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

Posts from the ‘Marine snails’ category

Whorling Wizardry

Here’s a big dose of wonder for you.

It’s the time of year when female Oregon Tritons are laying their eggs. These are BIG, predatory marine snails at up to 15 cm long.

Look at how many fertilized eggs are in each “capsule” and marvel at the shape of the egg mass. These capsules are referenced as “sea corn” for this species. It takes each female about 2 weeks to lay her eggs in this wondrously shaped clutch. A friend referenced the shape of the egg mass as being reminiscent of Van Gogh’s “Starry Night”. Agreed!

See the “blank” egg capsules? They have likely been preyed upon e.g. by shrimp, hermit crabs or other snail species. You can even see hermit crabs and snails in these images feeding on the eggs. Some hermit crabs are even sitting on females as they lay eggs. Oh the cheek!

See the hermit crabs and “blank” egg capsules?
I could not resist providing a closeup on this Whiteeknee Hermit from the previous photo.
Look at those eyes!
Closeup on a Blue Turban snail snacking on eggs (from previous photo).

Almost every time I see Oregon Tritons lay eggs, they are doing so as a group. Reportedly, up to 30 individuals have been found laying eggs together.

Why are there so many eggs? Because chances of survival are so low when there is no parental care (other than the architectural marvel of the egg case) and the young hatch into the soup of the Ocean. Planktonic larvae hatch out of the eggs at about 2 weeks of age.

With it taking 2 weeks for the young to hatch, and 2 weeks for Mom to lay the whole mass, the first capsules could be hatching by the time she is finishing her work. I learned from aquarist Casey Cook from her microscopic observations at the Aquarium of the Pacific that, “By hatch time there are significantly less in the egg [capsules] than at the beginning of the lay. We presume the babies eat each other to gain nutrients for creating their first shell layers.”



One study found that, in an aquarium, the larval stage for this species was up to 4.6 years and they only began metamorphosis into their adult form when something was available for them to settle on e.g. rocks (Strathmann and Strathmann, 2007). Further “time from metamorphosis to first reproduction was 3.3 years” (in these conditions in the aquarium).

The scientific name for Oregon Tritons is Fusitriton oregonensis. That’s a whole lot of Oregon in their name and the species is the official seashell of Oregon state (there’s trivia for you). However the range for this species is well beyond Oregon. They are found from northern Alaska to northern Mexico, and Japan. They are common around northeast Vancouver Island. Depth range is reported to be from the intertidal to 180 m. In my experience they are rarely in the intertidal however.

They are also known as the Hairy Triton. “Hairy” for the bristly “periostracum” you see atop the shells which appears to stop attachment of marine organisms. Some loose this bristly covering and, resultantly, can have a lot of settlement and growth on their shells.

The brown structure you see at the opening of the shell is the operculum. This is hard and made of keratin and serves as the door to close the shell. More about that in my “Shut the Door!” blog at this link.

Predatory? Yes! They are among the marine snail species that drill holes into prey, sedate, and slurp. From Invertebrates of the Salish Sea: “Feeds on ascidians, urchins, bivalves, sea stars, brittle stars, chitons, abalones, and polychaetes [worm species] . . . It produces sulfuric acid in its salivary glands, which may help in boring through shells. A gland in the proboscis secretes an anaesthetic used for subduing prey. It feeds with biting jaws as well as a radula . . . Humans should not eat this snail because it carries a pathogen in its salivary glands which can be fatal to humans.”

I have also seen this species scavenge on dead crabs, anemones and fish and eat Lingcod eggs.

Oregon Tritons scavenging on the head of a Lingcod.
Oregon Tritons mating. I hope you appreciate the mood lighting.

All photos: ©Jackie Hildering, northeast Vancouver Island in unceded Kwakwak’wakw Territory.

Oh look! It’s a Scalyhead Sculpin (indicated with arrow).

Stop! That’s not garbage! Moonsnail eggs

This blog is so overdue. Over a year ago, a social media post I made about moonsnails went viral. That’s how many people valued learning that these egg collars are NOT garbage.

Below, I provide the image and text from that viral post but . . . this blog grew into so much more. Read on, I truly believe you will be moved by the marvel of moonsnails.

Text provided with the above image: “Oh oh. With recent low tides it has surfaced again that (mostly) well-intentioned people are moving or “cleaning up” moonsnail egg collars. These are not garbage. They are wondrous constructions to house and protect moonsnail embryos (of several moonsnail species on our coast).

