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

Posts tagged ‘spawning’

Reaching New Heights? A Sea Cucumber Mystery.

This is an open case; one that has me bemused and amused.

While diving near the Great Bear Rainforest in Jackson Narrows, my buddy Tavish Campbell came upon a Giant Sea Cucumber in this very unusual position (Apostichopus californicus, aka California Sea Cucumber).

It was stretched straight up and down, head end up.

Giant Red Sea Cucumber reaching for new heights? Dive buddy - Tavish Campbell. ©Jackie Hildering

Giant Sea Cucumber reaching for new heights? Dive buddy – Tavish Campbell. ©Jackie Hildering

As you likely know, this species is most often horizontal; “face” down cruising up to around 4 meters a day along the ocean bottom, mopping up nutritious particles with mucus-covered bushy white tentacles. When there is good stuff stuck on the tentacles, these retract into the mouth (with sandy casts coming out the other end).

A Giant Red Sea Cucumber in its usual position, horizontal so that it can feed by mopping up particles. This one has a nudibranch crossing over it (Flabellina trephine). ©Jackie Hildering

A Giant Sea Cucumber in its usual position, horizontal so that it can feed by mopping up particles. This one has a nudibranch crossing over it (Flabellina trophina). ©Jackie Hildering

So why would this individual assume such a remarkably vertical position? Could it be feeding related? It was extending and retracting its mouth tentacles repeatedly but clearly this was not effective in gathering any snacks.

Giant Red Sea Cucumber with buddy Tavish Campbell. ©Jackie Hildering

Giant Sea Cucumber with buddy Tavish Campbell. Mouth tentacles extended. Note all the tube feed revealing its relatedness to sea stars and sea urchins (phylum Echinodermata). ©Jackie Hildering

My best hypothesis is that this was mating related. Giant Sea Cucumbers have separate sexes and rise up in a python-like position to release their sex cells (see figure below from A Snail’s Odyssey). This pose reduces the number of sex cells that settle to the ocean bottom, unfertilized.

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Giant Sea Cucumbers spawning in phython-like pose. Source: A Snail’s Odyssey.

Additional strategies to enhance the chances of fertilization are to twist back and forth and/or intertwine with a partner while releasing gametes. (This species will also catapult back and forth when trying to escape predation by Sunflower Stars).

Striving to ensure your DNA gets passed on does not happen randomly however. As with all broadcast spawners, there is a cue so that the release of sex cells is coordinated. (See my other blog “Sea of Love – Broadcast Spawning“). Giant Sea Cucumbers are known to mate in the shallows from April to August repeatedly “dribble spawning”.

Our high-reaching Giant Sea Cucumber friend was indeed in the shallows and it was significantly warmer there. Was the temperature a cue that it was time to mate? Was s/he trying to sense the presence of a partner or others of his/her kind already broadcasting?

Was s/he reaching to new heights to allow even better distribution of sex cells than the python pose?

Was this individual even old enough to mate as they do not sexually mature till age 4? It’s size certainly suggested it was older since maximum size for the species is reported to be 50 cm.

Had we had more air we could have waited and likely concluded what was up with this behaviour.

As is so often the case however I surfaced with even more questions and a greater sense of wonder about the life below. And yes, this time it may be that I was laughing so hard I was sputtering sea water as well.

Unsolved mystery! ©Jackie Hildering


More on the species’ spawning: “The gametes stream from a single gonopore within the ring of tentacles (but see Fig. 2), and fertilisation takes place in the open water. The eggs are relatively large and yolky in sea cucumbers, and develop to a feeding larval stage known as an auricularia. After a 3-5wk period floating in the plankton, the larvae metamorphose and settle to the sea bottom.” Source: A Snail’s Odyssey.


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Two Giant Sea Cucumbers in spawning position, April 2021 ©Jackie Hildering. The orange animals are Orange Sea Cucumbers and they were spawning too and what a spectacular spectacle that is. See my blog at this link. 


Sources / more information:

Gumboot Chitons Spawning!

I’m excited to share video with you of Gumboot Chitons spawning. These marine neighbours most often seem quite inanimate – having a life where they keep their undersides protected by sucking down hard on rocks but, when it’s time to mate . . . . . 

