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

Posts from the ‘Sea Slugs / Nudibranchs’ category

Slugs that Fly? The Great Winged Sea Slug.

Here’s a species that deserves the descriptor “Great” without doubt – the GREAT Winged Sea Slug.

I will never forget the first time I saw one of these tiny sea slugs “flying” underwater.  My brain came close to exploding. I did not know of their existence prior to one flapping past my mask.

Dive buddy Natasha Dickinson pointing at a Great Winged Sea Slug.

 

Gastropteron pacificum is usually no bigger than your thumbnail. Maximum length is ~2 cm long and with “wingspan” to 4 cm. The species is also referenced as the Pacific Wingfoot Snail and the Pacific Batwing Sea Slug. But, as mentioned, I prefer the reference to their greatness.

Just marvel at how they can propel themselves, as captured in this video.

 

I will ALSO never forget the first time I saw them spawning, so many of them on the sandy ocean floor, their egg masses expanding to be bigger than they are.

I try to document this every year, looking in areas with sand in from late March into May. I have found them, and their eggs, as shallow as 2m depth.

And sure enough, on March 31st, there they were again. They are gathering to mate!

March 31, 2020 – “Beach Camp” near Port McNeill at only about 3m depth.

 

The photos below show you what the peak of the spawn looks like. Photos are from May 26th, 2019. Just look at the number of them! How do they find one another? How many eggs in an egg mass? So many questions!

 

I bet you also want to know how it can be that their masses of fertilized eggs are bigger than the sea slugs themselves. I presume the masses must expand with seawater but  .  . .  I do not know.

As is the case for most terrestrial and sea slugs, Great Winged Sea Slugs are simultaneous hermaphrodites whereby both parents become inseminated and lay eggs. It’s a great strategy to maximize chances of reproductive success when finding a mate is particularly challenging and your babies hatch into the planktonic soup of the ocean.

 

Among my many wonderings about this species is: Why have I never seen Great Winged Sea Slugs swimming during the time they are aggregating to mate?  I learned from research by Claudia Mills in Friday Harbour (published in 1994), that only sexually mature animals swim AND that they were only observed doing so between September and February i.e. not while mating.

Why swim? In may work well to escape annoying divers and/or bottom feeding fish like Ratfish. The timing suggests that it allows for population dispersal – spreading out for food and/or mates. You would think that the fact that hatch as plankton would spread them out enough. Also, HOW do they then assemble in numbers like this? Is it possible that these sea slugs smell one another’s scent trails even in the ocean?

You can see faint trails here.

 

Please know that this species IS a sea slug but it is NOT a nudibranch. Great Winged Sea Slugs don’t have naked gills and adults do have an internal shell when adults. Great Winged Sea Slugs belong to the group of sea slugs known as “bubble shells” of the order “Cephalaspidea”. You can even see the bubble shell in some of these images.  Ronald Shimek creatively described these sea slugs as having “an internal shell that looks quite like a soap bubble and is about as durable.”

The wing-like structures are called parapodia. When the sea slug is not swimming, these “wings” wrap around the body forming a water-filled cavity. See what looks like a siphon? Part of the “head-shied” folds into a siphon directing water into the cavity. There’s also an exhalant siphon.

The photo above is from the first time I ever noted this species. I was able to follow one as it drifted to the bottom and then saw the siphon appear. This added to the sensation that my brain was going to explode with awe. I shared the photos with experts and learned that, at that time (2007) it was not known what any members of the family feed upon. This added to my appreciation / understanding of how little is known about marine species that are even common and in the shallows. Bill Rudman responded with “I suspect they may feed on small flatworms or other invertebrate with no hard parts – but that is just a guess.” Apparently Gastopteron are known to feed on detritus and diatoms but it a laboratory setting, To my knowledge, there has not been confirmation of the diet of the species when in the wild.

I hope, dear reader, that these words and images offer an additional chance to get lost in the natural world for a little bit. It offers me such comfort to see the steady flow of the natural world around me – from the courting of song birds, to the emergence of plants, and the mating of sea slugs.

Know that, right below the surface, there’s a world or greatness  .  .  . where slugs fly.

 


Note that if you see similar egg masses in the intertidal zone,I believe they are more likely to be from one of two other sea slug species that are also “bubble shell” sea slugs (order Cephalaspidea).