Detail: The female moonsnail forms one layer of the collar by gluing together sand grains with mucus; then the fertilized eggs are laid on this layer and THEN she seals them in with another layer of sand and mucus!

The female forms the collar under the sand and then forces it above the sand when done. The thousands of eggs develop in the the sand-mucus matrix. The process of making the egg collar takes 10 to 14 hours and reportedly starts at the beginning of a flood tide.

As long as conditions are good, the egg collars found on beaches are likely to have embryos developing inside them (if they are still rubbery and moist). When the egg collar is intact as you seen in the images above, the young have NOT hatched out. The collar disintegrates when the larvae hatch.

The larvae are plankton for 4 to 5 weeks and then settle to the ocean bottom to develop further. There is contradictory information on how long it takes the eggs to hatch (one reliable source relays about 1 week while another reports up to 1.5 months). The moonsnail species in the photo above is the Northern Moonsnail whose shell can be up to 14 cm wide (Neverita lewisii is also known as Lewis’ Moonsnail). Photos taken in British Columbia, Canada but there are moonsnail species, and their collars, off so many coasts.”

What has catalyzed my finally also adding this content to my blog is that Mickie Donley shared her video with me showing a female Northern Moonsnail pushing her eggs to the surface.

You might be wondering how a snail THAT big can fit into their shell. Through the rapid uptake of seawater, the foot of can inflate up to four times the size of what it is when in the shell The water is expelled when moonsnails squeeze back into their shells. They need such a big foot to dig for their clam prey AND for females to construct their egg collars below the sand.

The Northern Moonsnail is the largest moonsnail species to 14 cm long (Neverita lewisii). Males are smaller. Species reported to live to 15 years. It’s the most common moonsnail species off the coast of British Columbia.

With the entry to the shell having to be big, of course moonsnails need an “operculum”, a door-like structure that seals off the opening to the shell. See my “Shut the door” blog on opercula at this link.

A Northern Moonsnail’s operculum – the structure attached to the bottom of the animal’s foot so that when it retreats into its shell, the opening is sealed.
The structure indicated with the arrow is the moonsnail’s incurrent siphon, which draws fresh, oxygen-rich water in and over the moonsnail’s gills for respiration. The siphon is not related or connected to the water system in the foot.

Who drilled those holes? Moonsnails!

While some whelk species also drill holes into their prey with their radula (rough tongue-like structure), when moonsnail species drill holes into their prey, there is the sunken / bevelled edge you see here. Notice too how the hole is almost always near the “umbo” of their prey’s shell (highest part). That’s also a clue that the predator was a moonsnail species, not a whelk species. See bottom of my blog at this link for more information on the radula.

From Washington State’s Department of Ecology: “The average moonsnail takedown lasting 4 days as it drills ½ mm per day. In order to speed things up a bit, the moon snail produces hydrochloric acid and other enzymes to help dissolve the shell and liquefy the clam’s insides . . . Once a perfectly rounded hole is made in the shell, the moon snail inserts its tubular, straw-like mouth and slurps up the “clam smoothie” inside. It can take another day or so for the moon snail to ingest the clam innards. Talk about delayed gratification!”

Note that I have found moonsnail shells with holes drilled into them from . . . . a moonsnail.

Who goes there?
I believe the tracks in my image below are from Northern Moonsnails.

Moonsnails clearly need to live in sandy habitats. It’s where their prey live and they also need the sand to make their egg collars.


Notice the mucus trails behind the Northern Moonsnails in the images below. While I have found no research to support this, I wonder if the the mucus may have a chemosensory role so that individuals may more easily find one another for mating.

Other moonsnail species?

There are five species of moonsnail that range from Alaska to southern California or northern Mexico.

  1. Northern Moonsnail as shown in all the images above. Neverita lewisii is the biggest moonsnail species in the world (largest member of the Naticidae family).
  2. Aleutian Moonsnail – Cryptonatica aleutica to 6 cm across.
  3. Arctic Moonsnail – Cryptonatica affinis to 2.5 cm across.
  4. Pale Arctic Moonsnail – Euspira pallida to 4 cm acrross.
  5. Drake’s Moonsnail – Glossaulax draconis to 9 cm across and more common in California.
    Note that it is acceptable to use “moon snail” and “moonsnail”.
Aleutian Moonsnail (Cryptonautica aleutica). Notice the brown dots on the mantle in this species.

