DIVE LOG Australasia

positively identifiable Loggerheads were recorded back in Qld. That is a marathon voyage and a brilliant result. I regard this as one of the most amazing research projects; A successful and spectacular detective investigation that solved this most difficult puzzle. What happens as they swim from NZ to South America? Who knows? COMPARATIVE ANATOMY I am totally amazed that turtles have bones just like mine. Turtles with shoulder blades? What about the Humerus, Radius and Ulna as well as hands with fingers and even fingernails. Yep! It goes on and on… Ball and Socket joints? Yes! The upper arm bone, the Humerus is actually much more powerful than the Thigh Bone because it is responsible for most of the locomotion. In addition, it is useful to measure the age of the turtle using bone density. The fore flipper is much larger than the hind flipper; it is used for swimming and feeding. Marine turtles are unique in that they have both an internal and external skeleton. THE SHELL OR CARAPACE The turtle shell has 13 to 15 large defensive plates called scutes made of keratin. Keratin is the same as your fingernails. These scutes are living armour plates that protect the turtle from predators. The shell is sensitive to touch and has a rich supply of nerves and blood supply to the soft tissue underneath. The mid line of the shell in most turtles has five large central hexagonal scutes, the vertebral scutes. Then, there are four or five large lateral scutes, the costal scutes on each side which are sort of pentagons but are built to complete the shell and adjusted to show no gaps. The perimeter of the shell contains 25 to 28 smaller marginal plates. There is a flexible layer beneath to help disperse forces of pressure. The combination of hexagonal, pentagonal and four sided shapes of these interlocking scutes covers the turtle in a complex but perfect pattern to protect their insides. As always, engineering and mathematical features identified in the construction of turtle shells would reveal mind-blowing science. The turtle has experimenting with dome structures, material science in a very complex balance. It could well have potential for engineers to improve dome structures. Mother Nature mastered it millions of years ago. All turtles have thirteen to fourteen scutes, twenty eight ridges around its carapace as well as sixty bones The turtle shell includes their rib cage, spine, and sternum. It sits on a bony plate which is supported by very strong broad ribs. The underside skeleton is called the plastron. It is more flexible so that it can expand and contract when the turtle breathes or when it dives deep.

Admiring a beautiful big Green turtle in Komodo.

Col and his team of researchers helped to find answers to difficult questions like ‘How long do sea turtles live for?’ What is their life cycle? Do they return to the same area they were born at for breeding? A quarter of a million hatchlings were tagged over many years. Twenty nine years later, the first batch of adults were identified when they returned to Mon Repos beach. This confirmed ‘site fidelity’ for turtles. That is they return to the beach where they were hatched. He also helped to set up the Mon Repos Turtle Centre at Bundaberg to protect them. We used to dive with Loggerhead turtles on the NE coast of NSW in the 70’s and 80’s. We saw a dramatic decline in numbers. We are told populations decreased by 80%. A very sad experience indeed! The story of migration of hatchlings to adults amazes me. In summer, Hatchlings swim like mad from Mon Repos beach out hundreds of kms to sea. They travel in the open ocean to New Zealand. Around the age of five they turned up in Chile with a shell about 30 cms long. More than twenty years later, Col Limpus’ team proved that the first

Look closely at two nostrils, two large ‘scales’ between the eyes and a relatively small head.

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DIVE LOG Australasia #408 - October ‘24

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