L12 - Marine Reptiles Flashcards
Taxonomic overview?
Marine reptiles - approx 80 species. Sea snakes (70 spp), sea turtles (7 spp), salt water crocodile (2 spp), marine iguana (1 spp). Air-breathing: presence of lungs. Ectothermic (except for leatherback turtles), body covered with scales, oviparous & lay their eggs on land, except hydrophiinae family (true sea snakes) ovooviviparous.
What are sea snakes anatomy, family Elapidae, subfamily Hydrophiinae?
Eyes with fixed lens; thin, forked tongue. Distinct scales; ventral scutes extend across full width of belly. Males have longer tails than females. Sea snakes: lineage of venomous snakes. Most diverse group of marine reptiles yet poorly investigated.
What are the adaptations of sea snakes?
Fully marine except Laticauda (sea kraits, 5 spp, land or in water; lay eggs on (land). Laterally flattened body with a paddle-like tail for propulsion through the water. Wide range habitats (mud flats, reefs, seagrass, estuaries). Indo-pacific. All ovoviviparous except Laitcauda. Carnivorous: mainly feed on fishes and fish eggs.
What are the pop traits of sea snakes?
All but one species have k-selected traits (low fecundity, slow growth, late maturity (2yr) e.g. spine-bellied sea snake Lapemis curtus 3-6 clutch size. Beaked sea snake (Enhydrina schistosa) has R-trait (17.8 clutch size) & early maturity. Population is highly clustered as dispersal is limited with strong philopatry - no specific inter-habitat movement to locate suitable nesting sites (Rao et al. 2019 Aq Conserv). Cutaneous respiration (estimated 25% of requirements). Bites from sea snakes can be fatal for humans but sea snakes are not aggressive and have small mouths.
What is the geological history of sea turtles?
Tortoises one of the oldest reptile groups. Found in fossil record (Triassic - 200mya). Common in cretaceous (130mya). 4.5 Archelon; 2007 Desmatochelys padillai. Two extant families. Family Dermochelyidae: leatherback (softshell). Family Cheloniidae: green turtle, flatback turtle, olive ridley, kemp’s ridley, loggerhead turtle, hawksbill (hardshell)
What is the long-standing phylogenetic debate of turtle lineage?
3 competing hypotheses. Parareptiles (primitive reptiles), sister group of lepidosaurs (lizards, snakes), sister group of archosaurs (crocodiles, birds). Molecular studies: archosaurs (crocodiles, birds) are sister group of archosaurs. Morphological studies: lepidosaurs (tuatara, lizards, snakes) closest. Turtes =/ primitive reptiles as may have lost skull temporary holes secondarily
What is turtle anatomy?
Turtles are one of the most derived vertebrates. Encased in bone, limbs inside the ribs, horny beaks instead of teeth. Shell is the most distinctive feature. Scutes & shell of shell + head -> species ID (photoidentification).
How does sea turtles: morphology reflect marine habitat?
Turtles: flat shell, 4 flippers, cannot retract head or flippers. Tortoise/terrapin: shape varied, 4 limbs, can retract head/flippers. Green turtle Chelonia mydas.
Overview of sea turtles?
Body enclosed by a shell, or carapace Ribs are fused to the shell. All have powerful jaws with no teeth (beaks). Poikilotherms (do not require fixed temp) and ectotherms (body heat from external envy): restricted to the tropics, except for leatherbacks. 7 species - each specialist diet - sponges, crabs, molluscs, and other invertebrates. Green turtle is herbivorous (macroalgae, seagrasses) & diet related to sea temp. Leather back is obligate planktivore (jellivore)
What is the general shell structure in sea turtles?
Shell is part of skeleton - does not ‘match up’. Dorsal carapace (dermal bone), ventral plastron, carapace bone covered: horny scutes of epidermal origin (hard kinetin). Some families: shell modifications. Soft-shelled - no peripheral ossifications & epidermal scutes. Distal ends or ribs in flexible connective tissue. Carapace & plastron covered with skin.
Sea turtle shell structure terms?
a) epidermal scutes of carapace (L) & plastron (R). b) dermal bones of carapace (L) and plastron (R). c) Vertebral column, seen from inside of carapace.
What is the shell structure of the leatherback - Dermochelys coriacea?
