Gastrotheca gemma, Venegas & García-Ayachi & Echevarría & Paluh & Chávez-Arribasplata & Marchelie & Catenazzi, 2021

Venegas, Pablo J., Garcia-Ayachi, Luis A., Echevarria, Lourdes Y., Paluh, Daniel J., Chavez-Arribasplata, Juan C., Marchelie, Axel & Catenazzi, Alessandro, 2021, A new species of marsupial frog (Anura; Gastrotheca) from the Cordillera de Colan in northeastern Peru, Vertebrate Zoology 71, pp. 201-218 : 201

Gastrotheca gemma sp. nov.

Figs 2 , 3 , 4 , 5 , 6 and 8

Holotype.

PERU • 1 ♀, a brooding adult; Amazonas department, Utcubamba province, Cajaruro district, from the trail from Refugio Lechucita to El Hito; 5°36 ’58.7’’ S, 78°14 ’58.8’’ W; 3180 m a.s.l.; 25 Nov. 2019; P.J. Venegas, L.A. García-Ayachi, J.C. Chávez-Arribasplata, J.R. Ormeño, S. Bullard and A. Marchelie leg.; CORBIDI 21238.

Paratypes (3).

PERU • 1 ♀, adult; Amazonas department, Utcubamba province, Cajaruro district, from El Hito; 5°36 ’45.3’’ S, 78°15 ’2.9’’ W; 3300 m a.s.l.; 09 Nov. 2017; A. García-Bravo leg.; CORBIDI 19396 • 2 ♂, adults; Amazonas department, Utcubamba province, Cajaruro district, from Bosque Quemado; 5°36 ’8.5’’ S, 78°14 ’54.9’’ W; 3140 m a.s.l.; 28 Nov. 2019; P.J. Venegas, L.A. García-Ayachi, J.C. Chávez-Arribasplata, J.R. Ormeño, S. Bullard and A. Marchelie leg.; CORBIDI 21246-47.

Referred specimens (3).

CORBIDI 21239-41, three froglets that emerged from the dorsal brooding pouch of the holotype on 26 November 2019.

Diagnosis.

Assigned to the genus Gastrotheca by females possessing a closed brood pouch on the dorsum. A moderately large species (69.7 and 71.8 mm SVL in two females, 56.9 and 59.5 mm SVL in two males), with: (1) tibia length 57-59% SVL, longer than foot; (2) interorbital distance greater than width of upper eyelid (161-169%); (3) skin on dorsum coarsely granular in females and granular in males, not co-ossified with skull, lacking transverse ridges; (4) supraciliary processes absent; (5) heel lacking calcar or tubercle; (6) tympanic annulus wrinkled or tuberculate; (7) Finger I slightly shorter than Finger II, width of discs wider than digits; (8) finger webbing present basally, only between III and IV; (9) foot webbing between external toes extending to nearly antepenultimate subarticular tubercle on Toe IV, to penultimate subarticular tubercle on Toe V; (10) in life, dorsum green with numerous minute black flecks in females and green with scattered yellow dots in males, paravertebral marks absent; (11) head markings consisting of a chocolate or pale green labial stripe in females and males, respectively; (12) dorsolateral stripe absent; (13) flanks uniformly green in females and green with numerous dark green irregular flecks in males; groin yellowish green in both sexes; anterior surfaces of thighs green, posterior surfaces of thighs yellowish green with scattered irregular black flecks in females and dense black reticulations in males; ventrolateral region yellowish green; irises silvery with a light blue hue or turquoise with thin black reticulations with or without an orange ring; (14) gular region and chest green in females and yellowish green in males; venter yellowish green with or without a big dark grey patch in the middle in females and venter greenish cream in males; ventral surface of thighs yellowish green with a dark greyish brown patch on the centre in females and thighs pale brownish cream in males; palms, soles and ventral surface of tarsus dark grey or dark greyish brown; (15) brood pouch single, dorsal; (16) reproduction mode direct development.

