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

Posts tagged ‘egg masses’

Gold Dirona and Alabaster Nudibranch Egg Masses

An egg hunt mystery FINALLY came to an end for me, coincidentally, just before Easter when many of you were 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 / ribbons.

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.

There are big clues because sea slugs most often lay eggs on their food. So if I know their prey preference I can narrow down which  species laid the eggs.

Easiest of course is to have have 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 and also referenced as the “White-Lined Dirona” or “Frosted Nudibranch”).

You’ll note that they are very closely related (same genus) and it is thereby not surprising that their egg masses would look very similar. Both also often lay their eggs on the same species of Agarum kelp. In all these years, while I have often found both species mating, I 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.

 

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 egg masses 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.

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.

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

Please know that these differences would not be as clear if the eggs were older.

It’s estimated that there are ~350,000 eggs in one Alabaster Nudibranch egg mass. Source: WallaWallaEd. I do not know if this is the number of egg capsules (the dots you see), or if it includes the number of eggs in each egg capsule.

Sea slugs are reciprocal hermaphrodites which means that both become inseminated and lay eggs. One individual lays more than one egg mass as well. So many eggs are needed to ensure species survival when your young hatch out to become part of the planktonic soup of the Ocean.

Alabaster nudibranch laying eggs.

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!

Wolf-Eel – No Ugly Fish!

Don’t say it, please don’t say it. This is not an ugly fish. It hurts when people say this about Wolf-Eels. Such is the way when there is misunderstanding and disrespect for something you love. There is no ugly in Nature – only perfection. If the features of an animal appear foreign to you, it is because it fulfils a role in Nature that is truly awe-inspiring; possibly even beyond your imaginings.

Mr. and Mrs. Wolf Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Mr. and Mrs. Wolf-Eel near Port Hardy ©Jackie Hildering.

I hope to make this point by sharing with you why the Wolf-Eel  is “designed” as it is and how very wrong many of us are in our perceptions about this species. The Wolf-Eel (Anarrhichthys ocellatus), which can be as long as 2.4 m, is not an eel. Wolf-Eels belong in the Wolf Fish family (Anarhichadidae). They are desperately misunderstood. Wolf-Eels are not dangerous nor “mean”. The opposite is true. They are reclusive, anything but ferocious, quite sedentary and slow moving.

Mature male wolf-eel - about 2.2 m long. © 2008 Jackie Hildering

Mature male Wolf-Eel, about 2 m long. Can be 2.4 m ©Jackie Hildering.

Yes, they have large, fleshy, ossified heads and the species has sharp teeth but this is so they can do what so few marine species can – they can feed on spiny sea urchins, snapping them effortlessly into pieces without suffering a single puncture. They also feed on other hard-shelled animals like shellfish and crabs. Even the roofs of Wolf-Eels’ mouths are impenetrable with ossified, tooth-like projections (see photo below).

Each wolf-eel has distinct spots around their eyes which helps recognize them as individuals. © 2012 Jackie Hildering

Mature males are bigger and have fleshier heads. Each Wolf-Eel has distinct spots around their eyes which helps recognize them as individuals ©Jackie Hildering.

The upper jaw of a wolf-eel. Impenetrable to even urchin spines! © 2005 Jackie Hildering

The upper jaw of a Wolf-Eel. Impenetrable to even urchin spines! ©Jackie Hildering.

To my knowledge there has never been an attack on a diver UNLESS, and here comes the predictable thing, we choose to habituate them. Wolf-Eels spend a great deal of time on the ocean bottom in dens where, as divers, we have the enormous privilege of  “visiting” the same spot and seeing the same individuals for years. It is not just their address that makes them recognizable as individuals. Each Wolf-Eel has a unique pattern of black spots near their eyes.

Grandpa Wolf-Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Grandpa Wolf Eel near Port Hardy ©Jackie Hildering.

Some divers choose to feed them, leading to the Wolf-Eels associating us with food and that’s where accidents can happen and where the wild behaviour that lets animals survive, becomes compromised. It also makes them tragically easy targets for any spear diver wanting to poach them. There is no legal fishery for this species but there is a demand for them in the Asian market which is why there are also attempts to farm Wolf-Eels i.e. aquaculture. Not surprisingly, Wolf-Eels might also be defensive when accidentally caught by anglers. I found one account from 1959 where a commercial fisherman was bitten and “The teeth penetrated the hip-waders and broke the skin on both sides of the ankle.”

Mature male bearing the scars of battle. © 2011 Gord Jenkins.

Mature male bearing the scars of battle ©2011 Gord Jenkins.

The mature males do carry battle wounds supporting that they don’t just hang out in dens waiting for a snack to come by, but rather that they will occasionally duke it out with other male Wolf-Eels.It was long thought that Wolf-Eels always mate for life but, this is not always the case. The males do compete for females who will sometimes opt to swap dens and go live with the competitor. Sound like any other species you know? Wonder if it happens at mid-life? 😉

Wolf-Eels have long-lasting pair bonds, coming together when they are around 4-years-old and having their first clutch when they are around 7. In aquariums, their life expectancy is known to be at least 28 years. Both male and female juveniles are brownish orange and look even more eel-like, lacking the big head of the adults. As adults, the females are smaller and a darker brownish grey (both remarkably camouflaged for when they are in their rocky dens).