#1) Diomedes’ Aglaja (Melanochlamys diomedea to 1.5 cm long ): A fabulously wicked little sea slug that crawls under the sand looking for other sea slugs to snack on.

Diomedes’ Aglaja crawling through the sand in the shallows.

 

The black blob under the sand is a Diomedes’ Aglaja.Believe the blobs are this species egg masses.

#2) Spotted Aglaja (Aglaja ocelligera to 3 cm long): Usually also under the sand and prey to Diomedes’ Aglaja.

A rare good look at a Spotted Aglajid since they are usually burrowed in sand. Notice how one tail is longer than the other.

 

Two Spotted Aglajids above the sand, presumed one is following the other’s scent trail to get together to mate.

 

A Spotted Aglajid laying eggs! “Aglajids lay their eggs in the most interesting way. They release the egg stream around their rotating body, creating a coil or tube-like mass. They then dive into the sediment placing an anchor so the eggs, above, won’t wash away.” Source: Dave Behrens.


Sources:

 

For an additional blog about another bubble shell sea slug in the NE Pacific Ocean see – “Shelled Sea Slug! A small mystery solved.”


Classification of Sea Slugs 

My attempt at summarizing the cassification of the group to which sea slugs belong.
Last updated 2020-04-17. Source: World Register of Marine Species.

Regarding the photo below:
The Opalescent Nudibranch is a nudibranch.  Nudibranchs DO have external gills (hence “nudi” = naked and “branch” = gills). Adults do NOT have an internal shell.
The Great Winged Sea Slug is a “bubble shell” sea slug (Cephalaspidea). They do NOT have naked gills and adults DO have an internal shell.
There! Now don’t you feel better knowing that: (1) Not all sea slugs have naked gills and hence not all sea slugs are nudibranchs; (2) However, all nudibranchs are sea slugs.

Opalescent Nudibranch – 3 Distinct “Hermissenda” Species in the North Pacific Ocean.

As a result of making the following post on social media, I learned that there has been a change in classifying the “Opalescent Nudibranch”.

It was Robin Agarwal who educated me and shared the following incredible photo from Monterey, California.

As you can see, the species on the left is more similar to the one I posted and which we call the “Opalescent Nudibranch” in British Columbia.

However, it has been determined (2016) that there are 3 species in the “Hermissenda” genus (all are up to about 9 cm long). One is found in the Northwest Pacific Ocean from Japan to the Russian Far East so there is no worry about confusing that one on our coast.  But, for the other two species, their range overlaps in Northern California where Robin took the photo.

 

This has of course led to the need for two common names to differentiate them there. The species on the right is being referenced as the “Opalescent Nudibranch” (reinstating the species name Hermissenda opalescens). The one on the left has retained the name Hermissenda crassicornis and is being referenced as the “Thick-Horned Nudibranch” where the species ranges overlap.

However, off British Columbia’s coast we are only likely to see the species on the left with its range being from Alaska to Northern California. Thereby, I anticipate this beautiful species will keep on being referenced as the “Opalescent Nudibranch” in the vernacular.

What are the differences between these two species?  I am so glad you asked as I totally nerded out and made a summary table to differentiate the 3 species reported in the research “The Model Organism Hermissenda crassicornis (Gastropoda: Heterobranchia) Is a Species Complex“.

The table is just for you my fellow nudibranch nerds.

But, I’ll cut to the conclusion. Don’t be fooled by the colour of the two species found in the Northeast Pacific Ocean. The colour of the cerata in BOTH species can vary from light brown to dark brown to bright orange. Cerata are the structures on some sea slugs species’ backs that have both a respiratory and defence function. The tips contain the stinging cells (nematocysts) of the nudibranch’s prey e.g. hydroids.

The easy way to differentiate the two Hermissenda species in the Northeast Pacific Ocean, is to look for white lines on the cerata. The species most often found off the BC Coast has white lines. The other does not. See my photo below to note this easily identifiable feature (and, if you need some amusement, have a look for the little hermit crab).

 

And now, for that summary table I promised you.

Then, more photos of the beautiful Hermissenda species found off our coast – Hermissenda crassicornis.

I share these to show the variation of colour in the species  but also, because by any name and classification, there can never be enough photos of such a stunning ambassador for the colour and biodiversity found in these cold, dark seas.

