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 INVERTEBRATES’ category

Aristotle’s Lantern

What is so thought-provoking that it warrants the name “Aristotle’s Lantern”? It’s what the mouth-parts of urchins are called.

Today while I was submerging, there was a dead Green Urchin floating at the surface, spines rotted off but mouth still intact.

This allowed me to photograph the jaw parts outside the urchin’s shell (test).

Close-up on the dead Green Urchin’s underside with the mouthparts.

 

This is something I would not normally be able to photograph because I would have to lift an urchin to do so and I do not want displace the life I see. Also, because most dead urchins I find floating about have been “otterized”. An otterized urchin is where a predator has broken through the bottom of the urchin. Mammalian predators of urchins include River Otters, Sea Otters, Mink and humans. Wolf-Eels and Sunflower Stars are also predators. Another reason the mouth parts are difficult to photograph is because they can retract into the urchin when alive.

The photos included below of the full mouth structure are from another dead urchin whose “Lantern” I preserved. See how complex it is? There are 5 jaws made from plates of calcium, which are held together by muscle. When wanting to chew away at seaweed / algae, the structure is pushed out whereby the mouth opens and the urchin can chew by moving the structure side-to-side. You can imagine that chewing would wear down the calcium but no worries – the Lantern grows from the tip, reportedly at 1 to 2 mm / week.


Why are an urchin’s mouthparts called “Aristotle’s Lantern”? Because Aristotle is believe to have described them as “lantern-like” in Historia Animalium (The History of Animals) more than 2,340 years ago.

Indeed, the “horn lanterns” used in Aristotle’s time looked like the mouthparts; having 5 panes covered with cow horn that had been boiled and shaped. BUT there are biologists who disagree, believing that there were “historical ambiguities with the original translation” and that Aristotle was referencing the WHOLE urchin’s shell as being lantern-like, rather than just the mouthparts.

Oops – if that be true, Aristotle would not be happy that the mouthparts of urchins’ near relatives, sand dollars, are also referenced as “Aristotle’s Lanterns”.

There don’t you feel better now knowing all of this? I am here striving to lighten and enlighten . . . lanterns and all. 💙☺️💙

Here’s a “Shape of Life” video of urchins feeding, narrated to be oh so dramatic:

 


About regeneration, aging and life expectancy in sea urchins

Like sea stars and other  echinoderms, urchins can regenerate body parts e.g. their spines and tube feet. Research by Bodnar and Coffman (2016) found that this ability to regenerate lost or damaged tissues does not decrease with age in 3 local urchins species: the Variegated Urchin (Lytechinus variegatus), Purple Urchin (Strongylocentrotus purpuratus) and Red Urchin (Mesocentrotus franciscanus).

This is of particular interest since the life expectancy of these three urchin species is very different; respectively 4 years, 50+ years, and 100+ years. Yet, “the fact that all species showed the same consistent ability to regenerate tissue despite age and life expectancy undermines the current evolutionary theories of ageing. It was previously expected that species with shorter lifespans would invest fewer resources in maintenance and repair, perhaps to invest greater energy in reproduction. So this study has shed light on a new, unexpected factor that contradicts the current theory.” Source: Biosphere.

Regarding the life expectancy of Green Urchins (Strongylocentrotus droebachiensis) from Fisheries and Oceans Canada: “Aging techniques for B.C. Green Urchins are currently being developed by the Pacific Biological Station, but Green Urchins on the Atlantic Coast have been known to live from 20 to 25 years of age.”

 


See below for images of urchins feeding and of “urchin barrens” . Urchins are an important part of the marine ecosystem but when we killed off Sea Otters who eat urchins, this led to too much kelp being eaten. The resulting “urchin barrens” are a loss of habitat and food for other organisms and result is less carbon buffering and oxygen production by kelp.

