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Morphology of the Amazonian Teleost Genus Arapaima Using Advanced 3D Imaging
Miriam Scadeng1,2, Christina McKenzie3, Weston He1,4
1Department of Radiology, University of California, San Diego, San Diego, CA, United States.
Frontiers in Physiology
|May 13, 2020
Summary
The arapaima, a large air-breathing fish, possesses unique adaptations like a lung-like gas bladder and modified gills for hypoxic Amazon waters. These traits, alongside its large brain, are crucial for survival but also increase vulnerability to overfishing and habitat loss.
Area of Science:
- Ichthyology
- Comparative Anatomy
- Physiological Adaptations
Background:
- The arapaima (Arapaima gigas) is the largest extant air-breathing freshwater fish.
- It inhabits the hypoxic waters of the Amazon basin, where dissolved oxygen can be extremely low.
- Obligatory air-breathers, arapaima exhibit significant anatomical and physiological adaptations for survival.
Purpose of the Study:
- To conduct a comprehensive morphological assessment of the arapaima.
- To detail the anatomical and physiological adaptations enabling survival in low-oxygen environments.
- To create accurate 3D models of arapaima organs and their spatial relationships.
Main Methods:
- Magnetic resonance imaging (MRI) and computed tomography (CT) imaging.
- Gross necropsy and histological analysis.
- Segmentation of imaging data for quantitative 3D modeling.
Main Results:
- A large, lung-like gas bladder (1.96% body volume) with vascularized septa for gas exchange.
- Reduced gill surface area with blunted lamellae.
- Kidneys with interspersed hematopoietic and excretory tissue.
- A large telencephalon (28.3% brain volume) relative to other teleosts.
- Heart encased in lipid-rich tissue (0.21% body volume).
Conclusions:
- Arapaima possess remarkable adaptations, including a gas bladder analogous to lungs, enabling them to thrive in hypoxic conditions.
- These specialized traits, while vital for survival, make them susceptible to overfishing.
- Climate change and human activities pose significant threats to arapaima populations and their habitat.
