Conservation and Ecology of Marine Reptiles

MARE 494Dr. Turner

Summer 2011

Class Reptilia

Order Chelonia – marine turtles

Order Squamata – marine snakes and iguanas

Order Crocodilia – saltwater crocodile

Order SquamataFamily Elapidae - characterized by a hollow fixed front fang and neurotoxic venoms

Elapids are divided into two subfamilies, Elapiinae and Laticaudinae – 61 species

Order SquamataSnakes evolved from lizards ≈ 135 mya

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

They account for 86% of marine reptile species alive today

Classically 5 major groups of “sea snakes”Hydrophiids - ‘true’ sea snakes – 54 speciesLaticaudids - sea kraits – 5 speciesAcrochordids - file snakes – 3 speciesHomalopsids - mangrove snakes – 9 speciesNatricids - salt marsh snakes – 3 species

Hydrophiids - ‘true’ sea snakes The largest group of sea snakes

Evolved from Australian terrestrial elapids that returned to the marine environment around 30 million years ago

Have the same toxic venom and envenomation apparatus (they are proteroglyphs meaning they have fixed front fangs) as their terrestrial ancestors

Hydrophiids - ‘true’ sea snakes Have exploited the viviparity that exists in some of their terrestrial ancestors, and have thus freed themselves entirely from the need to return to land to breed

54 species of hydrophiid sea snakes

Laticaudids - sea kraitsComprise five species, four of which are marine

Are strongly banded and commonly seen in large numbers on beaches in south east Asia and some Pacific Islands

Laticaudids - sea kraitsSea kraits have also evolved from terrestrial elapids and are proteroglyphs and have highly toxic venom. However they are very placid and unlikely to bite unless provoked.

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

Acrochordids - file snakesComprise three species

One species is fully marine while the others live in estuaries and freshwater habitats

Are not venomous & give birth to live young

Homalopsids - mangrove snakesConfined almost entirely to estuarine environments

Are nine species found primarily in tropical Asian waters and northern Australian waters

Only three species are fully marine

Homalopsids are venomous but they are rear-fanged

Natricids - salt marsh snakesConfined to salt marsh environments

Three species of marine natricids

Confined to temperate & subtropical N. America

Are not venomous

Early stages of evolving marine adaptations

Order SquamataSubfamily Hydrophiinae – Sea snakes & sea kraits

Subfamily Elapinae – Cobras, coral snakes, terrestrial kraits

Subfamily HydrophiinaeSubfamily Hydrophiinae – Sea snakes & sea kraits

Sea kraits - amphibious (living on land and water), oviparous (returning to land to lay their eggs, have specialized ventral scales for crawling on land

Sea Krait

Subfamily HydrophiinaeSea snakes – fully aquatic (never leaving the water ovoviviparous (bear their young in the water) lack specialized ventral scales

Sea Snake

Sea Kraits

Sea Snakes

Sea Krait Distribution

Sea Snake Distribution

Sea Snake Diets

Sea Snake DivingAerobic dives average 13 minutes & 20 meters

Anaerobic dives increase time by 30-45 min 2 hr maxdepth – ave > 50 m; 90 m max

Sea Snake DivingOne elongate cylindrical lung that extends for almost the entire length of their body which is very efficient for gas exchange

Sea Snake DivingThey are also able to carry out cutaneous respiration

Oxygen diffuses from sea water across the snake’s skin into tiny blood vessels and carbon dioxide diffuses out

Venom!Sea snake venom is extremely toxic – neurotoxin + nasty enzymes lecithinase – lysis of eurythrocytes anticoagulase – delays or prevents blood cooagulation hyaluronidase – leads to diffusion of venom into cells

Paralyzes prey; for defenseNot usually aggressive – many victims on shore

Salt RemovalSea snakes are able to avoid excess salt accumulation from sea water using a salt excreting gland, the posterior sublingual gland that sits under the tongue

Skin of sea snakes is very resistant to water, and does not let water in the snake easily

One feature is that it does not resist water passage equally in both directions - allows the water to move inward faster than outward, thus giving it an advantage in the marine environment

Like all snakes and lizards, male sea snakes have two penises – hemipenes

Each is an autonomous independently functioning penis and only one is used during mating

Mating takes place for long periods and sea snakes must surface for air during that time

Repro-man

Diving 4 Images

                                                                                                               

All sea snakes except the latidcaudids give birth to live young after gestation periods that range from four to eleven months

Most species reproduce every year

Timing of the reproductive cycle highly variable

Born Free

Order SquamataFamily Iguanidae

Subfamily Iguaninae Marine, Fijian, Galapagos land, spinytail, rock, desert, green, and chuckwalla iguanas

Subfamily IguaninaeIguanas are lizards characterized by:

Diurnal life history, Distinctive eyelids, External eardrums, Dewlaps (throat pouches), 5 toes on each limb with sharp claws, Herbivorous (unlike most lizards)

Marine IguanaGalapagos Marine Iguana

(Amblyrhynchus cristatus) - Dark color (grey-black) helps absorb radiation from sun - ♂ more brightly colored: red, teal-green, and dull greenish - Adult ♂ are up to 1.7m (5.6 ft) long, ♀ 0.6–1m (2–3.3 ft), ♂ weigh up to 1.5 kg (3.3 lb).

Marine IguanaLaterally flattened tail, dorsal spines allow for efficient swimmingFeed on marine algaeRemove salt via salt glands in nose

Marine Iguana- ♀ lay 1-6 eggs in burrows dug 30-80cm deep - Eggs are laid in sand or volcanic ash up to 300m or more inland- ♀ guard the burrow for several days then leave the eggs to finish incubation (95 days)

Marine IguanaCan remain submerged for up to 60 min, though dives of 5 to 10 min are more commonIguanas spend much of their time restoring body heat ( from cold water) by sunning themselves on the rocks adjacent the shore

Order CrocodiliaFamily Crocodylidae

The saltwater or estuarine crocodile (Crocodylus porosus) is the largest of all living reptiles

Marine habitats in Northern Australia, the eastern coast of India and parts of Southeast Asia

Saltwater Crocodile♂ saltwater crocodile weighs 1,300 kg (3,000lb) and length can be 6m (20 ft) Greatest sexual dimorphism of any modern crocodilian; ♀ much smaller than ♂

India, S Pacific, Australia

Saltwater CrocodileUnlike other reptiles:Have a cerebral cortex, a 4-chambered heart, and functional equivalent of a diaphragm by incorporating muscles used for aquatic locomotion into respiration

Saltwater CrocodileSalt gland located in the mouth (modified salivary glands); salt is excreted through the tongue, spit out of the mouth