Week 11

Discussion

From an ukiyo-e print by Suzuki Harunobu (1725 – 1770). See discussion.

A Seascape-Related Topic

This week's painting subject, seascape, is way too broad a topic to handle in a single session, so I've narrowed the scope down to something more manageable.

About Turtles

Turtles are reptiles. The scientists have classified them all to the order Testudines, They all appear roughly similar to the one shown in the photo below, with variations. There are land-dwelling species, fresh-water based species, and ocean-water species.

In English language common usage, turtles may be called turtles, tortoises, or terrapins. The distinction is often based on one's nationality. In the U.S., for example, the word turtle usually applies to all testudines species, though tortoise is often used, too. In the United Kingdom, tortoises are the land-based species, terrapins are fresh-water dwellers, and turtles are sea dwellers. Some other countries have other conventions.

Turtles' most recognizable characteristic is the shell. They are no more able to separate themselves from their living, growing shells than humans are from their skeletons. In fact, their shells are part of their skeletons, composed of 50 to 60 plates.

The plates in the top part of turtle shells, called the carapace, grow from their backbones and some ribs. The plates on the relatively flat bottom, the plastron, grow from the shoulder girdle, sternum, and gastralia (abdominal ribs). The plates grow along with the turtle like human bones grow with the person.

The shell plates are covered with scales called scutes made of keratin, the same stuff that compose hair and fingernails. It is only through scutes that turtles get vitamin D in their diets; from exposure to ultraviolet B rays in sunlight. It used to be a practice to paint the shells of small pet turtles. It is sometimes still done today.

This practice prevents UVB rays from getting to the scutes to generate vitamin D and can damage the turtle's health. It can even be deadly.

Turtle shell shapes vary depending on the turtle species. Land dwelling turtle shells tend to have a more rounded carapace to better resist crushing assaults by enemies. Water dwelling shells are a little sleeker to support rapid swimming. Other comparisons are that sea turtles have webbed legs and lack the ability to retract their heads into their shells. They live almost their entire lives in ocean water, coming on land only to lay eggs on sandy beaches.

At least some species don't mind company when they do.

In 2020, about 250,000 Olive Ridley sea turtles came ashore in batches of 5,000 to 10,000 each to lay eggs at Rushikulya beach of Odisha’s Ganjam district in India.

In 2021 on an island in the Maldives in the Indian Ocean, 123 Hawksbill sea turtles hatched from this "nest". Females can lay as many as 200 eggs in one clutch.

The bad news is that estimates of the likelihood of hatchlings surviving to adulthood ranges from 1 in 1,000 to 10,000. They get eaten by seabirds and fish. What sea turtles eat depends on the species.

Various sources say that there are from 343 to 360 living and recently extinct turtle species. They agree, however, that there are only seven living sea turtle species.

Green Sea Turtle (Chelonia mydas)

Green sea turtles get their name because their flesh is green. They are large, growing up to 500 lbs. and up to 4 feet in length. They feed on sea grasses, seaweeds, algae and other forms of marine plant life. Their habit of grazing the tops of sea grass blades while avoiding the roots helps sea grass beds to grow healthier, generally improving the environment for many other marine species. They can be found in the sub-tropics and tropics worldwide. They are the only species that comes to shore to bask, but only in a few remote areas. They are an endangered species.

Hawksbill Sea Turtle (Eretmochelys imbricata)

Hawksbill sea turtles get their name from their sharp, bird-like beak. Adults weigh between 100 - 200 lbs. and grow from 2 to 3 feet in length. They feed almost exclusively on sponges. Various concentrations of Hawksbills range in tropical and some sub-tropical regions around the world, but are not found in the Mediterranean Sea. They are solitary but frequent nesters, nesting roughly 4 times per season at 2 week intervals. There are typically 140 eggs per nest, but the number can sometimes be as much as 200 eggs. Hawksbills are an endangered species.

