Sea Slugs! What are they?
They are a very interesting creature found crawling at the bottom of the sea, sometimes perched up on a rock or hanging by a sponge. If you have been on a recent dive and your guide pointed at one of them, what’s the first thing that came to your mind? With their tiny size, stunningly colorful pattern and fascinating structures, this cute fellas are called Nudibranch or Sea Slugs ( soft-bodied, and their overall shape is slug-like ). They are wide-spread here and we get a fair share of their variety in the Philippines. A common subject for underwater photographers who specializes in macro photography.
Most creatures known as sea slugs are actually snails that over time due to evolution lost their shells. The word sea slug is most commonly applied to nudibranchs and other marine gastropods without any obvious shells.
Below are some of the most common sea slugs I often spot on our reef sites in Boracay!
Nembrotha kubaryana eating a Stalked Green Ascidian
Some species ingest toxic chemicals from the sponges they eat and store away the single most noxious compound to use against their predators later on. So they are definitely not in the menu and taste yucky to predators, and even toxic when ingested.
Like a flowing skirt from the summer breeze
A sea slug with white body, gills and rhinophores which has a yellowish-orange marginal band on the mantle.
Funeral Jorunna (Jorunna funebris) | 6 cm at 12m
With a voracious appetite for sponges.
A sea slug that looks like a rice cake, fluffy marshmallow, a polka dot mochi or a cute cow 😀
A Ribbon Egg that is made of tiny Nudibranch embryos suspended in a jelly-like substance in a spiral, that curls loosely that looks like a pasta noodle and sometimes like a rose.
The jelly itself provides all the care it needs eliminating parental care.
They find their way across the ocean using little stalks with thin layers of folded tissue called rhinophores, which are chemically sensitive. Using these, they can sense the chemicals given off by their favorite food and takes on an adventure towards it.
These creatures are Hermaprodites. Each one of them are simultaneously a male and female. While mating they fertilize each other, but cannot fertilize themselves. What a vast world and the guys above found each other for a ménage à trois.
The “nudi” in nudibranch means naked, and the “branch” means gills. Their scientific name translates literally as “naked-gills”, because their ‘respiratory organ’ are exposed.
Willan’s Chromodoris (Chromodoris Willani), also called Toothpaste Nudibranch.
The most distinguishing external feature of this sea slug are the white spots or specks on both the gills and the rhinophores. It almost looks as if they are encrusted in thousands of sparkling diamonds
We don’t have to dive deep to find fascinating creatures. Some of them are just around the corner of the reef happily munching on a sponge!