Aglajidae Family of Nudibranchs

One Nudibranch of the Aglajidae Family can be found in this website:

Navanax, Navanax inermis. A representative of the Aglajidae Family of Nudibranchs.

Phylogeny:  Nudibranchs or Sea Slugs of the Aglajidae Family belong to the phylum Mollusca, the class Gastropoda and the order Cephalaspidea. The Aglajidae Family is in the superfamily Philinoidea, which is one of five superfamilies in this order. Aglajidae is one of ten families in this superfamily. The Aglajidae Family contains sixteen genera and ninety-five species, distributed as follows: Aglaja (6), Aglaona (2), Biuve (1), Camachoaglaja (9), Chelidonura (17), Mannesia (1), Mariaglaja (4), Melanochlamys (18), Nakamigawaia (3), Navanax (4), Niparaya (2), Odontoglaja (2), Philinissima (1), Philinopsis (16), Spinoaglaja (5), and Tubulophilinopsis (4). Species in the Aglajidae Family are also known as Swallow-tailed Slugs and Tailed Slugs.

Morphology:  Aglajid Slugs are typically characterized by having a very reduced internal shell, or no shell at all. 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. If they have an internal shell, it 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). Aglajid Slugs are generally very colorful. They are medium length slugs, reaching a maximum 25 cm (10 inches) in length.

Distribution: Aglajid Sea Slugs are found on (or just under the surface of) soft substrates including sand, mud, silt, and fine gravel. They live in the intertidal zone, and to depths of up to 200 m (656 feet). Aglajid Sea Slugs are found worldwide, in tropical to temperate seas. Eight species from the Aglajidae Family are found in Mexican waters.

Reproduction: Aglajid Sea Nudibranches are simultaneous hermaphrodites. They reproduce sexually with internal fertilization. Mating generally involves both individuals playing the part of both male and female, with a mutual exchange of sperm. The fertilized eggs are laid, as a gelatinous mass, on marine vegetation or the substrate.

Ecosystem Roles:  The Aglajid Sea Slugs are voracious predators that consume bivalves, crustaceans, flatworms, foraminifera, other opisthobranches and polychaetae worms. 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 other Aglajids, crabs, fish, and lobsters.