Presenter(s): Leandro Marx-Albuquerque
Faculty Mentor(s): John Postlethwait & Thomas Desvignes
Poster 28
Session: Sciences
The 16 recognized white-blooded Antarctic icefishes (Channichthyidae) are the only known vertebrates living without hemoglobin– the protein packed into red blood cells and responsible for oxygen transport throughout an organism. Red-blooded dragonfishes (Bathydraconidae), plunderfishes (Artedidraconidae), and “notothens” (Nototheniidae) are close relatives of icefishes and all possess hemoglobin. All four families are part of the Notothenioidei suborder. While the genetic mechanism that led to the loss of hemoglobin genes in icefish is well understood, whether icefish possess mature red blood cells remains contested. Therefore, our purpose was to decipher if red blood cell development (erythropoiesis) in icefishes progresses as it does in their red-blooded relatives. These investigations were conducted using head kidney histology samples and blood smears from six species of white-blooded icefishes and seven closely related red-blooded fish species (four dragonfish species, one plunderfish species, and two notothen species). We conducted a morphological analysis of erythropoietic cells using principal component analyses to differentiate and compare cell types across species. Our results indicate that icefishes have Pro-erythroblasts and some more advanced cells morphologically similar to red-blooded erythroblasts. Additionally, we observed that in plunderfishes and two of the four dragonfishes, the most developed erythropoietic cells are morphologically akin to erythroblasts. These results suggest that while hemoglobin was lost at the origin of the icefish radiation, the erythropoietic pathway was impaired earlier– likely in the common ancestor of plunderfishes, dragonfishes, and icefishes. Thus, our investigation provides a new perspective into the evolutionary history that led to the unique white-blooded icefish phenotype.