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Serpentes

Serpentes. Synapomorphies Movement Skull morphology Sensory adaptation - finding prey Killing Prey Mimicry Snake Families. I. Serpentes – synapomorphies. Limbless (or nearly so) – pectoral girdle & forelimbs totally absent

david-espinoza
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Serpentes

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  1. Serpentes • Synapomorphies • Movement • Skull morphology • Sensory adaptation - finding prey • Killing Prey • Mimicry • Snake Families

  2. I. Serpentes – synapomorphies • Limbless (or nearly so) – pectoral girdle & forelimbs totally absent • Highly kinetic skull that enables them to swallow prey that are much larger than themselves • Numerous vertebrae are • No eyelids/no external ears – • Long slender curved pleurodont teeth, some with specialized adaptations

  3. Snakes have numerous vertebrae, each w/a pair of ribs in the neck and trunk that create

  4. II. Movement • Rectilinear motion = individual movement of ventral scutes • Lateral undulation = • Concertina motion = accordion style • Sidewinding = body thrown in air in sideways arcs

  5. III. Skull morphology • Modified for feeding • the skull is highly specialized and allows for a special feeding apparatus that enables them to consume prey much larger than their own diameter • the 2 halves of the jaw are joined only by muscles and skin, • also, many of the skull bones are loosely held together so that the entire skull can flex asymmetrically to enhance the swallowing process Fig. 4-28

  6. Fang/tooth morphology • Teeth: located in two rows along the top and bottom jaw • 3 types of teeth:

  7. IV. Sensory adaptation – finding prey • Vision: • Infrared receptors • Jacobson's organs - pair of pit-like structures in the roof of the mouth; lined with olfactory epithelia that are highly folded to provide increased surface area for efficient detection of volatile chemicals

  8. Single Pair of "Dual" chambers • Higher Sensitivity • dual chamber pit improves sensitivity • Directional Information • target is straight ahead when temperatures are same in both pits • Depth Perception • anterior angle of pits provides "binocular" overlap • snake can judge distance to prey

  9. V. Killing Prey • Constriction –strikes prey, loop of body thrown on and around prey, additional coils of body encircle the prey • Biting – • Venom –

  10. Snake Venom ~20 different types of toxic enzymes • Myotoxic – • Neurotoxic - • Hemolytic -

  11. A muscular contraction pushes venom from the bottom of the cobra's fangs, while air expelled from the cobra's lung blows or sprays the venom at its intended victim.

  12. Snake fangs: • Rear-fanged snakes • Hollow-fanged snakes • Hinge-fanged snakes

  13. Inland taipan Oxyuranus microlepidotus

  14. VI. Reproduction • Courtship can be quite lengthy Females lay down a pheromone trail… Or males can give off pheromones… “breeding ball”

  15. VII. Batesian Mimicry in snakes: Dispholidus Thrasops Mimic Model Mimic Model Micrurus Lampropeltis

  16. Review of snake adaptations that make them amazing predators • Elongated body coupled with numerous vertebrae allows for advanced movement • Kinetic skull modified for feeding • Teeth and fangs for prey capture and venom delivery • Venom for digestion and immobilization • Jacobson’s organ • Pit organs

  17. Anomalepididae – Early Blindsnakes -Rhamphotyphops, parthenogenic

  18. Typhlopidae Widely distributed. Similar to the related families Anomalepidae and Leptotypholidae, the typhlopids are small snakes (usually <30 cm) with blunt heads and short, blunt tails. Due to their burrowing life style their eyes are vestigial. -lay eggs which may be retained in several species until the embryos are well developed.

  19. Leptotyphlopidae comprises about 90 species in two genera (Leptotyphlops and Rhinoleptis). -tropical distribution, and are found in tropical North and South America, Africa, and the Middle East and northwest India. They live in a variety of habitats, from rainforests to semideserts, and from termite burrows to trees tops. Leptotyphlopidae – Threadsnakes or wormsnakes Dinner for this threadsnake is an ant pupa often found under rocks or inside rotting logs.

  20. Uropeltidae – Shield-tail Snakes -presence of a large keratinous shield at the tip of their tail Southern India and Sri Lanka -Viviparous Cylindrophiidae (some consider these members of Uropeltidae) -Asian pipesnakes are shiny, stout, blunt-headed and short-tailed burrowers. They have black-and-white checkered bellies- Cylindrophis uses a head-mimicry display w/ the tail for defense mechanism

  21. Brightly banded in red and black (but without yellow bands), hence often called "false coral snake" (but it is not venomous). Fossorial, found in tropical rainforests of the Amazon Basin Vestigial hind limbs and a pelvic girdle are present as well. Vestigial eyes lie beneath a large head shield. Aniliidae – False coralsnake Anilius scytale

  22. Boidae – Boas Relatively large, stout snakes Most occur in the Neotropics although some species occur on Madagascar and in the southwest Pacific. Viviparous -vestigial hind limbs, “cloacal spurs” Pythonidae – Pythons tropical and subtropical – Africa, India, Australia - constricting snakes. These snakes lay leathery eggs. The female incubates the eggs and keeps them warm by constriction of her muscles, which generates heat. Most species are nocturnal with heat sensitive pits in their mouths.

  23. Acrochordidae – File snakes Adapted to aquatic lifestyle - Occur in both fresh & salt water Distributed in the Indo-Australian region Fish eaters Ovoviviparous & viviparous

  24. Viperidae – Vipers & Pitvipers (Crotalines) Typically have broad, triangular heads. Most are also heavy-bodied with relatively short, stender tails. Their long fangs permit deep penetration and envenomation of prey. The hinged-fang mechanism allows their storage against the roof of the mouth when not in use. Widely distributed (except Australia) Pit-organs of the crotalines lie on each side of the head between the nostril and eye and contain infrared receptors Crotalus

  25. This structure is made of loosely attached horny segments. A new segment is added each time the snake sheds. When vibrated, the rattle makes a buzzing sound characteristic of a disturbed rattlesnake.

  26. Elapidae – Cobras, seasnakes, mambas, death adders Fangs are permanently erect on the anterior ends of largely immovable maxillae and fit into grooved slots in the buccal floor when the mouth is closed. Found worldwide in tropical and subtropical regions except for Europe. Most oviporous, some ovoviviporous Black mamba Death adder

  27. Colubridae – diverse (1,800 sp.) Mostly Non-venomous (to humans), rear-fanged

  28. Boomslang – Venomous Colubrid

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