Gastrotheca gemma closely resembles G. aguaruna , G. carinaceps , and G. dysprosita from Peru, and G. turnerorum from Ecuador. Gastrotheca gemma shares with the aforementioned species a granular dorsal skin and a green dorsum, however the skin texture in G. gemma is coarsely granular, whereas it is weakly or finely granular in G. aguaruna and G. carinaceps , and granular in G. turnerorum . Furthermore, G. aguaruna differs by having finger I longer than II, and G. carinaceps finger I and II equal in size (finger I shorter than finger II in G. gemma ). Gastrotheca aguaruna has a dorsolateral row of warts or tubercles, absent in G. gemma . Gastrotheca turnerorum also can be distinguished from G. gemma by having brown flanks and a dark brown venter with cream spots, while G. gemma has yellowish green flanks. The new species and G. dysprosita have a coarsely granular dorsum, however G. dysprosita differs from G. gemma (character in parentheses) by having the interorbital distance smaller than width of upper eyelid (interorbital distance greater than width of upper eyelid), finger I and finger II equal in size (finger I shorter than finger II), dorsum with middorsal and dorsolateral stripes (dorsum without pattern), and venter cream with small brown spots (spots or blotches absent).

Gastrotheca gemma can be confused with green individuals of G. monticola and G. ossilaginis that also occur in the Andes of northern Peru ( Duellman and Venegas 2005; Duellman et al. 2014). Nevertheless, G. monticola and G. ossilaginis have the dorsum finely shagreen (coarsely granular in G. gemma ). Furthermore, Gastrotheca monticola differs from G. gemma by having the venter with scattered black spots (absent in the new species), and G. ossilaginis has the skin co-ossified with the skull (not co-ossified in G. gemma ).

Phylogenetically, G. gemma is sister to G. oresbios and closely related to G. psychrophila , G. spectabilis and G. stictopleura . The skin on the dorsum of the adult female holotype of G. oresbios , the single known adult specimen of this species, was described as smooth with scattered tubercles (see Duellman and Venegas 2016). However, after the examination of the holotype of G. oresbios , we considered its skin texture shagreen with scattered tubercles, while in G. gemma is coarsely granular. Furthermore, G. oresbios has an acuminate snout in dorsal view and the dorsum tan with brown paravertebral marks (the new species possesses a rounded snout in dorsal view and green dorsum without marks). Gastrotheca gemma can be readily distinguished from G. spectabilis , G. stictopleura and G. psychrophila by differences in skin texture of dorsum: smooth in G. spectabilis , finely shagreen in G. stictopleura and granular in G. psychrophila ; while in the new species is coarsely granular. Gastrotheca spectabilis has finger I equal in size to finger II whereas in the new species finger I is shorter than finger II. Gastrotheca spectabilis can be also distinguished from the new species by having a brown dorsum (dorsum green in G. gemma ). Gastrotheca stictopleura is dorsally green, like G. gemma , but possesses a white dorsolateral stripe bordered below by brown (dorsolateral stripe absent in G. gemma ). Gastrotheca psychrophila possess axilla, groins and hidden surfaces of hindlimbs blue or purple (yellowish green in G. gemma ).

Gastrotheca gemma was found in syntopy with G. abdita in the páramo, however both can be easily distinguished by their skin texture, being smooth in G. abdita . Furthermore, the dorsum is usually brown with paravertebral stripes in G. abdita , but green in the new species. Gastrotheca testudinea also occurs in Cordillera de Colán but at lower elevations (from 1700 to 2200 m a.s.l.). Gastrotheca testudinea differs from the new species by having the dorsum smooth and finger I longer than finger II. Additionally, as in G. abdita , the dorsum of G. testudinea is usually brown.

Description of the holotype.