Source of table information and photos: Lindsay, T., & Valdés, Á. (2016). The Model Organism Hermissenda crassicornis (Gastropoda: Heterobranchia) Is a Species Complex. PLoS ONE, 11(4), e0154265. http://doi.org/10.1371/journal.pone.0154265. Click to enlarge.

 

See my previous blog at the link for “Attack of the Sea Slugs” in which one Opalescent Nudibranch attacks another.

 

Feeding on Orange Hydroids. ©Jackie Hildering.

Hermissensa crassicornis feeding on Bushy Pink-Mouth Hydroids. Red-Gilled Nudibranch also snacking away in the background.©Jackie Hildering.

Hermissensa crassicornis on Eel Grass. ©Jackie Hildering.

With a “Jointed Three-Section Tubeworm”. ©Jackie Hildering.

Feeding on hydroids, Red Soft Corals to the left and crawling on a Red Ascidian (highly advanced invertebrate, the most advanced of all in the image). ©Jackie Hildering.

Hermissensa crassicornis feeding on Pink-Mouth Hydroids. Here you can very clearly see the distinctive white lines on the cerata. ©Jackie Hildering.

Hermissensa crassicornis on Bull Kelp. Hooded Nudibranchs in the background. ©Jackie Hildering.

On Red Soft Coral. ©Jackie Hildering.

Hermissensa crassicornis on Solitary Pink-Mouth Hydroid. ©Jackie Hildering

Hermissensa crassicornis egg mass. ©Jackie Hildering

Shelled Sea Slug! A small mystery solved.

Here’s a bit of a mystery that took me more than a year to sort out.

On April 27th, 2016, I found this egg mass while diving in Browning Pass with God’s Pocket Resort. This is to the north of where I live and is somewhere I only have the joy of diving a couple of times a year.

Mystery sea slug egg mass among horseshoe worms. (From Neil McDaniel re. worm ID – “they are Phoronids most likely Phoronopsis harmeri” – April 2016. ©Jackie Hildering.

I recognized it was likely a sea slug egg mass but did not know the species.

More than a year passed. On May 7th, 2017, I had a chance to dive the same site again and so hoped to find the species who laid the eggs. We quickly swam to where I had found the egg mass the year prior, into the shallows (~5m), and hovered over the ocean bottom strewn with bits of shell remains.

And I found these . . .

Tiny snail-like animals, plowing through the bits of shell and urchin remains. One, two, three . . . six of them!

I tried to calm myself down, to get photos, and to watch how, despite their soft bodies and the sharp bits of shell, they were able to even push under the surface.

They were Stripe Barrel Shells (Rictaxis punctocaelatus) with shells only to 2 cm long)!

A “Striped Barrel Shell” beside an urchin spine, giving a sense of how small these animals area. ©2017 Jackie Hildering.

These are often mistaken as being a marine snail (prosobranch) like a whelk but they are a type of “bubble shell” sea slug. They are also not nudibranchs. They have a thin shell and do not have “naked gills”. Therefore they do not belong in the “nudibranch” sub-group of sea slugs (opisthobranchs).  For the classification super nerds, see this link or the graphic at the end of this blog for my attempt at offering clarity.

Plowing down into the shell debris! ©2017 Jackie Hildering.

Please know that I am not suggesting that this is a rare species. Rather, they are hard to find. Their size makes them hard to see; divers often do not target the sand or shell-covered bottoms where they live; AND . . . . they are often just under the surface.

I was incredibly fortunate therefore to find them out and about – maybe feeding on algae and/or trying to smell where a mate might be (and we think WE’RE challenged in finding a partner!)

And how about those eggs? Are they a match?

Yes, they are! I was able to confirm this thanks to the knowledge and brilliant documentation of Jeff Goddard on the Sea Slug Forum (see below).

Source: Sea Slug Forum; Jeff Goddard. 

 

Another little mystery solved.

Another big influx of wonder about the life in the NE Pacific Ocean! 🙂


My attempt at summarizing the cassification of the group to which sea slugs belong.
Last updated 2020-04-17. Source: World Register of Marine Species.


For an additional blog about another bubble shell sea slug in the NE Pacific Ocean see – “Slugs that Fly? The Great Winged Sea Slug”

Bring in the Clowns

Update September 24, 2020 – Species has been reclassified into two.

