Colostethus ucumari, Grant, Taran, 2007

Grant, Taran, 2007, A new, toxic species of Colostethus (Anura: Dendrobatidae: Colostethinae) from the Cordillera Central of Colombia, Zootaxa 1555, pp. 39-51 : 40-48

Colostethus ucumari , new species

Figs. 1–8

Holotype: ICN 28598 (field number JHR 2404), an adult male collected by Javier Bustos, Erika Nadachos K., Michael Alberico, and Jorge Humberto Restrepo at Colombia, Departamento de Risaralda, Parque Regional Natural Ucumarí , Campamento La Pastora, Quebrada La Pastora, 2500 m above sea level, approximately 4°42’N, 75°29’W, 15–17 February 1991.

Paratopotypes: ICN 28599–600.

Paratypes: All from Colombia. ICN 28551–52, 28556, 28575–76: Departamento de Risaralda, Parque Regional Natural Ucumarí , Campamento La Pastora, Quebrada La Pastora, 2490 m. ICN 15636: Departamento de Quindío, Hacienda El Carelia, ca. 8 km E Salento, 2410 m. ICN 38766–69: Departamento de Risaralda, Pijao, Vereda Guamal, Finca La Cristalina, 2152–2250 m. UTACV 39728–29: Departamento de Tolima, 20.3 mi WNW Cajamarca. KU 133306–13: Departamento de Caldas, 6 km ESE Villa María, 2130 m. AMNH 104369–74: Departamento de Caldas, 5.5–6 km by road southeastward from Villa María, 2320 m.

Etymology: The specific epithet, ucumari , is used as a noun in apposition and refers to the Parque Regional Natural Ucumarí , where the type locality of Colostethus ucumari is situated. Ucumarí , in turn, is the Quechua name for the spectacled bear, Tremarctos ornatus .

Diagnosis: A medium to large species of Colostethus (maximum SVL approximately 27 mm for adult males, approximately 30 mm for adult females); dorsal skin texture posteriorly granular; cloacal tubercles present; Finger I and Finger II subequal in length; adpressed Finger IV reaching beyond distal subarticular tubercle of Finger III, longer than Finger II; Finger III swollen in adult males; throat, chest, and anterior belly pale with dark marbling or reticulation in both sexes; throat darker in males than in females, ranging from gray to black; black arm band of adult males absent; testes white; toes conspicuously fringed, free of webbing or with at most basal webbing between Toes III–IV; pale dorsolateral stripe present; pale ventrolateral stripe absent; pale oblique lateral stripe absent; pale paracloacal marks absent; medial lingual process absent.

Colostethus ucumari shares with C. imbricolus and C. panamensis the swelling of Finger III in adult males and the occurrence of conspicuous bright flash marks on the axilla, groin, belly, and concealed surfaces of the thigh and shank. It differs from both of those species in lacking a partial pale oblique lateral stripe and possessing a conspicuous pale dorsolateral stripe.

Colostethus ucumari differs from all other species of Colostethus except C. ruthveni and C. thorntoni in lacking a pale oblique lateral stripe (extending from groin to eye in C. agilis , C. brachistriatus , C. dysprosium , C. fraterdanieli , C. fugax , C. jacobuspetersi , C. lynchi , C. mertensi , and C. yaguara ; extending from groin midway along flank in C. furviventris , C. imbricolus , C. inguinalis , C. latinasus , C. panamensis , and C. pratti ). Colostethus ucumari differs from C. ruthveni in ventral coloration (marbled or reticulated ventral color pattern in C. ucumari , immaculate in C. ruthveni ), and from C. thorntoni in the degree of webbing (toes free or with at most rudimentary webbing between Toes III–IV in C. ucumari ; toes moderately webbed in C. thorntoni ) and the possession of a pale dorsolateral stripe (absent in C. thorntoni ). Colostethus ucumari further differs from C. agilis , C. alacris , C. brachistriatus , C. dysprosium , C. fraterdanieli , C. fugax , C. imbricolus , C. inguinalis , C. jacobuspetersi , C. latinasus , C. lynchi , C. mertensi , C. panamensis , C. thorntoni , and C. yaguara in possessing a pale dorsolateral stripe (absent in those species; present in C. furviventris , C. pratti , and C. ruthveni ). Colostethus ucumari is also the only species of Colostethus known to possess cloacal tubercles ( sensu Grant et al. 1997 ), although these structures are not always scored and may be lost as an artifact of preservation (Grant et al. 2006).

