Biology Flashcards
What are the two types of glands found in amphibian skin? What do they each produce?
Mucous - Secrete slimy protective layer. Prevents mechanical damage to skin, facilitates retention of body fluid, and provides a barrier against pathogens.
Granular - Synthesize and secrete a variety of compounds that protect against predators and compounds that have antibacterial and antifungal properties.
Where are granular glands found?
Usually on head and shoulders, can be scattered over the body. Parotid gland of toads located behind the eyes is a raised cluster of granular glands. Fire salamanders and many other salamander species also have parotid glands.
Defensive compounds found in parotid and granular gland secretions have what effects? Name specific examples.
Neurotoxic, cardiotoxic, myotoxic, hallucinogenic, hypotensive, and vasoconstrictive. Alkaloids in poison dart frogs (Dendrobatidae) and salamanders can cause vomiting, resp paralysis, and death. Granular secretions of extremely stressed X. laevis form thick, milky glutinous strands that cause gaping and yawning in snakes and are toxic to the frogs themselves.
What granular products do amphibians secrete to inhibit antimicrobial activity?
Peptides. Magainins produced by X. laevis. Bombesin, caerulein, and bradykinin.
Outside of predator defense and antimicrobial activity, what other products do granular glands secrete?
Pheromones used in courtship and mating, potent opioid, and bioadhesives for entrapment of predators and adhering during breeding.
How often do amphibians shed their skin? What does the process look like?
In cycles, ranging from days to weeks. Skin splits middorsally and animal uses limbs to climb out. Sheds commonly eaten.
What are nuptial pads?
Keratinized epidermal pads developed on males seasonally. Shed and regrown with synchrony with mating season.
What are seat or drink patches?
Located on ventral abdomen and hindlimbs of many hylind, bufonid, and ranid frogs. When pressed against a wet substrate, through action of arginine vasotocin and aquaporins, increase permeability and facilitate absorption of water.
What are skeletal modifications found in amphibians (salamanders, frogs, anurans, and X. laevis)?
Salamander - Skeleton largely cartilaginous.
Frogs - Ribs absent or greatly reduced.
Anuran - Fusion of postsacral vertebrae into elongate bone (urostyle) which articulates with sacral vertebrae and ilium. Fusion of tibia and fibula into tibiofibula.
X. laevis - Iliosacral joint articulates to allow cranial-caudal sliding along vertebral column, increasing hind limb propulsion forward and backward.
Describe tail autotomy.
Shared by many salamander species. If tail is grasped, will break through fracture plane and animal can escape.
What methods of respiration are used for larval and adult amphibians?
Larval - Gills
Adult - Gills, lose gills and use lungs, breathe with both gills and lungs, or use neither and utilize cutaneous resp.
What do X. laevis tadpoles and axolotls use for respiration? Adult plethodontids (legless salamanders)?
X. laevis and axolotls - Gills and lungs and gulp at water’s surface. Axolotls flex external gills to move water over filaments, behavior increases in warm water with decreased oxygen content.
Plethodontids - Lack gills and lungs, use cutaneous respiration.
What is the primary respiratory surface in most amphibians?
Skin, must be kept moist.
Describe process of lung breathing in amphibians.
Air is forced in and out by movement of buccopharyngeal floor. Lungs lack alveoli and rupture easily. In many frogs, trachea is short and bifurcation close to glottis (ET tube).
Describe the general heart structure in larval and adult amphibians. What are the exceptions?
Larval amphibians have a two-chambered heart, like fish. Adults have a three-chambered heart, with paired atria and single ventricle.
Plethodontids lack atrial division as they lack lungs. Hellbenders, mudpuppies, and sirens have partial interventricular septum.