Triopha modesta has been determined to be a trans-Pacific species and is far more likely to be off the coast of British Columbia and has both flat and branching tubercles and globular bits on their side (“relatively small and dendritic dorsal tubercles, two rows of arborescent tubercles on the dorso-lateral appendages of larger individuals”).

Triopha catalinae has been determined to be an eastern Pacific species (but there is overlap) and have large, conical or rounded dorsal tubercles.

Source; Jung, D., Gosliner, T.M., Choi, T. et al. The return of the clown: pseudocryptic speciation in the North Pacific clown nudibranch, Triopha catalinae (Cooper, 1863) sensu lato identified by integrative taxonomic approachesMar. Biodivers. 50, 84 (2020). https://doi.org/10.1007/s12526-020-01107-2

 


In having noted the recent “Creepy Clown” absurdity in the far off periphery of my life, I thought I would share the beauty of the clowns abundant below the surface at this time of year – Clown Dorids.

Clown Dorids are a species of nudibranch (Triopha modesta as of September 2020 to 7 cm).

Nudibranchs are sea slugs with naked gills and those in the dorid suborder most often have their plume of gills on their posterior (around the anus in fact). See the orange frills in the Clown Dorids in these images? Those are their gills.

Clown Dorid; gills on right @Jackie Hildering.

Clown Dorid with gills are on the right. It’s “rhinophores”, by which it smells its way around, are on the left, atop its head. ©2016 Jackie Hildering 

Many dorid species fully retract their gills when disturbed. Clown Dorids can only partial retract their gills.

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That’s all!  Clown Dorids cannot fully retract their gills like most other dorid species.
@2016 Jackie Hildering.

Note too the beautiful “oral veil” with papillae that aid Clown Dorids in finding food.

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Image allowing a good look at the Clown Dorid’s oral veil. ©2016 Jackie Hildering.

Also unlike many dorids, Clown Dorids do not feed on sponges. They feed exclusively on bryozoan species; those crusty colonies of organisms often found on kelp.

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Clown Dorid likely feeding on Kelp-Encrusting Bryozoan (Membranipora serrilamella).
©2016 Jackie Hildering.

There were a particularly large number of Clown Dorids on my dive this past weekend with many egg masses.

Sea slugs are reciprocal hermaphrodites. This of course makes good sense as a reproductive strategy when you are a slow slug and your offspring hatch out to be plankton. Reciprocal hermaphrodites have both male and female sex organs whereby both individuals are inseminated and lay eggs = way more eggs!

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Clown Dorids that have found one another (relying on smell and touch) and maneuvering into the mating position. ©2016 Jackie Hildering.

Nudibranchs mate right side to right side. If you look very carefully in the photo below, you can see a bump on the individuals’ right side. This structure is the “gonopore” and is usually retracted. They lock onto one another with their gonopores and both become inseminated.

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Clown Dorids extending their mating organs and about to lock on right side to right side.
(Ochre Star beside them.) ©2016 Jackie Hildering.

The gonopore may be easier to see in this image.

Clown Dorid - note the "gonopore" on the right near the nudibranch's head. ©2017 Jackie Hildering.

Clown Dorid – note the “gonopore” on the right near the nudibranch’s head. ©2017 Jackie Hildering.

The egg masses of each species of sea slug look different. However, it is very difficult to discern the eggs masses of some closely related dorids. The ideal is to find an individual laying the eggs.

Clown Dorid egg mass. Every little dot is an egg that will hatch as plankton into the sea. ©2017 Jackie Hildering.

Clown Dorid egg mass. Every little dot is an egg that will hatch as plankton into the sea.
©2017 Jackie Hildering.

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Another perspective on Clown Dorid egg masses. ©2016 Jackie Hildering.

However, in all these years, I have never managed to get a photo of a Clown Dorid laying eggs. Dive buddy Paul Sim has though. See his great image below.

paul-sim-clown_dorid_triophina_catalinae

Clown Dorid laying an egg mass. Note each little dot? That’s an individual egg! ©Paul Sim.

How’s that for bringing in the clowns?!

For you to enjoy, below are more non-scary clowns from this past weekend.

Clown Dorid near White-Spotted Anemone. ©2016 Jackie Hildering.

Clown Dorid near White-Spotted Anemone. ©2016 Jackie Hildering.

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Clown Dorid just below the surface in less than 5 m depth. Appears to be feeding on bryozoans.
©2016 Jackie Hildering.