Among other dendrobatoids formerly placed in Colostethus sensu lato in the Colombian Andes, Colostethus ucumari most resembles Hyloxalus abditaurantius , another robust frog of similar size with which it shares conspicuous bright flash marks in life (yellow in C. ucumari , orange in H. abditaurantius ), marbled or reticulated ventral coloration, a dark throat in adult males (due to presence of melanophores in C. ucumari and absence of iridophores in H. abditaurantius ), cloacal tubercles, and the absence of a pale oblique lateral stripe (both possess small, irregular, pale dots scattered over the flanks). Colostethus ucumari differs most conspicuously from H. abditaurantius in possessing a pale dorsolateral stripe (absent in H. abditaurantius ), having Finger III swollen in adult males (not swollen in H. abditaurantius ), and lacking toe webbing or having at most basal webbing between Toes III–IV (toes extensively webbed in H. abditaurantius ).

Measurements of holotype ( Fig. 2 ): SVL 22.1 mm; forearm length from proximal edge of palmar tubercle to outer edge of flexed elbow 5.1 mm; hand length from proximal edge of palmar tubercle to tip of Finger III 6.5 mm; shank length from outer edges of flexed knee to heel 10.0 mm; foot length from proximal edge of outer metatarsal tubercle to tip of Toe IV 10.4 mm; head width between angle of jaws 8.0 mm; head length diagonally from corner of mouth to tip of snout 7.3 mm; eye length from posterior to anterior corner 3.1 mm; eye to naris distance from anterior corner of eye to center of naris 1.9 mm; distance between centers of nares 3.1 mm; snout length from anterior corner of eye to tip of snout 3.4 mm; interorbital distance 2.7 mm; diameter of tympanum 1.2 mm.

Morphology: Adult males 22.1–27.0 mm SVL (n = 8; = 24.06±2.06); testes unpigmented (white), testis length approximately 1/3–1/2 eye length. Adult females 24.4–30.0 mm SVL (n = 12; = 27.27±2.08); mature oviducts unpigmented (white); mature ova approximately 2 mm in diameter, animal pole dark brown.

Ventral and lateral surfaces smooth. Dorsal surfaces with granules scattered irregularly in sacral region and (to a lesser degree) on thigh and shank. Well defined cloacal tubercles present ( Fig. 3 ). Postrictal and preaxillary tubercles (one each) elongate. Head width between angle of jaws 31–39% SVL, 1.0–1.3 times head length. Interorbital distance 30–37% of head width. Canthus rostralis gently rounded. Loreal region flat or weakly concave, not sloping to lips. Eye length 39–48% of diagonal head length. Eye-naris distance 55–66% snout length and 55–74% eye length. Nares slightly protuberant, directed posterodorsad. Tympanum well defined in well preserved specimens, concealed posterodorsally by low supratympanic bulge formed by superficial slip of m. depressor mandibulae. Diameter of tympanum 28–53% eye length. Teeth present on maxillary arch.

Hand length 26–31% of SVL and 1.2–1.3 times forearm length. Finger discs weakly to moderately expanded. Finger III of adult males swollen along preaxial side; postaxial swelling not detected ( Fig. 4 A); Finger III not swollen in adult females ( Fig. 4 B) or juveniles. Fingers lacking fringes. Metacarpal fold absent, although lateral edge of palm lacking melanophores. Finger I longer than finger II; Finger II extended to midlevel of distal subarticular tubercle of Finger III; finger IV extended midway between proximal and distal subarticular tubercles of Finger III. Relative finger lengths IV <II <I <III. Subarticular tubercles 1–1–2–2. All tubercles strongly protuberant; subarticular and thenar tubercles elliptical; palmar tubercle subcircular.

Shank and foot length 40–47% and 40–51% of SVL, respectively. Relative lengths of appressed toes I <II <V <III <IV ( Fig. 5 ). Toe III extended approximately midway between penultimate and ultimate subarticular tubercles of Toe IV; Toe V extended to distal edge of penultimate subarticular tubercle of Toe IV. Webbing absent or basal between Toes II–IV, lacking between others (formula II 2 –3.5 III 2.5– 4 IV). Fringes present on pre- and postaxial surfaces of all toes except Toe V, which lacks fringes. Discs weakly to moderately expanded. Tubercles strongly protuberant. Subarticular tubercles 1–1–2–3–2. Inner metatarsal tubercle elongate. Outer metatarsal tubercle subcircular, diameter roughly one half length of inner metatarsal tubercle. Medial metatarsal tubercle absent, but thickening of skin notable in most specimens (for discussion of relevance see Myers et al. 1991:23–24). Outer metatarsal fold absent. Tarsal keel well defined, straight or weakly curved (weakly curved in holotype), not enlarged proximally to form tubercle-like structure, extending diagonally from inner metatarsal tubercle along distal one half of tarsus.