An adult female (Fig. 2 and 3 ) in good state of preservation and with a piece of tissue removed from the left thigh for molecular analysis; SVL 69.7 mm; head wider than long; snout rounded in dorsal view, slightly inclined anteroventrally in profile; canthus rostralis round in section; loreal region slightly concave; lips rounded, broad; top of head granular; interorbital distance 173% of width of upper eyelid; internarial area flat; nostrils not protuberant, directed anterolaterally, to the level of anterior margin of lower jaw; diameter of eye is less than its distance from nostril; tympanum round, separated from the eye by a distance larger than the diameter of tympanum; tympanic annulus barely evident; supratympanic fold ill-defined, extending from behind the tympanum near to the insertion of the forelimb. Dentigerous vomerine processes narrowly separated medially, one bearing five teeth and the other six teeth.

Arm robust; ulnar tubercles absent; hand and fingers moderately large (TFL 38 % of SVL); fingers with basal web only between III and IV; discs large and rounded, width of disc of Finger III greater that diameter of tympanum; relative lengths of fingers I<II<IV<III; subarticular tubercles prominent, round in dorsal and profile views, none bifid; supernumerary tubercles, round; palmar tubercle ill-defined, bifid; prepollical tubercle large, elliptical. Hind limb robust; tibia length 59% of SVL; foot length 54% of SVL; calcar and tarsal tubercles absent; inner tarsal fold present; outer metatarsal tubercle absent; inner metatarsal tubercle elliptical, low; toes moderately long; relative length of toes I<II<III<V<IV; basal webbing between Toes I and II; webbing formula for other toes II1-2III1- 2½ IV2-1V; subarticular tubercles moderately large, rounded; supernumerary tubercles, numerous, and rounded; outer edge of toe V bears a fringe extending along the edge of foot.

Skin on dorsum coarsely granular; skin on flanks covered by enlarged flattened warts; skin on throat and chest weakly granular, ventral surfaces of thighs and arms coarsely granular; skin on belly granular; ventral surface of shanks smooth; two vertical rows of enlarged brown tubercles (three on left and two on right) below the cloacal opening. Tongue broad, suboval, not notched posteriorly, fully attached to mouth floor. Pouch opening V-shaped with anterior border at level of posterior edge of sacrum.

Measurements of the holotype (in mm).

SVL: 69.7, TIBL: 41.1, FL: 37.7, HL: 23.3, HW: 27.2, IOD: 9.7, EW: 5.6, IND: 3.9, ED: 5.8, EN: 7.2, TD: 3.9, FFL: 14.5, TFL: 26.8, TFD: 4.2.

Colour of holotype.

In life: dorsal surfaces green with numerous black flecks on dorsum, chocolate brown labial stripe, groins and ventrolateral region yellowish brown; forelimbs and fingers blotched with chocolate brown; hindlimbs with scattered black irregular flecks, numerous on shanks, larger on anterior surface of thighs, tarsus and feet; a chocolate brown stripe from the middle of thighs, running along knee, inner edge of shank and outer edge tarsus to toe V; toes chocolate brown. Ventral surface of throat, chest, forelimbs, belly and thighs yellowish green with a large greyish brown patch on the middle of the belly and a dark greyish brown patch on thighs; tibia and shanks green, ventral surface of tarsus, palms and soles dark greyish brown. Iris silvery with a light blue hue. In preservative (ethanol 70%): green coloration turns light blue and chocolate brown coloration turns pale brown on dorsal surface; ventrally, yellowish green coloration turns greyish light blue and dark greyish brown coloration turns light brown.

Intraspecific variation.

Morphometric variation of two males and two females is summarized in Table 2 . The single female paratype ( CORBIDI 19396) is identical to the holotype varying only in lacking scattered black flecks on hindlimbs and the greyish patch in the middle of the belly, and by having turquoise irises. Females are larger than males (SVL in females 69.7-71.8 mm versus SVL in males 56.9-59.5 mm). However, G. gemma shows a strong sexual dimorphism in skin texture and coloration. Males have the skin on dorsum granular with scattered enlarged warts, while females have coarsely granular skin. In addition, have scattered large flattened warts on the dorsal surface of hindlimbs, whereas in females is smooth.