I feel better! How about you?

There, I feel relief now that I have finally been able to commit this information about moonsnails to a blog.

I considered entitling this “Moonsnails – the Gateway Mollusc”. Why? The Northern Moonsnail is one of the first species that erupted the lava of interest within me for marine invertebrates. It started with two mysteries: I found a shell with a perfectly round hole drilled into it and . . . I found the strangest, grey, round, seemingly cemented coils of sand.

Look where it got me. 🙂

I hope this added to your knowledge and appreciation for marvellous moonsnails.

Female Northern Moonsnail pushing her eggs to the surface.
A different female Northern Moonsnail than in the image above digging back into the sand after pushing her egg collar to the surface.

More detail on moonsnail reproduction and feeding from Dr. Thomas Carefoot’s “A Snail’s Odyssey“

Reproduction:
Sexes are separate in moon snails [Neverita lewisii] and sperm transfer is direct via a penis . . . The fertilised eggs are enclosed one to a capsule and extruded from the female in a mucousy mixture that is combined with sand (left drawing below).

The colour of the egg collar depends upon the type of sand and other inclusions contained within it.


Each egg/embryo rests in a jelly matrix within an egg capsule. Moon snail veligers range in shell length from 150-200µm. The unusual shape of the egg collar results from the extruded mixture being moulded between the propodium and the shell before it sets into its final sand/jelly state (left middle drawing below).

The extrusion and moulding take place under the sand, commence at the start of flood tide, and take 10-14h. After the initial moulding is finished, the female works over the egg-collar surface one more time adding a protective sheath of sand and mucus (Right middle drawing below) and, at the same time, pushing the collar upwards to the sand surface (right drawing below).

Development within the capsule to a swimming veliger larva takes a week or so, and it is possible that the capsular fluid is utilised as food. Simultaneous with the emergence of the larvae from their capsules, the sand-mucus matrix of the collar disintegrates and the larvae swim freely in the ocean.

Feeding

Adult moon snails are strict predators and mostly eat bivalves. As many of their prey live at depths of up to 20cm or more, the snails have to burrow quite deeply to find them. Burrowing by moon snails is enabled by a large foot that is capable of inflating up to four times the shell volume through uptake of seawater. The inflation is quick, allowing fast penetration into and displacement of sand. The moon snail catches hold of its prey and hauls it to the surface to begin drilling.

Moon snails manipulate the shell of their bivalve prey so that the umbo is closest to the mouth. Whether this provides easiest handling, or whether it is to place the drill-hole directly over the bulk of soft body tissues, is not known.  Another special feature of drill holes of Neverita lewisii is that they are countersunk. This feature allows the predatory records of the snails to be monitored more closely than that of, say, whelks (whose drill-holes are less distinctive). After a hole is drilled, the snail extends its proboscis hydraulically and commences scraping and eating the soft internal tissues with its radula, which is at the tip of the proboscis.

Sources:

Carefoot, Thomas. A Snail’s Odyssey

  • Moonsnail feeding
  • Moonsnail reproduction
  • Moonsnail locomotion

Daily Kos, Marine Life Series: Moon Snails and Sand Collars

Gronau, Christian – Cortes Museum blog; The Biggest Moon of All

Lamb, A., Byers, S. C., Hanby, B. P., Hanby, B. P., & Hawkes, M. W. (2009). Marine life of the Pacific Northwest: A photographic encyclopedia of invertebrates, seaweeds and selected fishes. Madeira Park, BC: Harbour Publ.

Washington State Department of Ecology – We’re over the moon for the moon snail

Shut the Door!

[Note: Text below has been corrected / edited on January 5th. Corrections are marked in red.]

Marine snails have doors. Freshwater snails do too.

Some tubeworm species have them as well.

Yes they do.

They all make an “operculum”. That means “little lid” in Latin but, I’m sticking with referencing the structure being like a door. 🙂

See the operculum in my photo of an Oregon Triton below? It’s the structure sealing off the entrance to the shell.

Oregon Triton (Fusitriton oregonensis). That’s a Sunflower Star on the left. With that species now being in such trouble, it’s a clue that this photo was taken before the onslaught of Sea Star Wasting Disease.