Sea Star Wasting Disease, and specifically the devastation to Sunflower Stars (Pycnopodia helianthoides), has also led to urchin barrens because Sunflower Stars too are predators of urchins. For more information, see my blog “Wasted. What is happening to the sea stars of the NE Pacific Ocean?


Below are images of urchin barrens.

Sources: 

Red and White

Some red and white for you on Canada Day.

 

May we celebrate all that is wild, good and free.

May we truly know the privilege of it all.

May we be the neighbours and stewards who are as open-eyed and open-hearted as this land is large.


Photo: Two Rose Anemones touching, different colours, same species.
Aka Fish-Eating Anemone, Urticina piscivora to 30 cm across.

A Lone Giant

[If you are coming here from Instagram, please see this link for background on Sea Star Wasting and where to report sightings.]


Endangered? I gasped when I saw this adult Sunflower Star on my last dive and hung nearby for a little while. I found myself thinking in a way that could be interpreted as prayer.

Did you realize Sunflower Stars are now so rare – these giants that should be abundant on the coast from Alaska to Mexico?

 

Endangered? Many of us who have been monitoring Sea Star Wasting Disease since 2013 certainly think so and there is a campaign in Washington State to have them recognized as such.

There has been such misunderstanding and “ocean blindness” about what has been going on. Even reputable news outlets have put into the world information about the Disease that speaks of sea stars as if they were one species and hence, if some sea stars are sighted, well then everything is fine.

It’s not fine. At least 20 species of sea star have been impacted by Sea Star Wasting Disease. Some are recovering well but . . . this the world’s largest sea star species, the Sunflower Star, Pycnopodia helianthoides, is NOT.

We sometimes see waves of juveniles, maybe resulting from more adults being at depth who are close together enough that when they broadcast spawn,  fertilization results (broadcast spawning is when males and females release their sex cells into the water on cue). But, ultimately these juveniles disappear.

Sea Star Wasting Disease (SSWD) is the largest wildlife die off in recorded history. That be truth. But because it is happening below the surface there is less engagement, funding, and knowledge.

Does it matter? Yes, it matters a lot, ecologically and with regard to what the Disease may teach us.

Sunflower Stars have a similar ecological niche to Sea Otters re. grazing on urchins and maintaining kelp forests (see video below). You know that if Sea Otters were dying en masse we would certainly be engaged, invest in research, and want knowledge.

A close-up of the same individual.

What is the cause? Specifically for Sunflower Stars, it is known that there is a virus that has been around for more than 70 years that, since 2013, is having an unprecedented impact .

Why would a virus that is not new be able to have a greater impact? Due to stressors and yes, these are believed to be related to climate change.

To those wonderfully engaged humans who have read all of this, please know this is not an additional problem that requires novel solutions. You are the last people who I wish to burden, you who care as you do. The plight of Sunflower Stars is a symptom of what is the same set of problems re. short term economies, absence of precaution, fossil fuel use, and consumerism.

Reporting sightings? I have reported the sighting of this lone, adult Sunflower Star to add to the knowledge of the impacts of SSWD. Citizen science is so important to understanding. Further information on the Disease and where to report sightings of sea stars can be in my blog at this link. 

And to you dear Sunflower Star,
May you find another of your kind for the sake of biodiversity, ecology, human learning and understanding, and so that your species will not disappear from children’s drawings of life on our coast.

May it not be that we continue on a path where Sunflower Stars slip away from our memories, or that we end up talking to children about “There used to be these giant, colourful sea stars . . .”

💙

 

Sighting was made on June 15th, near Port McNeill.

Video below re. Sea Star Wasting Disease and ecological impacts.

 

Rose Star – No Two Alike

One species. So many colours.

That’s beauty. That’s biology.

 

Rose Stars have such diversity in colour and pattern, that the species is also known as the “Snowflake Star”; a name suggesting that no two are alike.

Am I trying to make some sort of point as it applies much more broadly? Why, whatever would make you think that? 😉

Surely we humans rejoice in the beauty of diversity?

