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When you are looking at a sea turtle, you are usually not just looking at a single organism. Sea turtles never swim alone. Many creatures live directly on or even inside a sea turtle. As for all animals, this so-called symbiotic relationship does not have to be negative of the turtle.

Mutualism

In a mutualistic relationship both organisms benefit from living closely together in a symbiotic relationship. We can for example observe this on cleaning stations. Different fish nibble on old skin and small creatures such as parasites living on the sea turtle. The fish gets dinner, the turtle a free surface clean!

Commensalism

In this type of symbiotic relationship, one organism benefits, the other is neither harmed nor helped. The most obvious hitchhikers catching a ride on a turtles shell are so called remoras. These fish use bigger sea creatures such as sharks, mantas or turtles as a MoneySlot taxi - even if occasionally a rather slow one.

They rest on the turtles shell, hide under them and just occasionally snatch a bit of discarded food from the turtle. We can sometimes see the turtles getting impatient with a remora, trying to shove it away with it's flippers.

Last year, we also spotted a rather unexpected hitchhiker on one of our named green turtles called GöWi - a sea cucumber! It most likely walked onto the turtles shell when the turtle had a nap earlier. It had to cling on quite tightly when the little turtle sped up and down the reef!

The same is true for this marine snail sitting on another juvenile green turtle we know very well called Beag.

Parasitism

Parasites are living in or on another organism, the so-called host. The parasite benefits, while the host is harmed in the process.

Most obvious organisms living on the outside of the turtle, so-called ectoparasites, are barnacles. These are not parasites per se, but become parasitic and harmful in excessive numbers. There are different types of barnacles known from sea turtles, the glueing and embedding types.

The typical barnacle uses a special substance it secretes, the 'cement', to glue itself onto a surface of the host. Glueing barnacles belonging to the genus Chelonibia are found on turtles, as their name already indicates (Chelonia = turtle).

Embedding barnacles infiltrate the skin or shell of the host turtle, thus causing more damage to the tissue. These barnacle wounds can also be an opening for bacteria to enter the turtles body, thus causing real illness.

Green turtle with embedded barnacles, Maldives
©Stephanie Köhnk

Excessive barnacle cover can be a sign of general bad health of a turtle. Usually sea turtles are debilitated first, and then become covered in an extensive amount of other organisms, such as barnacles and algae.

Luckily turtles are very resilient and can sometimes recover from such infestations.

Green turtle with algae, Oman ©Zoe Cox

Through our photo ID program, we have been able to document the development of a hawksbill in Noonu Atoll, which recovered from very high barnacle cover and seems to be doing very well again!

Hawksbill turtle Orimas with high barnacle cover
©Karin Nistler, Prodivers

What the Hitchhikers Can Tell Us

As turtles are endangered of becoming extinct, it is very important for us to know how healthy our present sea turtle populations are. Healthier populations are more likely to withstand further stress such as man-made pollution or climate change. Our photo ID program helps us monitor the presence of parasites or severely weakened turtles in certain areas.

Furthermore, the creatures living on a sea turtle might actually be able to tell us more about the origins of the turtle itself. Just like their host, the parasite also has a specific genetic code. In the future, we might be able to infer the source population of the olive ridley turtles we find entangled in ghost nets in the Maldives, without having to invasively take tissue samples from the turtle, but just by looking at the organisms living on the turtle.

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﻿Sea Turtle Hitchhikers - The Symbiotic Relationships of Sea Turtles | Olive Ridley Project

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When you are looking at a sea turtle, you are usually not just looking at a single organism. Sea turtles never swim alone. Many creatures live directly on or even inside a sea turtle. As for all animals, this so-called symbiotic relationship does not have to be negative of the turtle.

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Abstract

In nature, green turtles (Chelonia mydas) can exhibit nocturnal activity in addition to their typically diurnal activity cycle. We examined whether nocturnal activity in captive and free-living green turtles altered daily plasma profiles of melatonin (MEL) and corticosterone (CORT). In captivity, diurnally active green turtles expressed distinct diel cycles in MEL and CORT; a nocturnal rise was observed in MEL and a diurnal rise was observed in CORT. However, when induced to perform both low- and high-intensity nocturnal activity, captive green turtles exhibited a significant decrease in MEL, compared to inactive controls. In contrast, plasma CORT increased significantly with nocturnal activity, and further, the relative increase in CORT was correlated with the intensity of the nocturnal behavior. In free-living green turtles that performed nocturnal activity including: nesting, mate searching, and feeding/swimming behaviors, plasma profiles in MEL and CORT exhibited relatively little, or no, daily fluctuation. Our findings demonstrate that nocturnal activity in green turtles is often associated with MEL and CORT profiles that resemble those measured during the day. We speculate that these conspicuous changes in MEL and CORT during nocturnal activity could either support or promote behaviors that enable acquisition of transient resources important to the survival and reproductive success of green turtles.

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national center for biotechnology information

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Nocturnal activity in the green sea turtle alters daily profiles of melatonin and corticosterone - PubMed

# data[].attributes.attachment_link.description
In nature, green turtles (Chelonia mydas) can exhibit nocturnal activity in addition to their typically diurnal activity cycle. We examined whether nocturnal activity in captive and free-living green turtles altered daily plasma profiles of melatonin (MEL) and corticosterone (CORT). In captivity, di ...