 

Oregon Tritons are a big marine snail species with a shell up to 15 cm long (and with a range well beyond Oregon ie. known from northern Alaska to northern Mexico, and Japan). You can imagine how, if the snail did not have the operculum, a predator could still get access to the snail in its shell.

Lewis’ Moonsnails are another really big snail. Their shell can be up to 14 cm wide and look at the size of their bodies relative to the shell!

Lewis’ Moonsnail on the prowl (Neverita lewisii).

 

Even though they can release some water from their bodies to become smaller, they clearly need a big opening (aperture) to their shell to get back in.


It’s a space you do not want to leave wide open. Hence, the need for making an operculum to seal that opening.

Operculum from a Lewis’ Moonsnail. Shape, strength and size is perfect to seal off the entrance.

 

For snail species that may be found in the intertidal zone, closing the shell with the operculum not only protects them from potential predation, it also may offer them some protection from drying out. Greg Jensen, author of Beneath Pacific Tides, thankfully offered the following knowledge correcting my previous statement about how useful the operculum might be for this purpose: “Marine snails don’t generally use their operculum to seal the shell at low tide. They snug themselves up tight to a rock with their foot.”

He also shared that land snails, who do NOT have an operculum, avoid drying out by coming out in the cool of night or when it is otherwise damp. Another adaptation is that, when it gets too dry, they glue their shells onto a hard surface, sealed shut with dried mucous to retain moisture.

Not only does the snail make this shell-like structure, it also grows with the individual.  The operculum is attached to snail’s body so when the snail retreats, the door does its job. Not surprisingly, the shape of the operculum is a match for the size and shape of the opening, therefore varying between species. The three photos below show some differences.

Blue Topsnail with operculum (Calliostoma ligatum, shell to 3 cm across). Even really tiny marine snail species like Common Periwinkles have an operculum.

 

Leafy Hornmouth closing up with the operculum visible at the end of the snail’s foot (Ceratostoma foliatum, shell to 10 cm long). There’s a Three-Line Nudibranch on the upper right. 

 

Purple-Ringed Topsnail with opecullum visible (near a Green Urchin). Calliostoma annulatum, shell to 4 cm wide)

 

But what about hermit crab species who use the snails’ shells once they die? Since the operculum was attached to the body of the deceased snails, are the hermit crabs left with a wide open door?  Oh just look at how amazing nature is in making sure they too are protected within the shell. The photo below shows you why so many marine hermit crab species have one claw bigger than the other. The bigger claw seals off the entrance in lieu of the operculum!

Widehand Hermit in the shell of an Oregon Triton. Widehand hermit is Elassochirus tenuimanu.

 

Not all marine hermit crab species have this adaptation. Other options include choosing a smaller shell so you can “shake it off” and run like hell when threatened. It’s called the Taylor Swift strategy. I’m kidding! But let me know if you get the pop star word play.

I also mentioned that some tubeworm species make an operculum. See below. In the centre of the image there is a Red-Trumpet Calcareous Tubeworm (Serpula columbiana to 6.5 cm long).

Red-Trumpet Calcareous Tubeworm in the centre (Serpula columbiana to 6.5 cm long) with two Checkered Hairysnails (Trichotropsis cancellata to 4 cm long).

 

As a tubeworm, the species captures plankton drifting by with its crown (radioles). As the common name indicates, the operculum in this species is trumpet shaped. For the individual in the photo, the operculum is purple with white stripes.

I had initially stated that there’s a really good reason for this species to have the door and you are looking right at it. Those snails are kleptoparasites. “Klepto” as you likely know, means to steal (from ancient Greek). The Checkered Hairysnails use their long mouthparts (the proboscis) to try to suck up the food the worm captures before it gets to the worm’s mouth. HOWEVER, what I also learned from Greg Jensen is that the theft by the Checkered Hariysnails is apparently so stealth, that the tubeworm does NOT respond to their mouthparts by closing its operculum.

Thereby, the operculum may help these tubeworms protect their crown (and other body parts) but does not protect them from kleptoparasites. 

But YOU know what to do.

Unwelcome guests? Shut the door!

All photos ©Jackie Hildering, taken near NE Vancouver Island. 

There are times however where you want the door wide open IF you are a marine snail. The additional photos below include that information.

