Category: Sea slugs / Nudibranchs


Epic Egg Hunt Mystery Solved at Last! Gold Dirona and Alabaster Nudibranch Egg Masses.

Filed under: Sea slugs / Nudibranchs — 7 Comments
March 29, 2013

This week, an egg hunt mystery FINALLY came to an end for me, coincidentally, just before Easter when many of you will be involved in egg hunts too.

I dare say however that my hunt involved vastly more beautiful eggs; that the hunt was much more challenging and –  ultimately, much more rewarding!

One of my very, very favourite things to do, satisfying my “The Marine Detective” nature, is to solve the ultimate “whodunit” and match sea slug species with their egg masses.

Every sea slug species’ egg mass is distinct, comprising a fascinating diversity of intoxicatingly beautiful shapes and patterns.

It delights me (for reasons I can’t fully explain) that for many sea slugs in the northeast Pacific Ocean, I am able to see an egg mass and immediately know which species laid it.

Often it has been easy to figure out due to clues like sea slugs often laying eggs on their food or . . . having the good fortune to find a sea slug in the act of laying their eggs.

But for YEARS, I have been unable to differentiate the egg masses of two of the most beautiful sea slug species in these waters – the gold dirona (Dirona pellucida to 12 cm) and the alabaster nudibranch (Dirona albolineata to 18 cm aka “white-lined dirona” or “frosted nudibranch”).

You’ll note that they are very closely related (same genus) and it thereby stands to reason that their egg masses would look very similar. Both also often lay their eggs on the same species of Agarum kelp and in all these years I have often found both species mating, but  have never found either species laying their eggs.

But then, this week . . . just when I was noting the abundance of both species, how many egg masses there were and wishing, WISHING, I could find just one of them laying eggs – my dear dive buddy Jacqui Engel waved me over and pointed out a gold dirona laying eggs.

Gold dirona laying eggs.

Click to enlarge. Gold dirona laying eggs (Dirona pellucida to 12 cm).
©2013 Jackie Hildering

I was so jubilant, I screamed underwater (yes, I am The Marine Detective for a reason, such things really do delight me to this degree). Finally!  Mystery solved, I would be able to differentiate the eggs of the two species.

But then, Nature was even kinder to me.

On the very same day on the very same dive, after so many years, I also stumbled across an alabaster nudibranch laying eggs!

Alabaster nudibranch laying eggs.

Click to enlarge. Two alabaster nudibranchs. One on right laying eggs (Dirona albolineata to 14 cm).
©2013 Jackie Hildering;

Disbelief! Joy! Manic photo-taking!

I think you may marvel at how very similar the masses are but the difference, at least to me is clear.

The “pieces” of the gold dirona’s egg mass are more compact and more like rice kernels.

Gold dirona laying eggs.

Close-up. Click to enlarge. Gold dirona laying eggs (Dirona pellucida to 12 cm).
©2013 Jackie Hildering

The segments of the albaster nuidbranch’s egg masses are more scallop-edged and diffuse.

Alabaster nudibranch laying eggs.

Close-up. Click to enlarge. Alabaster nudibranch laying eggs (Dirona albolineata to 14 cm).
©2013 Jackie Hildering;

If you have read to this point – thank you!

Likely we are kindred in our love of marine biodiversity and the beauty that is sea slugs.

For as much as I love chocolate Easter eggs, I would forego them for the rest of my existence if it would allow my appetite for marine mysteries to be further satisfied!

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Of Sea Whips and Sea Pens

Filed under: Sea pens and sea quills, Sea slugs / Nudibranchs — 12 Comments
May 27, 2012

A patch of sea whips and sea pens (Halipteris willemoesi and Ptilosarcus gurneyi) Photo: Hildering

Awestruck yet again.

On yesterday’s exploratory dive – May 26, 2012 – my buddies and I discovered a “garden” of sea whips and sea pens at only 65′ (20 m). 

These are the most surreal looking organisms.

They are octocorals – colonies of 8-tentacled polyp-like animals.

The sea whips can reach a height of 2.5 meters.

This is another case where images speak louder than words.

Please enjoy the 2.5 minute video clip at the end of this blog item to meet the sea whips and sea pens and . . . the predators that stalk them.

Nudibranch fan alert !

 

For more information on orange sea pens:

Orange peel nudibranch (Tochuina tetraquetra) feeding on a retracted orange sea pen. Photo: Hildering.

Striped nudibranch (Armina californica) on the prowl for orange sea pens. Photo: Hildering.

Diamondback nudibranch (10 cm) heading for a white sea pen (Tritonia festiva and Virgularia sp.) Photo: Hildering

The BBC video below is from SW Tasmania in Australia, NOT Northern Vancouver Island, British Columbia and shows a different species of sea pen. However, I have included it as it shows, with time lapse photography, how sea pens can slowly deflate and retract in response to predation attempts by nudibranchs.

