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

Posts tagged ‘hooded nudibranchs’

Underwater Rainbows

Do you see them?

The January sun streaming down, the light refracted against the hooded nudibranchs . . . the underwater rainbows?!

Hooded nudibranchs are already such ethereal, other-worldy creatures, to see the rainbows dancing against their translucent bodies made me catch my breath and desperately want to capture the beauty for you.

May you dream of underwater rainbows and – maybe- fall even a little bit deeper in love with the NE Pacific Ocean.

For information on hooded nubibranchs (includes images and video of them swimming and their eggs), please see my previous blogs at this link. 

Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering

Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering

Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering
Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering

Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering

Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering

Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering

Hooded nudibranchs on giant kelp at about 3 m. © 2014 Jackie Hildering

They’re Back . . . Hooded Nudibranchs

In late August, some of my Young Naturalists alerted me that they had already seen hooded nudibranchs (Melibe leonina) around Port Hardy (B.C., CANADA).

[It so wonderful that these local children know and greatly appreciate nudibranchs.]

Late August is earlier than we historically have seen the hooded sea slugs gather in large numbers. Usually this happens in late September / early October with them beginning to lay eggs in the spring.

Hooded nudibranchs back in very large numbers. Late August 2010.

This week, I had the opportunity to check how many are already in the area and, it’s official – the hooded nudibranchs are very much back.

To see the video from today, click here (2-minute video).

For explanations on the natural history of hooded nudibranchs, please see my previous blog postings from April 10th, 2010 and May 2nd, 2010.

Hooded nudibranch egg masses (March 2011). Each mass is about 1 cm high. Each little white dot is an egg.

Hooded nudibranch egg masses (March 2011).

 


Hooded mystery #2 – Hooded nudibranch swimming

See last week’s post for Part 1 about Hooded Nudibranchs (Melibe leonina).

This week, I share video showing this remarkable sea slug when it is swimming. 

When viewing the clip, try to identify the animal’s “rhinophores”, the structures coming off the animal’s head that allow it to smell its way around. These structures have the shape of mouse ears but they pick up on chemical signals, not sound.  In last week’s posting I shared how the Hooded Nudibranchs come together to mate through being attracted by smell (pheromones).

Video from today of a swimming Hooded Nudibranch. 

The lobed structures on the animal’s back are the naked (nudi) gills (branchs). They can detach if the hooded nudibranch is threatened and are sticky. Maybe this is so that the predator is distracted by the gills sticking to it allowing the hooded nudibranch to have a greater chance of getting away.

Hooded Nudibranchs (up to 17.5 cm) on Giant Kelp.

I have included a second clip this week too, taken on today’s dive. No Hooded Nudibranchs in it, but Bull Kelp forest visions while on my “safety stop”; a 3-minute rest at 15 feet to offload nitrogen before surfacing. Thought you might like to take a dip with me!

Click here for kelp forest video from today’s dive.

 

Hooded Mystery – Hooded Nudibranchs and their eggs

©Jackie Hildering

Hooded Nudibranch – oral hood open to catch plankton. ©Jackie Hildering

The remarkable looking animals to the right are Hooded Nudibranchs (Melibe leonina up to 17.5 cm). A nudibranch is a type of sea slug that has naked (“nudi”) gills (“branchs”).

Starting in the fall, around NE Vancouver Island, they come together in order to mate and it is awe-inspiring to see 100s of them clustered together, delicate and ghost-like, clinging to kelp.

Often, you can see them swimming on the surface and many people mistake them for jellyfish. It is indeed one of the most alien looking of the 200+ sea slug species of our area. The large disc-like head lets it feed on plankton and small crustaceans and the lobed structures on the animals’ backs are the naked gills.

Hooded nudibranch swimming. ©Jackie Hildering

Hooded nudibranch swimming. ©Jackie Hildering

Since sea slugs can only sense light and dark, the way Hooded Nudibranchs signal one another is by emitting a fruity scent (pheromone) that attracts others of their kind. My personal experience after having picked up a dead Hooded Nudibranch on the beach, is that the smell is something like a mix of watermelon and grapefruit and the scent stayed on my hand for more than an hour. 

After mating, both animals lay eggs (they are hermaphrodites) and then, they die. You can find additional information about why sea slugs are hermaphrodites at this past blog posting. 

Hooded Nudibranch eggs. ©Jackie Hildering

Hooded Nudibranch eggs. ©Jackie Hildering

Typically in our area they lay their egg masses between January and April. Each ribbon of eggs is only about one centimetre wide and contains thousands of eggs.

Every dot is an egg capsule contains 15 to 25 eggs. After about 10 days, depending on temperature, the eggs will hatch into larvae that will be part of the zooplankton soup of the Ocean. The larva are called “veligers” and look very different from the adult Hooded Nudibranchs.

They have a shell and a big flap on their head with which they swim and feed on smaller plankton. After 1 to 2 months, they settle to the ocean bottom and change body shape and even digestive tract to become small Hooded Nudibranchs. 

A few of my video clips of this species below.





Unusually coloured Lions Mane Jelly near kelp draped in Hooded Nudibranchs. ©Jackie Hildering

Unusually coloured Lions Mane Jelly near Giant Kelp draped in Hooded Nudibranchs. ©Jackie Hildering

 

Hooded Nudibranchs on a rotting piece of Bull Kelp. ©Jackie Hildering

Hooded Nudibranchs on a rotting piece of Bull Kelp. ©Jackie Hildering