Oregon Tritons mating. That’s a time when you want opercula out of the way. Unlike may humans, they must mate with the door wide open. 😉 

 

Two other Oregon Tritons mating, opercula to the side. Like the mood lighting? You’re welcome.

 

Another Leafy Hornmouth with operculum visible at the bottom of the snail’s foot. And yes, there’s a Scalyhead Sculpin here too.

 

Another Red-Trumpet Calcareous Tubeworm. This one is out of its tube. There’s great diversity in colour in the species. See the trumpet-like operculum on the right?

 

Oh oh. This Red Calcareous Tubeworm has 7 kleptoparasites near!

Beware of taxi-crabs and “Cling like hell to your rock”

Oh how did I get to be today-years-old without knowing of this Robert Service poem that is so timely and speaks for a limpet?

His poem “Security” includes:

So if of the limpet breed ye be,
Beware life’s brutal shock;
Don’t take the chance of the changing sea,
But – cling like hell to your rock.

Yes!

Full poem is below which includes life lessons about taxi-crabs 🦀

Keyhole Limpet which I photographed near Port Hardy. Diodora aspera builds a shell up to 7.6 cm across.

 

Security
Robert Service

There once was a limpet puffed with pride
Who said to the ribald sea:
“It isn’t I who cling to the rock,
It’s the rock that clings to me;
It’s the silly old rock who hugs me tight,
Because he loves me so;
And though I struggle with all my might,
He will not let me go.”

Then said the sea, who hates the rock
That defies him night and day:
“You want to be free – well, leave it to me,
I’ll help you get away.
I know such a beautiful silver beach,
Where blissfully you may bide;
Shove off to-night when the moon is bright,
And I’ll swig you thee on my tide.”

“I’d like to go,” said the limpet low,
“But what’s a silver beach?”
“It’s sand,” said the sea, “bright baby rock,
And you shall be lord of each.”
“Righto!” said the limpet; “Life allures,
And a rover I would be.”
So greatly bold she slacked her hold
And launched on the laughing sea.

But when she got to the gelid deep
Where the waters swish and swing,
She began to know with a sense of woe
That a limpet’s lot is to cling.
but she couldn’t cling to a jelly fish,
Or clutch at a wastrel weed,
So she raised a cry as the waves went by,
but the waves refused to heed.

Then when she came to the glaucous deep
Where the congers coil and leer,
The flesh in her shell began to creep,
And she shrank in utter fear.
It was good to reach that silver beach,
That gleamed in the morning light,
Where a shining band of the silver sand
Looked up with with a welcome bright.

Looked up with a smile that was full of guile,
Called up through the crystal blue:
“Each one of us is a baby rock,
And we want to cling to you.”
Then the heart of the limpet leaped with joy,
For she hated the waters wide;
So down she sank to the sandy bank
That clung to her under-side.

That clung so close she couldn’t breath,
So fierce she fought to be free;
But the silver sand couldn’t understand,
While above her laughed the sea.
Then to each wave that wimpled past
She cried in her woe and pain:
“Oh take me back, let me rivet fast
To my steadfast rock again.”

She cried till she roused a taxi-crab
Who gladly gave her a ride;
But I grieve to say in his crabby way
He insisted she sit inside. . . .
So if of the limpet breed ye be,
Beware life’s brutal shock;
Don’t take the chance of the changing sea,
But – cling like hell to your rock.

 

I ensured this is indeed Robert Service in all his glory by ensuring it was in the “The Complete Works of Robert Service” (1945) but could not find further detail on when he wrote it.

My additional posts featuring limpets:

 

Who You Calling “Unstable”?

Don’t you hate when people use a provocative “hook” to get you to read their material? Yes, that’s what I’ve done but I promise you, it is worth it.

While I think all of us are a little unstable right now, this blog is not about me. It’s about the astounding adaptations of a little limpet assigned the name of “Unstable Limpet” (Lottia instabilis). 

Unstable? This species just limpetted along on its own evolutionary path!

Most other limpet species are shaped so they can suck down securely on a FLAT surface for protection This works well because these most often graze on algae encrusted rocks. But the Unstable Limpet can secure to a ROUNDED surface.

Which rounded surface? Oh I will never forget the first time I noticed this species and realized the marvel of the adaptation. Unstable Limpets are shaped to be able to hunker down on the cylindrical stipes (stem-like structures) and holdfasts of the kelp species upon which they also feed!

