? Octopus Primary Heart Does not Beat while Swimming?

[DWhatley]

I read an "8 fun facts about octopi" article that included the statement, "While octopi swim, this third heart doesn’t beat ...". The information on the two gill hearts was incorrectly stated but I wondered where this idea came from and found it in the Ten Curious Facts About Octopuses from the Smithsonian Science section. The author of the Care2 article clearly did not know anything about cephalopods and the Smithsonian article has some sketchy statements but does anyone know if the heart stopping while swimming has ANY validation? I had never heard it before and suspect it to be bunk but given the original source I am curious.

 

[Taollan]

Octopus systemic hearts will skip a heart beat or two when startled (http://jeb.biologists.org/content/78/1/87.full.pdf). That being said, I doubt an octopus heart will do more than that when swimming. The complete cessation of systemic heart function while swimming, one of the most energetically demanding activities and octopus does, seems to be not very advantageous.

 

[CephBirk]

I agree with Taollan. I've heard of their heart skipping a beat, but certainly never heard of stopping for any duration (especially when swimming).

 

[DWhatley]

Thanks @Taollan, the statement seems counter to logic and I know nothing about the author's expertise but, because of the original Smithsonian posting source , I was curious about how the thought was originated. I added the paper's link to the vulgaris section under octopodidae in the Cephalopod Species category. Where the article confirms that systemic heart arrest may be common, it appears to directly counteract the heart stopping while swimming notion in its discussion of the heart working harder with exercise.

It is also interesting that they mentioned the GPO can stop its systemic heart for at least an hour and allow the brachial hearts to do all the pumping but this is in a still state, not while swimming

...one can observe cases where the heart stops beating, apparently in the
absence of stimulation, while the animal is sitting quiet, breathing regularly and doing nothing obvious with its arms or body. These ' spontaneous' arrests usually last for a few seconds only in Octopus vulgaris Johansen & Martin (1962) observed cardiac in O. dofleini and reported that the systemic heart could stop for an hour or more without apparent ill effects, a sufficient circulation being maintained by the branchial hearts alone, which beat more vigorously than usual on these occasions.

I might have saved posting this until next February though as it confirms that, even in octopuses, love can make your heart skip a beat (at least for males)

This animal, (508) a male of 560 g, had a female introduced into his tank. His heart missed one beat then and two more as she moved towards him. Copulation followed, with further beats missed each time a spermatophore was passed from the mantle into the groove along the hectocotylized arm. There were no changes in beat frequency or mean blood pressure.

 

[mucktopus]

The references below are relevant as well. The system certainly isn't optimal by any stretch. Octopuses are stuck with an escape response (jetting) that's coupled to their ventilation mode. Fast jetting creates very high internal pressures in the mantle and can interrupt the heart, and at the same time also changes their normal breathing rate/intensity. Plus, the same muscles that get exhausted from too much swimming/jetting can also become too tired to breathe heavily. It's a total mess come to think about it!


Wells, M. J. (1990). Oxygen extraction and jet propulsion in Cephalopods. Can. J. Zool. 68, 815-824.
Wells, M. J., Duthie, G. G., Houlihan, D. F. and Smith, P. J. S. (1987). Blood flow and pressure changes in exercising octopuses Octopus vulgaris.
J. Exp. Biol. 131, 175-187

 

[Scott Giddings]

To my understanding, M.J. Wells's study in the late '80's (Wells et al. "Blood flow and pressure changes in exercising octopuses...." Journal of experimental biology 131, no. 1, 1987) establishes that the systemic and branchial hearts are arrested while jetting, or at least while the mantle is filled with water just prior to the jet. Per the study:

"(I)f the mantle cavity is used to generate a jet, there will be large pressures resisting the venous return to the hearts from the head and arms. . . . (T)he evidence available suggests that such a performance always stops the hearts."

A couple comments here describe this as "not very advantageous" @Taollan and "a total mess" @mucktopus. And, I agree, it does seem like a poor adaptation to have evolved and endured for thousands of millennia.

But I wonder. Since jet propulsion is chiefly used to escape predators, might there be an advantage in ceasing the electrochemical activity of the heart to more effectively evade predators like sharks, rays, and chimaeras that rely on electroreception to hunt? It would be like a submarine's evasive maneuver to "run silent, run deep." The octopus inks, jets away in cardiac and pulmonary silence, then settles in camouflage: a perfect disappearing act.

 

[DWhatley]

But I wonder. Since jet propulsion is chiefly used to escape predators, might there be an advantage in ceasing the electrochemical activity of the heart to more effectively evade predators like sharks, rays, and chimaeras that rely on electroreception to hunt?

Interesting reasoning!