Aglajidae Family of Sea Slugs

Navanax, Navanax inermis. A representative of the Aglajidae Family of Sea Slugs.

Phylogeny:  The Aglajid Sea Slugs are members of the Aglajidae Family of Sea Slugs. There are eighty-four species in the Aglajidae Family of which three are found along Mexico’s Pacific Coast. They are also known as Swallow-tailed Slugs and Tailed Slugs. Like Bubble Shells and Head-shield Slugs, Aglajidae Sea Slugs belong to the Phylum Mollusca. They are in the Class Gastropoda and Order Cephalsidea.

Distribution:  The Aglajid Slugs are found worldwide, in tropical and temperate seas. Aglajid Slugs are found on, or just under the surface of, soft substrates including sand, mud, silt, and fine gravel from shallow water within the intertidal zone to depths of 200 m (656 feet).

Morphology:  Aglajid Slugs may have a shell that is internal or external, calcified, non-calcified, developed, reduced, or absent. They have a hammerhead shark profile with broad heads, elongate bodies, and tapering tails. In many cases, the tails are paired, giving them the common name Swallowtail Sea Slugs. They have an internal shell that is a flattened coil shape. Their broad heads assist them in burrowing beneath the surface of soft substrates keeping the substrate medium out of the mantle. They all have rolled rhinophores, and many have enlarged parapodia (flap-like extensions of their foot). They are medium length slugs, reaching a maximum 25 cm (10 inches) in length. Aglajid Slugs are generally highly colorful.

Ecosystem Roles:  The Aglajid Slugs y are voracious predators that consume bivalves, crustaceans, flatworms, foraminifera, polychaetas and other opisthobranches. They have sensory cilia on the front of their heads that are used to track the scent trails of prey which they run down, and consume whole. In turn they are preyed upon by crabs, fish lobsters and other Aglajids. They can release a pheromone to attract potential mates.