Ranitomeya hwata, Twomey & Melo-Sampaio & Brown & Castroviejo-Fisher & Gagliardi-Urrutia & Padial & Poblete & Chaparro, 2025

Ranitomeya hwata new species urn:lsid:zoobank.org:pub:

Figures 2 View FIGURE 2 , 3 View FIGURE 3 , 4 View FIGURE 4 & 6 View FIGURE 6

Ranitomeya biolat View in CoL — Maldonado & Reichle, 2007 (MNK 8251; Fig. 1 View FIGURE 1 ); Melo-Sampaio & Souza, 2009; Melo-Sampaio, 2010

Dendrobates quinquevittatus View in CoL — Souza, 2010 (UFAC-RB field series 2994; Figure 3.16E View FIGURE 3 )

Ranitomeya sirensis — Brown, Twomey, Amézquita, Souza, Caldwell, Lötters, von May, Melo-Sampaio, Mejía-Vargas, Perez-Peña, Pepper, Poelman, Sanchez-Rodriguez, and Summers, 2011 (part: referred specimens from Acre, Brazil and Pando, Bolivia, e.g. Fig. 25 M)

Ranitomeya sp. Catuaba — Twomey, Melo-Sampaio, Schulte, Bossuyt, Brown, and Castroviejo-Fisher, 2023 (specimen MCP 13485 placed in phylogeny, Fig. 1 View FIGURE 1 ); Melo-Sampaio, 2023

Holotype. MNRJ 91674 ( Fig. 2 View FIGURE 2 ), an adult male collected on 16 March 2016 by Paulo Melo-Sampaio and Evan Twomey at Fazenda Experimental Catuaba, Senador Guiomard, state of Acre, Brazil ( 10.0727°S, 67.6239°W), 200 m elevation. GoogleMaps

Paratypes. Sixteen specimens in total. From Brazil: UFAC-RB 0419, an adult male collected on 19 February 1988 by M. B. Souza, F. N. Castro, and A. J. Cardoso at type locality. UFAC-RB 4157, an adult female collected on 28 March 2009 by PRMS at type locality. UFAC-RB 4160, an adult female collected on 2 April 2009 by PRMS and T. R. B. Silva at type locality. UFAC-RB 4592, an adult female collected on 15 August 2009 by PRMS and W. C. Silva at type locality. UFAC-RB 4585, an adult male collected on 1 November 2009 by PRMS at type locality. UFAC-RB 4595 (male) and UFAC-RB 4596 (female) collected on 28 November 2009 by PRMS at type locality. UFAC-RB 4597, an adult female collected on 20 January 2010 by PRMS and T. R. B. Silva at type locality. MCP 13635 (sex undetermined), collected on 16 March 2016 by PRMS and ET at type locality. UFAC-RB 3678, an adult male collected on 23 to 25 November 2000 by M. B. Souza, and R. Guerra at “Foz do Rio Tejo” (“mouth of Tejo River ”), Reserva Extrativista Alto Juruá, Marechal Thaumaturgo, Acre (approx. 9.05°S, 72.73°W, 250 m elevation). UFAC-RB 9699, an adult male collected in 2005 by J. R. D. Souza at Estação Ecológica Rio Acre, Assis Brasil ( 11.0012°S, 70.2132°W), 345 m elevation. UFAC-RB 9700, an adult male collected on 14 January 2019 by I. Prates, V. Prates, and PRMS, Reserva Florestal Humaitá, Porto Acre, Acre ( 9.7509°S, 67.6724°W), 190 m elevation. UFAC-RB 6531, an adult female collected on 13 September 2014 by D. P. Silva and D. C. Machado at Parque Estadual Chandless, Manoel Urbano, Acre ( 9.3804°S, 69.9230°W), 220 m elevation. MNRJ 95832, an adult female collected on 22 January 2016 by PRMS and J. Costa, Comunidade São José, Boca do Acre, Amazonas ( 8.9747°S, 67.8606°W), 135 m elevation. From Peru: MUBI 14866 (male) and CM 158616 View Materials (female), a breeding pair collected on 22 February 2014 by JMP, LAGG, JCC, and RG from the Sepahua River , in the buffer zone of Alto Purús National Park , Provincia Atalaya , Ucayali department ( 11.0527°S, 72.4565°W), 356 m elevation ( Fig. 3 View FIGURE 3 ). Measurements of the type series are provided in Table 2 GoogleMaps .