The dorsum in males ( CORBIDI 21246-47; Fig. 4C-F ) is green with scattered yellow dots, flanks green with numerous dark green irregular flecks, dorsal surface of hindlimbs greyish green with scattered yellow blotches, posterior surface of thighs yellow with a dense black reticulation, gular region yellow, venter greenish cream, and ventral surface of thighs pale greyish brown. Iris coloration in both male specimens were turquoise with thin black reticulations and with or without an orange ring (Fig. 4 ).

The froglets ( CORBIDI 21239-41) have the skin on dorsal and ventral surfaces smooth. In life, the dorsal coloration is green, sides of head brown, limbs pale brown, venter yellow and the iris is bronze.

Osteology.

Osteological description of a brooding female paratype of Gastrotheca gemma ( CORBIDI 19396) with a SVL of 71.85 mm.

Cranial osteology.

The skull of Gastrotheca gemma is wider than long and measures 22.7 mm in length from the jaw joint to the tip of the snout and 27.0 mm in width at the level of the quadratojugal. The skull is hyperossified, with well-developed pit-and-ridge dermal sculpturing (i.e., exostosis) on the frontoparietals, squamosals, maxillae, and nasals (Fig. 5A ). The exposed sphenethmoid has irregular vermiform ridging. The frontoparietals have a complete medial articulation with one another, and a moderately wide supraorbital and otic flange is present but does not form an articulation with the head of the squamosal (and therefore a temporal arcade is absent). The frontoparietal covers the anterior epiotic eminence, and the carotid canal is partially closed. The nasals are expanded, articulating with the pars facialis of the maxilla, and form a bony anterior orbital margin. The nasals overlap the anterior margin of the sphenethmoid and extend posteriorly but do not articulate with the anterior edges of the frontoparietal. The maxillary arcade is complete. The quadratojugal is broadly overlapped laterally by the maxilla. The large postorbital process of the maxilla articulates with the zygomatic ramus of the squamosal via a broad diagonal articulation, forming the posterior margin of the orbit (Fig. 5C ). The head of the squamosal has a moderately wide crest, and the otic plate of the squamosal covers 35% of the width of the crista parotica. The zygomatic ramus of the squamosal bifurcates distally, and the medial branch articulates with a high dorsal process of the anterior ramus of the pterygoid and the lateral branch articulates with the pars facialis of the maxilla. The anterior ramus of the pterygoid articulates with the lingual edge of the pars palatina of the maxilla. The premaxillae are broad and bear alary processes that are deflected posteriorly at a 25° angle, forming a high and slightly rounded snout in lateral profile. The palate is characterized by well-developed neopalatines that are widely separated from one another and form a posterior margin to the choana (Fig. 5B ). The prechoanal processes of the vomers are long and articulate with the lingual surface of the pars facialis of the maxilla and the neopalatines, supporting the complete anterior margin of the choana. The postchoanal processes of the vomers are short and support half of the medial choanal margin. The dentigerous processes of the vomers are located at the level between the posterior portions of the choanae. The parasphenoid is synostosed to the overlying prootics and exocciptials. The cultriform process narrows abruptly anterior to the optic fenestra and terminates posterior to the level of the neopalatines. The sphenethmoid is not synostosed with the prootic. There are 30 to 42 socketed, pedicellate teeth on each maxilla, 7 to 10 teeth on each premaxilla, and 5 teeth on each vomer. The dentary is edentate (Fig. 5D ).

Postcranial osteology.

