Green Sea Turtles, Family Cheloniidae, pictures, stock photos, images

Green Sea Turtles, Chelonia mydas, and Black Sea Turtles, Chelonia mydas agassizi: Are they separate species?

Anyone interested in sea turtles who wonders how many species there are will eventually encounter the issue of whether to count black sea turtles as a separate species or not. Genetically, black sea turtles, Chelonia mydas agassizi; also spelled agassizii, are indistinguishable from green sea turtles, Chelonia mydas or Chelonia mydas mydas. The IUCN, which records accounts of populations of endangered species, does not include black sea turtles in their database, referencing only green sea turtles, Chelonia mydas. However, in general practice, many discussions of sea turtles will refer to the eastern Pacific populations of green sea turtles as black sea turtles. Because SeaPics.com clients and photographers sometimes use the term black sea turtles when identifying the eastern Pacific variety, SeaPics.com will continue to recognize the designation, despite their being no definitive evidence that it is a separate species or even a valid subspecies.

According to the Marine Turtle Newsletter article, "Chelonia Agassizii - Valid or Not?", the eastern Pacific populations of green sea turtles commonly referred to as black sea turtles differ physically from green sea turtles elsewhere. The adults of the eastern Pacific variety tend to be smaller than green sea turtle adults in other parts of the world. They are also darker in color, have a domed carapace, and they exhibit more pronounced caudal dimorphism. Finally, there are subtle differences in skull shape.

Genetically, black sea turtles from the Pacific coast of Mexico and the Galapagos Islands have proven to be closely related. If this geographically compact group were distinguishable from all other green sea turtles around the world, then separate species or subspecies status could be argued. However, genetic similarity has been found between the Mexico/Galapagos population and populations of green sea turtles in Hawaii, Oman, Ascension Island, and the Atlantic coast of Africa as well. Thus taxonomists are reluctant to classify the eastern Pacific variety as a separate species or subspecies.

There is also dispute over the spelling of the Latin name "agassizi." The Marine Turtle Newsletter uses the spelling "agassizii." Wikipedia.org calls "agassizi" a "commonly-cited misspelling." However, Marinebio.org uses "agassizi." The spelling "agassizi" is used most commonly among the photographers submitting black sea turtle images to SeaPics.com, and a search with that spelling will yield the best search results.

Green and Black Sea Turtle information assembled from on-line sources by Kevin Miller on Nov. 30, 2007 for Seapics.com.

• Green and Black Sea Turtle information assembled from published and on-line sources by Kevin Miller on Nov. 30, 2007 for SeaPics.com.

For an excellent article on the green sea turtle/black sea turtle issue, see:

Parham, J. F. and G. R. Zug, 1996, Chelonia Agassizii - Valid or Not? Marine Turtle Newletter 72:2-5. http://www.seaturtle.org/mtn/archives/mtn72/mtn72p2b.shtml

Also see Wikipedia.org: http://en.wikipedia.org/wiki/Black_sea_turtle