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Big Orange Love – The Orange Peel Nudibranch

Filed under: Sea slugs / Nudibranchs — 6 Comments
February 14, 2011
Sea slug amidst red soft coral.

Orange peel nudibranch feeding on red soft coral. Photo: Hildering

Here’s your Valentine’s blog item. It’s all about Big Orange Love – the reproduction of the orange peel nudibranch (Tochuina tetraquetra).

These sea slugs are very aptly named since their skin is reminiscent of both the texture and vibrant colour of an orange. But, the name does nothing to indicate the size to which these giants can grow. They are one of the world’s largest sea slugs with literature reporting them to lengths of up to 30 cm. However, I swear I have seen them larger in our area and will strive to get the photographic proof.

As if this sea slug species’ colour, size and beautifully intricate white gills are not enough to create awe, you should see their eggs! I will never forget the first time I saw the huge tubular mass that looked like udon noodles. I think my brain almost exploded and I was propelled all the more feverishly on my “The Marine Detective” path, wanting to be able to identify the egg masses of all sea slugs in our waters (each species’ eggs look different).

This is the time of year when the orange peel nudibranchs mate and lay eggs.

It’s all to be seen on my “Big Orange Love” slideshow below. 

More on sea slugs and their eggs in previous blog postings at this link(scroll down).


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They’re Back . . . Hooded Nudibranchs

Filed under: Sea slugs / Nudibranchs — 14 Comments
September 7, 2010

In late August (2010), 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.

Update March 2011 - Eggs masses everywhere! Abundance of hooded nudibranchs still awe-inspiring. See images below for eggs masses.

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).

 


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“Exquisite Handiwork” – Sea Slug Eggs

Filed under: Sea slugs / Nudibranchs — 5 Comments
August 29, 2010

“Some of nature’s most exquisite handiwork is on a miniature scale, as anyone knows who has applied a magnifying glass to a snowflake.“

I was reminded of this Rachel Carson quote today when diving but found myself changing the ending to ” . . . as anyone knows who has seen sea slug egg masses.”

The image here is the egg mass of the Pacific sea lemon (Peltodoris nobilis), a sea slug up to 20+ cm; it’s egg mass up to some 20 cm as well.

The egg mass is the result of the sea lemons lining up right-side-to-right-side and both becoming fertilized. Being a hermaphrodite is of course a good design when you are a slow-moving slug that relies on smell to find its way.  More detailed information about sea slug mating can be found at this previous TMD blog entry.

Looking like rich, textured crocheting, the egg mass is indeed Nature’s exquisite handiwork.  It’s intricacy rivals that of any spider’s web and, in my perception, surpasses any human nanotechnology.

Seeing such beauty serves as testimony of Nature’s perfection and complexity. How we humans are newcomers to it all, unable to truly grasp the billions of years of design that proceeded our walking upright on earth. It should further motivate us all to walk with much smaller footprints so that we do not blunder and crush the systems that are Nature’s exquisite handiwork.

Follow the link below for images showing a close-up on the egg mass allowing you to see the individual eggs; the mating of the sea lemons; the egg laying and predation by a leather star. Click here.

Note: The sea lemon is often mistaken for other dorid species such as the Monterey dorid.  The easiest way to ID them correctly is to know that sea lemons have white gills. 

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Hooded mystery #2 – Hooded nudibranch swimming

Filed under: Algae/seaweed, Marine Invertebrates e.g. Sea Slugs, Sea slugs / Nudibranchs, Video / slideshows — 7 Comments
May 2, 2010

See last week’s posting for Part 1 on the hooded nudibranch (Melibe leonina).

Hooded nudibranchs (up to 10 cm) on giant kelp.

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).

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.

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 video of a hooded nudibranch swimming.

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


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Hooded mystery – hooded nudibranch and its eggs

Filed under: Marine Invertebrates e.g. Sea Slugs, Sea slugs / Nudibranchs — 8 Comments
April 25, 2010

The remarkable looking animal to the right is the hooded nudibranch (Melibe leonina). A nudibranch is a type of sea slug that has naked (“nudi”) gills (“branchs”).

Since late fall, I have observed hooded nudibranchs gathering at one of my favourite dive sites. 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 the thin strands of giant 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.

Since sea slugs can only sense light and dark, the way hood nudibranchs “call” one another is to send out a fruity scent (pheromones) 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. 

Yesterday, I found ample evidence that mating has been happening. I found many egg masses; images of which I have included at the link below. Each cluster of eggs is only about one centimeter wide and contains thousands of eggs. After about 10 days 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 plant plankton. After 1 to 2 months, they settle to the ocean bottom and change body shape and even digestive tract to become small hooded nudibranches.