Vertebral column. Eight presacral vertebrae, the low neural spines of the atlas and presacral II articulate while the remaining presacrals are non-imbricate (Fig. 6A ). Neural arches of presacrals III-VIII lack neural spines. The atlas lacks transverse processes, presacrals II-IV bear thicker and longer processes than presacrals V-VIII. The transverse processes of presacral III are expanded distally, those of presacrals II and IV are slightly expanded distally. The transverse process of presacrals II and VIII are anteriorly directed, those of presacrals III, VI and VII are perpendicular to the notochordal axis, and those of presacrals IV and V are posteriorly directed. Lengths of the transverse process of presacrals along with that of the sacral diapophyses (SD): SD > III > II > IV > V-VII > VIII. The anterior margin of the sacral diapophyses is perpendicular to the longitudinal axis of the vertebra column. The distal ends of sacral diapophyses are expanded, approximately twice the width of the base. Both anterior and posterior margins of the sacral diapophyses are straight. The lateral margins are convex. The urostyle is as long as the presacral portion of the vertebral column and has a bicondylar articulation with the sacrum. The shaft of the urostyle is dorsoventrally compressed in cross section. The width of the shaft of the urostyle is narrow anteriorly. The urostyle bears a dorsal crest along half of the bone shaft, the crest is higher anteriorly and gradually diminishes in height posteriorly.

Pectoral girdle.

Arciferal pectoral girdle (Fig. 6C ). Clavicles curved and concave. Clavicles are uniform in width, only the lateral region is wider. Laterally each clavicle is fused to the pars acromialis of the scapula. Medial tips of clavicles not in contact, reaching to the level of the anterolateral end of each clavicle. The clavicles do not reach the glenoid fossa. In ventral view, the sternal and glenoid ends of the coracoids have the same width and the midshaft has half the width of the lateral ends. The sternal end is flattened and the glenoid end is wide and slightly concave. The sternal ends of the coracoids are not in contact. The scapula is stout, longer than the coracoid. The pars glenoidalis is narrower than the pars acromialis. The suprascapular end is narrower than the zonal end. The coracoid and scapula form the margin of the glenoid fossa. Cleithrum and ossified portion of the suprascapula fused.

Pelvic girdle.

In dorsal view, the ilial shafts have a V-shaped configuration. The ilial shaft has a low dorsal crest (Fig. 6D ). The dorsal prominence is low but conspicuous, the associated dorsal protuberance is elongate, conspicuous and positioned above the dorsal margin of the acetabular fossa. The ventral anterior margin of the ventral acetabular expansion is straight and forms an angle of approximately 90° with the ilial shaft. The articulations of the ilium with the ischium and pubis are evident, but not the articulation of the pubis and the ilium.

Forelimb and manus.

The humerus has a prominent ventral crest, extending along more than half the length of the bone, higher at the proximal end of the humerus and gradually diminishing in height distally. The distal head (eminentia capitata) is expanded and it is wider than the glenoid head (caput humeri). The radioulna is flattened and distinctly wide distally; the sulcus intermedius is indicated by a distinct groove on the distal half of the bone. The carpus is composed by radiale, ulnare, distal carpal 5-4-3, element Y fused to distal carpal 2, and elements of the prepollex. The phalangeal formula is 2-2-3-3 (Fig. 6B ). The terminal phalanges have a rounded proximal base, from the base towards the tip become gradually narrower. The prepollex has two elements, including the base.

Hind limb and pes.

The femur is slightly sigmoid, shorter than the tibiofibula. The sulcus intermedius of the tibiofibula is shallow. The tibiale and fibulare are separated medially and fused at the proximal and distal ends. These bones are approximately half the length of the tibiofibula. There are four tarsal elements: element Y, two distal tarsals, and the prehallux. The element Y articulates with the prehallux. There is a single ossified element of the small prehallux. The phalangeal formula is 2-2-3-4-3 (Fig. 6B ). The terminal phalanges have a rounded proximal base, from the base towards the tip become gradually narrower.

Distribution and natural history.