Carapace of soft cartilage - thousands of polygonal bones embedded in carapace. Plastral bones reduced to a thin rim around plastron edge. Osteoderm overlays thick blubber layer overlaying ribs, nuchal bone, vertebrae & plastron bones. Blubber enables higher body temperature for deeper dives. The slight flexibility of the shell also allows deeper diving owing to great pressures at depth.
What is endothermy in leatherback turtles?
Dermochelys coriacea can maintain body temperature at ca. 25 degC, even in subpolar waters (<5 degC). Very thick layer of adipose tissue. Large body size and high insulation have been proposed as the main drivers behind the homeothermy of leatherback turtles: gigantothermy. Counter-current heat exchangers maintain the heat generated by swimming muscles inside the limbs, preventing hyperthermia in the rest of the body. Deepest dive for leatherback sea turtle was 87 minutes at 1186m.
What are the seven species of sea turtles?
Leatherback turtle - Dermochelys coricea
Australian flatback turtle - Natator depressus
Green turtle - Chelonia mydas
Hawksbill turtle - Eretmochelys imbricata
Loggerhead turtle - Caretta caretta
Kemp’s ridley turtle - Lepidochelys kempii
Olive ridley turtle - Lepidochelys olivacea
Lack of diversity across group?
All have the same basic morphology, all turtles breathe air, all turtles lay eggs in spring/summer - except leatherbacks; green turtle populations can lay year round at some equatorial rookeries. None exhibit parental care of the hatchings. Ectotherms: mostly tropical and subtropical, seasonally in temperate waters. Life history pattern types (Bolten 2003): 1. complete development in neritic zone - flatback, 2. development in oceanic & neritic zone - loggerhead, green, hawksbill, kemp’s ridley, 3. Complete development in oceanic zone - olive ridley, leatherback.
What are the selective pressure on sea turtles (both K- and r- traits)?
Sea turtle long distance migration Indian ocean case study 2012-2023: equipped 36 nesting green turtles with satellite tags. i. r-selective - egg-laying, high clutch freq, extended nesting season ii. K-selective, long distance migration
What is satellite tracking in sea turtles?
During the breeding season, very restricted movements. Mean clutch frequency = 6 (max 10). 100-160 eggs laid each time = up to 1000 eggs.
Sea turtles - What is the K-trait: long distance breeding migrations?
90 -> 5000 km. Straight routes, aerobic diving, optimum swim depths, energy conservation (>6month breeding season)
Sea turtles - Informing conservation planning?
Foraging: discrete, shallow (<50m) coastal sites. Consistent with Indian ocean diet of seagrass. Discovery: unknown deep (30m) seagrasses.
What is the saltwater crocodile, Crocodylus porosus?
Red list: least concern. Australia, indian ocean, some western pacific islands. Estuaries, mangrove forests, rivers, and the open ocean. Highly predatory (including humans). Can grow to over 7m (1300kg)
What is the American crocodile, Crocodylus acutus?
Red list : vulnerable. Tolerates seawater and can be found in lagoons and other coastal regions including hypersaline lakes (e.g. Lago enriquillo, Dominican republic). Widely distributed in florida, caribbean, pacific coast of central america. Males have been recorded >6m & >900 kg females smaller. Feed mostly on fish. NB other crocodiles (e.g. cuban crocodile) tolerate saltwater due to salt glands under tongue. Only 2 species thrive (C. porosus, C. acutus
What is the Marine iguana, Amblyrhynchus cristatus?
Red list: vulnerable, life duration : mean 12 yr (max 60 yr). One species endemic to galapagos islands; subspecies on islands differ in size, shape, colour. Only marine lizard known to forage in the sea. Spend a portion of their time in water, diving to feed on green & red algae near shore. Males also forage in sub-tidal. Gland removes salt from bodies & expelled via nostrils (sneezing).
What adaptations do marine iguanas have?
A large portion of their day is spent basking on the shore to warm up from their dives in the cold water surrounding the galapagos. Vulnerable to El Nino temp fluctuations (&climate change). Low availability of food - respond by shrinking (up to 6.8cm or 20% shorter). Can repeat growth/ shrinking multiple times. Cartilage/connective tissue forms 10% of length so thought they reabsorb bone matter. Females seen to shrink more than males (linked to extra energy to produce eggs.
