Thursday, December 6, 2018

[Herpetology • 2018] Siren reticulata • Description of An Extant Salamander (Caudata: Sirenidae) from the Gulf Coastal Plain of North America: The Reticulated Siren

Siren reticulata
Graham, Kline, Steen & Kelehear, 2018

 photos: Pierson Hill

The salamander family Sirenidae is represented by four extant species that are restricted to North America. Sirens are abundant throughout the southern United States and are among the world’s largest amphibians, yet the biology, ecology, and phylogeography of this group is poorly-known. In this study we use morphological and genetic evidence to describe a previously unrecognized species from southern Alabama and the Florida panhandle. We name this species the Reticulated Siren, Siren reticulata. Future studies will enable more precise phylogenetic information about S. reticulata and will almost surely reveal additional undescribed species within the family.


Fig 1. (A) Siren reticulata paratype specimen captured in Okaloosa County, Florida.
(B) Location of Siren reticulata captured in 2009 by D. Steen and M. Baragona.
(C) The type locality of Siren reticulata, Walton County, Florida.

Siren reticulata, sp. nov.
Reticulated Siren

Etymology: This animal has been colloquially referred to as the Leopard Eel. However, given that the species is neither a leopard nor an eel, we selected Reticulated Siren as a more appropriate formal common name. The specific name, reticulata, is a reference to the reticulated pattern typical of all specimens we examined.

Diagnosis: Like all Sirenids, S. reticulata has an elongate, eel-like body shape, two forelimbs, no eyelids, a lateral line, enlarged external gill fimbriae associated with gill slits, and a horny beak in place of the premaxillary teeth typical of other salamanders. There are only two known genera in the family Sirenidae: Pseudobranchus and Siren. The genus Pseudobranchus (dwarf sirens) includes two species (restricted to Florida, southern Georgia, and South Carolina) and is diagnosed by the presence of only one gill slit and three digits on each limb. The species we describe herein is assigned to the genus Siren based upon its large size, presence of four digits on the forelimbs, and three permanent gill fimbriae with three associated external gill slits. The dorsum of S. reticulata is olive-grey with lighter yellow-green flanks. It has an obvious and striking dark reticulate spotted pattern beginning at the gill arches and continuing to the tail (Fig 1A). Some specimens show a decided boundary where the spotting pattern ends along the flanks, while others show continuous spotting along the flanks that continue onto the ventral surface. The venter is a lighter olive green-yellowish color and in some specimens, it is also sparsely covered with irregular spots.

Fig 3. Bayesian inference consensus tree for sirens and Pseudobranchus axanthus outgroup using five gene sequences: CytB, COI, ND5, 12S and 16S. The tree was generated in MrBayes and run for 5 million generations using a partition scheme determined using Partition Finder 2. The top number is probability generated in MrBayes. The bottom number is the maximum likelihood % from 1,000 bootstraps generated in RAxML. Accession numbers are in Table 2.

Life history and ecology: Due to the difficulty in acquiring specimens and this species’ apparently limited distribution, little is known of S. reticulata life history and ecology. Clearly, research on this topic is an urgent need. Most of what we know of this species is consistent with the general habits of other described species of sirens. The holotype contains hundreds of tiny developing follicles, suggesting that females have high fecundity, a feature also exhibited by S. lacertina. Mating, fertilization mode (e.g., external or internal), nests, and eggs are undescribed. However, we emphasize that this information is scarce even for long-recognized S. lacertina or S. intermedia.

Sean P. Graham, Richard Kline, David A. Steen and Crystal Kelehear. 2018. Description of An Extant Salamander from the Gulf Coastal Plain of North America: The Reticulated Siren, Siren reticulata PLoS ONE. 13(12): e0207460.  DOI: 10.1371/journal.pone.0207460  
New species of giant salamander discovered in Florida via @NatGeo


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