Brasilotyphlus guarantanus Maciel, Mott & Hoogmoed, 2009
|Species Description: Maciel AO, Mott T, Hoogmoed MS 2009 A second species of Brasilotyphlus (Amphibia: Gymnophiona: Caeciliidae) from Brazilian Amazonia. Zootaxa 2226:19-27.|
Brailotyphlus guarantanus exhibits dentition in three series and lacks splenials (inner mandibular teeth) that other caecilian families display. Both monocuspid and bicuspid series of teeth are present within the mouth of B. guarantanus. The premaxillary and maxillary teeth are a series of similarly sized monocuspid teeth, whereas the prevomerine and palatine series are composed of roughly equally sized bicuspid teeth that are smaller than the premaxillay-maxillary teeth. The maxillary teeth may extend to or posteriorly beyond the posterior border of the choanae. The choanae are positioned relatively far apart from one another. The dentary teeth are also monocuspid and are around the same size as the premaxillary-maxillary teeth. Collected specimens were observed to have a maximum of 25 monocuspid premaxillary-maxillary teeth, 13 bicuspid prevomerine teeth, 14 bicuspid palatine teeth, and 21 monocuspid dentary teeth. A very distinctive gap, or diastema, is present between the prevomerine and palatine series, the former creating a short semi-circle within the dentition of the skull. The anterior end of the tongue is attached anteriorly to the gums located behind the dentary teeth (Maciel et al. 2009, Maciel and Hoogmoed 2011).
The body is subcylindrical and vaguely wider than it is deep. The first nuchal collar is well defined both ventrally and dorsally, whereas the second nuchal collar is partially fused with the first body annulus on the underside of the organism. Each of these collars has a single noticeable dorsal transverse groove, the second nuchal collar having a more distinct transverse groove than the first. The third nuchal groove is incomplete ventrally. This species exhibits 151 - 170 primary annular grooves that completely ring the body, except for at the most three anterior annular grooves that are intersected ventrally, along with the grooves posterior to the vent. Primary folds are incomplete, not meeting ventrally. Dermal scales can start around primary annular groove 145, but generally start at primary annuli 154 and 160. The grooves have a maximum of two rows of dermal scales per fold. There are no subdermal scales. Most specimens completely lack secondary annular grooves, however three specimens were found with two incomplete secondary annuli. The vent is transversely positioned on the organism and in some specimens, irregularly shaped. Rarely, in some specimens there are two paired anal papillae located on either side of its midline about the anterior of the vent disc. Ten to 13 anal denticulations are present on most specimens collected, each specimen having generally the same number on the anterior and posterior edges of the vent (the holotype having five anterior and six posterior anal denticulations respectively). A small terminal shield is present in this species, with a weak vertical keel being present on the terminal shields of most specimens. Generally, there are no annuli beyond the vent (Maciel et al. 2009, Maciel and Hoogmoed 2011).
The main difference between B. guarantanus and the very similar species, B. braziliensis, is that B. guarantanus has more primary annuli (151 to 170 versus 142 to 147) and fewer secondary annuli (0 to 2 versus 23 to 36) than the latter. Furthermore, the maxillary teeth in B. guarantanus are found to reach the level of the posterior edge of the choanae or extend beyond them posteriorly, whereas the maxillary teeth in B. braziliensis do not reach the level of the choanae. While both species have dermal scales, B. guarantanus only has dermal scales located near the terminal end of the body (in the holotype, starting from the 145th annulus) whereas B. braziliensis has dermal scales that start near the 25th annulus. Additionally, while B. braziliensis has four to seven secondary folds along its primary annuli, B. guarantanus rarely have any secondary folds, however, a three specimens in the type series have two incomplete secondary folds. Lastly, B. guarantanus may possibly be more slender than B. braziliensis as a whole, however the number of B. braziliensis specimens available is very small, making it hard to observe meaningful differences between the two similar species (Maciel et al. 2009).
A significant diastema between the prevomerine and palatine series is the single known difference between the genus Brasilotyphlus and the genus Microcaecilia. Due to this being the only difference known between both genera, Brasilotyphylus and Microcaecilia may be considered synonymous, although further research is needed to definitively class these two similar groups together (Wilkinson and O’Connor et al. 2013).
In life, B. guarantanus has an overall lavender background color. This species exhibits two different body coloration patterns. One color variation is dark lavender starting at the terminal end of the body, becoming gradually lighter as you move toward the direction of the head. The other color variation is a uniform pale lavender across the entirety of the organism’s body. The ventral and lateral areas of the body are slightly more pale than the length of the dorsal side of the body. Additionally, the area around the vent, the mandible and parts of the head are less pigmented than the rest of the body. Some specimens also have a very thin, darkened longitudinal mid-ventral stripe along the posterior half of the body that faintly contrasts with the background color of the remainder of the body. Preserved specimens take on an overall brownish or grayish coloration (Maciel et al. 2009, Maciel and Hoogmoed 2011).