They do also sometimes need to do battle for den space with a Giant Pacific Octopus.  This is likely another driver for the male’s having such fleshy heads – they are better able to survive the wounds inflicted by such battles.

Clearly, another unique feature about this species is their eel-like body. They are the only member of their family that have this body shape. The long tail serves in locomotion, powering them forward with big, slow, s-shaped waves while being stabilized with the long dorsal and pectoral fins (see video below). Having a long tail also allows them to den-up, curling up and around in narrow spaces between rocks and . . . wait for it . . . it lets them hold onto their eggs.

Mr and Mrs Wolf-Eel tending their egg mass © 2005 Jackie Hildering-

Mated pair tending their egg mass. Note how much darker and smaller the female is ©Jackie Hildering.

Female Wolf Eel guarding eggs. March 2016 @Jackie Hildering.

Female Wolf-Eel guarding eggs. ©Jackie Hildering.

Mating apparently most often occurs between October and December, with the female releasing eggs after the male prods against her swollen abdomen. He then wraps around her to fertilize the 7,000 to 10,000 white to yellow eggs that she will mould into a ball shape. This mass does not need to adhere to anything because the parents will take turns wrapping their tails around the mass, holding and turning it for good aeration until the +/- 3.5 cm young hatch some 13 to 16 weeks after fertilization.

Juvenile wolf eel. © 2010 Jackie Hildering-

Juvenile Wolf Eel ©Jackie Hildering.

The juveniles settle into the adult sedentary lifestyle between the ages of 6 months and 2 years (presumably dependent on food supply and den availability). One juvenile is even known to have travelled a minimum of 1,000 km; having been tagged in Port Hardy, BC and found back in Willapa Bay, Washington two years later. It was long thought that Wolf-Eels always mate for life but, this is not always the case. The males do compete for females who will sometimes opt to swap dens and go live with the competitor. Sound like any other species you know? Wonder if it happens at mid-life?

The Wolf-Eel is indeed akin to us in so many ways. It is a homebody that likes crunchy snacks and prefers that they come right by the front door; they are great parents and are docile unless fighting for home or partner. They invest in durable relationships and – they are only as strange looking as we terrestrial bipeds would appear to them.

And if all of that is not enough for you, see the photo below for the indisputable reasoning for by Wolf-Eels are NOT ugly fish!

Statler the Muppet is cute and loveable. Ergo - so are wolf-eels. Case closed!!

Statler the Muppet is cute and loveable. Ergo – so are Wolf-Eels. Case closed!!

 

Range: Sub-tidal to 226 m; Baja California (Mexico) to the Aleutian Islands (Alaska); west to Russia and south to the Sea of Japan.

Mr. and Mrs. Wolf Eel on February 16, 2013 near Port Hardy. © 2013 Jackie Hildering

Mated pair near Port Hardy ©Jackie Hildering.

Me and a mature male wolf eel.

Me and a mature male Wolf-Eel ©2012 Norris Colby.

Mature male wolf-eel. © 2007 Jackie Hildering

Mature male Wolf-Eel ©Jackie Hildering.

Mature male wolf-eel. © 2007 Jackie Hildering

Mature male Wolf-Eel ©Jackie Hildering

For these and more images of the Wolf-Eel, please see my gallery at this link. 

Remarkable video of a mature male Wolf-Eel eating a Giant Pacific Octopus by Andrew Eve.

Sources:

“Exquisite Handiwork” – Sea Slug Eggs

“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 is up to some 20 cm as well.  Every little dot you see contains up to 20 fertilized eggs. So many eggs are needed when your young are hatched into the planktonic soup of the sea. 

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.  Its 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.


Note: The Sea Lemon is often mistaken for other dorid species such as the Monterey Dorid (Doris montereyensis).  The easiest way to ID them correctly is to know that Pacific Sea Lemons have white gills. See the photos below and note how, although the body colour can be different, the colour of the gills is always white. The gills of the Monterey Dorid are yellow. The other difference, albeit more subtle, is that the little brown bits of colour do not extend to the top of the tubercles in Pacific Sea Lemons and the brown does go to the tips in Monterey Dorids. The tubercles are those bumpy little structures all over the sea slugs. Also, every sea slug species’ egg masses looks different which  provides further ID clues. The egg masses of Monterey Dorids are not quite as intricate. 

[Update 2020: I promise I will provide a blog showing the differences in IDs and egg masses of Pacific Sea Lemons, Monterey Dorids AND two more species which add to the ID confusion – Freckled Sea Lemons and Heath’s Dorids. Just need a bit of time!]

Close up on a Pacific Sea Lemon’s (Peltodoris nobilis) egg mass. Every dot contains up to 20 fertilized eggs.

 

Peltodoris nobilis egg laying (note the Brittle Star arms coming out of the crack).

 

Peltodoris nobilis mating – always right side to right side in slugs with gonopores linked so both become inseminated and lay eggs = simultaneous hermaphrodites.

 

The following photos give more of a sense of the variation in colour in this species.

 


More mating and eggs masses

3 Pacific Sea Lemons, two mating, one egg mass. Individuals appear to lay multiple egg masses to increase the chances of young surviving to adulthood. Not the white gills. 

Mating. These two were right beside the egg mass in the following photo.