\u201cI thought the story was solved when we did our work on Antarctic icefishes,\u201d Detrich said. \u201cBut then the noodlefishes came along and surprised me. It turns out there may be more species than we think that don\u2019t rely on red blood cells to transport oxygen.\u201d<\/p>\n
Detrich\u2019s lab at Northeastern University looked closely at the genomic structure of Antarctic icefish and discovered they had lost their ability to produce red blood cells due to the deletion of hemoglobin genes over millions of years.<\/p>\n
The thinking is that icefish were able to survive and thrive without red blood cells carrying oxygen from gills to their tissues because the chilly seawater around Antarctica is rich in dissolved oxygen, Detrich said.\u00a0<\/p>\n
\u201cThat means that the Antarctic icefishes are able to rely on oxygen that\u2019s physically dissolved in their blood fluid,\u201d he said.\u00a0<\/p>\n
However, that genetic explanation doesn\u2019t work for white-blooded Asian noodlefish, which swim in much warmer waters, from the coasts and river systems of China, Korea, Japan and eastern Russia, south to Vietnam.<\/p>\n
\u201cThey live in a very different environment,\u201d Detrich said. \u201cThey don\u2019t have the advantage of a cold and oxygen-rich environment like the Southern Ocean.\u201d<\/p>\n
The Chinese scientists who studied Detrich\u2019s work reached out to him, he said. \u201cThey wanted to know what was going on.\u201d<\/p>\n
![\"H](\"https:\/\/www.newsbeep.com\/ie\/wp-content\/uploads\/2026\/01\/Dietrich1400.jpg\")
H William Detrich, a world-renowned professor emeritus of marine and environmental sciences, studied the \u2018other\u2019 white-blooded fish with Chinese researchers. Photo by Matthew Modoono\/Northeastern University<\/p>\n
Collaborator Jinxian Liu from the Qingdao Marine Science and Technology Center in Qingdao, China, said that after reading Detrich\u2019s works, he wondered \u201cwhether our Asian noodlefishes \u2026 share a similar evolutionary pathway.\u201d<\/p>\n
In particular, the scientists wanted to know what was happening with the hemoglobin genes as well as the gene for myoglobin, which is the protein that makes red meat red and binds oxygen in the cells of the meat.<\/p>\n
\u201cAs part of this collaborative effort, we demonstrated that Asian noodlefish \u2014 all 12 species \u2014 have lost the myoglobin gene as a single event that occurred in their most recent common ancestor,\u201d Detrich said.<\/p>\n
In addition, they found various mutations to their hemoglobin genes that rendered them nonfunctional, he said.<\/p>\n
\u00a0\u201cBut unlike the icefishes, they hadn\u2019t completely deleted the hemoglobin genes,\u201d Detrich said. \u201cRather, they had smaller mutations that prevented the genes from expressing a functional hemoglobin protein.\u201d<\/p>\n
The short life span of the Asian noodlefish holds clues about how it evolved to live without red blood cells, Detrich said. Unlike Antarctic icefish, which live six to seven years or more, Asian noodlefish measure their life spans in a year.<\/p>\n
Although noodlefish adults can reproduce at the end of their short lives, they retain numerous juvenile or neotonic features.<\/p>\n
\u201cIn a number of other fish species, juveniles don\u2019t need to make red blood cells because they are small and slender and can absorb oxygen through their scaleless skins,\u201d Detrich said.<\/p>\n
But while most of these species have longer lives and will go on to make red blood cells as adults, Asian noodlefish don\u2019t need to because they remain, in essence, juveniles.<\/p>\n
\u201cThe work is important because it shows that historical contingency also plays an important role in the evolution of biodiversity,\u201d Liu said.<\/p>\n
Comparing the evolution of myoglobin and hemoglobin expression in Asian noodlefish and Antarctic icefish, Detrich said, \u201cIt\u2019s a different set of environmental circumstances and a different set of molecular outcomes. \u00a0<\/p>\n
He said he was pleased that he and his colleagues in China had their research published in the July issue of Current Biology, which featured the Asian noodlefish on its cover.<\/p>\n
\u201cThere\u2019s more than one way for fish to lose the production of myoglobin, hemoglobin and red blood cells \u2014 that\u2019s what we discovered in this paper,\u201d Detrich said.<\/p>\n
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