Additional referred material. MCP 13485–13489, MCP 13506 ( Fig. 3 View FIGURE 3 ), and MCP 13511, all skinned carcasses, collected on 16 March 2016 by PRMS and ET at type locality. UFAC-RB 4158, a juvenile collected on 28 March 2009 by PRMS at type locality. MUBI 14867, an egg clutch from the Sepahua breeding pair. MNK 8251, and adult frog of undetermined sex from Pando department, Bolivia ( Maldonado & Reichle 2007) .

Etymology. Among the indigenous peoples inhabiting the Upper Purus River drainage are the Manxineru, who use several terms to refer to native spiny bamboos, known in Portuguese as taboca. One of these words, hwata , is a generic term for the native Guadua Kunth, 1822 bamboos ( Virtanen et al. 2022), of which there are at least nine species in the region, including the locally dominant G. sarcocarpa and G. weberbaueri ( Carvalho et al. 2013) . As the new species appears to be strongly associated with Guadua bamboo, we chose the specific epithet hwata to reflect this connection and to honor the indigenous peoples who inhabit the same region as the new species. The specific epithet is used as a noun in apposition.

Diagnosis. Twomey et al. (2023) retrieved the new species unambiguously nested within the vanzolinii group of Ranitomeya . Besides this phylogenetic inference, the new species is assigned to the genus Ranitomeya due to the combination of the following characteristics: small adult size (< 18 mm SVL), conspicuous and bright dorsal coloration, with pale limb reticulation, first finger distinctly shorter than the second, inner metacarpal tubercle present ( Fig. 4 View FIGURE 4 ), maxillary teeth absent. Further assigned to the vanzolinii group of Ranitomeya based on its advertisement call, which is a high pitched, tonal trill of approximately 1–2 s in length (see below for further details and comparisons of calls). The following characteristics in combination distinguish Ranitomeya hwata from all other members of the vanzolinii group: (1) dorsal stripes fine, yellow in life, and largely unbroken along the length of the body, (2) ventral color patch absent in life, (3) gular region yellow in life and lacking spots, with a distinct black band delimiting gular and belly coloration, and (4) belly with fine and regular black spotting and pale blue reticulation in life.

