Marine Turtles
(Families Cheloniidae and Dermochelyidae)

Out of the 12 living families and 250 species of turtles, only 2 families and 8 species are marine turtles. There are 7 species in the family Cheloniidae. These are the hard-shelled turtles. The remaining species is the Leatherback Turtle of the family Dermochelyidae. This is a soft-shelled turtle and the largest marine turtle.

Marine turtles share several common characteristics. They all have relatively nonretractable extremities. They have roofed skulls. Their limbs are connected to flippers with 1 or 3 claws. All of them are large turtles. Their reproductive habits are similar, but they seem to have different specialized feeding habits. They have large salt glands used to excrete excess salt ingested with salt water.

Over their lifetime they will have survived in three different habitat types. As hatchlings, they have to face the gauntlet of the high-energy beaches. Apparently they then swim to convergence zones in pelagic waters to grow. As they reach 20-25 cm they somehow find their way to the benthic feeding grounds in relatively shallow, protected waters.

Green Sea Turtle
(Chelonia mydas)

This is the largest of the hard-shell turtles. Its carapace varies from black to gray to greenish or brown with bold streaks or spots. It has a yellowish-orange plastron (the ventral surface of the shell) in Hawaii. It forages over sea grasses or algae, but is also found over coral reefs on rocky bottoms. Most feeding occurs under turbulent conditions. It is assumed that at its post-hatchling pelagic stage it is omnivorous. Juveniles have been seen eating sponges, seaweed and jellyfish. Hawaii has only one form of seaweed that is not common and not a major food source. It is found to feed on 9 species of algae in Hawaii. From tagging, we know that Hawaiian Green Sea Turtles settle at a specific foraging ground and leave only to reproduce on the low sandy islands at French Frigate Shoals. One such spot is along the Kona Coast where they have delighted divers over the years.

Hawksbill Turtle
(Erethmochelys imbricata)

The young Hawksbill has a heart shaped carapace that becomes more elongated as it matures. The sides and rear of the carapace are sharply serrated in all but the very old turtles. The scutes (enlarged bony dermal plates or scales) are unusually thick and overlapping at the rear of the carapace. These epidermal scutes are often richly patterned with irregular radiating marble streaks and comprise the tortoise shell that unfortunately is so richly prized by commerce.

The Hawksbill has a v-shaped jaw and an elongated head that tapers to a point. I never realized that this was a Hawksbill until years after I took this photo, in spite of the obvious difference in the carapaces of these two species..