Female gumboot chiton

Female! ©2016 Jackie Hildering

First just a little background: “Chitons” are marine molluscs (soft bodied animals) that, rather than having one of more shells to protect themselves, they have 8 armoured plates surrounded by a thick band of muscle. This allows them to suction onto surfaces very effectively since the 8-plates give such flexibility that they can even get a good grip on surfaces that are not flat.

There are many members of the the chiton class but the Gumboot Chiton (Cryptochiton steller; aka Giant Pacific Chiton) is very unique in its appearance.

It’s another “the biggest of its kind in the world” that inhabits the cold, rich waters of the northeast Pacific. It can be 33 cm long and about 2 kg. They are very slow growing and very long lived! This source reports that chitons that are 15 cm long are likely 20 years old and that they may live to be more than 25.  That’s one old gumboot!

The Gumboot Chiton is also the only chiton species that has flesh completely covering the 8 plates. The texture and colour of this “girdle” offers them great camouflage and is where the “gumboot” descriptor comes from. The genus name “Cryptochiton” relates to this camouflage and that the 8 plates are hidden under the girdle. These plates are very uniquely shaped, and well-described with the name “butterfly shells”.

Smaller dead Gumboot Chiton. Image shows the thick band of muscle with which Gumboot Chitons secure themselves. Fish species is Longfin Sculpin. ©Jackie Hildering.

Small dead Gumboot Chiton. Image shows the thick band of muscle with which Gumboot Chitons secure themselves. Fish in this images is a Longfin Sculpin. ©Jackie Hildering.

Apparently some First Nations did sometimes chew on this species but I am SURE that this is not the cultural origin of some people referring to this species as “wandering meatloaf”!

I don’t know where I picked this up, but I believe that one of the First Nations’ names for gumboot chitons translates (very) loosely, into “stuck on rock with face forever”. This would be an incredibly good descriptor since most chitons stay “face” down, grazing on algae by scraping with the sharp teeth-like structures in their radula. Thereby, they don’t expose their soft bodies and reduce the chance of predation. 

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Gumboot Chitons feeding on dead Bull Kelp. ©2016 Jackie Hildering.

I once found a Gumboot Chiton that had been dislodged by a predator at low tide. It is then that I learned that they have the ability to curl up on themselves like a pill bug!

But outside of a rare experience like this, you don’t often get a chance to see how very alive and animal-like they are.

Unless . . . they are spawning as they were on May 20th, 2012. 

 

Up came the bodies of the Gumboot Chitons, into a very unique funnel-like shape. The “gonadal pores” are near the bottom end of the animals, but by positioning themselves in this shape, they channel the sex cells upward.

I could clearly see which Gumboot Chitons were male and which were female!

It was just remarkable to see this, feeling truly as if some secret world was being revealed, and the coordinated timing of the spawning was astonishing.

Of course when you are a broadcast spawner, you need to release copious amounts of sex cells and need to do so at the same time or there will be even less chance that egg meets sperm. You can imagine how many eggs need to be fertilized too if any of your zooplankton offspring are going to survive since so many animals feed on plankton.

To my knowledge, science has not concluded exactly what the cues are for “Hey fellow Gumbooot Chitons, it’s annual spawn time NOW!”  It has to be temperature, light and/or amount of food that determines that the time is right.

Hum . . . seems to me that those cues may be significant between individuals of our species too!

Additional images:

Chiton plates on the right are those of the Gumboot Chiton.

Chiton plates on the right are those of the Gumboot Chiton.

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Sometimes individuals have this mottled colour pattern. ©Jackie Hildering.

Gumboot Chiton predated on by Sunflower Star

Gumboot Chiton being ingested by a Sunflower Star. Unknown if this was the result of predation or if it is scavenging i.e. that the Gumboot Chiton was already dead. ©Jackie Hildering.

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NOTE: I would normally NEVER disrupt a chiton as this would potentially damage the animal. The Gumboot Chiton in this image had been dislodged by a predator and was lying upside down. Used it as an opportunity to discuss ethics with the Sunset School students. We decided to right it and put it on a rock so that s/he could be protected again by sucking down ©Jackie Hildering.