Comparisons. Based on morphology, advertisement call, and our phylogenetic analysis (see also Twomey et al. 2023), Ranitomeya hwata is nested within the vanzolinii species group and thus we focus our comparisons on only members of this clade. Diagnostic characters of the new species given in parentheses. (Note that call comparisons are given in the next section.) Ranitomeya vanzolinii has a dorsal color pattern consisting of yellow dots or irregular dashes (vs. yellow stripes) on a black background. Furthermore, the ventral color pattern in R. vanzolinii consists of yellow and black marbling (vs. pale blue with fine black spots). Ranitomeya sirensis is variable in coloration but can consistently be distinguished by the presence of a “ventral color patch”, that is, a patch on the belly of the same color as the dorsal coloration (vs. patch absent in R. hwata ). This ventral color patch is also present in southern populations of R. sirensis , including those near the type locality of the former R. biolat , allowing for a simple diagnosis between the two species, barring the occasional aberrant individual (see Brown & Twomey et al. 2011, Fig. 25N for an example). Ranitomeya imitator is also variable, and striped populations occurring in the lowlands of northern San Martin and Loreto, Peru can most reliably be distinguished from R. hwata by ventral color pattern, where R. imitator lacks the distinctive black band delimiting gular and belly regions (vs. black band present and regular, occasionally broken in the middle in R. hwata ). There are also differences in breeding biology, with R. imitator demonstrating pair-bonding and monogamy (vs. polygyny in R. hwata ), as well as call differences (see next section). Ranitomeya aetherea , R. aquamarina , R. cyanovittata , and R. yavaricola all have blue, greenish-blue, or yellowish-green dorsal markings in the form of dots, dashes, or stripes (vs. yellow stripes). Additionally, all of these species can have bluish belly coloration similar to R. hwata , but have black spots that are generally much coarser, irregular, and occasionally sparse (vs. spots fine, black, and mostly round in R. hwata ), and with a gular color that matches the belly color (vs. yellow gular color and pale blue belly in R. hwata ). In the case of R. aquamarina , the gular region and belly can be of subtly different color, fading from bluish-green on the gular region to yellowish-green on the belly, but the distinctive two-toned color scheme of R. hwata (yellow gular region and pale blue belly, separated by a black band, with no fading) is not observed. Ranitomeya flavovittata has yellow dots or dashes on the dorsum (vs. continuous yellow stripes that are rarely broken in R. hwata ). The ventral coloration between the two species is similar (both with a yellow gular color and pale blue belly), but the black patterning in R. flavovittata is more marbled and irregular, with larger black patches (vs. black spots fine and mostly round in R. hwata ). The two species can also be distinguished by their calls (next section). Most notably, R. aetherea , R. aquamarina , R. cyanovittata , R. flavovittata , and R. yavaricola all lack the distinctive black band of R. hwata that delimits the gular and belly regions.

Bioacoustics. Three male Ranitomeya hwata were recorded during 2009 at the type locality. The advertisement call is typical of the vanzolinii group, consisting of a high-pitched, tonal trill ( Fig. 5 View FIGURE 5 ). The following values are based on average values for each calling male. Call length 1.25– 1.78 s, with 48–66 pulses per call, pulse rate 36–49 pulses/s. Dominant frequency 5884–6064 Hz.

The combination of a relatively long call length with a high pulse rate yields an exceptionally high number of pulses per call. This is diagnostic against all other members of the vanzolinii group, except for R. sirensis , which can produce up to 55 pulses per call, and R. cyanovittata , for which no call data exist. Compared to the species in its sister clade ( R. aetherea , R. aquamarina , R. flavovittata , and R. yavaricola ), Ranitomeya hwata has a longer call length, with more pulses per call, and a higher pulse rate ( Table 3). Compared to the other (non-sister) species in the vanzolinii group, Ranitomeya vanzolinii has a shorter call length, fewer pulses per call, a lower pulse rate, and a lower dominant frequency than R. hwata ( Table 3). Ranitomeya sirensis can produce a call as long as or exceeding the length of R. hwata , but with a lower pulse rate and dominant frequency ( Table 3). Ranitomeya imitator overlaps with R. hwata with respect to call length, pulse rate, and dominant frequency, but has a lower number of pulses per call (9–46), which is noteworthy given the large sample size for this species ( N = 132; Twomey et al., 2015).

Description of holotype. The holotype is an adult male, 15.3 mm SVL. The skin is nearly smooth on the dorsum and weakly granular on the venter. Snout weakly rounded in dorsal and ventral view, sloping and truncate in lateral view. Canthus rostralis rounded, loreal region vertical. Upper eyelid width is half interorbital distance. Eye 1.8 mm in length; tympanum 0.5 mm in diameter.

Forearm and upper arm of nearly equal length, 20% of SVL. Hand length 27% of SVL. Relative lengths of fingers III> IV ≈ II> I. First finger 79% length of second. Finger discs moderately expanded on fingers II, III, and IV, weakly expanded on finger I. Unpigmented palmar and inner metacarpal tubercles present; unpigmented proximal subarticular tubercles present on all four fingers; finger III also has distal subarticular tubercle. Fingers lack fringes and webbing.

