Marine Biology Lecture 9

Marine Reptiles:

Amniotic Egg: an egg covered by a protective shell and containing a liquid filled sac in which the embryo develops.

  • advantages allowed are elimination of free swimming larvae, and eggs to be laid in a dry place.

Amnion: a liquid filled sac that contains the developing embryo of some vertebrate animals.

Yolk sac: a sac like structure in amniotic eggs that contains a supply of food.

Allantois: an embryonic support membrane that functions in elimination of wastes and is found in some vertebrates.

Chorion: an embryonic support membrane that functions in gas exchange and is found in some vertebrates.

Physiological Adaptations:

  • circulatory system is more advanced than fishes.

  • Fishes have gills, 2 chambered hearts, 1 atrium, and 1 ventricle.

  • Reptiles have lungs, 3 chambered heart, 2 atria, and 1 ventricle.

Order Crocodilla:

  • order of large reptiles that appeared 84 million years ago.

  • Closest living relative to birds

Family Gharials

Family Alligators and Caiman

Family Crocodiles

Alligators:

  • wider and shorter heads, u shaped snouts, upper jaw wider than lower jaw, teeth in lower jaw fit into depressions in upper jaw, and prefer freshwater.

Crocodiles:

  • narrow and longer heads, v shaped snouts, upper and lower jaws same width, crocodiles better tolerate seawater due to salt glands.

Saltwater Crocodile: saltwater crocodile weighs 1300kg and length can be 6m. Females are much smaller than males.

  • have a cerebral cortex, 4 chambered heart, and functional equivalent of a diaphragm by incorporating muscles used for aquatic locomotion into respiration.

  • Salt glad located in the mouth and salt is excreted through the tongue/spit out of the mouth.

Sea Turtles (order Testudines):

  • return to land to lay eggs, rest, and bask which is thermoregulation.

  • 2 families which are Cheloniidae and Dermochelyidae

  • 7 or 8 species found throughout 3 tropical oceans.

Marine Adaptations:

  • lost capacity of tail undulation, developed shortened and rigid body form and corselet which is a breastplate, and modified limbs

Shell Composed of 2 Layers:

  • Outer Layer- composed of Keratin; a tough protein found in reptilian scales.

  • Inner Layer- composed of bone; shell fused to vertebrate.

Carapace: dorsal surface of a turtles shell

Plastron: ventral surface of the turtles shell

Family Cheloniidae:

Honu (green sea turtle); turtle grass and limu

Honu’ea (hawksbill sea turtle); sponges

Olive Ridley sea turtle; jellyfish, snails, shrimp, and crabs

Loggerhead sea turtle; jellyfish

Leatherback sea turtle; conchs, clams, crabs, sponges, fish, sea urchins, shrimp

Arribadas nesting: females nest synchronously at the same time.

Sea Turtles Feeding: all turtles lack teeth and have a beak like structure to capture and secure prey.

Sea Turtles Feeding Reproduction:

  1. Nesting must occur during condition which are conducive to adult activity

  2. Nesting must occur during conditions that favor embryo development and survival

  3. Hatchlings must emerge into conditions that are conducive to their survival

Sea Turtles Courtship:

Precopulatory behaviors: head bobbing, position in water column, head head bumps, nuzzling, biting, movement of flipper, dinner.

  • The male mounts the female and uses enlarged claws on fore and hind flippers to hold carapace.

  • Curls long tail to bring cloacea into contact

  • This can last up to 10 hours or more

Sea Turtles Nesting:

All species lay several clutches during a nesting season

  • lay white spherical cleiodoic eggs with flexible calcareous shells (50-130).

  • Size of egg differs between clutches and among species

  • Hatch after 6-13 weeks of incubation depending upon the temperature

  • Large eggs produce large hatchlings.

  • Hatchlings typically emerge at night with two major problems they face being lethal temperature and predators.

  • Females are produced at warm temperatures and males are produced at cool temperatures.

Salt Glands:

Reptiles have a unique variety of organs used as salt glands.

Sublingual glands - sea snakes

Lingual glands - crocodiles

Nasal glands - lizards

Lachrymal gland - sea turtles

Order Squamata:

Snakes evolved from lizards 135 million years ago

  • there are approximately 70 species of sea snakes living in our modern oceans

  • Account for 86% of marine reptile species.

5 Major Groups of Sea Snakes:

  • Hydrophiid; sea snakes

  • Lacticaudids; sea kraits

  • Acrochordids; file snakes

  • Homalopsids; mangrove snakes

  • Natricids; salt marsh snakes

Family Elapsidae

Subfamily Hydrophiinae

  • The largest group of sea snakes. Evolved from Australia 30 million years ago and have the same toxic venom and envenomation.

  • Have fixed front fangs like their ancestors.

  • Fully aquatic and never leaving the water. They lack ventral scales.

Subfamily Laticaudinae

  • are strongly banded and commonly seen in large numbers on beaches in south east Asia and some pacific islands.

  • sea kraits have evolved from terrestrial elapses and are proteroglyphs with highly toxic venom.

  • Are very placid and unlikely to bite unless provoked

  • Are the only group of sea snakes that are oviparous (egg laying) and must return to land to breed.

  • They live on land and in water and have special ventral scales for crawling on land.

Sea Snake Diving: One elongated cylindrical lung extends almost the entire body length for efficient for gas exchange. Also diffuses O2 from skin into blood vessel from seawater.

Sea Snake Reproduction:

Hemipenes: paired penises found in snakes and lizards.

  • each is autonomous independently functioning penic and only one is used during mating. Mating takes place for long periods and sea snakes must surface for air during that time.

Marine Iguana: laterally flattened tail, dorsal spines allow for efficient swimming. They feed on marine algae and remove salt via salt glands in their nose.

  • they can remain submerged for up to 60 min though dives of 5 to 10 min are more common.

  • Iguanas spend much of their time restoring body heat by sunning themselves on rocks by the shore.c

Marine Reptiles:

Order Crocodilia

  • Gharils

  • Alligators and Caiman

  • Saltwater Crocodile

Order Testudines:

  • Green sea turtle

  • Hawksbill sea turtle

  • Olive Ridley sea turtle

  • Loggerhead sea turtle

  • Leatherback sea turtle

Order Squamata

  • true sea snakes

  • Sea kraits

  • Marine iguanas