More information:

  • Reproductive structures of Clown Dorids from the Sea Slug Forum – click here.
  • Colour and diet in Clown Dorids from A Snail’s Odyssey – click here.

Sea Angels and Sea Butterflies?!

My dry suit has been hosed down and is drying in the sun; my regulator is soaking in fresh water; the washing machine is chug chug chugging with the clothes used over the last days of diving; and my head and heart are full of so much I want to share.

I’m back from another trip organized to God’s Pocket Dive Resort just beyond Port Hardy . . . more than 11 hours spent underwater over the last days. Such an escape. Such an immersion in wonder and that sense of humility that comes with submerging in the force that sustains this planet. Such an opportunity to learn.

I saw my first Sea Angel.

My buddy and I had been drifting along for about an hour. We had schooled with rockfish; hung next to Orange Sea Pens as they bowed in the current; and marvelled at the abundance of anemones and their babies, studding the forests of kelp. We had done our safety stop with a seeming snowfall of pulsing Aggregating Jellies streaming down around us in the sun’s beams.

 

Thousands of Aggregating Jellies aka Umbrella Jellies. Eutonina indicans to 3.5 cm across. Collective noun for jellies is "smack". ©2016 Jackie Hildering.

Thousands of Aggregating Jellies also known as “Umbrella Jellies”. Eutonina indicans to 3.5 cm across.
Collective noun for jellies is “smack”. ©2016 Jackie Hildering.

 

Close-up on Aggregating Jelly aka Umbrella Jelly. Eutonina indicans to 3.5 cm across. ©2016 Jackie Hildering.

Close-up on Aggregating Jelly –  Eutonina indicans to 3.5 cm across.
©2016 Jackie Hildering.

 

We had already been further awed by Sea Butterflies “flying” by our masks. Sea Butterflies are planktonic sea slugs!  They are “pteropods” – swimming shell-less molluscs whose “wings”(ptero) are their feet (pods). This genus does have an internal gelatinous “pseudoconch” (false shell) and the brown dot you see in my image is the gut.  Sea Butterflies feed by forming a mucus web up to 2 m in diameter in which they trap smaller plankton and bits of organic matter. Oh to see that. It was apparently first documented in the 1970s by researchers while SCUBA diving.

Sea Butterfly - Corolla spectabilis. Dark spot is the gut. ©2016 Jackie Hildering.

Sea Butterfly – Corolla spectabilis. Dark spot is the gut. See this link for more species information and a video (with excited diver vocals) of a swimming Sea Butterfly. 

 

All those jellies and Sea Butterflies pulsing around us and then, just when I was about to break the surface back into the world where gravity has such a stronger hold on me, I saw it! So small, tiny wings pulsing . . . a Sea Angel!

 

Image #1 of the Sea Angel - Cliopsis krohni to 4 cm long. Also known as a "Sea Cherub". ©2016 Jackie Hildering.

Image #1 of the Sea Angel – Cliopsis krohni to 4 cm long. Also known as a “Sea Cherub”.
©2016 Jackie Hildering.

 

Image #2 of the Sea Angel. ©2016 Jackie Hildering.

Image #2 of the Sea Angel. ©2016 Jackie Hildering.

 

Image #3 of the Sea Angel. ©2016 Jackie Hildering.

Image #3 of the Sea Angel. ©2016 Jackie Hildering.

 

This is another species of planktonic, “winged” sea slug (but the adults of this species are completely shell-less; they do not even have pseudoconch). Sea Angels are a rarity so far to the north and are only occasionally seen at the surface (found to depths of 1.5 km).  Their presence is likely due to warmer waters (El Nino and possible climate change) and a big northwest wind that had raged a couple of nights prior. The wonder of it, to see something so otherworldly, to know of its rarity in this area, and to get a sense of its planktonic fragility – surviving from a larval stage, escaping predation by fish, and to be carried by the currents in the vastness of the sea.

It may be hard to imagine but this species is a voracious predator! Cliopsis feeds on other planktonic snails by grabbing them with a long proboscis (which can be up to two times its body length), a sharp radula and hooks made of chiton!

 

Screen grab from the "Plankton Chronicles" showing a Sea Angel feeding! See amazing 1.5 min clip here http://planktonchronicles.org/en/episode/pteropods-swimming-mollusks/.