Femur and tibia length nearly equal, each roughly 40% of SVL. Relative lengths of toes IV> V ≈ III> II> I. First toe with no appreciable disc, disc weakly expanded on toe II, moderately expanded on toes III, IV, and V. Two unpigmented metatarsal tubercles present at base of foot, one medial to base of toe I, the other at the base of the fifth metatarsal. Proximal subarticular tubercles at base of toes I, II, and V. Toes III and V each have a single distal subarticular tubercle while toe IV has two. Toes lack fringes and webbing.

In preservative, there are three complete dorsal stripes, pale grey in color, of equal width, extending from the head to the base of the dorsum. The medial stripe extends to the tip of the snout. Between the eyes and the groin, all three stripes are unbroken and form no perpendicular ramifications. On the head, the two lateral stripes branch medially and the left stripe joins the medial stripe. Two pale grey lateral stripes are present, running from the tip of the snout, under the nostrils, eye, and tympanum, extending posteriorly to groin. The ventral edge of the lateral stripes blends into the coloration of the venter while the dorsal edge is well-defined. The arms and legs are pale bronze in preservative, with fine black spotting. The spotting is sparser on the ventral surface of the limbs. Dorsally, the spotting is interrupted at the insertion of the arms and legs, giving the impression of weakly defined pale grey axillary and inguinal patches. On the ventral side, the gular region is bare and silvery-grey, framed with melanic pigmentation that is fine anteriorly along the mouth and thick along the posterior margin below the eyes. This latter pigmentation is also thickened laterally on the underside of the head, between the eyes and arms. The belly is pale grey with black spots; spots mostly round; larger than spots on limbs.

Coloration in life and variation. Among the type series, the snout shape varies from rounded to truncate in dorsal view. In life, the dorsal stripes are typically complete between the eyes and the groin, but in rare cases one of the lateral dorsal stripes may be broken. Between the eyes and the groin, perpendicular ramifications that connect medial and lateral stripes are seldom observed, found only in a single adult (MCP 13488) and occasionally in metamorphs. Between the eye and snout, stripe variation is much more pronounced. Commonly, a partial or complete stripe is seen running across the head just anterior to the eyes, forming a cross pattern on the nose. Dorsal and ventral limb coloration varies from silvery grey to pale blue, the former being more common. Pale yellow patches, weakly defined, are present dorsally at the limb insertions. Ventrally, the gular region is always yellow and strongly delimited from the belly coloration by a black band. In some individuals this band is medially broken or irregular. Variation in belly coloration is minimal. Reticulation is always pale blue; some individuals have finer or coarser black spotting but relatively speaking (i.e., compared to the sister clade), the black spots on the belly are fine and mostly round. Overall, Ranitomeya hwata exhibits remarkably little variation in color pattern across its range.

Tadpole. Although we are unaware of any preserved material that would allow a detailed tadpole description, several live tadpoles were extracted from bamboo culms and photographed between 2009 and 2010, allowing for a brief description of their external morphology and development. Upon hatching ( Fig. 6a View FIGURE 6 ), tadpoles are pale grey with two round black eyes located on top of the head. As they develop (e.g. at a total length of approximately 26 mm), coloration darkens, with the body appearing uniform brownish-grey, fading towards translucent grey along the length of the tail. By approximately Gosner stage 40, the yellow dorsal stripes are faintly visible ( Fig. 6g View FIGURE 6 ). This is also the point where maximum size was reached, with a total length of 28 mm. Froglets are generally 12 mm long after metamorphosis.

