Chelonians Honor

Nature Study

Requirements

1. Describe the main characteristics of chelonians and tell why chelonians are classified as reptiles.

   Answer: Chelonians have a bony shell (upper carapace + lower plastron), a retractable head, a toothless jaw (horny beak), adapted legs (webbed in aquatic species, robust in land species), and are oviparous. — The shell is a fusion of ribs + vertebrae + skin bones. The jaw with a beak (no teeth) cuts vegetables or fish. They have lungs instead of gills even in aquatic species. Sea turtles can hold their breath for 1-3 h. Lineage dating back 220 million years. About 350 living species today.

2. By what other names are chelonians known?

   Answer: Chelonians are known as: turtles (general and sea), terrapins/freshwater turtles (cágados), tortoises (land), some aquatic species, and testudines (technical term). — In Brazil, the jabuti (tortoise) is exclusively terrestrial. The cágado is a freshwater turtle with a laterally retractable neck. The word 'tartaruga' (turtle) refers more often to sea turtles and some freshwater ones. Testudines is the scientific name of the order. Visual differences help: the tortoise has a domed shell; the cágado is flatter.

3. What are the two lineages (suborders) of chelonians?

   Answer: The two suborders are: 1) Cryptodira — they retract the neck backward into the shell, folding it in a vertical S; this includes sea turtles, tortoises, and most species. 2) Pleurodira — they fold the neck sideways (to the side) to shelter the head under the edge of the shell; they predominate in the southern hemisphere (Brazil, Africa, Australia), such as the freshwater turtles. — Cryptodira is the larger suborder (250+ species). Pleurodira exists mainly in the southern hemisphere (Brazil, Africa, Australia). The difference evolved 150 million years ago. The lateral neck protects the spine, but the vertical S allows for more biting force. Both are scientifically recognized monophyletic groups.

4. Make an illustration of the internal anatomy of a turtle.

   Answer: You should draw/print and identify the internal parts: heart (3 chambers), lungs, liver, stomach, intestines, kidneys, bladder, eggs (in females), small brain, nervous system, skeleton fused with the shell. — The heart has 3 chambers (2 atria + 1 ventricle). The large lungs occupy the upper part of the shell. The liver is bulky and reddish-brown. The skeleton is fused with the shell — unique in the animal kingdom. Sea turtles have salt glands in their eyes (they eliminate excess salt through their 'tears').

5. Name:
   • Five species of land chelonians;
   • Five species of freshwater chelonians;
   • Three species of giant chelonians.

   Answer: 1) Five species of land chelonians: red-footed tortoise (Chelonoidis carbonaria), yellow-footed tortoise (Chelonoidis denticulata), Greek tortoise (Testudo graeca), leopard tortoise (Stigmochelys pardalis), and Russian tortoise (Testudo horsfieldii). 2) Five species of freshwater chelonians: slider turtle (Trachemys), bearded toad-headed turtle (Phrynops), red-eared slider (Trachemys scripta elegans), mata mata (Chelus fimbriata), and snake-necked turtle (Hydromedusa tectifera). 3) Three species of giant chelonians: Galápagos tortoise (Chelonoidis niger), Aldabra giant tortoise (Aldabrachelys gigantea), and leatherback sea turtle (Dermochelys coriacea). — Recognizing land, aquatic, and giant species helps to understand the diversity of chelonians and the importance of preserving them.

6. Choose one species from each of the options in the previous item and describe, for each one, the common names and the scientific name, the physical characteristics, habits, diet, reproduction and other interesting facts.

   Answer: For each chosen species (tortoise, freshwater turtle, sea turtle): popular and scientific name, size/weight, shell (shape/color), habitat, diet (herbivore, carnivore, or omnivore), reproduction (egg-laying, number of eggs, incubation time), and curiosities such as longevity or specific social behavior. — The red-footed tortoise (Chelonoidis carbonaria) eats fruits and flowers and lives 80+ years. The Amazon river turtle (Podocnemis expansa) is the largest freshwater turtle of the Americas. The green sea turtle (Chelonia mydas) is a marine herbivore and migrates thousands of km. Detailed documentation helps in the conservation of endangered species.

7. Answer the following questions:
   • What is the main factor for the development of chelonian eggs?
   • What is the diet of land and aquatic chelonians?
   • How do chelonians breathe?
   • What is the main threat to these reptiles?
   • How many years did the oldest chelonian in the world live?
   • How do you tell a male tortoise from a female?
   • What is the largest species of sea turtle in the world?
   • Out of a thousand sea turtle hatchlings, how many reach adulthood?
   • What are the factors that cause many turtles not to reach the sea after hatching?
   • Which species of sea turtle is the most endangered?

