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 . . . . .
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”.
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.
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!