Oh Yeah, Developmental Biology!

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Saltwater Crocodile embryos. Image 1 15 days after fertilisation. Image 2 just prior to hatching. 

The saltwater crocodile (Crocodylus porosus) is the largest of allcrocodilians, and the largest reptile in the world, with unconfirmed reports of individuals up to an impressive eight to ten metres in length, although a maximum of five to six metres is more usual(2) (3) (5). The species has a relatively large head, with a pair of ridges that run from the eye along the centre of the snout. Adults are generally dark in colour, with lighter tan or grey areas, and dark bands and stripes on the lower flanks. The underside is creamy yellow to white, becoming greyer along the tail. The juvenile is usually pale tan, with black stripes and spots on the body and tail, which gradually fade with age, although never disappear entirely. Female saltwater crocodiles grow to a smaller size than males, normally reaching a maximum length of 2.5 to 3 metres (3).

With its long, powerful tail, webbed hind feet, and long, powerful jaws, the saltwater crocodile is a superbly adapted aquatic predator. As in all crocodilians, the eyes, ears and nostrils are located on top of the head, allowing the crocodile to remain almost totally submerged when lying in water, helping to conceal it from potential prey, while a special valve at the back of the throat allows the mouth to be opened underwater without water entering the throat (2) (6). The saltwater crocodile is considered to be more aquatic than most crocodilians, and is less heavily armoured along the back and neck (3).