Screen grab from “Invertebrates of the Salish Sea”. Caption: “The uneven edges of the shell of Lottia instabilis can easily be seen in this end and side view. The shell is shaped to fit snugly around a round stipe instead of a flat surface.”

I suspect that, like their flat-shelled brethren, Unstable Limpets have a specific spot to which they “home” and where their shell fits perfectly.

As is supported by others’ observations, I have found Unstable Limpets living / feeding on Old Growth Kelp (Pterygophora californica) and Split Kelp (Laminaria species).

Underside of an Unstable Limpet on the stipe of kelp.
An individual with a lot of coralline algae growing on its shell.

I hope that this little limpet leads to you reflect anew on the wonder of the natural world around us and . . . about how being “unstable” just might mean being better adapted to the conditions you are in. It may even be of benefit in having a unique place and perspective in the world. 🙂

Below are further details about the species and an explosion of my photos documenting them.

Unstable Limpets and a Brooding Anemone on the stipe of Old Growth Kelp.

Size: To 3.5 cm across

Known range: Northern Alaska (Kodiak) to Southern California (San Diego) from the intertidal to 73 metres depth.

Variation: Greg Jensen reports that: “Some members of this species settle on rocks, where they develop a more conventional limpet sharp and are difficult to distinguish from other limpets. This rock form was previously known as Lottia ochracea.” (Source: Jensen)

Behaviour: If touched by predatory sea star species, the Unstable Limpet “vigorously” runs away. Predatory sea star species referenced in the study are Six-Rayed Stars( Leptasterias hexactis), Sunflower Stars (Pycnopodia helianthoides), and Ochre Stars (Pisaster ochraceus ). It was unclear to me from reading a summary of the research (and being unable to find the original paper) if this response behaviour is different if the Unstable Limpet is on its “feeding scar” (a bit of an indentation in the surface of the kelp). It may be that it responds then like the Seaweed Limpet (Discurria insessa) which “usually responds to contact by elevating its shell (“mushrooming”) and rocking from side-to-side, but rarely moving away from the scar.” (Source: Snail’s Odyssey).

Little limpet. Long stipe of kelp.
This individual may have had another limpet species feeding on the algae on its shell.
I believe you can see the scars here of where the limpet has been feeding on the kelp.

The following photos offer additional perspectives on two of the individuals shown in photos above.

I believe you can see where this individual has been feeding and yes, thats a lovely hat of algae that is growing on the shell.

Sources:

  • Jensen, Gregory C, Daniel W. Gotshall, and Miller R. E. Flores. Beneath Pacific Tides: Subtidal Invertebrates of the West Coast. , 2018. Print.
  • Lamb, Andrew, Sheila C. Byers, Bernard P. Hanby, Bernard P. Hanby, and Michael W. Hawkes. Marine Life of the Pacific Northwest: A Photographic Encyclopedia of Invertebrates, Seaweeds and Selected Fishes. Madeira Park, BC: Harbour Publ, 2009. Print.
  • Homna, L. 1995. DISTRIBUTION, ABUNDANCE, AND REPRODUCTION OF THE ALGAL SPECIFIC LIMPET, LOTTIA INSTABILIS, Master’s Thesis. Moss Landing Marine Laboratories, San Francisco State University. 77pp.
  • Snail’s Odyssey; Limpets & relatives – Predators & Defenses: Escape-crawling from Seastars
  • Walla Walla University. Invetebrates of the Salish Sea – Lottia instabillis

Who Goes There? Scrape marks on rocks.

Update: 4 pm PDF October 26
Looks very likely that these tracks have been made by a limpet species. Further information under UPDATES below.

Here’s an unsolved mystery, that led to another unsolved mystery, and I suspect there will be more related mysteries to come. 🙂

It began with the photo shown below with an ID request by Marcie Callewart John and Stephen Lindsay. Stephen had taken the photo of the underside of this rock in Stewardson Inlet in Clayoquot Sound, SW Vancouver Island, British Columbia. 

They wrote: “We were wondering about your thoughts on these markings. . . . Limpet or chiton feeding marks? Or egg attachment marks?”


I knew that the markings were from the radula of a grazing marine mollusc but not WHICH mollusc.

Marine and terrestrial snails and slugs (including nudibranchs), limpets and chitons all have incredibly strong “rasping tongues” covered with teeth-like structures called radula. In moon snails and some species of whelk, the radula are strong enough to drill holes into shells so that they can feed on whatever mollusc relative lives inside the shell.