Click here for my photos of hooded nudibranchs and their egg masses (includes images from yesterday’s dive).

Click here for video of a hooded nudibranch swimming. 

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Sea Slug Easter Eggs For You!

Filed under: Marine Invertebrates e.g. Sea Slugs, Sea slugs / Nudibranchs — 6 Comments
April 3, 2010

Giant nudibranch egg mass at the base of a tube-dwelling anemone.

To follow up on last week’s posting, I now share images of the giant nudibranch swimming and of its egg-laying behaviour.

I know that these are the strangest eggs you will see this Easter!

The story of how the eggs come to be is pretty unique too.

There are no girl or boy sea slugs. They are both male and female; they are hermaphrodites. This means that when sea slugs mate, both animals “get pregnant” and lay eggs.

Sea slugs need this adaptation because it is really difficult for them to find another of their kind.  They are relatively slow moving animals that depend on feel and smell to get around.

They don’t search around aimlessly for a mate though. That would be a waste of energy. The chances of finding a member of their own kind are greater near their favourite food.  To make this clearer, imagine that you were someone who really loved eating pizza and you wanted to find someone else who loved pizza.  The best place to find them would be at  . . . a pizza parlour!

For the giant nudibranch, you know from last week’s posting that they love to eat tube-dwelling anemones so they are likelier to meet a mate around this prey.  They also may give off chemical signals (pheromones) to announce that they are in the area and “looking for love”.

Compared to faster animals that can see though, the chances of sea slugs finding one another are much smaller.  So when they do meet, it is important that they really make it count and have as many babies as possible especially since the eggs will hatch into plankton. This means that many baby sea slugs will become dinner for filter feeders like anemones and barnacles.

How to have as many babies as possible?  Both should lay eggs! This is why they are hermaphrodites; not just a male or female.  The sea slugs line up right side to right side and exchange cells so that they can both lay eggs.

I will share much more about the love life of sea slugs in future postings. Every sea slug species lays eggs that look very different. One of the “cases” I have worked on the longest is to figure out what each species’ eggs look like. A great clue in trying to figure this out is that sea slugs most often lay eggs on their food.

You can imagine my delight when I found a big mass of eggs at the base of a tube-dwelling anemone!  Knowing that the giant nudibranch preys on this species, the chances were very, very good that these were its eggs.

When you follow the link, you can see a larger picture of the eggs mass and get an idea of just how many eggs are in this string (each dot is an egg).

I have also included video of the giant nudibranch swimming for your Easter weekend pleasure.  You’ll see that the nudibranch swims upwards but, when it wants to go down, it just stops moving and gently drifts back down to the ocean bottom. You’ll also see that I am pointing my dive light at the animal and how this makes colours look different underwater.

Click here for the giant nudibranchs eggs and swimming behaviour.

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Who’s eating who?

Filed under: Marine Invertebrates e.g. Sea Slugs, Sea slugs / Nudibranchs, Video / slideshows — 2 Comments
March 28, 2010

This week’s “case” features the giant nudibranch (Dendronotus iris) and the tube-dwelling anemone (Pachycerianthus fimbriatus).

Giant nudibranch looking for dinner, the tube-dwelling anemone

Nudibranchs are sea slugs with naked (“nudi”) gills (“branch”) and this species is indeed “giant” at up to 30 cm (12 inches). Like all sea slugs, they have a very poor sense of sight and find their way around largely by touch and detecting chemicals.

The giant nudibranch’s favourite snack is the tube-dwelling anemone. Anemones’ stinging cells (nematocysts) serve as a good defence to most predators but not to the giant nudibranch. Nudibranchs that feed on animals with stinging cells actually incorporate the stinging cells and use them as their own defence!  They “steal” the anemone’s weapons.

This anemone species is therefore adapted to also withdraw into a tube to get away from the predator sea slug.

And the battle is on! The giant nudibranch patrols the sandy ocean plains “looking” for the tube-dwelling anemone. When it finds one, it rears up and pounces, mouth parts extended in the hopes of grabbing onto the anemone. When the anemone senses the nudibranch’s attack, it withdraws into its tube.

Wait till you see what happens to the giant nudibranch!

At the link below, I provide you with the video of such an attack. I have also included a collection of photos to show you colour variation in this nudibranch species and photo stills of the attack behaviour.

I did not catch the conclusion of the attack in the video but read the video’s caption to find out what happens. Be sure you know “Who eats who”!

Via “The Marine Detective” there will be many more postings about this and many other Northeast Pacific sea slug species.

Click here for video and photos.

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