External sexual dimorphism is only apparent for head width and head length, in which males have both slightly wider and longer heads than females. Other variation within B. guarantanus is in respect to annular count, the annulus where dermal scales begin, body width (taken at the mid-body), the presence or absence of a dorsal transverse fold on the first nuchal collar, the presence or absence of a terminal vertical keel, and coloration pattern (Maciel et al. 2009, Maciel and Hoogmoed 2011).
Distribution and Habitat
Life History, Abundance, Activity, and Special Behaviors
This species is most likely a dedicated burrowing species since it either lacks eyes or has small eyes covered underneath bone. In general, the genus Brasilotyphlus is made up of terrestrial species that either dwell in litter or burrow in moist soils (Wake 1992).
Trends and Threats
Like most amphibians, B. guarantanus is threatened primarily by habitat loss. Areas of caecilian microhabitat in Mato Grosso state have been flooded due to human dam activity and effected caecilian populations are most likely locally extinct (Faria and Mott 2011). In broader terms, habitat loss through deforestation, agriculture, and developmental projects are the main threats affecting populations of this species in Brazil (Silvano and Segalla 2005). Since this species is found in tropical forests, it is susceptible to the threat of deforestation.
Possible reasons for amphibian decline
General habitat alteration and loss
At the time of its description, B. guarantanus was only one of two species in the Brasilotyphlus genus, the other being B. braziliensis. The genus Brasilotyphlus was established in 1968 to accommodate Gymnophis braziliensis, which had several unique morphological characters that differentiated it from the Gymnophis genus. Thus, Brasilotyphlus braziliensis was the first species of its genus and B. guarantanus was the second species described in the genus (Maciel et al. 2009).
Limited data is present on the biology and phylogeny of caecilians due to a multitude of factors such as difficulty of studying fossorial organisms in the field and the fact that many of these organisms are found in low-density populations within very limited ranges (Wake 1992).
Many Brasilotyphlus specimens have been misclassified as Microcaecilia (Maciel et al. 2009), however, character analysis shows many similarities between Brasilotyphlus and the unrelated African genus, Boulengerula, which allows Brasilotyphlus to be distinguished from Microcaecilia (Wilkinson and O’Connor et al. 2013).
The species epithet “guarantanus” refers to the locality in which the species was discovered, Guarantã do Norte, state of Mato Grosso, Brazil (Maciel et al. 2009).
Faria, H. A. B., Mott, T. (2011). ''Geographic distribution of caecilians (Gymnophiona, Amphibia) in the state of Mato Grosso, Brazil with a new state record for Caecilia mertensi Taylor 1973.'' Herpetology Notes, 4, 53-56.
Maciel, A. O., Hoogmoed, M. S. (2011). ''Taxonomy and distribution of caecilian amphibians (Gymnophiona) of Brazilian Amazonia, with a key to their identification.'' Zootaxa, 2984, 1-53.
Maciel, A. O., Mott, T., Hoogmoed, M. S. (2009). ''A second species of Brasilotyphlus (Amphibia: Gymnophiona: Caeciliidae) from Brazilian Amazonia.'' Zootaxa, 2226, 19-27.
Silvano D. L., Segalla, M. V. (2005). ''Conservation of Brazilian Amphibians.'' Conservation Biology, 19, 653-658.
Wake, M.H. (1992). ''Reproduction in caecilians.'' Reproductive Biology of South American Vertebrates. Hamlett, W. C. , eds., Springer-Verlag, New York City, New York, 112-114.
Wilkinson, M., O’Connor, A., Nussbaum, R. A. (2013). ''Taxonomic status of the neotropical caecilian genera Brasilotyphlus taylor, 1968, Microcaecilia taylor, 1968 and Parvicaecilia taylor, 1968 (Amphibia: Gymnophiona: Siphonopidae).'' Occasional Papers of the Museum of Zoology University of Michigan, (744), 1-12.
Wilkinson, M., Sherratt, E., Starace, F., Gower, D. J. (2013). ''A New Species of Skin-Feeding Caecilian and the First Report of Reproductive Mode in Microcaecilia (Amphibia: Gymnophiona: Siphonopidae).'' PLoS ONE, 8(3), 1-11.
Originally submitted by: Hannah Horowitz, Mayra Mariscal-Velasquez, Jessica Kwok (first posted 2018-05-03)
Edited by: Ann T. Chang (2018-05-11)
Species Account Citation: AmphibiaWeb 2018 Brasilotyphlus guarantanus <https://amphibiaweb.org/species/7402> University of California, Berkeley, CA, USA. Accessed Oct 4, 2022.
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Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 4 Oct 2022.
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