A particularly strange critter that is not really a fish, even though it does swim, is causing concern on Spain’s southeastern coast. It is on the coast of Alicante and in a lagoon in Murcia known as the Mar Menor – Spanish for ‘minor sea’ – located on the Mediterranean shore, that an invasive tropical species has been found. The Centre for Marine Research at Alicante University has begun looking into the invasion of the coastline by a mobile and frilly mollusk that goes by the name ‘ragged sea hare’ or ‘shaggy sea hare’ because of the fleshy knobs and appendages that cover its soft and shell-less body. Moving slowly along the bottom as it dines (it’s strictly vegan), sea hares are mostly green to greenish-brown. It also has spots of an intense and radiant blue.
The common name for this species come directly from the Latin ‘lepus marinus’, which is a reference to its rounded shape and two nostril-like rhinophores that project from the head. It must have been one hungry Roman who confused this thing with a hare or a rabbit.
Bursatella leachii, its taxonomic name, is a marine gastropod mollusk. In other words it is a critter that moves along shallow water on its belly that serves as its foot. Or the other way around. It is a distant relative of not only the octopus and squid, but also bivalves such as tasty mussels, clams, and oysters. Which is not to say that sea hares are edible. Which is to say that it is not commonly eaten by Westerners and Middle Easterners. Needless to say, it is Asia (who knew?) where things such as sea cucumbers (disgusting) and sea stars (weird) are eaten avidly. Usually, sea hares are stir-fried in sauce. In Hawaii, sea hares are called Kualakai and are wrapped in ti leaves and baked in an pit oven called ‘imu.’
Aquarists value them for cleaning up unwanted algae, as well as cyanobacteria known as red slime algae. Once they have devoured the algae in one aquarium, they are passed on to another. Aquarists who keep marine fish are known to share a sea hare between members of a group of hobbyists.
Spanish researchers are seeking to understand how the sea hares they have found, representing the Bursatella leachii species, are able to live in a lagoon that is notable for its high salinity and temperature fluctuations. The invading mollusk is thought to have originated in the Red Sea and the Eastern Mediterranean, which have higher levels of salinity than Spanish waters in general. Normally, it is found in estuaries and tidal pools, rather than sandy bottoms. Therefore, Mar Menor is a very nice place for the frilly sea hares. Related species are found along the coasts of the Caribbean Sea, and the Indian and Pacific oceans.
Even while the shape-shifting sea hare was first detected in Mar Menor in 2008, there has since been a veritable population explosion of the tropical mollusk in the lagoon. Professor Francisca Giménez Casalduero of Alicante University is hoping to determine a cause for the exponential rise in the biomass consisting of sea hares in Mar Menor, as well as determine with which other organisms it is found. Leading a team of 38 researchers, divers and volunteers, she also conducted an environmental impact study despite bad weather.
In 2007, examples of Bursatella leachii were found in Alfacs Bay in the delta of the Ebro River, apparently feeding on Caulerpa prolifera seaweed and Cymodocea nodosa sea grass. These were approximately 4 inches in length. However, there are some reports that sea hares can reach much larger sizes depending on their environment. Local fishermen had not encountered this species in the past at the western limits of the Mediterranean sea, and were a little spooked to find their nets actually clogged by thousands of individual sea hares. Boris Weitzmann, a researcher at Spain’s Centre for Advanced Scientific Research, wrote in 2008 that he was concerned that sea hares could become an invasive species.
Sea hares can become kind of big. The largest related species, Aplysia vaccaria, is known to reach almost a yard in length and 30 pounds in weight. Whoa. That is the largest known gastropod species. Sea hares have squishy bodies that surround an internal shell. They are also, well, confused. They are hermaphroditic, which means they have male parts and female parts.
Some sea hares are able to burrow into soft sedimentary sea bottoms and leave only their tubelike nostrils showing in order to deter predators. Using these rhinophores, sea hares have a particularly good sense of smell and are also able to detect chemicals. In the case of these gastropods, the adage ‘You are what you eat,’ applies beautifully: their color corresponds directly to whatever plant they are eating. Thus, they are red when they eat red algae. They can also release ink as an underwater smokescreen to confuse their enemies. The color of their ink can be white, purple or red, depending on what they have been eating.
Sea hare: Scientific classification
(unranked): clade Heterobranchia
Binomial name: Bursatella leachii
Three subspecies have been described:
Bursatella leachii africana
Bursatella leachii guineensis
Bursatella leachii leachii
Bursatella leachii pleii (synonym: Notarchus pleii
Bursatella leachii savigniana (synonyms: Bursatella savigniana; Notarchus savignyanus )
Spero News editor Martin Barillas is a former US diplomat, who also worked as a democracy advocate and election observer in Latin America. He is also a freelance translator.