 

Notice that above this Rose Star, there is another local, marine ambassador for diversity of colour within a species.See the Blue-Line Chiton (Tonicella undocaerulea)?

Please see additional photos (and slideshow) below to get a further sense of the diversity, the beauty, and the perfection.

Species information:

  • Crossaster papposus to 34 cm but in British Columbia the maximum size is believed to be 17 cm.
  • They can live to at least age 20. Species is slow growing. Maximum size is reached around age 10.
  • Even the number of arms varies. Most Rose Stars have 11 arms but number ranges from 8 to 16. From personal communication with zoologist Neil McDaniel: ” I did counts of 63 images I had on file [all from British  Columbia’ and nearly 90% (87%) had 11 arms, about 10% had 10 and 3% had 12.”
  • They are SPEEDY! Zoologist Neil McDaniel clocked them at 50 cm/min. Larger individuals were documented to travel over 5 meters in 12 hours. They are speedy because they are serious predators.
  • Diet is known to include sea pens, nudibranchs, bryozoans, bivalves (e.g. clams), juvenile urchins and tunicates. Their diet is likely broader than this as they are not picky eaters. I often see them in rocky habitats covered by coralline algae species (see photo below) and believe that is, at least in part, because the prey there include Orange Social Tunicates. They are one of the few species of sea star known to feed on nudibranchs.
  • How they feed: When they feel their prey, and are hungry, they retract their sensory tube feet (tube feet at the tips of their arms), and then stretch up on their tippy toes (extending their terminal tube feet) to be higher and able to “pounce” on their prey when on the ocean bottom. Smaller prey are swallowed whole. Larger prey are held with the tube feet and, as is the case with other sea star species too, they evert their stomach OUT OF THEIR BODIES and into or over their prey.
  • Research supports that Rose Stars can sense potential prey and other sea stars by smell (distance chemoreception).
  • In the photos below you will also see the intricacy of the surface of sea stars. You will see:
    • Spines
    • Pedicellaria = amazing little structures that can nip off the tube feet of other species of sea star e.g. the predatory Morning Sun Star (Solaster dawsoni).
    • The tufts are “papulae”. They are the gills / respiratory organs of the sea star. They can retract into the surface of the sea star’s body.
  • Range: Bering Sea to Puget Sound; Arctic Ocean, North Atlantic Ocean, North Sea, western Baltic Sea.
  • Depth: Found from the shallows of the intertidal to ~1,200 m. Believed to more often be in low current areas.
  • I saw little impact on this species from Sea Star Wasting Disease around NE Vancouver Island BUT Rose Stars were hit very badly in 2014 in other areas e.g. Sechelt Inlet, British Columbia (McDaniel, pers. comm.). See photo at the end of the blog. The species seems to be rebounding, unlikely Sunflower Stars which remain devastated across their range. [Note: this information has been updated from a previous version of this blog.]

 

 

 

Rose Star and retracted Orange Zoanthids. Some are likely being snacked upon.

 

 

 

 

 

 

Very typical habitat for where I find Rose Stars. I believe their prey on these coralline algae covered rocks include the small orange animals you see = Orange Social Tunicates. Notice too that there is another Blue-Line Chiton. 

The next 3 images are of the same individual.

 

Slideshow:

Sources: 

One of many Rose Star ravaged by Sea Star Wasting Disease near Sechelt, British Columbia.
Photo ©Neil McDaniel.
See Neil’s information about SSWD at this link.

 

In a Galaxy Far, Far Away . . .

 

 

In a galaxy far, far away . . .

Oh wait no, this was yesterday, diving in a soup of Red Eye-Medusa.

Imagine the water thick with plankton to the extent that it actually feels soupy, and throughout, these jellies are suspended . . . like little, living fairy lights in the dark.

When the visibility is poor like this, it of course limits what else can be seen. But, when you’re in the dark, that’s where you are and that’s where there is still much learning to be done and beauty to be seen.