Loggerhead Sea Turtle (Caretta caretta)

Loggerheads are named for their large head and strong crushing jaw. That makes them well adapted to consume their favorite foods; crabs, conchs, and whelks. They grow from 200 to 400 lbs. and can get up to 4 feet long. Loggerheads are found throughout temperate and tropical regions of oceans worldwide. They are one of the most common sea turtles found in U.S. waters with Florida being a favorite nesting area. One population of Loggerheads spends most of its time feeding in the waters of Baja California, but migrates all the way across the Pacific Ocean to nest in Japan. Their status is listed as vulnerable worldwide but are considered threatened in the U.S.

Olive Ridley Sea Turtles (Lepidochelys olivacea)

Named for their pale green carapace, Olive Ridley turtles are relatively small, growing to 75 to 100 lbs. and 2 to 2½ feet in length. The mass nesting events (called arribadas) like the one shown above occur in only a few places around the world. Elsewhere, they are solo nesters. They like to eat crabs, shrimp, lobster, urchins, jellies, algae, and fish. Because they gather together in large numbers during arribadas, it is estimated that 60,000 of them die by being caught and drowned in shrimp trawling nets in Central American waters alone each year. Olive Ridley sea turtles are the most numerous sea turtle species, but their numbers have dropped 50% since 1960.

Kemp’s Ridley Sea Turtles (Lepidochelys kempii)

The smallest of all sea turtles, Kemp's Ridley turtles grow from 75 to 100 lbs. and 2 feet in length. They are the only species of sea turtle that nests primarily during the day. Their preferred food is crabs, but they also eat fish, jellies, shrimp, and a variety of mollusks. Kemp's Ridley turtles are found primarily in the Gulf of Mexico, but range as far north as Nova Scotia. Kemp's Ridley turtles are critically endangered. In the 1980s, the population was reduced to 200 nesting individuals. Due to turtle excluder devices being installed on commercial trawlers and beach protections, the numbers have grown to 7,000 to 9,000 nesters today.

Flatback Sea Turtles (Natator depressus)

The relatively flat back of these sea turtles is what gives them their name. Adults weigh 200 lbs. and grow to approximately 3 feet. They nest only in Australia which has classified them as vulnerable. Their favorite foods are sea cucumbers, jellies, soft corals, shrimp, crabs, molluscs, fish, and seaweed. Flatback sea turtles lay the fewest number of eggs per clutch; averaging only 50. Their hatchlings tend to be larger than those of other sea turtles, however, which may help in their survival.

Leatherback Sea Turtles (Dermochelys coriacea)

Leatherbacks are the largest of all the sea turtles, weighing in at as much as 2,000 lbs. and 8 feet in length. Average sizes are 600 to 800 lbs. and 5 to 6 feet. Another unique feature is that they have no shells, Leatherbacks get their name from their thick, leathery skin. The species is very old. Leatherback fossils show that they have been around for more than 150 million years. They eat nearly their own body weight daily of soft bodied invertebrates like jellyfish and tunicates. They can dive 4,000 feet below the surface of the ocean in search of prey. Leatherbacks have the widest distribution of all sea turtle species due to their tolerance for cold water. Leatherbacks are listed as vulnerable.

Artwork

In Japanese folklore, there is a story about Urashima Tarō, a fisherman who rescued a turtle. The turtle rewarded him by carrying him on his back to the Dragon Palace (Ryūgū-jō) beneath the sea where he was entertained by the princess Otohime. After what seemed to him like a few days, he returned to his village and discovered that a century had passed while he was gone. When he opened a forbidden jeweled box given to him by Otohime, he turned into an old man.

Suzuki Harunobu (1725 – 1770)

Harunobu was the first artist to apply recently developed full color technology to ukiyo-e prints (nishiki-e). Many artists did pictures illustrating Urashima Tarō's story, Haruobu, among them. He produced a parody of the story in the print below titled Young Woman Riding a Turtle (1765).

Japanese artists frequently painted turtles with wide, flowing tails like the one above. The "tail" is really a stream of algae growing on the turtle's back. That wasn't supposed to happen until the turtle was at least 500 years old. The longer the turtle lived, the longer the algae tail. If the age seems unrealistic, remember that this is folklore.

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