Melibe is a genus of sea slugs, nudibranchs, marine gastropod mollusks in the family Tethydidae. Other common names include “Hooded Nudibranch” and “Transparent Nudibranch”.
Most nudibranchs are carnivores, but their prey is usually comprises of slow-moving animals such as sponges or bryozoans. In contrast, melibe is an active predator which traps fast-moving free-swimming animals such as small crustaceans and amphipods, using its extendable oral hood.
The melibe is like no other nudibranch or sea slug, Instead of a rasping tongue, it sports a unique oral hood that captures small planktonic animals. The large expandable oral hood, fringed with sensory tentacles, opens and is thrown forward in order to catch food. A single pair of rhinophores on the hood are rounded and earlike. 4-6 pairs of flat paddle shaped cerata run along its dorsum in two rows. A close look may reveal the digestive tract, visible as dark branching lines running down the length of the body.
Melibe and the giant kelp plants they live on have matching colors—yellowish brown to olive green with a translucent body which reaches approximately 15cm upon maturity.
Although they prefer to stay attached to a surface, melibe do swim when dislodged or if they’re approached by a kelp crab, then they close their hood to reduce drag. Most predators avoid the noxious secretions of nudibranchs; but the kelp crab is an exception. The noxious secretions of the melibe are said to exude a fruity smell.
The life span of the melibe is approximately 1 year, they die shortly after laying their eggs.
To feed, a melibe firmly attaches itself to a kelp blade and then sweeps its raised hood downward or to the side. When food lands on the lower surface of the hood, themelibe sweeps together the two sides of the hood, and its fringing tentacles lock in the prey. The hood contracts to force the captured food into the melibe’s mouth.
Prey include amphipods, copepods, mysids, other small crustaceans, small mollusks, small jellyfish and ctenophores, larvae of other invertebrates and occasionally small fish.
Melibe are hermaphrodites (they have both male and female sexual organs), and fertilization occurs internally. The animal can lay as many as 30,000 eggs, which are enclosed in a long, gelatinous yellow or cream-colored ribbons which form tight coils or wavy folds.
Where to Find Melibe
The melibe is usually found on eelgrass and other seaweeds near low tide and below, and in kelp forest in deeper water.
While we have yet to encounter one of these in Thailand – we do find encounter them in the sea grasses found near our Komodo Dive center.
This unique and amazing animal is neither collected nor hunted, but its existence depends on healthy kelp forests and other seaweed beds. Sludge and other pollutants smother tiny kelp plants during their microscopic stage.