Yep = life metaphor.


Polyorchis penicillatus are up to 10 cm in size and they are “sink fishing” when hanging like this (detail below).

Look at the bottom of the bell for the red “eyes” (eyespots / ocelli). These can sense light intensity, helping the jelly know which way is up.

The stomach is in the middle and the gonads are the elongate organs surrounding that. Species has up to ~160 tentacles (more often around 100). This jelly species makes “hopping” motions. In part, this is believed to help when feeding near the seafloor by stirring up prey (true story).


More detail on feeding from the University of Oregon:
They feed in both the water column and on the bottom, using different methods for each (Mills et al. 2007). On the bottom, they perch on their tentacles and eat benthic organisms by touching the sediment with their manubrium [stomach with mouth at tip]. Sometimes, they will hop on the sediment, likely to stir up possible prey or move to a new location (Mills 1981, 2001). In the water column, they use “sink fishing” to find their prey. During sink fishing, the medusae extend their tentacles out from their bell and let the distal ends sink downward. They either maintain their position in the water column or sink slowly and catch prey with their tentacles. When a prey item touches a tentacle, the medusa will use that tentacle to bring the prey to the manubrium, though large prey sometimes require more tentacles; this process causes cessation in swimming and crumpling (Arkett 1984).”


#YouAreWhereYouAre

Another Red-Eye Medusa at the same site in Port Hardy.
Species of sea star on the anchor chain is a Leather Star.


Source of annotated diagram below and ALL you wish to know about the species:

Polyorchis penicillatus, A publication of the University of Oregon Libraries and the Oregon Institute of Marine Biology Individual species.

Living Gems #1 – Candy-Stripe Shimp

I went diving yesterday in an area where I knew there were Crimson Anemones. My hope was that if I took my magnifying glass and my macro lens MAYBE I would find a few Candy-Stripe Shrimp.

 

LOOK! One little Crimson Anemone had ~40 Candy-Stripe Shrimp!

This species of shrimp is almost always found in association with this species of anemone and must be immune to its stinging cells (nematocysts). The shrimp get the benefit of snacks and the anemone MAY get protection. From Greg Jensen’s Crabs and Shrimps of the Pacific Coast”: “The shrimp are believed to feed primarily on egested material [think poop] and the sloughing tissues of their host anemone”.

Greg observed in his aquarium (anecdotally) that Candy-Stripe Shrimp would share space on an anemone with other shrimp species (Kincaid’s Shrimp) but immediately attacked another shrimp species believed to harm the anemone – Snyder’s Blade Shrimp. Maybe this is what the anemones get out of the deal. 

Candy-Stripe Shrimp can be up to 4.5 cm but these were all around 1 cm or less. What else was extraordinary in this “encounter” is that these shrimp usually dart away as soon as an annoying photographer shows up. That did not happen. So for you, LOTS of photos of these colourful marvels and their possible symbiosis / coevolution.

Shrimp = Lebbeus grandimanus
Crimson Anemone = Cribrinopsis fernaldi to 30 cm tall. Candy-Stripe Shrimp have also found in association with a few other anemone species but most often with Crimson Anemones.

Tomorrow I will post about another “living gem” I documented on this dive. That is, another species that shatters the notion that these cold, dark waters do not explode with colour and biodiversity. 🙂

 

 

Tunicates – Your Distant Cousins?

Here’s one of your highly evolved and wonderfully unique marine neighbours.

It’s one of many species of tunicate in the NE Pacific Ocean. The tunicates, as simple-looking as they may appear to you, are our closest invertebrate relative*.

That’s how complex their anatomy is.

Five colonies of Mushroom Tunicate. I believe this is Distaplia occidentalis.

So here are some fascinating facts that may help influence how we perceive organisms that look very different from us.

Tunicates have a unique exoskeleton called a tunic.

Some tunicate species are solitary, living as distinct individuals. Please see further down in this blog for my photos of other species of local tunicates. These will reveal the great diversity in this phylum. 

Photo showing how a colonies of compound tunicate species share a stalk. Gee I wonder why some are called Mushroom Tunicates? Insert cheeky grin here.
I am uncertain of which species of compound tunicate this is. 

But this is a species of COMPOUND tunicate where individuals live together in the colony, within one tunic. The individuals in the colony are called zooids. The zooids have specialized functions that can serve the collective colony. In this species each individual has its own incurrent siphon and pharynx (think throat) to bring in water to filter feed. But individuals share digestive, reproductive and circulatory organs and excurrent siphons (to carry water out). Oh, by the way, tunicates are the only animals known to have a heart that can pump in two directions; they can reverse the direction of circulation.

They are hermaphrodites where reproduction occurs both by cross-fertilization and self-fertilization. The fertilized eggs are brooded inside the colony in a brood pouch and the timing of when parents hatch out the relatively large tadpole-like larvae has been found to be influenced by light (morning appears to be preferred). The larval stage of these animals is tadpole like, including having a primitive backbone (as is the case in all tunicate larvae). Reportedly development from fertilized egg to larval release is around 4 weeks (at 12 degree C) for the species.

Photo showing the diversity of colour in Mushroom Tunicates.

Some species of tunicate have been found to have bacteria associated with them providing chemicals that ward off predators and disease-causing microorganisms. You can imagine there is strong interest in how these chemicals might be of use to humans re. antibacterial properties.
And in case this all isn’t wild enough colonial species of tunicate are known to regenerate their complete body from a group of cells named “blood cells.” This too makes them of particular interest to we human distant relatives who evolved to NOT be able to regenerate body parts.

*Tunicates are classified as chordates because, the tadpole-like larvae stage has the following structures: notochord, dorsal nerve tube, and muscle tissue behind the digestive tract (postanal tail).

As a personal note to you who  are interested and caring enough to read this far: I have just lost myself for several hours striving to synthesize this information. I have deadlines to meet for other tasks and yet, and yet . . . this compulsion to understand, educate, and connect. Thank you very much for making it feel worthwhile.

After the following photos, there is excellent, detailed information on tunicates from Dr. Laura Cole.


Photos of other species of tunicate living in the NE Pacific Ocean.
Note that there are many more species that what I show here.

 

Solitary tunicate species: Pacific Sea Peach, Halocynthia aurantium, to 15 cm tall. Species like this have led to tunicates sometimes being referenced as “Sea Squirts” due to to larger, solitary species of tunicate having the “tendency to squirt seawater periodically from the main branchial siphon to back-flush sediments, other indigestible matter, and small animals from the filtering basket (about 10 times per hour in some species). Source: Snail’s Odyssey. 

 

Another Pacific Sea Peach.

 

Solitary tunicate species: Glassy Tunicate, Ascidia paratropa to 15 cm tall. 

 

Solitary tunicate species: Sea Vase – multiple individuals “reaching” out of a crack in a wooden piling. Ciona savignyi to 15 cm tall.

 

Solitary tunicate species: These Transparent Tunicate have a problem. This species gets invaded by a wicked parasite (as opposed to all those gentle and meek parasites out there) . . . the Spotted Flatworm! This species of flatworm curls up, sneaks in through the tunicate’s branchial siphon, unrolls, eats the tunicate’s internal organs over 3 to 7 days and then moves on, leaving behind the empty tunic. They are species specific parasites, apparently specializing in invading Transparent Tunicates. The dark coil you see here is the waste inside their rectums. Transparent Tunicate = Corella willmeriana to 7.5 cm tall.
Spotted Flatworm = Eurylepta leoparda to 2.5 m.

 

Social tunicate species: Light-Bulb Tunicate. Clavelina huntsmani to 5 cm tall.

 

Compound tunicate – a stalked compound tunicate. Not certain of species.

 

Compound tunicate species: Red Ascidian. Aplidium solidum to 20 cm across.

 

Compound tunicate species: Lobed Compound Tunicate. Cystodytes lobatus, irregular size and shape, can be more than 50 cm wide.

 

Compound tunicate species: Lobed Compound Tunicate. Cystodytes lobatus with a feeding Orange Sea Cucumber.

 

Compound tunicate species: Lobed Tunicate and Mushroom Tunicates (and a whole lot more) 🙂

 

 

Compound tunicate species: May be Pale Mushroom Compound Tunicate. Aplidiopsis pannosum to 5 cm wide. 

 

Pygmy Rock Crab in the shell of a dead Giant Acorn Barnacles, surrounded by multiple species of compound tunicate

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Further information on tunicates from Dr. Laura Cole, from her much-valued resource – a Smithsonian blog “Tunicates — Not So Spineless Invertebrates” from June 2018. 

About 3,000 tunicate species are found in salt water habitats throughout the world. Although tunicates are invertebrates (animals without backbones) found in the subphylum Tunicata (sometimes called Urochordata), they are part of the Phylum Chordata, which also includes animals with backbones, like us. That makes us distant cousins.

The most common tunicates are sometimes called sea squirts because when touched or alarmed by a sudden movement, their muscles contract and the water in the animal shoots out. They are sessile after their larval stage, meaning that they remain attached to a hard substrate, such as dead coral, boat docks, rocks or mollusk shells, all of their adult lives. The name “tunicate” comes from their outer covering, called the tunic, that protects the animal from predators, like sea stars, snails and fish. Unlike the sessile sea squirts, other kinds of tunicates float in the water their entire lives. The salps and pyrosomes are mostly transparent tunicates that look a bit like jellyfish floating freely—some pyrosomes have be known to reach 60 feet (18 m) in length. Much smaller but still visible to the naked eye are the larvaceans—tiny tadpole like creatures that live inside a small house that they build and regularly replace.

[Note there are two related The Marine Detective blogs: (1) “Pyrosomes! Say What?” at this link and (2) “Otherworldly Drifter. Mind Blown” at this link.]

What unites these diverse groups and makes them our relatives? All animals in the Phylum Chordata have a notochord, a flexible backbone like structure, at some point in their lives.

Sea squirts have a notochord only in the larval stage which they use to swim and find an ideal place to attach—one that is bathed in particle-rich waters, since like all tunicates they are filter feeders and rely on water currents for food and nutrients. Once a good location is found, the larva attaches with a suction-like structure and metamorphosis begins. The notochord shrinks and gets absorbed into the body as the animal changes into an adult, and the tunic forms as the transformation occurs. The animal will then spend its days feeding on tiny particles from the water, primarily bacteria. 

There are two types of sea squirts: solitary and colonial. The solitary animals live separately all of their lives inside of their tunics. Each has two siphons—the oral siphon that receives the nutrient rich current and the atrial siphon that excretes the waste. Colonial species share a common tunic and sometimes also share the atrial siphon. Colonies of sea squirts are formed as a result of budding—when the larva settles and changes into the adult form, it then splits (or buds) to produce new individuals, called zooids. Colonies can be a few centimeters to several yards wide depending on food availability and predation.  

Sea squirts don’t look much like us as adults on the outside, but they have a digestive system similar to ours—with an esophagus, stomach, intestines and a rectum. But there are plenty of other differences. Unique to the benthic tunicates is a heart that reverses its beat periodically. It’s still a mystery to researchers why the tunicate heart will circulate blood through the heart in one direction and then switch to the opposite direction, or if the ability gives them some sort of advantage. 

On land, we don’t encounter sea squirts that often, although they are increasingly eaten by some Mediterranean, Asian and South American countries. Not only is the soft body inside of the tunic eaten, but the tunic itself can be pickled and enjoyed later. Compounds from several tunicate species could be useful in medical treatments for diseases ranging from cancer to asthma. Tunicates act as ocean purifiers, since they consume bacteria, and they can send a message that heavy metals are present in ecosystems where they are found, since they absorb metals like zinc and vanadium. Because they like to attach to hard surfaces, sea squirts are often found on the underside of boats, or inside motors, where they can wreak havoc on equipment, and some have become invasive species after being transported from their native ranges. Their relatives the pyrosomes, also called sea pickles, sometimes wash up in large numbers on the shore and are known for their bioluminescence

Like with many a large family, most of us don’t know about these distant relatives found in the ocean, but that doesn’t mean they aren’t worth keeping an eye on.”


Further sources include:


Invasive Tunicates

This is an example of an invasive tunicate found off the coast of British Columbia (and many other places). It’s the Lined Compound Ascidian, Botrylloides violaceus.


Super Mom! Up to 300 young under her care.

This is a Brooding Anemone (Epiactis lisbethae to 8 cm across).

She may not have a backbone but she’s a Super Mom!

As many as 300 young can be clustered around her in up to 5 rows, benefitting from the protective canopy of her tentacles which contain stinging cells (nematocysts). The offspring remain here until big enough to stand a good chance of surviving on their own. They then crawl toward independence, claiming their own piece of the ocean bottom.

Brooding anemone 1

Note: This blog was initially published in 2013. Reposting for Mothers Day 2020.


I am awestruck by this species’ beauty and reproductive strategy. It is also a reminder of how little we know about marine species that the Brooding Anemone was not recognized as a distinct species until fairly recently (1986), and it still so often gets confused with the Proliferating Anemone (Epiactis prolifera).

I share my marine “detectiving” about this species with you to provide a further example of how extraordinary our marine neighbours are and maybe, thereby, help inspire greater conservation efforts.

But yes, the timing of the blog is no accident. It may be that reflection upon an anemone Super Mom stimulates thought about our human mothers – just in time for Mother’s Day.

So here goes . . . bear with me as I build to clarifying the reproduction of our featured species.

© 2013 Jackie Hildering one time use only-4240156


Anemones have many reproductive strategies.

For many species, reproduction can be asexual as well as sexual with strategies like budding off offspring; splitting into two; or pedal laceration where a torn piece of the bottom of the anemone can grow into another anemone!

Some species are hermaphrodites with highly diverse ways by which offspring develop into adults.

In species that have separate sexes, many are broadcast spawners where Mom and Dad release their eggs and sperm into the ocean around them. Fertilization and development thereby happens in the water column.

Then, for only some 20 species of the world’s more than 800 kinds of anemone, there are those in which the female captures the males’ sex cells as they drift by and draws them into her digestive cavity to fertilize her eggs. She “broods’ her young.

Some such anemone species are internal brooders.  The young develop inside Mom until they hatch and are expelled into the water column as planktonic larvae.

But then there’s Super Mom – the Brooding Anemone (Epiactis lisbethae). She’s an external brooder.

After she has fertilized the eggs inside her digestive cavity with the sperm she has captured, the young develop inside her until they hatch into planktonic larvae. THEN, they swim out of her mouth, settle on her body under the tentacles and grow into little anemones that feed themselves.

When the offspring are big enough to stand a good chance of survival without the protection of Mom’s tentacles, they shuffle away to independence, leaving space for next season’s young.

The brooding anemone’s young are all of the same generation and are therefore all about the same size.

However, there is a second externally brooding anemone species in the eastern North Pacific where you most often see young of different sizes huddled under Mom’s tentacles. This species – the Proliferating Anemone (Epiactis prolifera) is the one that very, very frequently gets confused with the Brooding Anemone.

Proliferating anemone.

Proliferating Anemone with young (Epiactis prolifera). Often confused with the Brooding Anemone (Epiactis lisbethae). 