Gastrotheca gemma is only known from three close localities on the summit of the Cordillera de Colán, at elevations from 3130 to 3180 m a.s.l. (Fig. 7 ). The three close known localities for this species lay in the Peruvian Yunga ecoregion according to Olson et al. (2001). The localities of El Hito and Bosque Quemado are within the Santuario Nacional Cordillera de Colán, a natural reserve protected by the Peruvian government (Fig. 7 ). The new species inhabits the páramo and the ecotone between páramo and humid montane forest. We found the holotype, a brooding female, basking at 1400 hours on 25 November 2019 on top of a bush at 1.5 m above the ground, in a scrub patch with Chusquea spp. ( Poaceae) at the border of a summit covered by páramo vegetation. At El Hito we found another brooding female ( CORBIDI 19396) at 1200 hours on 9 October 2017 during a cloudy day, perched on Stipa grass ( Stipa sp.). We found the two male paratypes at night (1900 hours) on a patch of spiny ground bromeliads in a swamp area full of scrubs and Chusquea spp.

Syntopic species include G. abdita , Pristimantis atrabracus , P. corrugatus , P. sp. and Ctenophryne sp. Three completely developed froglets emerged from the holotype’s dorsal pouch during the photographic session. All froglets were similar in size (SVL between 11.30 and 11.33 mm). One paratype ( CORBIDI 19396) is a brooding female with 34 embryos in her pouch (Fig. 8 ).

We did not detect infection by the fungal pathogen Batrachochytrium dendrobatidis (Bd) in the three sampled specimens of G. gemma ( CORBIDI 21238, 21246-47), but Bd prevalence among syntopic frogs was 10.2% (Bayes 95% credible interval with Jeffrey’s priors: 3.7-18.7%). Among six infected frogs, only one had ZE > 10,000, a threshold known to be associated with elevated mortality ( Kinney et al. 2011; Catenazzi et al. 2017): G. abdita CORBIDI 21281 had ZE = 12,904 zoospore equivalents. Overall, Bd prevalence and infection loads were low compared to other frog assemblages in the high Andes ( Catenazzi and von May 2014).

Etymology.

The specific epithet comes from the Latin word " gemma ", a substantive meaning precious stone or gem. This specific name is used in apposition and refers to the turquoise coloration, in life, of the eyes of the new species of marsupial frog, which resembles the coloration of a turquoise stone.

Figures

Figure 2. Preserved holotype of Gastrotheca gemma sp. nov. (CORBIDI 21238; female, SVL = 69.7 mm) in dorsal (A) and ventral (B) views.

Figure 3. Some morphological details of the preserved holotype of Gastrotheca gemma sp. nov.: dorsal (A) and lateral (B) views of the head, and views of palm (C) and sole (D). Scale bar 5 mm. Photographs by LAGA.

Figure 4. Three living adult specimens of Gastrotheca gemma sp. nov.: (A-B) dorsolateral and ventral views of female holotype (CORBIDI 21238), 69.7 mm SVL, with a zoom of its eye; (C-D) dorsolateral and ventral views of the adult male paratype (CORBIDI 21246), 57.0 mm SVL; (E-F) dorsolateral and ventral views of the adult male paratype (CORBIDI 21247), 59.5 mm SVL, with a zoom of its eye. Photographs by AM.

Figure 5. Skull of Gastrotheca gemma sp. nov. (CORBIDI 19396) as visualized via Micro-CT scanning in dorsal (A), ventral (B), and right lateral (C) views. (D) Mandible in dorsal view. Scale bar = 5 mm.

Figure 6. Skeleton of Gastrotheca gemma sp. nov. (CORBIDI 19396) as visualized via Micro-CT scanning in dorsal view (A). (B) Left manus and pes in ventral view, (C) pectoral girdle in ventral view, and (D) ilium in right lateral view. Scale bar = 5 mm.

Figure 7. Geographical distribution of Gastrotheca gemma sp. nov. and closely related and similar species from Ecuador and Peru.

Figure 8. Skeleton and 34 embryos in pouch of Gastrotheca gemma sp. nov. (CORBIDI 19396) as visualized via Micro-CT scanning in dorsal (A) and right lateral (B) views. (A) Scale bar = 10 mm.