Screen grab from the “Plankton Chronicles” showing a Sea Angel feeding!
See amazing 1.5 min clip at this link.

 

And yes, their diet includes Sea Butterflies. Sea Angels can eat organisms up to three times their size!

When a Sea Angel comes into contact with a Sea Butterfly’s feeding web, it reels it in, dragging the Sea Butterfly with it. When close enough, the Sea Angel then uses its probosis to “cut” the Sea Butterfly from its psuedoconch and eats it.

The marvel of it all, the delicate balance of this planktonic world about which so few of us have knowledge but which can be so impacted by our activities. There is concern about the impact of ocean acidification (caused by our carbon use) on the development of these organisms.

As always, don’t be despondent. See the beauty, know your connection, and recognize the common solutions and great gains of caring more  . . ..  and consuming less.

Attack of the Sea Slugs!

[Update March 2018 – There has been a reclassification of this species of nudibranch whereby Hermissenda crassicornis  is also being referenced as the “Thick-Horned Nudibranch. Please see my blog at this link for that information.]

This is an Opalescent Nudibranch (Hermissenda crassicornis).

Opalescent nudibranch. The white batch is a colony of animals known as kelp-encrusting bryozoan. © 2014 Jackie Hildering; www.themarinedetective.ca

Opalescent nudibranch – species up to 8 cm long. The white patch on the right is a colony of animals known as “kelp-encrusting bryozoan”. © 2014 Jackie Hildering; http://www.themarinedetective.ca

Here is one climbing giant kelp with hooded nudibranchs in the background.

Opalescent nudibranch © 2014 Jackie Hildering; www.themarinedetective.ca

   © 2014 Jackie Hildering; http://www.themarinedetective.ca

I know! Aren’t they astonishingly beautiful? Opalescent Nudibranchs are one of the most powerful ambassadors for shattering the misconception that warm waters are home to more colourful life. They truly help in raising awareness about the incredibly exotic and vibrant life hidden just below the surface in the dark, rich, cold waters of the NE Pacific.

But they help with something else too.

I recently received a video clip of Opalescent Nudibranchs from Tavish Campbell, taken while with Pacific Wild documenting the life that would be at risk if tanker traffic came to Caamano Sound. Tavish, who is a fellow-diver and appreciator of all things marine, asked, “Hey Marine Detective, what’s going on here?!”  What I saw led me to realize how this species is also a very powerful engager for addressing another default notion we humans seem to have.

We tend to bestow judgemental labels on animals depending on our interpretation of their beauty.  We are inclined to think beautiful animals are “nice”, “cute” and “benign”, and foreign looking animals are “mean”, “ugly” and/or “bad”.

While I appreciate that some organisms may be more aesthetically pleasing than others, there is no “ugly” in Nature and there certainly isn’t “bad”.  Organisms look and live as they do because it works. Their appearance and behaviours are the result of expanses of time longer than we humans, as newcomers, can truly appreciate. Organisms’ adaptation allow them to survive and fulfil their niche in Nature’s puzzle so that there is the greatest chance of balance. [Insert “God” instead of “Nature” if this is your preference.]

Therefore, for example, there are no “bad” kinds of orca but rather orca populations whose job in Nature is to eat other marine mammals. There are dolphins that sometimes kill other marine mammals without this being for the purposes of food (no matter how much this conflicts with the “Flipper-like” identities we have imposed on them). Sea otters do things that definitely are NOT cute and .  . . it also means that beautiful sea slugs will also do what they need to in order to survive.

I take such comfort in not needing to judge Nature. It just is. In contrast, human behaviours too often do NOT enhance the potential of balance in Nature or even the chances of our own survival.

So here’s the jaw-dropping video. Ready . . .?

Opalescent Nudibranchs in all their beauty, are extremely voracious predators and, as is evident in the video, will also attack their own kind. Reportedly, fights most often result when the animals come into contact head-to-head. The animal closest to the head or end of the other has the advantage of getting in the first bite and thereby the greater likelihood of killing their opponent and eating them.

But, they are hermaphrodites, they need one another to mate! As hermaphrodites, there is not even male-to-male competition for females! So why, when your chances of finding a mate as a sea slug are already pretty limited, would you kill another of your kind instead of mating with them?

