title: Morphometry of retinal vasculature in Antarctic fishes is dependent upon the level of hemoglobin in circulation.
abstract: 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 approximately 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.
authors.affiliation: School of Marine Sciences, University of Maine, 5751 Murray Hall, Orono, ME 04469-5751, USA.
authors.forename: Jody M
authors.initials: JM
authors.lastname: Wujcik
authors.forename: George
authors.initials: G
authors.lastname: Wang
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Eastman
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Sidell
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D000864:Antarctic Regions; D006400:Hematocrit; D006454:Hemoglobins / Q000032:analysis*; D007091:Image Processing, Computer-Assisted / Q000379:methods; D010473:Perciformes / Q000033:anatomy & histology*; D010781:Photography / Q000379:methods; D012171:Retinal Vessels / Q000033:anatomy & histology*; D013045:Species Specificity
chemical_list: D006454:Hemoglobins