Vertebrate Biology and Ecology PDF

Edgewood Howard College Nelson R Pietermaritzburg Westville Campus Campus Mandela Campus Campus Campus Vertebrate Biology and Ecology  Systematics Extant amphibians Class: Amphibia Orders: Anura (frogs and toads) Caudata (salaman...

Edgewood Howard College Nelson R Pietermaritzburg Westville Campus Campus Mandela Campus Campus Campus Vertebrate Biology and Ecology  Systematics Extant amphibians Class: Amphibia Orders: Anura (frogs and toads) Caudata (salamanders and newts) Gymnophiona (caecilians/apoda) Amphibians are four- limbed and ectothermic vertebrates of the class Amphibia. Systematics Extant amphibians Class: Amphibia Orders: Anura (frogs and toads) Caudata (salamanders and newts) Gymnophiona (caecilians/apoda) The first land vertebrates! Transition from water to land noticeable in today’s amphibians. Adaptations to both – life on land and in the water. Ancestor: lobe-finned fish 360 million year old amphibian Ichthyostega  The first land vertebrates! Transition from water to land noticeable in today’s amphibians. Adaptations to both – life on land and in the water. Ancestor: lobe-finned fish By looking at this video of the mud-skipper – an amphibious fish(!) that walks using its strong pectoral fins– we can visualise how ancestral fishes first made their way out of the water onto land.  The first land vertebrates! The first semi-land vertebrates! Transition from water to land noticeable in today’s amphibians. Adaptations to both – life on land and in the water. Amphibia → “amphi” = of two/both kinds + “bios” = life Amphibians typically start out as larvae living in water. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Tadpole Adult  The first land vertebrates! Transition from water to land noticeable in today’s amphibians. Adaptations to both – life on land and in the water. Amphibia → “amphi” = of two/both kinds + “bios” = life Metamorphosis The first land vertebrates! Transition from water to land noticeable in today’s amphibians. Adaptations to both – life on land and in the water. Moving to land has advantages and disadvantages. For example: New food sources (plant, insects) No competition from other vertebrates More oxygen -> more efficient respiration -> more energy -> more mobility -> increased prey capture Gravity pulls -> movement needs more energy Respiration (gas exchange) and loss of water (drying out) Temperature extremes and UV radiation The first land vertebrates! Transition from water to land noticeable in today’s amphibians. Adaptations to both – life on land and in the water. Body plan reflects adaptations to both – life on land and in the water. External fertilization. Sperm is not mobile. Egg and sperm unite in water. Egg not adapted for terrestrial environment. No shell (means drying out). Gills for gas exchange in water Lungs for gas exchange in air Permeable skin in all life phases! Skeletal system with four legs -> to stand an move on land. Absent in aquatic phase (not needed). Tail for swimming. Amphibian Locomotion Amphibian Locomotion Amphibian skin Gas exchange DIFFUSION Vessels Amphibian skin Vessels Amphibian skin Defense Types of poison: - Cardioactive steroids (CAS) Skin irritation, pain, tissue damage, irregular heartbeat. Found in toad secretions. - Tetrodotoxin (TTX) Neuroactive. Numbness, dizziness, muscle paralysis, Found in salamanders and poison dart frogs. Over 5000 species Terrestrial, semi-terrestrial and aquatic adults. Oviparous and viviparous (rare) reproduction. Predators: Tongue adapted to capture insect prey. Prey: poisonous mucus glands in skin Wide field of vision. Over 650 species Internal fertilization! Female picks up and stores male spermatophore until she lays eggs. Embryo develops externally. Oviparous, ovoviviparous, viviparous. Over 150 species Caecilians Extinct and extant relatives are grouped as the clade Apoda (“A” = without “poda” = limbs → without limbs) Caecilians Extinct and extant relatives are grouped as the clade Apoda (“A” = without “poda” = limbs → without limbs) Caecilians Not a snake, not a worm Snakes have scales, while caecilian skin is made up of ring-shaped folds encircling the body. Caecilians differ worms because they possess a backbone and a skull. Caecilians use their skulls to burrow Evolution and adaptation: through soil. Tentacles detect chemicals, including those released by prey. Caecilians Evolution and adaptations Ancestor lived 275 mya Looked similar to salamander: Four legs, tail, small Burrowing in leaf litter on the search for prey and Deeper into soil to hide Caecilians use their skulls to burrow from predators. through soil. Tentacles detect chemicals, including those released Legs disappeared, skull became by prey. stronger, body lengthened and a coiled set of tissues called tendons evolved. Eyes reduced (covered), tentacles evolved to sense prey. Caecilians Biology and Life history traits Reproduction: Most lay eggs in water or moist soil (amphibians). Wide range of reproductive modes: aquatic larvae to terrestrial juveniles. Birth of independent living young. Fetus consume yolk, then Some caecilian babies scrape off and “uterine milk” (oviduct eat the outer layer of their mother’s secretions) scraped off with skin, which is dead but loaded with embryonic teeth. nutrients. Parental