I hypothesize that it would have to do with the balance between needing to eat and needing to mate and/or that there is some sort of genetic competition going on. That’s all I got. Insert rap awe and wonder here. I may not know why they do what they do but I do know, there has to be an advantage to their survival.

What I also know for sure is that this gives a whole new meaning to “slugging it out”!

Opalescent nudibranch egg mass. http://jackiehildering.smugmug.com/Underwater/Sea-slugs/

Opalescent Nudibranch egg mass. Every species of nudibranch has distinct egg masses i.e. they are species specific.  2014 Jackie Hildering; http://www.themarinedetective.ca

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

Nudibranchs on an Offshore Whale Survey?!

How does studying whale acoustics lead to increased knowledge about the depth range of nudibranchs?

Orange doto.

Just a little more is now known about the orange doto’s depth range. Photo: Hildering.

Let me take you deep and share an experience from my recent time offshore in the eastern North Pacific on a DFO cetacean survey.

This is the Canadian Coast Guard Ship – the J.P. Tully.

JP Tully.

CCGS J.P. Tully. Photo: Hildering

Among the offshore science expeditions undertaken upon the Tully, are surveys by DFO’s Cetacean Research Program.  These line transect studies provide an estimate of cetacean abundance, as well as an opportunity to ID individual whales and collect feeding and genetic information. The knowledge about abundance and location is of particular importance for the large whales that were hunted so intensely and require protection under Canada’s Species at Risk Act.

These are Autonomous Underwater Recorders for Acoustic Listening (AURAL-M2s).

AURAL-M2s

AURAL-M2s. Photo: Sheila Thornton.

AURALs are hydrophones that can be deployed to 300 m, making time-spaced recordings (e.g. 15 minutes every hour) for up to a year.  Such acoustic monitoring is a very important supplement to the cetacean vessel surveys. The AURALs are of course placed very strategically, in remote, offshore locations. By passively recording whale calls, the AURALs can provide information about the location and seasonality of whale species which may aid in determining critical habitat.

The AURALs are a wonder of technology. It is of course no problem to get something to the bottom of the ocean but, getting it back to the surface so you can retrieve your equipment and data is not so simple. It is achieved with an acoustic release (“D” in the diagram below). Once the vessel is positioned so that there is no chance of the device coming up under it, a sound signal is sent to the device and the AURAL releases from its anchor and floats to the surface thanks to the big yellow buoy.

AURAL- M@

AURAL-M2. Click to see an enlarged, labeled schematic on the Multi-Electronique webpage.

These are two perplexed black-footed albatrosses! A big yellow orb has just popped up to the surface as a result of the acoustic release signal. This AURAL was at 226 m depth at the Bowie Seamount, 180 km west of Haida Gwaii. It had been there for a  year.

AURAL + Albatross

Black-footed albatross just after the buoy with the AURAL recording device came up from 226 m.

Here, the highly skilled Coast Guard crew get the AURAL back aboard the ship so that the data can be retrieved and, ultimately, analyzed for whale vocals.

AURAL retrieval

Coast Guard deck crew expertly retrieves the AURAL. Photo: Hildering

But, there was also a year’s worth of growth on the buoy and who knows what you might find . . .

Nudibranchs! Three species found and even one species with eggs!

3 nudibranch species on the aural that had been at 226 m. Photo: Hildering.

3 nudibranch species on the AURAL that had been at 226 m. BC aeolid; bushy-backed nudibranch and orange doto. Click to enlarge. Photo: Hildering.

  • Top: BC aeolid (Catriona columbiana to 1.5 cm); eggs also found.
  • Left: Bushy-backed nudibranch (Dendronotus venustus to 3 cm; previously Dendronotus frondosus)
  • Right: Orange doto (Doto amyra to 1.4 cm)

By examining the AURAL that had been at 226 m, it confirms that these 3 species of nudibranch have a range to at least that depth.

BC aeolids + egg mass.

Sheila Thornton (marine mammal researcher and fellow nudibranch nut) providing a size comparison for the BC aeolids and their egg masses that were found on the AURAL. Click to enlarge. Photo: Hildering

I shared the find with those who have nudibranch expertise much greater than my own (Dave Behrens via Andy Lamb) and learned that for two of the species, there had been no previous record for them at this depth.

It has long been known that some nudibranch species range to depths of at least 700 m. However, you can imagine what a a challenge it is to get species specific depth information. We camera carrying scuba divers can’t help beyond 40 m depth (deeper if diving with mixed gases).

