Description
Sphaenorhynchus mirim is a relatively small frog with a snout-vent range of 15.7 – 18.2 mm for males. Only males were collected at the time of the species description. The small head is shorter than wide. The snout is slightly acute and rounded in profile and truncate in dorsal view. The forward directed, large nostrils are located at the tip of the snout and set widely apart from each other, approximately the same length as the eyelid width. However, the internarial distance is smaller than the distance between the nostrils and the eyes, and the length of the eye diameter. The large eyes protrude and are slightly longer in length than the distance between the eyes and the nostrils. The eyes are also set widely apart. The evident canthus rostralis is rounded. The convex loreal region is slightly oblique. The tympanum is concealed. The mouth opens ventrally and the vomerine teeth are absent. The singular vocal sac is well developed, located subgularly, and extends into the chest without lateral longitudinal folds (Caramaschi et al. 2009).

The arms are robust with the forearms being somewhat hypertrophied and lacking any dermal folds. The webbed hands are large and the fingers are robust with a relative length of I < II < IV < III. The finger webbing formula is I 2 – 2 II 1 – 2 III 2 – 1 IV. The unwebbed parts of the fingers are fringed. The tips of the fingers have well developed round adhesive discs, with the first disc being somewhat smaller than the others. The subarticular tubercles are large and round. There are no supranumerary tubercles. The outer metacarpal tubercle is large and round and there is no inner metacarpal tubercle. A finely granulose nuptial pad can be found on the base of the first finger (Caramaschi et al. 2009).

The legs are also robust. The thigh is slightly longer than the tibia. The two parts combined are approximately 85% of the snout-vent length. The foot is longer the lengths of either the thigh or tibia. The foot has a weak dermal fold located along the interior surface of the tarsus. The robust toes have a relative length of I < II < III < V < IV and a webbing formula of I 1 – 2^- II 1 – 2 III 1 – 2⁺ IV 2 – 1 V. The toes end in well developed, round, adhesive discs that are smaller than the finger discs. The subarticular tubercles are large and round, and like the fingers, there are no supranumerary tubercles. The inner metatarsal tubercle is large and oval while there is no outer metatarsal tubercle (Caramaschi et al. 2009).

The body is robust and oval shaped. The dorsum and vocal sac are smooth. The ventrum and seat pad portion of the thigh are granulose. There is a small vestige of the tail present in adults. There is no anal flap (Caramaschi et al. 2009).

Sphaenorhynchus mirim is typically smaller than other species of the genus, which have snout-vent lengths between 20.5 - 41.0 mm, except for S. carneus and S. pauloalvini, which have snout-vent lengths between 14.2 - 20.3 mm. Additionally, the lack of brown lines or white stripes on the dorsolateral region and of distinctive white spots under the eye distinguish it from other species except S. carneus, S. dorisae, and S. planicola. It can be differentiated from S. carneus by the focal species having a more truncated snout in the dorsal view, less webbing on the hands and feet, and by its geographic range. From S. dorisae, and S. planicola, the focal species can be differentiated by its lack of white dermal folds on the arms and legs, the lack of a white anal flap, and the lack of a triangular appendage on the heel. From S. pauloalvini the focal species can be distinguished by having a rounded snout in the profile and concealed tympanum. (Caramaschi et al. 2009).

For live specimens the species is uniformly bright green on the dorsum and limbs. There are white dots scatted on dorsum and limbs that do not form any distinct pattern. The vocal sac and belly are whitish green. The fingers and toes are yellowish green. The silvery golden irises have a few black vermiculations (Caramaschi et al. 2009).

No females were described in the original description. The male specimens were congruent in regards to color and morphology. Males also possessed both vocal sacs, indicating sexual maturity, and small remnants of tails (Caramaschi et al. 2009).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Sphaenorhynchus mirim is found in Northern Extreme Microregion in the vicinity of Lagoa Nova, Fazenda Gemada, Municipality of Mucurici, State of Espírito Santo, Brazil. The species lives in a tropical climate at an elevation of about 250 m above sea level (Caramaschi et al. 2009).

The region that S. mirim is found was originally covered in rainforest but was converted to agriculture in the early 20th century. Currently, the rainfall index is lower and the region is dedicated to agriculture (Caramaschi et al. 2009).

Life History, Abundance, Activity, and Special Behaviors
Sphaenorhynchus mirim is terrestrial and found in freshwater (IUCN 2011). The original specimens were found at night in a large, shallow pond covered with emergent and floating vegetation located in an a cattle field. The pond had a high concentration of humic acid (Caramaschi et al. 2009).

Sphaenorhynchus mirim retains the remnants of a tail after sexual maturity (Caramaschi et al. 2009).

There is evidence of early sexual maturity in S. mirim. In related S. bromelicola, tadpoles near metamorphosis had well developed reproductive systems, which was believed to allow the species to breed as soon as metamorphosis has occurred. Because the tadpoles and juveniles had otherwise normal development, it is unlikely that this early sexually maturity was caused exclusively by environmental pollutants. Given the early sexual maturity in S. mirim, S. botocudo, S. bromelicola, and S. palustris but not in other species in the genus, this phenomenon requires further investigation as to its cause and purpose (Caramaschi et al. 2009).

Dendropsophus elegans, Dendropsophus minutus, and Scinax alter can be found sympatrically with S. mirim (Caramaschi et al. 2009).

Trends and Threats
The area where this species is found was previously covered by rainforest but is now converted to extensive agriculture, including coffee, papaya, manioc, and cattle farming. The pond in which they were found is located in a cattle field and the pond is black because of dissolved humic acid in it. However, this species seems to be able to tolerate the modified habitat, making it unclear if habitat degradation is affecting the species' survival (Caramaschi et al. 2009). The current population trend is unknown (IUCN 2011).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing
Local pesticides, fertilizers, and pollutants
Long-distance pesticides, toxins, and pollutants

Comments
The species authority is: Caramaschi, U., Almeida A.P., Gasparini J.L. (2009). “Description of two new species of Sphaenorhynchus (Anura, Hylidae) from the State of Espírito Santo, Southeastern Brazil.” Zootaxa 2115: 34–46.

At the time of the species description, only fourteen known species were in the genus, Sphaenorhynchus (Caramaschi et al. 2009).

The members of the genus Sphaenorhynchus can all be found in open areas, typically with medium to large ponds, near forests, but not in the forests. They are also good colonizers that can be found in both degraded and pristine areas (Caramaschi et al. 2009).

The species epithet, “mirim” is a reference to the species’ small size derived from the Tupi-Guarani language of Brazilian Indians (Caramaschi et al. 2009).

References

Caramaschi, U., Almeida A.P., Gasparini J.L. (2009). ''Description of two new species of Sphaenorhynchus (Anura, Hylidae) from the State of Espírito Santo, Southeastern Brazil.'' Zootaxa, 2115, 34-46.

IUCN SSC Amphibian Specialist Group (2011). Sphaenorhynchus mirim. The IUCN Red List of Threatened Species 2011: e.T185661A8454275.

Species Account Citation: AmphibiaWeb 2018 Sphaenorhynchus mirim <https://amphibiaweb.org/species/7302> University of California, Berkeley, CA, USA. Accessed Nov 25, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 25 Nov 2024.

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