Sauropsids and Synapsids: Part 2 The Kidney Kidney Function: Terrestrial Environment: Desiccating Water conservation is a priority Some secondarily marine (also desiccating) N2 waste must be stored and therefore must be less toxic Synapsids: Mammalian kidney has a unique capacity to produce urine that is more concentrated than blood Multistep process with filtration, reabsorption, secretion Concentration of filtrate takes place in elongate Loop of Henle (especially in a desiccating environment: longer loop = more concentrated urine) N2 wastes in the form of urea, less toxic, less metabolically costly Have bladder storage of urine (****Absent in Sauropsids****) Storage of urine probably reflects scent marking in mammal species Marine mammals Excrete salt normally through very concentrated urine Sauropsids Most lack long loop of Henle (Therefore cannot produce concentrated urine in the kidney) However, some can further concentrate wastes in the cloaca Only turtles have a bladder, others possess cloaca only N2 wastes Varied forms in Turtles (do make urine) Uric acid in all others Conserves water (semi-solid waste matter) but metabolically costly Secondarily marine Sauropsids (turtles or snakes?) often have salt glands (rid body of excess salt) Evolved independently every time Nasal (birds) Lacrimal (tear duct) Lingual (under tongue) Turtles Where do they fit in the tree? Sister group of diapsid reptiles Primitively anaspid? Or did they lose the feneestrae Fossil Record 1. Pareiasaurs - Candidate for closest relative to turtles 2. Chinese Fossil turtle (2008) only has ventral part of shell and no carapace - Shell is formed as an extension of the ribs, and not dermal bone What makes Turtles distinctive? Shell (Plastron and Carapace) For a Tree: You need Shared Derived Traits (Rltp patterns) Also Need Unique derived traits to distinguish a single group (Shared Primitive traits, cannot give us relatedness information) **Turtles do not have many shared derived traits with other Amniotes** Turtle Shell as Adaptation and Constraint: Limb girdles enclosed in rib cage Vertabrae fused into carapace Ribs fused into carapace and plastron Side neck turtles (Southern Hemisphere) ? Primitive Condition Advantages: Protection Water Conserving Disadvantages: No possibility of fast locomotion Low range of movement Slow growth Limited space for added storage Adaptation: Shell Fused from ribs/vertebrae Constraint: Not a very large realm of possibility for continuing adaptation (No real adaptive radiation possible) Not able to respire like other amniotes Speed is cost Respiration: Not able to use trunk muscles for ventilation Limits ability for Negative pressure breathing Use muscles that move gut up against the lung to push air out, and drops to allow air back in When pulled back in the shell, no room to empty and fill lung, cannot breathe When a turtle is upside down, Impaitred ability to breathe Apnea , Not breathing Circulation: 3 chambered Heart, 2 Atria and 1 Ventricle Ox and DeOx blood does have the ability to mix, though unlikely due to timing/valves? Timing helps separate O and deO blood in ventricle (like frog heart) Partial Septum Ride in wall of Ventricle Muscular Ridge (MR) Divides ventricle temporarily when contracted Can even be advantageous to have 3 chambers Flexible responses to environmental changes Also : Atrioventricular Valve (AVV) Shaped like upside-down Y Allows blood from the left atrium to enter one side of the ventricle and from the right atrium to enter the other side When contracted, it looks like and upside down T to prevent backflow into the 2 atria ?Partial Compartmentalizatoin? Also linked to heart pumping cycle Turtles can tolerate some mixing of the blood, they are not that active (wider physiological tolerances are good, next weeks lectures?) Cardiac Shunt (Diving Shunt) Works by shifting the blood away from the pulmonary circuit Blood ?shunted?away from lungs More efficient when turtles are diving and not breathing Higher blood pressure in systemic circuit during this time Also functions in Apnea, when Retraction in shell Diving response Upside down Benefits of the 3 Chambered Heart No need for coronary circulation The ventricle always has some Oxygenated blood passing through it, no need for a coronary artery Can shift blood between the pulmonary and systemic circuits (In a 4 chambered heart, the one ventricle would never receive O2 blood, would need a supply from coronary) Conservation of Turtles Many spp are threatened or endangered Vulnerability Long lived, with late/slow reproduction Explosive Breeding Problem ? an environmental catastrophe could wipe out a year of offspring Predation Pressure Slow Movement Explosive breeding Humans and Turtles Habitat destruction Competing uses for habitat Environmental Sex determination Diseases and Pet turtles Pet turtles can transmit diseases to turtles in the wild Lepidosaurs Include the Tuatara, and Snakes, and Lizards Covered with scales, shed skin Transverse cloacal slit 4 limbs is the primitive body plan Leglessness has repeatedly evolved Snakes are 1 specialized lineage of lepidosaurs Determinate growth (squamate reptiles) Sphenodontids or Tuatara More primitive Diapsid Skull Parietal Eye New Zealand Formerly on N and S islands, now only on uninhabited islands 2 Spp S. punctatus More common species S. guntheri recently recognized, confined to single island Threatened Associated with sea birds? Colonial nesting Eat arthropods and scavenge Lizards ? A Paraphyletic group Primitive body plan Diverse Ecologically Very small to large in size Many are insectivorous, but also herbivorous and carnivorous 2 Major Groups 1. Iguania 2. Scleroglossa Iguania Iguanids, chameleons, agamids Scleroglossa All other lizards Snakes Amphisbaenians How are legless lizards different from snakes? Only lizards have an external ear opening, and movable eyelid Snakes have immovable eyelid Snakes and Amphisbaenians Variety of different specializations for leglessness Leglessness has evolved around 50 to 60 times or more Squamates More kinetic skull Stronger Grip Loss o flower temporal bar Other changes to skull and limb girdles
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