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Physiology

Beneath the Waters: A Giant Discovery

Paper: Graham SP, Kline R, Steen DA, Kelehear C (2018). Description of an extant salamander from the Gulf Coastal Plain of North America: The Reticulated Siren, Siren reticulata. PLoS ONE 13 (12): e0207460. https://doi.org/10.1371/journal. pone.0207460

The Reticulated Siren. Notice the net-like pattern over its body which Graham et al. (2018) named the species after. Click for larger photo. Source: Graham et al. (2018)

Beneath the lakes, marshes, and swamps in southern Alabama and the Florida Panhandle lurks an unknown creature: a large amphibian rumored to be as long as a human’s arm! Luckily, this critter is not North America’s version of the Loch Ness monster, but rather a previously undescribed salamander. Scientists recently identified the Reticulated Siren as a new type of giant salamander, measuring about 61 cm in length and weighing 221 g. The salamander isn’t quite the stature for the makings of a new amphibian-based monster, but certainly an amazing discovery in the scientific world.

The axolotl, the ancestors of modern day salamanders, have very prominent gill fimbriae. Notice the fringe like protrusions on each side of its head! Source: Flickr, AJC1.

The Reticulated Siren, Siren reticulata, is a member of the salamander family Sirenidae, which consists of completely aquatic, eel-like species with external gill fimbriae (Latin for “fringe”, fimbriae are filaments which line external gill slits) and front limbs. There are two genera of Sirenidae categorized by the number of toes on their front limbs and number of gill slits: Pseudobranchus (three toes and one gill slit) and Siren (four toes and three gill slits). While scientists have recognized two species within the Siren genus (the Greater Siren, one of the largest salamanders in the world, and the Lesser Siren), not much is known about them otherwise

Beginning as early as 1970, researchers have collected and documented the Reticulated Siren from Alabama and Florida without explicitly classifying it as a distinct and new species of salamander. Nine years after its first observation, turtle trappers caught two Reticulated Sirens in Alabama. Much later, in 2009, David Steen (one of the authors in the current study) collected his first Reticulated Siren in Alabama as well. The most recent encounter was in 2014, when three Reticulated Sirens were collected in Florida.

Genetic tree for the genera Siren and Pseudobranchus. Click for larger photo. Source: Graham et al. (2018)

Through genetic, such as DNA extraction and comparison, and morphological, such as documenting physical measurements and characteristics, analyses, Graham et al. (2018) found that the Reticulated Siren is indeed an undescribed and unrecognized salamander in the family Sirenidae and genus Siren. Previously, the animal had been referred to as a Leopard Eel; however, Graham et al. (2018) deemed the name ill-suited to the species since it is neither a leopard nor an eel. Rather, focusing on its unique reticulated (net-like) pattern, characteristic of every specimen they had collected, the scientists decided on Reticulated Siren (Siren reticulata). Similar to other members of the Sirenidae family, the Reticulated Siren has a long, eel-like body with front limbs, a lateral line, and external gill fimbriae. Because of its large size, the presence of four toes on its front limbs, and three gill slits, Graham et al. (2018) classify the new salamander within the Siren genus. These newly discovered salamanders have only been found in the shallow, freshwater marshes between Florida and Alabama, a beaver-impounded stream and swamp in Okaloosa County, Florida, and finally the Fish River stream and bottomland forest in Baldwin County, Alabama.

Records of Reticulated Siren spottings and collection. Click for larger photo. Source: Graham et al. (2018).

Scientists do not know much about this new, giant species of salamander. Graham et al. (2018) plead for further research exploring not only the exciting species, but also other members of the Sirenidae family and Siren genus. The researchers posit their study insinuates that there are other species of Siren that exist undescribed or unidentified that future research can uncover.  Additionally, since the Reticulated Siren has just been identified as a unique species, Graham et al. (2018) explain that scientists must work to uncover more information on its morphology, genealogy, ecology, and even conservation. Policy cannot protect the species if science doesn’t first fully study them to ultimately explain their population status and potential threats they face.

The Reticulated Siren is one of the largest species of amphibians still existing today, the first species of its family identified since 1944, and one of the largest species in its family to be described in the United States in over 100 years. Steen tells National Geographic Reporter, Jason Bittel, that the Reticulated Siren was “’…basically this mythical beast’”. With Graham et al.’s (2018) new study describing and identifying the species, the Reticulated Siren is certainly no longer mythical, but remains an awe-inspiring and exciting discovery to celebrate and explore further in the future. What other giant salamanders lie hidden beneath North American waters? What new information can the Reticulated Siren tell us that we previously did not know? This new critter could be the catalyst for some nerdy and necessary intrigue into giant, North American salamanders.

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