So it’s not a big scientific discovery.  Compared to the data the AURAL will reveal about endangered whales, it’s just a sea-slug-sized discovery.

This is me – back on survey duty looking for much bigger organisms but delighting in how collecting data to help save whales, led to learning a bit more about the little guys.

TMD - DFO survey

Spotter duty on the DFO Cetacean Program’s offshore survey. July 2013. Christie McMillan photo.


 

See the CSAS technical report is by Linda Nichol and Dr. John Ford on the importance of the line transect surveys to the recovery of endangered cetaceans: Information relevant to the assessment of critical habitat for Blue, Fin, Sei and North Pacific Right Whales in British Columbia.

A few more photos from this DFO cetacean survey will soon be posted in this FaceBook album. 

Scroll down at this link to hear samples of marine mammal vocals recorded by AURALs.

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!

Of Sea Whips and Sea Pens

A patch of Sea Whips and Orange Sea Pens. Photo ©Jackie Hildering.

Awestruck yet again.

My buddies and I discovered a “garden” of Sea Whips and Orange 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 polyps filter feed on plankton. 

The Sea Whips can reach a height of 2.5 meters (Halipteris willemoesi). Orange Sea Pens can be 48 cm tall (Ptilosarcus gurney)

Information on Orange Sea Pens from the Monterey Bay AquariumA graceful creature of the seafloor, this sea pen resembles a plump, old-fashioned quill pen. Its colors range from dark orange to yellow to white. Each sea pen is a colony of polyps (small anemonelike individuals) working together for the survival of the whole. The primary polyp loses its tentacles and becomes the stalk of the sea pen, with a bulb at its base—the bulb anchors the sea pen in the muddy or sandy bottom. The various secondary polyps form the sea pen’s “branches” and have specialized functions. Some polyps feed by using nematocysts to catch plankton; some polyps reproduce; and some force water in and out of canals that ventilate the colony.”

But this may be another case where images speak louder than words.

Please enjoy the following photos and clips of Sea Whips and Orange Sea Pens and . . . the predators that stalk them.

Nudibranch fan alert !

 

Orange Sea Pen. They are octocorals - colonies of 8-tentacled polyp-like animals so that polyps can filter feed on plankton. Colony up to 48 cm. Can retract as a defence to being disturbed. ©2016 Jackie Hildering.

Dive buddy Natasha Dickinson with Orange Sea Pen at full height (up to 48 cm) so that polyps can filter feed on plankton. Photo ©Jackie Hildering. 

Orange Peel Nudibranch (Tochuina gigantea) feeding on a retracted Orange Sea Pen. Photo ©Jackie Hildering.

Diamondback Nudibranch feeding on a retracted Orange Sea Pen. ©2016 Jackie Hildering.

Diamondback Nudibranch feeding on a retracted Orange Sea Pen. ©2016 Jackie Hildering.

Orange Sea Pen fully retracted into its burrow. For a summary of research into this retraction response to predators see this link from a Snail’s Odyssey ©Jackie Hildering.

Striped Nudibranch (Armina californica) on the prowl for Orange Sea Pens. Photo ©Jackie Hildering.

 

Striped Nudibranch feeding on the “pen” of an Orange Sea Pen. Giant Sea Cucumber on left.  ©Jackie Hildering.

Diamondback Nudibranch (10 cm) heading for a White Sea Pen. Photo ©Jackie Hildering.

2.5 minute clip below is of Sea Whips and Orange Sea Pens and the predators that stalk them.

Video: 1-minute of an Orange Sea Pen and Graceful Decorator Crab in the current in front of Port McNeill, BC.

 

_JH15424

Orange Sea Pen that has retracted as a defence to being disturbed by a predator – a Diamondback Nudibranch! Additional nudibranch predators include Striped Nudibranchs and Orange Peel Nudibranchs and small aeolid species like Opalescent Nudibranchs when the octocorals are smaller. Leather Stars and Sunflower Stars are also predators of Orange Sea Pens. Nudibranch species may not only benefit from the nutrients but may also incorporate the stinging cells of the sea pens for their defence. The nudibranchs are able to sense the presence of the sea pens from a distance by scent (using their rhinophores). Sea Stars also prey on Orange Sea Pens. Photo ©Jackie 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.

 


For more information: