I finally observed some of the most cryptic nudibranchs on our coast!
The Cryptic Nudibranchs you see here are only about 1 cm long and look at how astoundingly evolved they are! They are virtually invisible on the Kelp-encrusting Bryozoan which is growing on Bull Kelp at this time of year. This species of nudibranch is also known as Steinberg’s corambe (Corambe stinbergae to 1.7 cm).
You can see in the photos here that we found some of the nudibranchs mating and there were many of their egg ribbons (each of those coils has a lot of eggs that result from both parents becoming inseminated and laying eggs).
You can also see where they have been feeding on the bryozoans (colonies of animals).
I have looked for them for years knowing their range is from Alaska to Baja California, Mexico.
What made the difference in now being able to find them:
(1) Getting the clue from Robin Agarwal to look at the kelp fronds that were REALLY tattered with the Kelp-encrusting Bryozoan colonies .
(2) Having a skilled dive buddy willing to join me in burying our heads in old, tattered kelp in the surge for 30 minutes instead of looking at all the big, colourful life at this dive site. Thank you Janice Crook!
(3) Once we knew what the egg ribbons looked like (those s-shaped little masses), we had a really good clue and knew better where to look even more closely for the nudibranchs.
Now on to finding the SECOND really cryptic nudibranch species that feeds on Kelp Encrusting Bryozoans – Corambe pacifica to 1.5 cm long and whose egg masses are tiny, flat coils.
For more photos and my previous blog on what Kelp-encrusting Bryozoans look like, please see my other blog “Kelp Lace? Bryozoans”.
And so it begins. It’s the time of year when the annual kelps like Bull Kelp begin to break down. It’s then that Kelp-encrusting Bryozoans really get a chance to colonize the kelp as you see in these photos.
Every little box is an individual animal. It’s a “zooid”. The oldest member is in the middle and the others all originated from that one by asexual reproduction.
The zooids filter feed on plankton with the tentacles you see in this wonderful video by friend Karen Johnson. These crowns of tentacles are known as lophophores.
“Kelp-encrusting Bryozoan” (Membranipora membranacea) is also known as “Kelp Lace Bryozoan”. It’s no mystery how either common name was inspired. Each circular colony is approximately 20 cm wide.
If you are lucky enough to live near the Ocean, look at the kelp that washes ashore for these colonies. The colonies in these photographs where on Split Kelp (Laminaria setchellii) and Bull Kelp (Nerocystis luetkeana).
What on earth is a “bryozoan”?
From Beachkeepers: “Bryozoans are colonial animals that arrange themselves in circular (radial) fashion, often with the oldest (and first to settle) individual in the middle. . . . The ‘box’ of the zooid is made of either a tough protein (like what you would find in crab shells) called chitin, or what you would find in coral reefs, calcium carbonate. This body box has an opening where the bryozoans extend their feeding apparatus (that looks a lot like a sea anemone) called a lophophore. Yes, they have predators! [Some species of] nudibranch will eat them, though they can reproduce asexually to form the colony back to size after a nudibranch has been grazing on them. Sometimes, when they grow back, they’ll even grow chitonous spines on their body walls to discourage the nudibranchs from coming back. These spines usually form on the individuals on the outside edge of the colony.”
Detail about this bryozoan species – Kelp-encrusting Bryozoan. From Invertebrates of the Salish Sea: “Bryozoans start from a single individual zooid (an ancestrula) which repeatedly reproduces asexually to form a colony. In this species, the oldest individual is in the middle. Colonies of this species usually begin to be noticeable in late spring and grow through summer into fall. By fall they may form extensive crusts on the kelp and many colonies have merged with one another. In many bryozoans there are various types of zooids but in this species there is only one type of zooid which serves for feeding, for reproduction, and for defense. The colony appears to be a simultaneous hermaphrodite, or male zooids may develop first. They do not brood their young. Eggs are fertilized then released, and quickly develop into cyphonautes larvae which may feed and develop as plankton for several months. The larvae settle when they encounter kelp such as Laminaria or water with an excess of potassium ions. The small white nudibranch Doridella steinbergae [reclassified to Corambe steinbergae] may be found living and feeding on these colonies but it blends in so well it is difficult to see . . .” Note there is a second similar looking cryptic nudibranch that can found on these bryozoans and that is Corambe pacifica. Corambe pacificahas a notch at the back. Corambe steinbergae does not. I have never managed to find these cryptic nudibranchs. Grateful to Karolle Wall and Robin Agarwal for their photos below.
What happens to the kelp?
It is the natural cycle of kelp species like Bull Kelp, that at this time of the year, the large version (the sporophyte) begins to break down. Spore packets drop to the bottom of the Ocean which create a different version of the kelp. It’s Alternation of Generations and here is my blog about that wonder. Other kelp species like Giant Kelp are not annuals. They remain year round.
Note: Some report that this species of bryozoan is an invasive in the Atlantic. However, “recent genetic studies indicate that this species is a complex of a number of long-separated clades. The only verified invasion is its introduction from the Northeast Atlantic to the Northwest Atlantic” (Source: Nemesis).
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!
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.
Big questions often come from little people and there are so many times that I have been asked by children why I reference the limbs of an octopus as “arms” and not “tentacles”.
Here’s why: Arms have suckers down the full length of the appendage. Tentacles only have suckers near the tip. Thereby, all eight octopus appendages are arms while squid have two tentacles and eight arms. Further, the purpose of tentacles is generally limited to feeding where arms have more functions. Octopuses use their limbs for feeding, locomotion, reproduction (if male*), defence, etc!
Oh and why are they called “arms” vs. “legs”? Because octopuses’ appendages have more purposes than just locomotion.
There are scientists who have put forward that some octopus species use two of the limbs mostly for locomotion whereby they would have two “legs” and six “arms” but let’s avoid that debate!
While we are on the topic of semantics and cephalopods, and anticipating that there will be those who question my use of the plural form of “octopus”, please note the origin of the word octopus is Greek, not Latin. Thereby “octopuses” or “octopods” is truly more correct than “octopi”. From a strict linguistic perspective, the most correct is “octopods” but I choose not to use that. I think if I were to say “octopods” it would distract what I am trying to communicate that is more important that grammar. I might also come across as pretentious and have fewer human friends 🐙.
There, don’t you feel much better armed to speak for our awe-inspiring eight-legged neighbours? Or, are you up in arms?
I have relayed my observations to marine worm researchers but want to share with you too. It’s just too fascinating not to do so. These finds emphasize yet again how little we know even about marine species that are just below the surface. I also hope that by sharing my observations here, it may lead to other divers being on the lookout for these interactions and potentially adding to the knowledge about interactions between necklace-worms and anemones.
My observations involve what I believe are two species of necklace-worm. Each is interacting with a different species of anemone. In both cases, the species of necklace-worm is unconfirmed. The polychaete* researchers I have been in contact with have asked for samples of the worms to allow for microscopic examination and potential DNA analysis.
*Polychaetes are the “many-bristled” worms. They are worms that have a pair of paddle-like appendages / bristles on each segment. Most species of worm in this class are found in the ocean or in brackish water and there are about 15,000 known species globally. Polychaetes “are ubiquitous in the ocean, burrowing and hunting in the sand, crawling on algal covered rocks, living in self-made tubes, or swimming in the water” (Encyclopedia of Biodiversity, 2013).
Note that observations and photos here are from the Pearse Islands and Plumper Islands on northeast Vancouver Island in the territory of the Kwakwaka’wakw in depths less than 17 metres / 50 feet.
Necklace-Worm Species #1 and Proliferating Anemones: I have written about this previously but include the observations here again so that the information about these necklace-worm / anemone interactions is bundled in one place. It involves a species of necklace worm appearing to bite into Proliferating Anemones (Epiactis prolifera to 8 cm wide).
My first observation of this interaction goes back all the way to 2008 when I documented the following thanks to the keen eye of my dive buddy Natasha Dickinson.
I do not know if the necklace-worm dislodged the anemone of if the anemone let go in an attempt to get away. We came upon this scene when the anemone was already upside down.
I have only noted this interaction twice since then. See photos below.
For those who have Lamb and Hanby’s Marine Life of the Pacific Northwest, you may note that this species of necklace-worm looks like AN22 which is referenced as a “mystery necklace-worm”. But again, collection of a sample would be needed to confirm species ID.
Necklace-Worm Species #2 and Short Plumose Anemones:
On February 12, 2022 I saw THIS.
There are necklace-worms in those slime tubes! Where you see the circles is where other Short Plumose Anemones once were (Metridium senile to 10 cm tall and 4 cm across).
Were they always at this site? I have done a quick review of past photos and see a few of them in photos back to 2013. Variables in why I may not have noticed them before are that: (1) they were much more apparent as a result of the dislodged anemones; (2) there may be more of them now; and (3) we usually don’t focus on the spot where the concentration of these worms were (we usually dive deeper).
So TODAY’S mission was to return to this dive site and focus on the interaction between this species of necklace-worm and Short Plumose Anemones. How abundant are they? Are they biting the anemones?Are the worms anywhere other than around Short Plumose Anemones? Are the anemones using their acontia as a defense against the worms? Acontia are defensive strands filled with stinging cells (nematocysts) that are ejected when an anemone is irritated / threatened / stressed. The acontia can extend far beyond the anemone, providing longer distance defense than the stinging cells in an anemones tentacles.
To answer those questions: – I found the slime tubes almost everywhere there were Short Plumose Anemones at this site. I did not find them anywhere else i.e. this species of necklace-worm’s slime tubes were only around Short Plumose Anemones. – I only found a few Short Plumose Anemones using their acontia but it seems more likely that they were being used against other anemones. I cannot know if the anemones dislodge themselves as a defense. There were only a few places where there were the circles of slime tubes where an anemone had once been. There were far more places where the slime tubes were in amongst Short Plumose Anemones. – YES I do believe this species of necklace-worm is biting into the Short Plumose Anemones. See below for abundant photos from today.
I will of course provide updates as I learn more via the researchers and other divers / underwater photographers. As always, I hope it is a source of wonder for you to learn more about these species, their adaptations and interactions, AND how much we humans still have to learn about the natural world around us. 🙂
All photos below are from March 6, 2022.
Below, you can contrast the same spot after 22 days. There has been a lot of change but again, I do not know how much the anemones would move around and/or dislodge in the absence of the worms. Oh no, is this now going to be my life? In addition to trying to document individual Humpback Wales and Tiger Rockfish, now I am going to try to document individual Short Plumose Anemones?! Probably.
See the juvenile here to the right of my buddy Natasha? There, right beside the mating Yellow-Rimmed Nudibranchs. This Sunflower Star was in just 5 metres of water.
Today’s two Sunflower Stars are the first I have seen in twelve hours underwater over the last three months and believe me, I have been looking. I only saw one before that. They are such a rarity now. Will these two survive? I have seen waves of juveniles before and then they disappear. Their plight appears to be linked to climate change.
Hope? With action . . . yes, there is shining hope.
Without action . . . no.
Please hang in there. Please read on.
I have been struggling too, looking for escape / reprieve from global realities as another “atmospheric river” is forecast to fall on parts of our province. It is so tempting to want to hide especially if we see the problems we are facing as disparate. They are not.
I have had to remind myself of the common solutions so that I see a way forward that is not guided by the faintness of blind hope; paralyzed by fear and overwhelm; and / or obfuscated by the din of values and voices that serve the few for a brief time.
Common solutions include: to know, live and share the GAINS that come from using LESS (fossil fuels, dangerous chemicals, disposables, less consumerism generally); to speak for truth and science and to have compassion for those who cannot; to exercise our power as voters and consumers to serve future generations; and to care and act on the knowledge of connection to others – across time, cultures, distance, and species.
In short, it’s a really good time to be a good human.
I had to dig for these words for myself. As always, may they serve you too.
For those who are not yet aware, I include the reality of Sea Star Wasting Disease (SSWD) below. A link to a summary of the research and where to report sightings is in my blog at this link.
Since 2013, more than 20 species of sea star have been impacted by SSWD from Mexico to Alaska. There is local variation in intensity of the disease and which species are impacted. It is one of the largest wildlife die-off events in recorded history. Sea stars contort, have lesions, shed arms, and become piles of decay.
Currently, some species of sea star appear to have recovered while others remain very heavily impacted. Sunflower Stars (Pycnopodia helianthoides) have been devastated and were added to the International Union for Conservation of Nature (IUCN) list as Critically Endangered. There are current efforts to have Sunflower Stars assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) with hopes that they receive protection under Canada’s Species at Risk Act.
There is NOT scientific consensus about the cause. Current hypotheses focus on (i) a virus and (ii) low oxygen at the surface of the sea star’s skin maintained due to bacteria. What is consistent in is that changing environmental conditions appear to allow the pathogen (be it bacteria or viruses) to have a greater impact.
The best current source for a summary of the research is Hamilton et al (August, 2021). From that source: ” . . . outbreak severity may stem from an interaction between disease severity and warmer waters” and “Though we lack a mechanistic understanding of whether temperature or climate change triggered the SSWD outbreak, this study adds to existing evidence that the speed and severity of SSWD are greater in warmer waters”.
What I believe to be the reality off the coast of British Columbia is that there are refuges of Sunflower Stars at depth where it is colder. They spawn with some young then settling in the shallows where they may succumb to the pathogen if stressed by warmer water.
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 protectmoonsnail 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.
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.
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.
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).
Aleutian Moonsnail – Cryptonatica aleutica to 6 cm across.
Arctic Moonsnail – Cryptonatica affinis to 2.5 cm across.
Pale Arctic Moonsnail – Euspira pallida to 4 cm acrross.
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”.
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.
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.
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.
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.
Here’s a post about anemone enemies (say that 5 times).
See those really long tentacles extending from the Short Plumose Anemones in the following image? These are “catch tentacles” that can extend to be up to four times longer than the feeding tentacles.
Short Plumose Anemones reach around with these specialized, extendable tentacles and THEY ATTACK if they come in contact with a different species of anemone, or others of the same species who do not have the same DNA (are not their clones).
The tip of the specialized tentacle breaks off and kills the cells in the spot where they touch their anemone enemy. Apparently this can even kill the target anemone. Short Plumose Anemones on the outside of a group of related clones are more likely to use / develop these specialized tentacles.
Short Plumose Anemones AND Giant Plumose Anemones also have nematocysts (stinging cells in their feeding tentacles) AND they have acontia. See following image. These are defensive strands filled with stinging cells that are EJECTED from their mouths or through the anemones’ bodies when threatened or stressed. These threads extend far beyond the anemone and provide longer distance defence than the stinging cells.
None of the stinging cells of local anemone species impact we humans. But how I wish I had some acontia! Yes, I have defence envy. 🙂
From Invertebrates of the Salish Sea: ” Animals on the border of a clone often develop up to 19 “catch tentacles”, which generally occur close to the mouth. These tentacles, which are larger and more opaque than the other tentacles, have special nematocysts and are unusually extensible (they can become up to 12 cm long or more). They probe the area around the anemone. While they do not respond to food, they DO fire when they contact either A. elegantissima [Aggregating Anemone] or another clone of M. senile. When it fires, the tip of the tentacle breaks off and sticks to the victim, which may retract and bend away. Tissue damage can generally later be seen in the stung area, and the attacked individual may even die.”
These are Great White Dorids. Yes, they are a species of nudibranch and the individuals featured here are mating, prowling for sponges AND succeeding in laying their astounding egg masses.
EACH dot you see in the egg masses (photos below) contains 8 to 12 fertilized eggs. They are laid by both parents because it makes a lot of sense to be a hermaphrodite when you are a sea slug and your eggs hatch into the sea. More fertilized eggs = more chances of some young surviving.
