Description
Allobates paleovarzensis, like most other Allobates species, is small and cryptically colored to fit their tropical lowland forest habitat. The snout-vent length range of males is 18.27 – 22.42 mm, and the snout-vent length range of females is 18.67 – 21.57 mm. The body is slender. Males have a larger average head length than females (male: 6.13 ± 0.39 mm and female: 5.88 ± 0.46 mm). The head is slightly longer than wide and the head width is 28% of snout-vent length. The snout is blunt, broadly rounded to nearly truncate in dorsal view and acutely rounded in lateral view. The nostrils are slightly protuberant laterally and open posterolaterally. The eye length from the anterior to the posterior corner of the eye is 2.36 ± 0.19 mm for males and 2.41 ± 0.22 mm for females. The tympanum is round, directed posterolaterally, and posterodorsal part of it is concealed by the slip of the m. depressor mandibulae. The skin is granular on the dorsal surface of the body and legs, with the granules being the weakest on the head. The ventral surface of the skin is smooth. The forearm is slender and is 82% the length of the upper arm. There is no ulnar fold. The relative finger lengths are III > I > II = IV and there is no basal webbing or fringes. The discs on all of the fingers are expanded. Finger III of males is weakly swollen and slightly wider than females. The palmar tubercle is 12.1% of hand length, and nearly round. The thenar tubercle is 1/3 of the palmar tubercle length and oval shaped. Fingers I, II, and IV have one subarticular tubercle, and Finger III has one basal and one distal subarticular tubercle. The basal subarticular tubercles on Fingers I and II are the largest. The inner metatarsal tubercle is oval and the outer metatarsal tubercle is round; there is no media metatarsal tubercle. There is a metatarsal fold, but no tarsal fold. The relative toe lengths are IV > III > V > II > I with basal webbing only appearing between Toes III and IV. No lateral fringes can be found on any toes. The discs on Toes I, II, III, and IV are larger than the width of the toes, and Toe V is slightly larger than Toe I. When appressed, Toe I reaches the distal edge of the subarticular tubercle of Toe II. Toes I and II have one subarticular tubercle, Toes III and V have two, and Toe IV has three (Lima et al. 2010).

DIAGNOSIS:

Allobates paleovarzensis is genetically distinct from the other three Allobates that are found in the same region. They can also be differentiated from similar species by minor morphological differences. Compared to A. brunneus and A. crombiei, A. paleovarzensis lacks a dark diamond shaped or hourglass shaped pattern on the dorsum. On the other hand, A. olfersioides has an intercrossing “X” pattern on the dorsum while A. paleovarzensis does not. Compared with A. masniger, A. paleovarzensis has a dorsolateral stripe present while A. masniger does not. We can also distinguish A. paleovarzensis from A. caeruleodactylus, A. conspicuus, A. fuscellus, A. granti, A. subfolionidificans, A. sumtuosus, and A. trilineatus by its larger snout-vent length in both females and males. The call of A. paleovarzensis can be distinguishable from that of A. caeruleodactylus, A. granti, A. marchesianus, A. nidicola, and A. subfolionidificans (Lima et al. 2010).

COLORATION:

In live adults, the background color is a uniform light brown and gets darker on the head from the dorsal view. Adults have tan dorsolateral stripes, and those with darker dorsum have more distinct stripes than others. The tips of the granules are dark-brown and the legs are light brown with darker brown granules on the dorsum. Some individuals have thin dark brown vertical stripes on the middle of the tibia and the foot. From a ventral view, an adult female in life has a yellowish throat and chest, and a deep yellow belly. Reproductive males had a grayish-violet throat, a chest with lighter coloration in the center, and melanophores dispersed on the vocal sac in the upper chest. Both sexes have a narrow white stripe on the ventrolateral side from upper lip or below the eye to the groin. The ventral surface of hands and feet is brown. In preservative adults, the background color is generally dark brown on the dorsum, and the dorsolateral stripe is a distinct darker brown color from the snout and above the eye to the tip of the urostyle. The dorsal surface of the arm is cream with dark brown flecks and the dorsal surface of the leg is pale brown with a narrow brown stripe on the tibia in most of the specimens. The oblique dark brown lateral stripe presents in the inguinal area is short and diffuse. Sexual dimorphic coloration on the ventral side of live adults fades in preserved specimens (Lima et al. 2010).

VARIATION:

No significant variation was found in snout-vent length or other measurements of the observed 30 males and 15 females. However, there are some noticeable sexual dimorphic variations in colorations and morphology. One variation between males and females is that Finger III is weakly swollen in all males and the width of the middle of the third phalange on Finger III is significantly greater in males than in females (Lima et al. 2010).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Brazil

View distribution map in BerkeleyMapper.

Allobates paleovarzensis is only found in parts of paleovárzea forests along a small river, the Paraná do Castanho, in Amazonas, Brazil. Their habitat, the paleovárzea forests, are ancient floodplains of the Amazon River and its tributaries that carry high nutrient load and are no longer affected by seasonal inundation. The known type locality is 50 km west of Mananus and 40 km west of Manacapuru. All specimens used to describe the species were collected from the same locality at an elevation of 50 m, but the full elevation range is unknown (Lima et al. 2010).

Life History, Abundance, Activity, and Special Behaviors
Allobates paleovarzensis is diurnal and terrestrial. They are mostly found on the periphery of the water left from the seasonal flow of rivers (Lima et al. 2010, Rocha et al. 2018).