In the grazing molluscs, it is the tongue studded with radula that enables them to scrape algae off rocks.

ICT scan of limpet radula from The Scientist Magazine.

I thought the radular scraping were more likely from a marine snail than a limpet or chiton BUT needed expertise bigger than my own to solve this “who done it”. Thankfully, I could reach out to Rick Harbo, author of Whelks to Whales.

Rick confirmed these were radular markings but did not recognize which marine snail made them. He had a mystery of his own. See below.

 

 

This led to input from Dr. Douglas Eernisse, professor of Biology at the University fo California, Santa Cruz.  He did not recognize the specific tracks in Stephen’s or Rick’s photos. He shared the image below showing OTHER radular tracks but with a big difference. His photo showed the marine snail species making the tracks. See the Black Turban snails having dinner? To give you an idea of scale, maximum size of Black Turbans is 4.5 cm.

 

So out into the world this blog goes in the hopes of engagement and interest and maybe even that someone has documented similar tracks as those in Stephen’s and Rick’s photos with the grazers caught in the act.

I hope it makes you smile too to reflect on how we humans still have so many mysteries to solve. Just peering under a rock or any algae covered surface could lead to another mystery, leaving you wondering “Who goes there?!”

Schematic to give a sense of how the radula are positioned in gastropods (represented by the black zigzag line). I am emphasizing here that both marine and terrestrial snail and slug-like animals have radula. Source of image: Wikipedia. 

UPDATES

Information shared by Jason Knight points solidly  toward a limpet species being who made these tracks.

  1. The screen grabs below are from Dale Fort’s blog with the same image also being found on the website of the Field Studies Council in the United Kingdom for the Common Limpet (Patella vulgata). We do not have this species in British Columbia but the similarity in the pattern certainly supports that a species of limpet made the tracks in Stephens’ image.

Limpet radula marks on the rock

2) The following screen grab is from Smithsonian Ocean, photo by Helen Scales. The species of limpet is not specified.

 

Extra:  A fascinating study from 2015 found that limpets (generally) are the “bulldozers of the seashore”. The study found that their “teeth” (radula) are made of the strongest biological material ever tested (and these teeth are less than a millimetre long)! The strength is the equivalent of one string of spaghetti holding up 1,500 kgs. From Professor Steven Hawkins, of the University of Southampton. “The reason limpet teeth are so hard is that when they’re feeding, they actually excavate rock. In fact, if you look at their faecal pellets they actually look like little concrete blocks – because by the time it’s gone through their gut it’s hardened.” (Barber et al).

Related TMD blog:

Sources:

More tracks made by gastropods

Terrestrial: 

Tracks made by a species of garden slug, Richmond British Columbia. Photo: George Holm.

 

Tracks made by a Banded Garden Snail, Cepaea nemoralis in Queensborough, New Westminster, British Columbia Photo: George Holm.

Abseiling Sea Snail

Go ahead, say that 5 times “abseiling sea snail, abseiling sea snail, abseiling sea snail . . .”

Now that you’ve warmed up and possibly developed a lisp, here are some details about a marine snail species that can climb, has an incredible sense of smell, and can deter much bigger predators.

Meet the Wrinkled Amphissia. No, I do not make up these names.

Amphissa columbiana can be up to 3 cm long, and is also known as the “Wrinkled Dove Snail”. 

 

Climbing

In this species, a gland near the foot secretes thick mucus that allows them to climb up and down and suspend themselves in the sea.

See the two photos below. I know it is so difficult to see the mucus strand.

Scavenging

Where are they abseiling to?

These marine snails are big time scavengers and are very active, using their long siphon to smell out the dead (photo below shows the siphon well).

It appears they can detect the chemicals of decay incredibly well in the water. Often a pile of them are scavenging together.

Wrinkled Amphissa amid Fringed Filament-Worms. If you look really closely you can even see some of the snail’s eggs attached the shell of the snail in the foreground. ©Jackie Hildering.

 

From Braidwaithe et al 2017 regarding feeding. “They appear to locate food resources primarily through chemosensory cues, often following conspecific mucus trails and sometimes congregating around actively feeding sea stars. The chemical cues that draw A. columbiana to food act as feeding stimulants; the addition of scent from a damaged animal induced the snails to feed on healthy prey. The ability to sense chemical cues from damaged animals, including those being consumed by feeding sea stars, creates scavenging opportunities other gastropods may be unable to exploit.”

