Friday, March 02, 2007

Friday Fish: Chaenocephalus aceratus

The Blackfin Icefish, a member of the Crocodile Icefishes, family Channichthyidae, are somewhat famous for being the only vertebrates to lack red blood cells. They have lost the genes responsible for haemoglobin and myoglobin, two important blood-oxygen-carrying proteins, and this apparently led to the loss of their RBCs as well. Their physiology is a bit different from their close relatives in other fish families as a result, and they have higher relative blood volume (the proportion of body mass that's blood) and a generally more-efficient circulatory system. However, this doesn't fully compensate for the loss of RBCs - their metabolisms are actually a bit slower than relatives, apparently because they cannot supply oxygen to tissues fast enough to be really active.

There are not many pictures of these fishes out there on the web, and they certainly don't live in the tropical regions where Lucy does her fieldwork, so I present here the only species that I found two pictures of. The diver below is almost certainly completely crazy, and may be working with a lunatic company whose site I found.

Thanks to Langmann for suggesting this Friday Fish.

Recommended Reading:
Kock KH. 2005a. Antarctic icefishes (Channichthyidae): a unique family of fishes. A review, Part I. Polar Biol 28: 862-895.
Kock KH. 2005b. Antarctic icefishes (Channichthyidae): a unique family of fishes. A review, Part II. Polar Biol 28: 897-909.

Near TJ, Parker SK, Detrich HW III. 2006. A genomic fossil reveals key steps in hemoglobin loss by the antarctic icefishes. Mol Biol Evol 23: 2008-2016.
Sidell BD, O’Brien KM. 2006. When bad things happen to good fish: the loss of hemoglobin and myoglobin expression in Antarctic icefishes. J Exp Biol 209: 1791-1802.


langmann said...

Now thats what I'm talking about!

Nice fish. Its impressive that anything can survive without red blood cells. I did a straw poll at work regarding the lowest hemoglobin (Hb) level people had seen in humans. One doc had a guy with a Hb of 6. (Normal ~140). This guy was still concious and lying there in bed acting normal. Now he won't be running any marathons - let alone cruising down the hall...

Thanks for the references as well.

Anonymous said...

Great pictures. Actually all 16 of the Channichthydiae lack Hb not just Aceratus, one still has the gene for Hb but it's nonfunctional. I think 5 of them lack Mb.

Anonymous said...

I thought they still have the genes for hemoglobin but they just aren't activated.