jim hardy said:
Made me think of a 1957 Asimov essay "The Sea Urchin and We"
wherein he stated the Sea Urchin is the most primitive creature with iron based hemoglobin.
Dont know why that stuck with me. Maybe because i'd recently got stung by one...
Anyhow , Asimov said once Mother Nature gets a chemistry she likes she sticks with it.
This seems to agreeSea Urchins may be our evolutionary "Kissin' Cousins",
,,, but don't try it. .
old jim
Not sure why I doubted either you nor Asimov, but I did.
It might be because 1957 was quite a while ago, and science kind of evolves.
And perhaps that I had somewhere in the back of my head, that star fish and sea urchins were related in some way. Which I confirmed they do. They both belong to the phylum Echinodermata, which also lists Sea Cucumbers, Sand Dollars, et al.
Anyways, I googled the bejeezits out of this assertion that "the Sea Urchin is the most primitive creature with iron based hemoglobin" and came up with the following:
Evolution of Hemoglobin
Hemoglobin is derived from the myoglobin protein, and ancestral species just had myoglobin for oxygen transport. 500 million years ago the myoglobin gene duplicated and part of the gene became hemoglobin. Lampreys are the most ancestral animal to have hemoglobin, and the ancestral version was composed of dimers instead of tetramers and was only weakly cooperative. 100 million years later, the hemoglobin gene duplicated again forming alpha and beta subunits. This form of derived hemoglobin is found in bony fish, reptiles, and mammals, which all have both alpha and beta subunits to form a tetramer (Mathews et al., 2000).
Of course, in the course of that research, I learned what a myoglobin is.
per wiki:
Myoglobin (symbol Mb or MB) is an iron- and oxygen-binding protein found in the muscle tissue of vertebrates in general and in almost all mammals. It is not related to hemoglobin, which is the iron- and oxygen-binding protein in blood, specifically in the red blood cells.
Of course, given that I have no formal training in biology, and most of the articles skimmed through are "Greek to me", I could be wrong.
Unfortunately, I was never able to definitively nail down whether or not sea urchins have iron based blood.
But from wiki:
Sea_urchin, Circulation and respiration
"Sea urchins possesses a hemal system with a complex network of vessels in the mesenteries around the gut, but little is known of the functioning of this system."
Which kind of indicates to me that perhaps more research needs to be done on these little creatures.
ps. Just sent a tweet to
Sarah McAnulty, asking her about this. She's a squid biologist, and may not know the answer off the top of her head, but she has many smart friends.
I just realized I haven't learned anything new recently.
