Ontogeny and morphometrics of the gills and swim bladder of air-breathing striped catfish Pangasianodon hypophthalmus

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The air-breathing fish Pangasianodon hypophthalmus has been shown to have highly plastic branchial surfaces whose area (SA) increases with temperature and aquatic hypoxia. This modulation occurs through development of inter-lamellar cell mass (ILCM). Paradoxically, in conditions where this fish has been shown capable of covering its entire aerobic scope from the water phase, it has been shown to have a very small branchial SA. To address this paradox, we measured the SA, harmonic mean diffusion distance (tau(h)) and calculated the anatomic diffusion factor (ADF) of the branchial and swim bladder surfaces in fish ranging from 3 to 1900 g at 27 degrees C in normoxia. Since the lamellae were distinguishable from the ILCM, we measured the actual SA as well as the potential SA if ILCM were lost. As a result of low tau(h), P. hypophthalmus has a high capacity for branchial oxygen uptake with or without ILCM. Actual and potential gill ADF were 361 and 1002 cm(2) mu m(-1) kg(-1), respectively, for a 100 g fish and the ADF of the swim bladder was found to be 308 cm(2) mu m(-1) kg(-1). By swimming fish to exhaustion at different temperatures, we show that modulation of this SA is rapid, indicating that the apparent paradox between previous studies is eliminated. Regression analysis of log-log plots of respiratory SA in relation to body mass shows that the gill scales with mass similarly to the SA in active water-breathing fish, whereas the swim bladder scales with mass more like the mammalian lung does. This fish presents a combination of respiratory surfaces not previously seen in air-breathing fish.

Original languageEnglish
Article number168658
JournalJournal of Experimental Biology
Volume221
Issue3
Number of pages11
ISSN0022-0949
DOIs
Publication statusPublished - Feb 2018

    Research areas

  • Anatomic diffusion factor, Gill plasticity, Pangasius, Scaling, Stereology, GOLDFISH CARASSIUS-AURATUS, TROUT SALMO-GAIRDNERI, PANGASIUS-SUTCHI PANGASIIDAE, RESPIRATORY SURFACE-AREA, FISH GILLS, VERTICAL SECTIONS, CRUCIAN CARP, PHYSICAL PROPERTIES, SUSTAINED EXERCISE, OXYGEN-CONSUMPTION

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