Join me in the cold, dark, life-sustaining NE Pacific Ocean to discover the great beauty, mystery and fragility hidden there.

Posts tagged ‘sex in the sea’

Great White! Not what you think . . .

Great White!
Not quite what you were expecting?  

These are Great White Dorids. Yes, they are a species of nudibranch and the individuals featured here are mating, prowling for sponges AND succeeding in laying their astounding egg masses.

Mating Great White Dorids: Reproduction of nudibranch species is always right-side-to-right-side; attached by structures called “gonophores”. As reciprocal hermaphrodites, both parents become inseminated and lay eggs.

EACH dot you see in the egg masses (photos below) contains 8 to 12 fertilized eggs. They are laid by both parents because it makes a lot of sense to be a hermaphrodite when you are a sea slug and your eggs hatch into the sea. More fertilized eggs = more chances of some young surviving.

Even after so many years, I find the intricacy and diversity of sea slug egg masses something of jaw-dropping wonder. Not such a good thing when you are supposed to hold a regulator in your mouth while diving. 🙂

Scientific name of this species is Doris odhneri. They can be up to 20 cm long and their egg masses can be at least that size too.

Body design is classic for the sub-classification of nudibranchs that is “the dorids”. Those tufts on their hind ends are the gills and the projections on their heads (which all nudibranchs have) are the sensory rhinophores (rhino = nose). It’s how they smell their way around to find mates, food and whatever else is important in their world.

Notice in the next photo how dorid species are able to retract their gills when disturbed by the likes of an annoying underwater photographer.

Gills retracted.

Amazing too to think of the importance of smell in the sea isn’t it? Why is the individual in the following photo reared up like that? I believe it allows a better position to smell / detect the chemicals of food and/or a mate. Maybe they are even releasing pheromones? Note that is me musing. There is no research I know of to support this.

Same individual as in the first photo in this blog. I asked super sea slug expert, Dave Behrens, about this behaviour years ago and his response was: “I will agree the “rearing” is unusual in this group of dorids. Rearing is common amoung phanerobranch dorids (those that cannot withdraw their gill) . . . Although we will never know for sure, the behavior is thought to be a way for the slug to elevate itself above the substrate in search of chemical clues for its favorite prey.”

In featuring this species, the Great White Dorid, you see that not all nudibranch species are super colourful. But they are all super GREAT.

Species is also referenced as the GIANT White Dorid or Snow White Dorid, or White Dorid or White-Knight Nudibranch . . . etc. Known range is from southern Alaska to California but it’s a species I don’t see often where I dive around northeastern Vancouver Island. 

Another perspective on a Great White Dorids astonishing egg mass.
Prowling for sponges, a mate, or both. 🙂
Poor photo (because my camera housing had moisture in it that condensed in front of the lens) BUT this image shows a Great White Dorid laying an egg masss. It’s one of the times I caught a Great White Dorid in the act whereby I could know what the egg masses look like for this species (albeit that there are some closely related species of nudibranch that lay very similar looking egg masses).

All photos taken in Kwakwaka’wakw Territory, NE Vancouver Island ©Jackie Hildering.