care: Hatched/born juveniles scrape off epidemis Matriphagy of mother (no injuries). Caecilians Ecology Diet of adults: earthworms and aquatic or terrestrial soil insects such as termites and ants. Carnivore predators! Tentacles to detect chemical traces of prey. Prey to: snakes, chickens, hawks, pigs, tenrecs, fish Skin produces defensive toxins with poison glands. Skin receptors with resistance to neurotoxic snake venoms. Systematics Extant amphibians Class: Amphibia Orders: Anura (frogs and toads) Caudata (salamanders and newts) Gymnophiona (caecilians/apoda) Reptiles as prey Hiding from predators As a first line of defense, species may try to avoid being seen by their predators. Nocturnal life Reptiles as prey Hiding from predators As a first line of defense, species may try to avoid being seen by their predators. Nocturnal life Camouflage Reptiles as prey Startling predators  Reptiles as prey Startling predators When startled, frillneck lizards (Chlamydosaurus kingii) extends their frills to warn off potential predators or intruding males. Disruptive camouflage  Reptiles as prey Startling predators When startled, horned lizards (Phrynosoma spp.) startle the predators by squirting blood at them.  Reptiles as prey Startling predators When startled, the Mozambique Spitting When startled, horned lizards (Phrynosoma Cobra (Naja mossambica) spits venom spp.) startle the predators by squirting blood at very accurately, up to a distance of 2 m, them. aiming for the eyes  Reptiles as prey Warn predators Venomous Harlequin snake Venomous Coral snake Aposematism  Reptiles as prey Warn predators Harmless Scarlet kingsnake snake Venomous Coral snake Copycat liar Honest signaller Batesian mimicry Reptiles as predators Camouflage (again) Cryptic coloration that makes it difficult to spot the animal against Its background. Mimicry One organism (the mimic) counterfeits the signal of a second organism (the model), thereby deceiving a third organism (the dupe). Reptiles as predators Snakes and their sensory adaptations to catch prey Ecological diversity: The live on the ground, in the ocean, on trees, … All are carnivores, predating on all kinds of animals Reptiles as predators Snakes and their sensory adaptations to catch prey Ecological diversity: The live on the ground, in the ocean, on trees, … All are carnivores, predating on all kinds of animals Reptiles as predators Snakes and their sensory adaptations to catch prey The pit organ A sensory sense that detects heat! Reptiles as predators Snakes and their sensory adaptations to catch prey The pit organ A sensory sense that detects heat! Reptiles as predators Snakes and their sensory adaptations to catch prey The pit organ A sensory sense that detects heat! Reptiles as predators Snakes and their sensory adaptations to catch prey The pit organ A sensory sense that detects heat! Reptiles as predators Reptiles as predators Snakes and their sensory adaptations to catch prey The scale sensilla of sea snakes The head of a beaked sea snake (Hydrophis schistosus) and a close up of a single scale on its head. Reptiles as predators countershading  The chameleon – a summary of reptile ecology The chameleon – a summary of reptile ecology It lays eggs The chameleon – a summary of reptile ecology It is ectotherm The reptile skin The chameleon – a summary of reptile ecology It is prey and a predator camouflage  The chameleon – a summary of reptile ecology It is prey and a predator mimesis Mimicry of non-living models (inanimate) Imitation of leaves Chameleons in the wild live on trees and are surrounded by leaves. In order to protect themselves from predators they move forth and back to blend with leaves moving in the wind. The chameleon – a summary of reptile ecology It is prey and a predator Morphological adaptations Feet The chameleon – a summary of reptile ecology It is prey and a predator Morphological adaptations Eyes They move independent They give 360° vision They focus on two things The chameleon – a summary of reptile ecology It is prey and a predator Morphological adaptations Tongue Three parts Long Fast Sticky Importance of Reptiles in ecosystem Reptiles are the vital part of food chains as prey, predators, and as pollinators. Pest Control prevent the spreading network of rodents which carry dreadful diseases. Fish Control presence of crocodiles prevents the population increase of fish species. Dead Animals clear the environment also maintain the balance in the food chain. Prey Items source of food for other animals. Humans and Reptiles Interactions hunted the reptiles for the food Reptiles could be poisonous Humans use the poison of snakes for the medical purposes. Reptiles The reptile egg Most reptiles lay their shelled eggs on land. Function: Shells protect the eggs from drying out. Fertilization occurs internally, before the eggshell is secreted. Reptiles The reptile egg Most reptiles lay their shelled eggs on land. Function: Shells protect the eggs from drying out. Fertilization occurs internally, before the eggshell is secreted.  