vary, depending on age. Adults normally reach 40 cm in length and weigh around 1 kg when fully mature. The sea hare is often black in colour, but can vary from dark brown to brown with an orange or red line. The wings are folded at its side, when spread out it is almost circular in shape. The edge of the wings are red. They have a soft body and can release a dark purple fluid when threatened by predators.  A sea hare has poor vision, their simple eyes can only detect light and dark.


The colour of the ink comes from a pigment in the red algae that makes up part of the sea hares diet. Squirting ink is the last defense of the sea hare, often used when the mottled sea hare is taken into the mouth of a fish, or after been biten by a lobster. The purple ink and the sticky white opaline are produced in seperate glands. They can be released seperately, or together when required. Both inking and the use of white opaline are used against hungary predators and a deterrant against attackers. They are aslo excellent swimmers.


During the spring, the beginning of the seaweed growth introduces the metamorphosis of the plankton-like larva to the young sea hare. It’s life cycle lasts sadly, only one year, beginning in February and ending in September. Each sea hare is both male and female, a hermaphrodite, having both sexual organs. The animal with the larger sexual drive takes on the role as the male, the weaker of the two acts as the female. As an adult animal, they mate several times and lay eggs until they die in September. The adulthood lasts only 4 months of their lives.  A nest of the Mottled Sea Hare contains any where in the region of 26 million eggs, they hatch afer 15 days, although most are eaten by predators.


The mottled sea hare is a nocturnal animal with an economical metabolism. Due to its very short life span, it requires little food to survive, thus spending most of its time reproducing. Their diet consists mainly of red, brown and green algae, with a preference to the seaweed Ulva lactuca.


Photo was taken by Janet Bulmer at Dive Smart Gozo

Dive site: Mgarr ix-Xini