I have strived to clarify the many differences between these two externally brooding anemone species in the table below but to summarize: the Proliferating Anemone is smaller and does not have striping all the way down the column; adults are hermaphrodites; breeding happens year round; there are far fewer young clustered under mom’s tentacles; and they start off there as fertilized eggs, not as free-swimming larva.

The main similarity between these two species is and yes, I am going to use a tongue twister here since I believe it is inevitable when discussing anemones: with anemone mothers like these, baby anemones are protected from their anemone enemies!

Now off you go, share some ocean love with a Super Mom!

There are so many human females out there worthy of awe.
Where, were we to consider how many young they have shielded and helped to independence, the number might well be 300 or more. 

brooding vs. proliferating table

Click to enlarge. Table summarizing the differences between Brooding and Proliferating Anemones.

 

Brooding anemone with young (Epiactis lisbethae) - all the same age. ©2016 Jackie Hildering.

Brooding Anemone with young (Epiactis lisbethae) – all the same age. ©2016 Jackie Hildering.

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Sources:

Hermit Crabs with Sponge Homes

Please see photo below.

You are looking at two animals, not one. 

Alaskan Hermit Crab = Pagurus ochotensis to 5.3 cm long. The yellow eyes and “sheen” on the legs help in IDing this species. See how uniquely reflective the legs are? This species often lives in a shell made by a Northern Moon Snail (until a suberites sponge dissolves it away 😉 ).

 

This is an Alaskan Hermit Crab (who resides in front of Port McNeill, not Alaska).

Living on his/her back is a “Hermit Crab Sponge”.

This sponge species (Suberites latus) settles on the shell home of some hermit crab species and can completely dissolve the shell away.

Having a sponge home has its advantages. It is light. Also, the sponge will grow whereby the hermit crab need not find a new home as would be the case if it outgrew a shell home.

But, it can be awkward to tote around when it gets really big. See an example below.

Bering Hermit with a huge suberite home relative to its size. (Pagurus beringanus to 2.6 cm).

 

 

Yes, the hermit crab could leave the sponge and get another home if one were available. But, there is risk when outside your home, be it ever so brief.

Another disadvantage is when you have unwelcome house guests.

See below to get a sense of the inconvenience when a sponge predator crawls on your back.

 

Close-up on the inconvenienced Mud Hermit Crab.

From top to bottom: the big yellow animal is a Monterey Dorid (nudibranch species – gills are on left). This nudibranch is feeding on the Hermit Crab Sponge (tan colour) and then, see the tiny face? That’s a Mud Hermit Crab who isn’t going anywhere for a little while (Pagurus capillatus to 4 cm).!

Here’s another Mud Hermit Crab. See the bite out of the sponge? I initially found this individual upside down. The resulting photo of the underside of the sponge gives you a sense of how the sponge is shaped to the hermit crab’s body.

 

Note too how all the hermit crabs included in this blog have one claw bigger than the other?  This is the case for many hermit crab species and it allows them, when they retreat into their home, to seal off the opening to the shell or sponge with the bigger claw. They close the door to their home.

In the photo below, see how the larger claw seals off the hole for the hermit crab on the right? I suspect this interaction captured in this photo more about mate selection that it is about home envy.

 

 

I hope this “who is sponging off who” interaction provides some wonder for you at a time when safety in homes is such a reality for our species too (re COVID-19). 

Be safe whatever, and wherever, your chosen home.  💙 


The Hermit Crab Sponge is Suberites latus to 20 cm long, 6 cm wide and 4 cm high.
Source for these dimensions is “Beneath Pacific Tides” by Greg Jensen.


 

Bluespine Hermit with sponge home  (Pagurus kennerlyi to 3.5 cm long)

 

Juvenile Alaska Hermit who will benefit from the sponge growing bigger.

 

Bering Hermit Crab interaction. This too is more likely about dragging around a potential mate.

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.