Pacific green turtles, or black turtles

by Volunteer Coordinator STPS · June 24, 2021

*An Eastern Pacific green sea turtle may be different in coloration, carapace shape, and overall size from other green sea turtle populations.*
*Photo courtesy of U.S. Fish and Wildlife Service*

By Brianna Forte

The green sea turtle is arguably one of the most iconic sea turtle species, with its light green skin and speckled brown shell popping up as soon as you do a generic Google search for “sea turtle.” But did you know that just like humans, green sea turtles come in various shapes, sizes, and colors?

The Chelonia mydas, commonly known as the green sea turtle, is mainly found in tropical and subtropical waters and migrates long distances between feeding grounds and where it hatched.

In a study conducted by Rocío Álvarez-Varas and others in 2019 titled “Identifying genetic lineages through shape: An example in a cosmopolitan marine turtle species using geometric morphometrics,” it was found that the carapace of green sea turtles is distinct among the three main regions where they live. The green sea turtles included in the study were from the Atlantic, Eastern Pacific, and Western Pacific genetic lineages. The study found that green sea turtles from each region had a specific shell shape unique to that population.

The Eastern Pacific population mentioned in the study is known locally in Hawaii and Mexico as the Pacific green turtle and black turtle respectively. In some cases, the black sea turtle (Chelonia mydas agassizii) has a shell so dark it looks black at first glance.

According to Sea Turtle Camp, other differences between the black and green sea turtle include the black sea turtle being smaller overall, the black sea turtle having a smaller head, and the black sea turtle having a more teardrop-shaped shell compared to the green sea turtle’s oval-shaped shell. Despite these physical differences, black and green sea turtles maintain similar behaviors, such as having similar diets which include green algae and seagrasses.

Although there are distinct differences between the Pacific green turtle and the green sea turtle, it still gets murky as to whether the Pacific green sea turtle is simply a subspecies of the green sea turtle or a completely separate species. Based on DNA analysis conducted by Stephen Karl and Brian Bowen in 2001, genetically the Pacific green turtle is not different from the green sea turtle. Meanwhile, in recovery plans proposed by the National Marine Fisheries Service and the U.S. Fish and Wildlife Services in 1998, the Pacific green sea turtle was addressed as its own separate species. In a blogpost by Jacques-Olivier Laloë, a PhD student at Deakin University in Australia, it was stated that scientists use both the species and subspecies scientific names when referring to the Pacific green turtle.

So, although green sea turtles come in all different shapes, sizes, and colors depending on their region, it is still not agreed upon whether the Pacific green turtle is a subspecies or its own species. Regardless of the taxonomic designation of the Pacific green turtle, they are still facing the same threats that green sea turtles and all other species of sea turtles are facing. Pollution, habitat destruction, vessel strikes, and more are all responsible for endangering the Pacific green sea turtle. Regardless of whether there are seven or eight total sea turtle species, let’s learn about our scaly friends and do what we can to protect them.

Sources:

https://www.worldwildlife.org/species/green-turtle

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6779254/