The species
—Dermochelys coriacea (Vandelli, 1761)
Leatherback turtle
Status : IUCN 2021 Red Book: Vulnerable Species
This species belongs to the family Dermochelyidae which is represented by the only genus: Dermochelys Blainville, (1816). This genus is monospecific, it is represented by the only species Dermochelys coriacea (Vandelli, 1761). The leatherback turtle is among the largest living reptiles, the largest species of sea turtles known.
Adults are easily distinguished from other species by the carapace covered by a coriaceous skin devoid of plates and carrying 7 dorsal crests and 5 ventral. This shell is an integral part of the animal’s body, so it cannot retract its neck or legs, unlike all other turtle species. The small, scaleless head has a W-shaped beak with two strong, powerful, sharp triangular tips. The broad limbs do not bear claws in adults. The body color is mainly black dorsally with white spots that become more abundant on the sides and very dense at the bottom of the body giving it with the limbs a white color .
The lute is mainly pelagic and only approaches the coasts at the time of laying. It is the most suitable among sea turtles in cold waters thanks to a very powerful thermoregulation system and a very important layer of fat, despite the fact that the turtles are described as cold-blooded animals.
The largest nesting sites are in the eastern Pacific Ocean and the western Atlantic Ocean. The spawning cycle is 2 to 3 years and the female lays 4 to 5 times a year. Eggs and newborns are, along with those of the Flat-footed Turtle, the largest among sea turtles.
In the Mediterranean, the nesting of the leatherback turtle is an unknown phenomenon despite the fact that this turtle is often caught by different fishing gear. This nesting took place sporadically only once at the end of the 19th century.
—Chelonia mydas (Linnaeus, 1758)
Green sea turtle
Status : IUCN 2021 Red Book: Endangered Species
This species belongs to the family Cheloniidae and the genus: Chelonia (Brongniart, 1800). The green turtle gets its name from the color of its fat. The Black Turtle of the Western Pacific Coast, Chelonia agassizi, which many scientists classified as an eighth species, is now considered a subspecies of Chelonia mydas.
This turtle has a slightly flat body with an oval shell. The head, relatively small, carries a pair of long prefrontal plates. The smooth shell with plates that do not overlap, usually consists of: 5 vertebral plates, 4 pairs of costal plates whose most advanced pair is never in contact with the pre-central plate and 12 pairs of marginal plates. The plastron has 4 sub-marginal plates and the limbs each have only one claw.
The green turtle colonizes tropical and subtropical waters. The Green Turtle is a solitary species that migrates between nesting and feeding areas. This species of turtle nests in the Mediterranean, the population of this species is classified as globally endangered. The phenomenon of nesting is limited to the eastern basin on the beaches of Cyprus and Turkey but also in a lesser way in Syria, Egypt and Lebanon.
The green turtle usually lays 2 to 5 times a year at intervals of about 2 weeks. The spawning cycle lasts 2 years but can vary between 1 and 4 years. This turtle digs fairly deep nests where it puts a hundred eggs. The green turtle is the only herbivorous species among sea turtles. It feeds on seagrass and often swallows animals that live in seagrass.
—Caretta caretta (Linnaeus, 1758)
Loggerhead sea turtle
Status: IUCN Red Book 2021: Vulnerable species.
In the Mediterranean, the loggerhead has a status of species of minor concern
The Caretta Caretta Sea Turtle frequents the temperate, subtropical and tropical waters of the Atlantic, Pacific and Indian oceans.
It is even present in the cold waters of Argentina, Canada and Russia. The majority of nesting sites are in temperate and subtropical regions.
The head, relatively large, carries two pairs of prefrontal plates. The shell usually consists of: 5 vertebral plates, 5 pairs of costal plates whose most advanced pair touches the nucal plates and 12 pairs of marginal plates. The plastron has 3 sub-marginal plates and the limbs each have two claws.
The colonization of the Mediterranean by this species took place during the last 10000 years when this region warmed up allowing the phenomenon of nesting to take place on its beaches. Genetic studies show that the Mediterranean nesting female population is isolated from that of the Atlantic.
The nesting of the sea turtle was limited almost exclusively to the eastern basin of the Mediterranean but we are currently witnessing the laying of an increasing number of nests in the western basin. The main focus is on the beaches of Greece, Turkey, Cyprus and Libya, many of which have been monitored for several years.
