By Nirmal Shah
The torti soupap or terrapin (also known as mud turtle) is well known in Seychelles. Actually, biologists said that there were 3 species in Seychelles. One became extinct – the Seychelles terrapin Pelusios seychellensis is known from only 3 specimens collected in the 19th century and kept at the Natural History Museum in Vienna and the Zoological Museum in Hamburg. Despite recent searches for this species no further specimens have been found. “Consequently, it was assumed the species had been exterminated”, says Professor Uwe Fritz, director of the Museum of Zoology at the Senckenberg Natural History Collections in Dresden.
In a study published in the open source journal PLOS ONE, Heiko Stukas, Richard Gemel and Fritz have demonstrated that actually the species was never an endemic. Genetic analysis of the original specimen from the museum in Vienna proves that the terrapin was another species, Pelusios castaneus, widespread in West Africa.
The species Pelusios seychellensis has therefore never existed. Taxonomists had always been puzzled that the supposed Seychelles species looked so similar to the West African mud turtles.
Last year, another team led by Fritz published a study that showed that another terrapin species, Pelusios subniger, was not endemic to the Seychelles but had been introduced by man. So now 2 species of terrapins are off the list of Seychelles endemic animals.
A couple of biologists have been very keen in labelling terrapin and tortoise species as endemic. The French taxonomist Roger Bour resurrected Pelusios seychellles as an endemic species in 1983. In addition, Bour renamed the Seychelles population of Pelusios castanoides and Pelusios subniger as the new Seychelles subspecies Pelusios subniger intergularis and Pelusios subniger parietalis. However , based on the genetic evidence we now know that at least 2 species are not endemics, with the third probably the same as well.
The museum specimens of Pelusios seychelles are now believed to have been mislabelled. As for the other species they could have introduced from the African mainland as food sources. Perhaps traders or slavers brought them. Torti soupap was, in fact, eaten by Seychellois in the past.
Conservation programmes for these terrapins in the Seychelles will now have to be revised, and scarce conservation funding used for species that are clearly native and are in danger. I think that since the terrapins are protected by specific legislation even this needs to be reviewed.
Journal Source, PLOS ONE: http://goo.gl/SDhlq