Distribution. Ranitomeya hwata is a lowland species, distributed throughout much of the state of Acre, Brazil, and extends into southeastern Peru in Ucayali department near the village of Sepahua ( Fig. 7 View FIGURE 7 ). Additionally, it is known from one site in Amazonas, Brazil (Reserva Extrativista Arapixi), Pando department in northern Bolivia, and from Rio Acre (which forms the border of Acre and Madre de Dios) ( Freitas et al. 2020), making its presence in Madre de Dios department of Peru a virtual certainty. The species occurs at elevations ranging from 190 to 356 m, with the most distant known localities separated by approximately 575 kilometers. Drawing a minimum convex polygon around all known localities, the extent of occurrence of R. hwata is approximately 121,000 km 2. As much of this habitat is protected (e.g. Alto Purús National Park, Chandless State Park, Reserva Extrativista Chico Mendes, Reserva Extrativista do Alto Jurua), we suggest this species be listed as Least Concern following the IUCN Red List criteria ( IUCN 2024).

Natural history. Throughout its range, Ranitomeya hwata is found in close association with Guadua bamboo. This is true not only for the populations in Brazil, but for the Peruvian population as well. The two Peruvian paratypes were found while clearing a patch of Guadua for a campsite, together inside a culm guarding a clutch of eggs. Other species in the vanzolinii group are also known to use Guadua in certain locations, such as Ranitomeya vanzolinii ( Souza 2009) , Ranitomeya sirensis (as biolat ) ( von May et al. 2009; Waldram 2008), and Ranitomeya aquamarina (personal observation), as well as non-native bamboo such as Dendrocalamus asper ( e.g. R. sirensis near Tingo Maria, Peru). All three of these latter species exhibit some flexibility in their choice of phytotelmata, using tree holes, Xanthosoma spp. (as well as non-native Alocasia spp. ), small bromeliads, Ischnosiphon spp. ( Marantaceae ), and Phenakospermum guyannense (Streliziaceae) when available. In the case of Ranitomeya hwata , reproductive behavior was monitored intensively at the type locality over a span of two years ( Melo-Sampaio 2010) and we have only one observation of this species breeding outside of Guadua , which was in Phenakospermum guyannense , known in Portuguese as bananeira brava and in Spanish as patujú gigante ( Fig. 6h View FIGURE 6 ). In the publication documenting R. hwata in Bolivia ( Maldonado & Reichle 2007), it is mentioned that the specimen was collected in a pitfall trap located within a patch of P. guyannense , but that this species is more frequently associated with Guadua weberbaueri .

At the type locality, between 2009 and 2010, PRMS studied the reproductive ecology of Ranitomeya hwata . Water-filled bamboo culms were installed to observe preferences in tadpole deposition height ( 0.5 to 4 m) during weekly visits in the rainy season (January to April) and bi-weekly visits in the dry season (May to September), and again weekly from October to December. The highest deposition occurred during the rainy season, and even in the dry season, when culms were available, tadpole deposition still occurred. These observations also indicate that nurse frogs transport tadpoles away from the site of oviposition into new culms. One of the paratypes (UFAC-RB 4585) was transporting a tadpole at the time of collection. Although this specimen lacked vocal slits, direct inspection of the gonads confirmed that it was a male. Males call in the early morning hours (around 06:00h), sporadically decreasing frequency during the warming part of the day (10:00h to 14:00h), and ceasing around 17:00h. Males were not heard vocalizing at night, although tadpole transport activity has been observed until 20:00h ( Fig. 6a View FIGURE 6 ). Males are polygynous and can recruit up to three females in the same culm, achieving multiple matings and optimizing the spawning site, which usually contains one or two eggs ( Fig. 6c View FIGURE 6 ). Cannibalism among tadpoles was not observed, and up to four tadpoles were found sharing the same phytotelm ( Fig. 6d View FIGURE 6 ). The main enemies of the tadpoles in the phytotelmata are damselfly naiads ( Microstigma spp. and Mecistogaster spp. ) and mosquito larvae ( Toxorhynchites sp. ) ( Fig. 6f View FIGURE 6 ). In one case we observed a mosquito pupa ( 10.5 mm total length) and young tadpole ( 13.1 mm total length) in the same bamboo culm, suggesting that the tadpoles do not prey on the mosquito larvae.