 

Wrinkled Amphissa aggregation scavenging on a dead Rat Fish. The much larger snails feeding here are Oregon Tritons (Fusitron oregonensis to 13 cm long).The Tritons might follow the scent trails of the Amphissas to the food!

 

Photo above and below. Wrinkled Amphissas and Oregon Tritons snacking on a dead Lingcod. Nothing is wasted in the wild. ©Jackie Hildering.

Biting

They also have a wicked defense against sea stars where they insert their mouth parts (proboscis) into one of the grooves on the underside of the arms of predatory sea stars, biting a nerve.

From Braidwaithe et al  2010″The injury, which generally repelled the attacking sea star, immobilized the affected arm, rendering it useless for several days. The biting defense appears to be effective against several sea star species and may reduce predation on A. columbiana.” Some crab species do feed on them. 

Such remarkable adaptations in a sea of remarkable organisms which means I will be writing blogs and allotting abundant alliteration for a long, long time to come.

Adapting over thousands of years

I am sharing the photo below to give a sense of the diversity in the mollusc phylum to which snails belong.

“Mollis” means soft in Latin and the molluscs are our soft-bodied terrestrial and marine invertebrate neighbours. Their phylum is the second largest (the insects take first place). Note that all the organisms in this photo start off as larvae in the planktonic soup of the Ocean.

You can imagine how excited I was to chance upon  5 highly diverse marine mollusc species in one small area.

 

Details about the species in the photo:

– To the left of the Wrinkled Amphissa is a Keyhole Limpet who makes its own hat-like shell and grazes on rocks (preferred diet is bryozoans). Limpet species need to suction down hard on a flat surface because they do not have a shell to cover its underside. The individual here is in a risky position as a predator could easily flip and consume limpet. Too cool not to share with you is that engineers have found that the “teeth”  of limpets (the radula) are made of the strongest biological material ever tested (and the teeth are less than a millimetre long)! Note that marine snails like the Wrinkled Amphissa are protected not only by a shell, but they have an operculum which serves like a door to close the entrance to the shell when the snails withdrawn into its shell.

– Below the Wrinkled Amphissa, a Blue-Lined Chiton. Chitons make 8 plates to protect themselves. They are grazers like limpets. They too need to be able to suction down to protect themselves but do not need to be on a flat surface since the plates allow them to “contour” onto the surface.

– To the right of the Wrinkled Amphissa is a species of sea slug known as the Pomegranate Aeolid. It has “naked gills” and is therefore in the group of sea slugs known as “nudibranchs”. Sea slugs are marine mollusc without ANY shell or plates for protection. They are protected by feeding on animals with stinging cells (nematocysts) which become incorporated into those structures on its back (they are called cerata and also function as the naked gills for respiration). Specifically, Pomegranate Aeolids feed on Raspberry Hydroids which were only acknowledged as a new species in 2013. Scientific name is “Zyzzyzus rubusidaeus” and again, I do NOT make up these names. 🙂 See photo below.

– Below the chiton, if you look very carefully, is a very tiny sea slug species. I believe this is a Sea Cherub – a type of sea slug that swims and does not have naked gills (and therefore is not a nudibranch).

Not in the photo but to be considered too in the incredible diversity among marine molluscs is – octopuses!

Pomegranate Aeolid feeding on Raspberry Hydroids. ©Jackie Hildering.

Sources:

Anita Brinckmann-Voss & Dale R. Calder (2013). “Zyzzyzus rubusidaeus (Cnidaria, Hydrozoa, Tubulariidae), a new species of anthoathecate hydroid from the coast of British Columbia, Canada” (PDF). Zootaxa. 3666 (3): 389–397.

Lee F. Braithwaite, Anthony Rodríguez-Vargas, Miles Borgen, Brian L. Bingham  (2017).”Feeding Behavior of the Wrinkled Dove Snail Amphissa columbiana,” Northwest Science, 91(4), 356-366.

Lee F. Braithwaite, Bruce Stone, Brian L. Bingham (2010). “Defensive Behaviors of the Gastropod Amphissa columbiana,” Journal of Shellfish Research, 29(1), 217-222.