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What changes occur when a salamander undergoes metamorphosis?
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Caudata
Tiger salamanders (Ambystoma tigrinum) are widespread across much of the United States. Although they are generally black with yellow blotches, bars, spots, or even stripes, some are lighter in colour or have olive markings. Tiger salamanders belong to the mole salamander family, Ambystomatidae.
When a salamander undergoes metamorphosis, it experiences a period of major reorganization mediated by hormones from the thyroid and pituitary glands. While these changes are less dramatic than those seen in frogs, they typically include the following structural and physiological modifications:
- Respiratory and Circulatory Changes: Gills are resorbed and gill slits close as lungs develop and branchial circulation is modified.12
- Skin and Fins: The skin thickens as dermal glands develop, and the caudal (tail) fin is resorbed.2
- Head and Sensory Structures: The mouth and eyes enlarge, and eyelids develop.12
- Feeding Apparatus: A tongue pad appears, and the gill skeleton and musculature are reorganized to create the mechanical system required for projecting and retracting the tongue. Additionally, a maxillary bone forms, and teeth develop on the maxillary and parasphenoid bones.12
- Internal Systems: The urogenital system is modified, with the kidney transitioning to produce concentrated urea rather than dilute ammonia.2
Some species may exhibit paedomorphosis, where they retain larval features throughout their lives.1