   Answer: Answers to the usual questions of this item: 1) What determines the sex of the hatchlings? The incubation temperature of the eggs in the sand: higher temperatures produce more females and lower temperatures produce more males (temperature-dependent sex determination). 2) How/on what do they feed? It varies by group: land species (tortoises) are herbivores (fruits, leaves, sprouts); freshwater species (cágados) are omnivores (fish, insects, plants); sea turtles vary (the green is an herbivore of algae and seagrass, the loggerhead eats mollusks and crustaceans, and the hawksbill eats sponges). 3) How do they breathe? They all breathe through lungs (pulmonary respiration), even aquatic ones, which need to surface to take in air; some aquatic species capture additional oxygen through the skin and the cloaca. 4) What are the main threats? Hunting and egg collection, accidental fishing, pollution (plastic and chemicals), destruction and occupation of beaches and habitats, and climate change. 5) What is the oldest one on record? Adwaita, an Aldabra giant tortoise, estimated at about 188 years old when it died (2006). — Sex determined by temperature — above 30°C females are born. Hatchlings are easy prey (gulls, crabs, fish). Urban lights confuse the hatchlings' orientation toward the sea. Plastic in the sea looks like a jellyfish. The leatherback turtle weighs 600 kg+. Adwaita died in Calcutta in 2006.

8. Why is the preservation of chelonians important to human beings? How does ocean pollution become harmful to turtles?

   Answer: The question has two parts. 1) Why preservation is important for human beings: chelonians maintain the balance of ecosystems (sea turtles control jellyfish populations and help keep reefs and seagrass beds healthy; tortoises disperse seeds in the forests), sustain food chains, generate income through ecotourism and sustainable fishing, serve as indicators of environmental health, and have value for scientific research. 2) How sea pollution is harmful to turtles: plastic (bags and fragments) is mistaken for jellyfish and ingested, causing intestinal obstruction, a false sense of satiety, and death by starvation; discarded nets and trash (ghost fishing) trap and drown the animals; oil and chemicals intoxicate them and damage their eyes, skin, and gills/lungs; sewage and excess nutrients favor diseases (such as fibropapillomatosis, linked to tumors), and light pollution on beaches disorients the hatchlings, which head toward the city lights instead of the sea. — Green turtles prune seagrass, keeping reefs healthy. Plastic bags resemble jellyfish — the main food of several species. 1 million sea turtles die per year from plastic, according to the WWF. Bycatch (accidental fishing) is another major threat. Conservation is urgent.

9. How do sea turtles make use of smell, hearing and sight in relation to their reproductive cycle?

   Answer: Sea turtles use all three senses in the reproductive cycle. 1) Smell: they detect chemical compounds in the water and sand, which helps the female recognize and locate the beach where she was born (an olfactory imprint acquired at birth) to lay her eggs. 2) Hearing: they perceive low-frequency sounds and vibrations (such as the breaking of the waves), which helps in orienting themselves to approach the coast and choose the nesting site. 3) Sight: they see well underwater and use visual cues; when they leave the sand, the hatchlings orient themselves by light — they seek the brightest reflection of the horizon over the sea to reach the water (which is why artificial light on beaches disorients them). Sight also helps the female assess the environment when she comes up the beach to nest. — Sea turtles memorize chemical signals of the beach where they were born (philopatry). They return decades later to lay eggs in the same place. Their hearing picks up sounds of 100-700 Hz. Hatchlings follow the reflection of the moon/stars on the sea — urban lights confuse this instinctive visual orientation.

10. How do female sea turtles manage to return to the beach where they were born to lay their eggs?

    Answer: They use magnetic navigation: they detect the Earth's magnetic field like an internal compass, memorizing the exact magnetic coordinates of their native beach when they are born. — Turtles have magnetite crystals in the brain that function as a biological compass. Studies show that they turn in the wrong direction if exposed to artificial magnetic fields. Philopatry is instinctive — even when taken to another continent, they return to the original beach. Precise biological navigation that science is still studying.

11. What is responsible for most of the accidental deaths of marine chelonians worldwide?

    Answer: Accidental fishing (bycatch) with trawl nets and gill nets kills hundreds of thousands of turtles per year globally. Other causes: ingestion of plastic (bags mistaken for jellyfish), collisions with vessels and chemical pollution. — It is estimated that 250,000 sea turtles die per year in fishing nets. TEDs (Turtle Excluder Devices) are devices mandatory in some nets that reduce mortality by 97%. Brazil requires a TED in shrimp fishing. Plastic additionally kills thousands — tons reach the oceans daily.

12. Complete one of the items below:
    • Visit an institution that works in the care, preservation, and prevention of extinction of turtles. Write a report recording how that institution operates and which points you found most interesting;
    • Research online about an institution that works in the care, preservation, and prevention of extinction of turtles. Write a report of at least 300 words describing the institution's history, how it operates, and what results have been observed to date;
    • Take part in an awareness campaign in your community about the preservation and prevention of extinction of turtles.

    Answer: Choose 1 option: 1) Visit TAMAR (Brazil), Aqualung or similar and write a report with your observations. 2) Research online: history, work, results — a report of 300+ words with sources. — Project TAMAR (Sea Turtles) is a worldwide reference — it has operated since 1980 and has released more than 32 million hatchlings. Research centers in Praia do Forte (BA) and Fernando de Noronha. Wikipedia and the official website (tamar.org.br) have reliable data. Local awareness can save lives.