Allobates paleovarzensis mating is initiated by vocalizations. Male frogs vocalize from leaves. Mating calls recorded in the wild were most intense in the morning than at any other time of the day. Two types of calls were recorded in the wild: advertising and mating calls. Both call are characterized by continuous emission of grouped notes separated by silent intervals. Mating calls have a lower frequency (3,260.3 ± 131.43 Hz v.s. 3,446.0 ± 107.51 Hz respectively) and a higher note modulation (1,356.2 ± 214.6 Hz v.s. 1,639.4 ± 196.4 Hz) than advertisement calls. No defense calls have been observed in, but it is speculated that they do perform defense calls too (Rocha et al. 2018).

They are sexually active during the rainy season during which males produce more significant vocal activity to attract the opposite sex. The exhibit a cephalic amplexus mating position for 80 seconds on average (Rocha et al. 2018).

Eggs are laid on moist surfaces like leaves, and the male takes care of the eggs after the female releases them from the body. The mean clutch size is 29 eggs. The fertilized egg initially has milky grey pigmentation, but the egg shows two distinct poles after 48 hours. Eggs reach the tadpole stage in about 21 days, and until then, the eggs are in the care of a male frog. After hatching, the male transports 3 to 60 tadpoles to nearby water bodies by attaching the tadpoles to his back. Males leave their territory after transporting the tadpoles, which suggests that no further parental care is given to the offspring (Rocha et al. 2018).

The tadpoles remain in the water body until metamorphosis, which takes around 88 days. However, a longer period of metamorphosis has also been observed in a few tadpoles (Lima et al. 2010).

The tadpoles eat the vegetation available in the water body and dead insects. As they develop, their diet changes to be more carnivorous at the later stage of their development. Adult frogs eat insects they catch with their tongue (Lima et al. 2010).

As far as defense is concerned with A. paleovarzensis, no comprehensive study has found the details of the defense. However, it has been speculated that male frogs have different vocalization for defense (Rocha et al. 2018).

Larva
For A. paleovarzensis tadpoles, the following description is based on a sample of 32 tadpoles in stage 39. The body is ellipsoidal dorsally and flattened laterally. The snout is bluntly rounded both dorsally and laterally. The eye-naris distance is 0.66 ± 0.04 mm. The eyes are dorsal and directed laterally, and the small naris are dorsolateral and directed anterolaterally. The vent tube is 1.10 ± 0.19 mm long and dextral. The caudal musculature is deeper than the dorsal and ventral fin. The oral apparatus is marginate, 0.186 ± 0.01 mm in width, and located anteroventral. The anterior labium has four large papillae on the lateral margin and the posterior labium and an additional 16 to 19 papillae are on the posterolateral margin. The lower jaw is V-shaped and deeper than the upper jaw sheath. The labial tooth row formula is 2(2)/3(1). Tooth row A-1 is complete and tooth row A-2 is interrupted medially (Lima et al. 2010).

The color of tadpoles in life is yellow-brown with scattered dark brown flecks on the dorsal and lateral body surfaces as well as tail musculature. The ventral surface is transparent, and the anterior ventral surface has a transverse irregular line of dark brown and white flecking. All collected specimens have a distinct dark brown bar marking from snout through eye, approximately to the midbody. For preserved tadpole specimens, the dorsal and lateral body color are light grayish brown with dark brown flecks, giving them a mottled appearance. The ventral surface is still transparent, and the anteroventral surface has grayish coloration. A distinct dark brown bar stripping is visible from snout through eye, to approximately the midbody (Lima et al. 2010).

Trends and Threats
Allobates paleovarzensis is listed as a “Near Threatened” species because, although the population is stable, there is a threat of extinction of flora and fauna in the Amazon rainforest from deforestation and human encroachment. Energy production, mining, and biological resource use are also a threat for A. paleovarzensis. Global warming and climate changes can also affect the ecosystem of the region where A. paleovarzensis inhabitants, which can jeopardize their status (IUCN 2010).

Relation to Humans

PHYLOGENETIC RELATIONSHIPS:

ETYMOLOGY:

The species epithet, “paleovarzensis” refers to the paleovárzea habitat in which this species is found. The paleovárzeas are ancient floodplains of the Amazon River that have tributaries that are no longer subject to seasonal flooding (Lima et al. 2010).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Prolonged drought
Mining
Climate change, increased UVB or increased sensitivity to it, etc.

References

Grant, T., Frost, D. R., Caldwell, J. P., Gagliardo, R., Haddad, C. F. B., Kok, P. J. R., Means, D. B., Noonan, B. P., Schargel, W. E., and Wheeler, W. C. (2006). ''Phylogenetic systematics of dart-poison frogs and their relatives (Amphibia: Athesphatanura: Dendrobatidae).'' Bulletin of the American Museum of Natural History, (299), 1-262.

IUCN SSC Amphibian Specialist Group (2020). “Allobates paleovarzensis (amended version of 2012 assessment).” The IUCN Red List of Threatened Species 2020: e.T190492A175784790. https://dx.doi.org/10.2305/IUCN.UK.2020-2.RLTS.T190492A175784790.en. Downloaded on 19 February 2021

Lima, A.P., Caldwell, J. P., Biavati, G,. Montanarin, A. (2010). “A new species of Allobates (Anura: Aromobatidae) from paleovárzea forest in Amazonas, Brazil.” Zootaxa 2337, 1-17. [link]

Rocha, S. M. C., Lima, A.P., Karfer, I. L. (2018). "Reproductive behavior of the Amazonian Nurse-Frog Allobates paleovarzensis (Dendrobatoidea, Aromobatidae)." South American Journal of Herpetology 13(3), 260-270. [link]

Species Account Citation: AmphibiaWeb 2022 Allobates paleovarzensis: Amazonian Nurse-Frog <https://amphibiaweb.org/species/7414> University of California, Berkeley, CA, USA. Accessed Sep 24, 2023.

Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 24 Sep 2023.

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