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Mating green turtles, Maldives

Turtle Courtship and Mating

Sea turtle mating is a rare and amazing sight to observe in the wild. Most sea turtles species are solitary creatures and only come together during mating season. Mating can actually be a dangerous activity for sea turtles! The male holds onto the female and she has to support the weight of both of them whilst at the same time regularly surface for air.

Courtship

When sea turtles reach maturity and are ready to reproduce, they migrate from their feeding grounds to the beach where they were born. Female turtles swim back every 2-3 years, while male turtles migrate annually. Green sea turtles reach maturity at about 20-25 years of age, depending on a number of factors such as food availability, for example.
This pair of green sea turtles was observed mating at the Six Senses Laamu house reef on the morning of the 10th of June 2018. Video by Saha Haslim
As part of his courtship behaviour, a male turtle will approach a female sea turtle and gently bite her neck and flippers . If she does not try to get away, the male climbs onto the female turtle's back and holds on to her carapace with the long, sharp claws of his front flippers. The way he hooks on to the edge of the female's shell often results in a scratched shell and bleeding wounds in the soft parts of her body. Copulation can take place on the surface or under water.

Mating

Both male and females' reproductive organs are located at the base of their tails in their cloaca - a combined intestinal, urinary, and reproductive organ. Males have a very long tail while females have a short tail. The male's penis is located in his cloaca. He reaches his tail underneath the posterior end of the female's shell to inseminate her cloaca.

Mating can take several hours. Afterwards, the male will try to hang on to his partner's shell to prevent other males from mating with her. Several males may compete for one female at the same time, aggressively biting his tail and flippers to get him to let go of her.

Mating is not easy for a female sea turtle. She must support both her own xcasinobonuses and the male's weight and regularly swim to the surface for them to breathe. This is even more difficult when several males compete for her and she may be at risk of being drowned.

After the male and female separate, they mate again with other sea turtles. A female will mate with several males and store the sperm for several months until she is able to fertilize all of her eggs and start nesting.

Nesting

A female sea turtle can lay several clutches of eggs in one season. The eggs are all fertilized by a variety of males, which contributes to the genetic diversity of the population. The females are very vulnerable when they come on land. They are not well adapted to for life out of water and therefore move very slowly.

As she starts laying her eggs, she goes into a trance-like state. Once finished, she covers the egg chamber with sand. On average, an egg chamber can contain anywhere between 70 and 125 eggs. She then crawls back into the ocean and leaves the hatchlings to fend for themselves.

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Sea turtle mating is a rare and amazing sight to observe in the wild. Most sea turtles species are solitary creatures and only come together during mating season. Mating can actually be a dangerous activity for sea turtles!

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Diet

As they age their diet significantly changes. When less than 200 mm in length they mainly eat worms, small crustaceans, aquatic insects, sea grass and algae. When green sea turtles grow larger than 200 mm in length, they generally eat only sea grass and algae. When adult, green sea turtles become strictly herbivores. Their jaws have fine serrated edges that help in eating vegetation.

Nesting

Green sea turtles nest at intervals of 2 or more years. They're known to nest between 2 to 5 times per season and lay an average of 115 eggs in each nest. Their eggs incubate for about 60 days.

When they hatch an enduring struggle starts. The young hatchlings make for the open water, running the gauntlet of predators waiting on the beach, in the air and in the water. Many will die before they even reach the ocean.

Of those that make it this far, possibly only about 1 in 10,000 will grow to be adults, the surviving females eventually returning in several years to lay their own eggs.

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Diet As they age their diet significantly changes. When less than 200 mm in length they mainly eat worms, small crustaceans, aquatic insects, sea grass and algae. When green sea turtles grow larger than 200 mm in length, they generally eat only sea grass and algae. When adult, green sea turtles become strictly herbivores.

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One animal that a green sea turtle has a symbiotic relationship with is a remora: a kind of fish. It is a commensalistic relationship where the fish benefits but does not hurt the turtle. Although, sometimes the turtle gets fed up with the fish and tries to push it away.

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While green sea turtles are mostly active during the day, they are sometimes seen active during the night as well.

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Green sea turtles are solitary animals, meaning they spend their lives alone. They only come together to mate.

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Sea turtle eggs are fertilized by many different males, increasing genetic diversity. However, only about 1 in 1000 hatchlings make it to adulthood.

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Green sea turtles are a special case in the food web/chain, since they change levels in the chain over time. When they are hatchlings, they are secondary consumers, but as they mature, they become primary consumers.

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Green sea turtles sexually mature at 20-25 years of age.
The males will fight for a female, firmly mounting her. The female will have to support the weight of the both of them, constantly resurfacing for air.

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Once they mature, green sea turtles become strict herbivores. They eat algae, sea grass, and other plant matter.

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As hatchlings, green sea turtles eat worms, insects, small crustaceans, sea grass, and algae.

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Green Sea Turtles reside mostly in nearshore sea grass. They will rarely be seen in open ocean.

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A lovely photo of one of our turtle friends!

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Mass (Adult): ~350lbs
Size (Adult): 5ft(1.5m)
Size (Hatchling): 2in(5cm)
Lifespan: 60-70yrs
*Each turtle has unique face markings, much like humans have unique fingerprints!

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Status: Endangered
Binomial Nomenclature: Chleonia mydas
Phylum: Chordata
Common Name:
Green Sea Turtle