Even after so many years, I find the intricacy and diversity of sea slug egg masses something of jaw-dropping wonder. Not such a good thing when you are supposed to hold a regulator in your mouth while diving. 🙂
Scientific name of this species is Doris odhneri. They can be up to 20 cm long and their egg masses can be at least that size too.
Body design is classic for the sub-classification of nudibranchs that is “the dorids”. Those tufts on their hind ends are the gills and the projections on their heads (which all nudibranchs have) are the sensory rhinophores (rhino = nose). It’s how they smell their way around to find mates, food and whatever else is important in their world.
Notice in the next photo how dorid species are able to retract their gills when disturbed by the likes of an annoying underwater photographer.
Amazing too to think of the importance of smell in the sea isn’t it? Why is the individual in the following photo reared up like that? I believe it allows a better position to smell / detect the chemicals of food and/or a mate. Maybe they are even releasing pheromones? Note that is me musing. There is no research I know of to support this.
In featuring this species, the Great White Dorid, you see that not all nudibranch species are super colourful. But they are all super GREAT.
Species is also referenced as the GIANT White Dorid or Snow White Dorid, or White Dorid or White-Knight Nudibranch . . . etc. Known range is from southern Alaska to California but it’s a species I don’t see often where I dive around northeastern Vancouver Island.
A female Giant Pacific Octopus hunting . . . photos brought to the surface for you on April 4, 2021.
This individual lives north of Port Hardy, in Browning Pass.
She’s a giant among other giants.
The Giant Plumose Anemones stand tall above her, at up to 1 metre in height.
Her arms feel between the rocks to flush out prey, her mind processing all she detects from her eight limbs, her vision, and the further stimuli upon her skin.
A China Rockfish is hovering nearby, likely often accompanying her when she is hunting to benefit from what prey emerges when touched by her arms.
Her colours change, flashing white at times. Then, again camouflaged among the boulders covered with the pink of coralline algae species, and studded with Orange Cup Corals and the plumes of feeding tentacles of Orange Sea Cucumbers.
Two humans are in awe at chancing upon her and being able to hover, navigating the space between not wanting to disturb and also wanting to amplify the wonder above the surface, hoping it somehow contributes to being better humans.
We’re aware too that we are limited by how much air remains in our tanks; the nitrogen building in our blood; and the cold creeping in through our dry suits (despite the adrenaline surge of watching her).
But she, she is limitless here.
She is perfection.
I know this was a female because the third arm on the right does not have a “hectocotylus”. Male octopuses have a specialized arm with no suckers at the tip called the “hectocotylus arm” by which they hand off spermatophores to the female. In Giant Pacific Octopuses, the hectocotylus arm is the third on the right. See more in my recent blog “Giant Pacific Octopuses, How Do They Mate?” at this link.
You can see that the pupil’s shape is very different from ours. Their retina is very different too.
Octopuses and other cephalopods have only one kind of photoreceptor cell while we have rod cells and three types of cone cells allowing us to see in colour. So how can cephalopods discern colour when they have only one kind of light receptor in their eyes? And they must be able to discern differences in colour. Consider how they signal with colour and how they camouflage.
Research from 2016 puts forward that their uniquely shaped pupils act like prisms, scattering light into different wavelengths (chromatic aberration), rather than focussing the light into a beam onto the retina. The hypothesis, tested with computer modelling, is that cephalopods can then focus the different wavelengths onto their retina separately by changing the distance between the lens and the retina, thereby separating the stimuli and discerning colour. Note that the sharpness of their vision is believed to be different for different wavelengths / colours.
Even with their eyes closed, octopuses can detect light with their skin. This is tied to their ability to camouflage with the photoreceptors in their skin responding to specific wavelengths of light (different wavelengths = different colours).
Note too that octopuses do not have eyelids. They have have a ring-shaped muscular fold of skin around the eye that closes in the way of an eyelid (especially when some annoying human is taking photos).
More Octopuses Hunting
Here’s the link to another experience where we saw a Giant Pacific Octopus hunting AND interacting with a Wolf-Eel (includes video).