Meeting Abstract

P1.101  Jan. 4  Hypoxia-Induced Developmental Plasticity of Respiratory Structures in the Blue Gourami, an Air-Breathing Fish BLANK, TM*; BURGGREN, WW; U North Texas taramonet@yahoo.com

Environmental factors can alter relative development of individuals, though how this influences the transition to bimodal respiration in air-breathing fish is unknown. Here we examine the effects of hypoxia on respiratory development in the blue gourami, Trichogaster trichopterus. Adult gouramis are obligatory air-breathers, using “labyrinth” organs in epibranchial chambers to extract aerial O2. Larvae rely on aquatic respiration prior to labyrinth development. We hypothesized that chronic aquatic hypoxia alters gill morphology and accelerates labyrinth development, leading to earlier respiratory transition. Embryos were reared in normoxic (Nx=21% O2) or hypoxic (Hx=13% O2) water, and at 10-30mm total body length (TBL) were used in dissections of respiratory structures. Body size became highly variable as development progressed, thus morphometric measurements were based on TBL rather than chronological age. Relative gill arch (GA) length (GA length/TBL) of Hx was significantly shorter at GA1 (0.145) and GA3 (0.091) than Nx (0.150, 0.099). Filament density (filaments/GA length) did not differ between groups, but relative filament length (filament length/TBL) of Hx (0.018) at GA1-3 increased significantly over Nx (0.014). Density of secondary lamellae (SL/filament length) was significantly reduced in Hx (58.0 SL/mm) compared to Nx (63.6 SL/mm), but total SL was ~4% greater in Hx. Relative surface area (SA) of the labyrinth (labyrinth SA/total body SA) increased ~40% in Hx (0.0032) over Nx (0.0023) through 18mm TBL. Thus exposure to hypoxia throughout development alters morphology of respiratory structures in blue gourami. Future physiological studies, including aquatic/aerial respirometry, will determine the effects that these morphological changes have on respiratory transition in this species.