Morphometry of retinal vasculature in Antarctic fishes is dependent upon the level of hemoglobin in circulation

• Published in: Journal of Experimental Biology
• Main Authors: Wujcik, Jody M., Wang, George, Eastman, Joseph T., Sidell, Bruce D.
• Format: Text
• Language: English
• Published: Company of Biologists 2007
• Subjects: Research Article; Antarctic; Antarc*
• Online Access: http://jeb.biologists.org/cgi/content/short/210/5/815; https://doi.org/10.1242/jeb.001867

We quantitatively assessed ocular vascular patterns of six Antarctic notothenioid fishes that vary in their expression of the circulating oxygen-binding protein, hemoglobin (Hb). Digital image analyses revealed marked differences in vessel morphometries among notothenioid species. Hemoglobinless (–Hb) icefishes display mean vessel length densities that are greater ( Chaenocephalus aceratus , 5.51±0.32 mm mm–2; Champsocephalus gunnari , 5.15±0.50 mm mm–2) than those observed in red-blooded (+Hb) species ( Gymnodraco acuticeps , 5.20±0.46 mm mm–2; Parachaenichthyes charcoti , 4.40±0.30 mm mm–2; Trematomus hansoni , 3.94±0.08 mm mm–2; Notothenia coriiceps , 2.48±0.21 mm mm–2). –Hb fishes also have mean vessel diameters that are ∼1.5 times greater than vessel diameters of +Hb species (–Hb, 0.193±0.006 mm; +Hb, 0.125±0.005 mm). Vascular density index (VDI), a stereological index that is affected by both vessel number and length, is greatest in –Hb C. aceratus (3.51±0.20) and lowest in +Hb N. coriiceps (1.58±0.14). Among four +Hb species, there is a direct relationship between red blood cell content and retinal vasculature. Hematocrit (Hct) is inversely correlated to vascular density ( r 2=0.934) and positively correlated to intervessel distance ( r 2= 0.898) over a >2.3-fold range of Hct. These results indicate that anatomical capacity to supply blood to the retina increases to compensate for decreases in oxygen-carrying capacity of the blood.