Other species not found in the Mediterranean
—Lepidochelys olivacea (Eschscholtz, 1829)
Olive ridley sea turtle
Status : IUCN 2021 Red Book: Vulnerable Species
This species belongs to the family Cheloniidae and the genus Lepidochelys (Fitzenger 1843).
Lepidochelys olivacea owes its name to the olive-green color of its shell. Its distribution is circumglobal in the tropical oceans. It is perhaps the most abundant turtle in the Pacific and Indian oceans. It measures 50 to 75 cm and weighs 40 to 50 kg. It is known for its massive landings (arribadas) of females spawning on the beaches of the peaceful coasts of Central America (Mexico, Costa Rica, Panama), as well as in South America, on the coasts of Surinam.
The head is of medium size, it carries two pairs of prefrontal plates and appears triangular in dorsal view. At the level of the shell, a large nuchal plate is in contact with the first costales. A polymorphism of the scales of the carapace is typical of this species with 5 to 10 costales on each side, very often asymmetrical and a vertebral number of 5 but which can also vary between 4 and 9. The plastron carries 4 sub-marginal plates, each with a small pore at its marginal posterior limit.
This species enters very occasionally in the Mediterranean.
—Lepidochelys kempii (Garman, 1880)
Kemp’s ridley turtle
Status : IUCN 2021 Red Book: Critically Endangered Species
This species belongs to the family Cheloniidae and the genus Lepidochelys (Fitzenger 1843).
Lepidochelys kempii is the rarest and most discreet. It is also the smallest: from 45 to 70 cm for 30 to 50 kg. It lays mainly on the Mexican beach of Playa de Rancho Nuevo.
The Kemp’s turtle is one of two species of turtles with a rather restricted geographical distribution. It prefers warm waters, within the north and south isotherms of 20°C. Adults are generally found only in the Gulf of Mexico, but juveniles and immature individuals may occur in tropical and temperate coastal areas of the north-western Atlantic Ocean.
The head has two pairs of prefrontal plates. The shell, almost circular, usually has: 5 vertebral plates, 5 pairs of costal plates whose most advanced pair touches the nucal plates and 12 pairs of marginal plates. The plastron has four sub-marginal plates, each with a small pore.
This species enters very occasionally in the Mediterranean.
—Eretmochelys imbricata (Linnaeus, 1766)
Hawksbill sea turtle
Status : IUCN 2021 Red Book: Critically Endangered Species
This species belongs to the family Cheloniidae and the genus Eretmochelys (Fitzenger 1843).
The nested turtle is the most tropical of all marine turtles, mainly related to coral formations. It is also found in shallow waters with seagrass or algal meadows, including lagoons and coastal bays. It never reaches high population densities. Nesting is confined between 25°N and 35°S, mainly in the tropical region, with very few isolated reports outside these latitudes.
Eretmochelys imbricata weighs 60 to 90 kg for a size of 60 to 120 cm. Omnivore, it feeds on sponges making its skin toxic to humans. This feature allowed him to stay away from poachers interested in meat. However, it is hunted for its beautiful scales that are easy to turn into handicrafts such as combs or jewelry.
The head is small and has two pairs of prefrontal plates. Its shell is very easy to recognize from other species. It is called a nested turtle because its scales overlap one above the other. The shell usually consists of: 5 vertebral plates, 4 pairs of coastal plates and 12 pairs of marginal plates. The plastron has four sub-marginal plates.
The presence of the nested turtle in the Mediterranean is very rare.
—Natator depressus (Garman, 1880)
Flatback turtle
Status : IUCN 2021 Red Book: Deficient Data Species
This species belongs to the family Cheloniidae and the genus Natator (McCulloch, 1908).
Natator depressus is the marine turtle with the most restricted range. It meets exclusively between Australia, Papua New Guinea and Indonesia. This species has a very low emigration rate outside its main range and does not exceed the continental shelf. To date, only a few beaches in northern Australia seem to shelter them for their reproduction.
Her diet of sea cucumbers, shellfish and jellyfish makes her a carnivorous turtle. Its name comes from its particularly flat shell.
It measures 95 to 130 cm and weighs 100 to 150 kg. Its head has a single pair of prefrontal plates. Its shell usually consists of: 5 vertebral plates, 4 pairs of coastal plates and 12 pairs of marginal plates. The plastron has four sub-marginal plates.
This species has never been observed in the Mediterranean.