Eggs, Babies or Both Australian three-toed skink (Saiphos equalis)  Eggs, Babies or Both Australian three-toed skink (Saiphos equalis) Reptiles Reptiles are ectotherms Reptiles such as lizards and snakes are sometimes described as “cold-blooded” because they do not use their metabolism extensively to control their body temperature. An ectothermic reptile can survive on less than 10% of the food energy required by a mammal of the same size. However, they do regulate their body temperature by using behavioral adaptations. But the reptile clade is not entirely ectothermic; birds are endothermic, capable of maintaining body temperature through metabolic activity. Thermoregulation They are also poikilotherm. Thermoregulation  Thermoregulation Sunbathing and shade  Thermoregulation Circulatory Adaptations Galápagos marine iguanas control blood flow to the skin to alter their heating and cooling rates. Thermoregulation Physiological colour change Namaqua Chameleon (Chamaeleo namaquensis) showing thermoregulation with dark to absorb sunlight, Namib Desert, Namibia Namaqua Chameleon (Chamaeleo namaquensis) showing thermoregulation with panting, white color to reflect sunlight and raising off ground, Namib Desert, Namibia Is it a girl or a boy? – it depends on the temperature Temperature-dependent sex determination is observed all reptilian groups The thermosensitive period of sex determination in crocodilians. (A) Several crocodilian species display the female-male-female (FMF) pattern of sex determination. Extreme temperatures (below 32°C and above 34°C) produce primarily females and intermediate temperatures (between 32 and 34°C) produce primarily males. (B) The thermosensitive window of sex determination in crocodilians initiates as early as stage 15 of embryonic development and persists until the period of gonadal differentiation (stage 24). Reptiles have fully developed lungs. Some reptiles have mechanisms that assist in their breathing. For example, aquatic turtles have more permeable skin, similar to amphibians, but they still rely on their lungs to breathe. Turtles can hold their breath for hours underwater with some of them able to hold their breath for as long as 4 to 7 hours. Similarly, alligators and crocodiles are capable of holding their breath for about two hours. The ecology of reptiles Where do reptiles live, how do reptiles live, and which role do they play in ecosystems? Where do reptiles live?  Food Webs of South Africa Savanna Trophic levels Trophic levels  The ecology of reptiles What is their trophic position? l a ry u cab Herbivory Carnivory Insectivory Piscivory Omnivory ’s vo ist Herbivores, Carnivores (Predators (primary and higher ), Scavengers) l o g o Second and third trophic level. Primary and secondary consumers. Ec  Edgewood Howard College Nelson R Pietermaritzburg Westville Campus Campus Mandela Campus Campus Campus Biol210 Vertebrate Biology and Ecology  Phylogeny Reptiles Reptiles are cold-blooded, which means that they rely on heat from their surrounding to warm up. They are vertebrates and have dry skin, covered with scales or plates. Reptiles breath through lungs. Most reptile species eat other animals, and most lay eggs on land to breed. Reptile groups alive today include lizards, snakes, tortoises, turtles, crocodiles, and alligators. Where are the birds? Reptiles The reptile skin Reptiles The reptile skin Reptiles have scales that contain the protein keratin (as does a human nail). Function: Scales help protect the animal’s skin from desiccation and abrasion.  Reptiles The reptile skin Reptiles have scales that contain the protein keratin (as does a human nail). Function: Scales help protect the animal’s skin from desiccation and abrasion. Reptiles shed when growing. Oberhäutchen layer β-layer mesos layer α-layer (keratinocytes) tissue of the epidermis stratum basale (germinal layer) basal lamina tissue of the dermis Reptiles The reptile skin Reptiles have scales that contain the protein keratin (as does a human nail). Function: Scales help protect the animal’s skin from desiccation and abrasion. Reptiles shed when growing. Reptiles The reptile skin Reptiles have scales that contain the protein keratin (as does a human nail). Function: Scales help protect the animal’s skin from desiccation and abrasion. Reptiles shed when growing. Ecdysis: This process is necessary for growth. Greek “ekdusis” =“put off.” A process by which reptiles shed their old skin. Exuviae: skin that is shed. Greek = “things stripped from the body.” Reptiles The reptile skin Ecdysis in snakes.  Reptiles The reptile skin Ecdysis in snakes. GL—germinative layer, IG—inner generation of epidermis, OG— outer generation of epidermis, SL—separation line, S—slough Reptiles The reptile skin No ecdysis in turtles Reptiles The reptile skin Can they sense anything? Reptiles The reptile skin Can they sense anything? The reptile skin Colours! The reptile skin Colours! The reptile skin Colours! Signalling: Warning! Mate attraction Communication Mimicry Camouflage Colour-change in chameleons Colour-change in chameleons Colour-change in chameleons Colour-change in chameleons Colour-change in chameleons Colour-change in chameleons Colour-change in chameleons Colour-change in chameleons Reptiles Function and ecological consequences Scales are a type of watertight skin that allows The reptile skin them to live on land. shells are hard and protective. Firstly, the old and worn skin is replaced and secondly it helps to get rid of parasites (mites and ticks). Communication Camouflage