 |
| Allobates velocicantus Souza, Ferrão, Hanken & Lima, 2020 |
Abstract
Nurse frogs (Aromobatidae: Allobates) are probably the most extensively studied genus by taxonomists in Brazilian Amazonia. The southwestern portion of Amazonia is the most species-rich: as many as seven species may occur in sympatry at a single locality. In this study, we describe a new species of nurse frog from this region. The description integrates data from larval and adult morphology, advertisement calls and DNA sequences. Allobates velocicantus sp. nov. is distinguished from other Allobates mainly by the absence of hourglass-shaped dark marks on the dorsum and dark transverse bars on the thigh; a throat that is white centrally and yellow marginally; basal webbing on toes II and III; finger I longer than finger II; and an advertisement call composed of 66–138 pulsed notes with a note duration of 5–13 ms, inter-note intervals of 10–18 ms and a dominant frequency of 5,512–6,158 Hz. Tadpoles of the new species have 3–4 short, rounded papillae on the anterior labium, 16–23 papillae on the posterior labium, and a labial keratodont row formula 2(2)/3(1). This is the fifth species of Allobates described from the state of Acre, southwestern Brazilian Amazonia.
 |
| Figure 6: Coloration in life of adult Allobates velocicantus sp. nov. (A–C) Holotype, male, INPAH 41342, SVL = 15.3 mm. (D– F) Male, INPAH 41341, SVL = 15.4 mm. (G–I) Female, INPAH 41344, SVL = 16.6 mm. (J–L) Female, INPAH 41345, SVL = 17.4 mm. Photographs by Albertina Pimentel Lima. |
 |
| Figure 10: Habitat and breeding behavior of Allobates velocicantus sp. nov. (B) A calling male (INPAH 41343). (C) A female ovipositing (uncollected). (D) Egg clutch containing 13 eggs with animal pole covered by melanin. (E and F) Male collecting tadpoles to transport to a pond (INPAH 41347). (G) Male with tadpoles on his back (INPAH 41347). In both clutches, eggs were deposited on the adaxial surfaces of green leaves. Photographs by Jesus R. D. Souza. |
Allobates velocicantus sp. nov.
Allobates sp. CdS MCP10187 (MCP10188) Grant et al. (2017).
Diagnosis. Allobates velocicantus sp. nov. is characterized by (1) small size, SVL 14.9–16.2 mm in males and 16.0–17.4 mm in females; (2) dorsal color pattern predominantly light brown, with no dark patches and marks; (3) dorsum granular; (4) dark brown lateral stripe from the tip of the snout to the groin; (5) light dorsolateral stripe absent or inconspicuous in living specimens but present in preserved specimens; (6) light but incomplete ventrolateral stripe; (7) oblique lateral line diffuse; (8) snout slightly rounded in dorsal view; (9) tympanum inconspicuous; (10) paired dorsal digital scutes; (11) supernumerary tubercles absent; (12) distal tubercle absent on finger IV; (13) discs moderately expanded on fingers I–IV; (14) finger I slightly larger than finger II; (15) finger III of males with similar width along phalanges; (16) dermal lateral fringes and webbing absent on fingers; (17) metacarpal ridge absent; (18) carpal pad absent; (19) excrescences on thumbs absent; (20) dark gland on arm absent; (21) basal webbing present between toes III and IV; (22) metatarsal tubercle present; (23) light “half-moon” shaped paracloacal mark; (24) superior eyelids dark brown; (25) iris metallic bronze; (26) pupil large, black, horizontal semielliptical; (27) transverse bars on thigh absent; (28) dark brown spots on tibia; and (29) advertisement calls formed by 66–138 pulsed notes (emitted in multiple exhalations) with a dominant frequency of 5,512–6,158 Hz.
Etymology. The specific epithet is derived from the Latin words velox (= fast) and cantus (= singing), in reference to the high note-repetition rate of the advertisement call of the new species.
Proposed standard English name: fast singer frog.
Proposed standard Spanish name: sapito del canto veloz.
Proposed standard Portuguese name: sapinho do canto acelerado.
Phylogenetic placement. The new species is assigned to the genus Allobates based on its phylogenetic position presented in the present study and in Grant et al. (2017).
 |
| Figure 10: Habitat and breeding behavior of Allobates velocicantus sp. nov. (A) Understory of the lowland ombrophilous open forest at the type locality, municipality of Mâncio Lima, state of Acre, Brazil. (B) A calling male (INPAH 41343). (C) A female ovipositing (uncollected). (D) Egg clutch containing 13 eggs with animal pole covered by melanin. (E and F) Male collecting tadpoles to transport to a pond (INPAH 41347). (G) Male with tadpoles on his back (INPAH 41347). In both clutches, eggs were deposited on the adaxial surfaces of green leaves. Photographs by Jesus R. D. Souza. |
Natural history notes. Allobates velocicantus sp. nov. inhabits the litterfall of primary and secondary lowland ombrophilous open forest (Fig. 10A). Populations of this species were found in terra firme forest either close to or distant from small forest streams. The new species uses leaves of small shrubs in the forest understory as egg deposition sites; two clutches (nine tadpoles and 13 eggs) were found in this situation. On 13–15 February 2019, during the middle of the rainy season, males were found calling between 8:00 and 18:00 h, and always perched between 10 and 30 cm above the ground. A pair of adults was observed courting: the male was leading the female to an egg deposition site, and he emitted a courtship call while both frogs were moving. As the male started emitting another advertisement call, the female stopped following. Arriving at the egg deposition site, the male jumped on to a leaf (adaxial surface), which was located around 20 cm above the ground, and continued to emit advertisement calls interspersed with courtship calls. After a few moments, the female jumped to the leaf with the male and approached him, initially touching snouts before turning her back to him. The male then jumped onto the female’s dorsum, while also sliding its hand to her head. The male remained in that position—cephalic amplexus—for 2 min before jumping from the leaf. The female remained in place for a few moments but then began moving, turning clockwise 30°, stopping, and repeating that pattern several times, always turning clockwise. The length of time the female stopped between movements ranged from 2 to 10 min, while she deposited eggs (Fig. 10C). Overall, egg deposition lasted 40 min before the female abandoned the leaf, leaving behind a clutch of 13 eggs. Each egg had a distinctly pigmented animal pole and was encased within cloudy jelly (Fig. 10D). The clutch was collected immediately after the female abandoned it, the embryos maintained alive through hatching, and the resulting tadpoles reared to Gosner stages 27–37 before being sacrificed and preserved.
The second egg clutch had nine tadpoles at aquatic-transport stage. The male (INPAH 41347) jumped onto the egg clutch and made circular movements inside it, at which time the tadpoles began to wriggle towards his dorsum, eventually climbing onto it (Figs. 10E–10G). This event lasted for 5 min.
Conclusion:
Allobates velocicantus is differentiated from its congeners based on external morphology of adults and tadpoles, advertisement call and molecular analyses. The species represents an excellent model to study the ecological and physiological adaptations to solar radiation on eggs of Allobates. However, the conservation of A. velocicantus is threatened by the expansion of illegal logging, cattle ranching, and agriculture.
Jesus R.D. Souza, Miquéias Ferrão, James Hanken and Albertina P. Lima. 2020. A New Nurse Frog (Anura: Allobates) from Brazilian Amazonia with A Remarkably Fast Multi-noted Advertisement Call. PeerJ. 8:e9979. DOI: 10.7717/peerj.9979