Color in preservative: Dorsum ( Fig. 2 A) dark brown or brown with dark brown blotches (as in holotype); granules dark brown. Pale dorsolateral stripe varying from pale brown to conspicuous cream or whitish gray, extending from tip of snout along canthus rostralis, outer edge of upper eyelid, and lateral edge of dorsum toward (but not reaching) tip of urostyle, not dropping toward base of thighs. Flank ( Fig. 2 C) dark brown with scattered pale (white or gray) flecks and dots. Pale ventrolateral and oblique lateral stripes absent. Otic region dark brown. Loreal region and snout dark brown; upper lip dark brown with white or gray dots.

Ventral coloration sexually dimorphic ( Figs. 6–7 ). Both sexes marbled or reticulated anteriorly (extending posteriorly onto belly), but throat of adult males (i.e., region that becomes distended when vocal sac inflated) is darker, ranging from gray to black.

Dorsal, anterior, and posterior surfaces of arm brown with dark brown spots and blotches, often with small pale flecks and dots. Axilla lacking melanophores, forming flash mark. Ventral surfaces white or cream. Palmar surfaces brown; contact surfaces gray or lacking melanophores. Dorsally Fingers I and II proximally mostly white or gray with brown blotches, darker distally; Fingers III and IV mostly brown.

Dorsal surface of thigh gray or brown with diffuse darker brown transverse bands that align with bands on shank and foot of flexed limb. Anterior surface of thigh gray or brown with diffuse darker blotches; posterior surface gray or brown fading ventrally; pale paracloacal mark absent. Exposed surfaces of shank and foot gray or brown with dark blotches and diffuse transverse bands that align with those of dorsal surface of thigh. Ventral surface of thigh and concealed surfaces of shank and foot immaculate white or cream, forming flash marks. Plantar surfaces brown; contact surfaces gray or lacking melanophores. Dorsal surface of preaxial portion of foot and Toes I–III mostly cream or white; postaxial portion of foot and Toes IV–V mostly gray or brown.

Color in life ( Figs. 1 , 8 ): Charles W. Myers’s field notes at AMNH report AMNH 104369–73 as brown with blackish brown interorbital and dorsal markings and a light but not sharply defined bronzy dorsolateral stripe. Sides of head and body brown with bluish-white dots (lacking on flank of female AMNH 104370). Posterior surface of thigh indistinctly mottled brown and black; ventral surface of thigh pale greenish gray. Iris bronze with black flecking or mottling. Adult male AMNH 104369 ( Fig. 8 A) with a gray throat and pale blue chest and lower lip margin. Females (e.g., AMNH 104371; Fig. 8 B) and juveniles all with throat and chest pale blue with black or gray scribbling or blotching (i.e., throat not gray). All specimens with bright golden-yellow coloration on underside of arms and in axilla, on belly, and on concealed surfaces of shank.

John D. Lynch’s field notes at ICN report ICN 15636 as brown with vague paler flecks and vague dorsolateral stripe. Throat and anterior venter pale blue with dark network. Lemon yellow patch in axilla, lowest groin, and behind knee. Iris dark brown. Posterior thighs dark gray-brown.

Toxicity: Charles W. Myers (field notes taken 2 December 1976, deposited at AMNH) observed that paratypes of Colostethus ucumari exuded a milky secretion along the sides of the body, posterior side of thighs, and concealed surfaces of shanks. In January 1977, John W. Daly analyzed extracts of the skin of AMNH 104371 for toxicity at NIH by injection into mice (John W. Daly in litt., 20 December 2006; for procedures see Daly et al. 1994). Injection of the methanol extract caused some initial agitation and twitching, followed by normal activity. However, injection of the aqueous extract caused not only twitching, but also some gagging, followed by a period of inactivity. The identity of the water-soluble compound responsible for these toxic effects was not determined.

Mass spectral analysis in February 1977 showed the alkaloid fraction from the non-toxic methanol extract to contain small amounts of unknown compounds, none of which corresponded to any known dendrobatid alkaloids. The nature of these compounds could not be pursued at that time because of the limited quantities. Current reexamination using high resolution gas chromatographic mass spectral analysis of the thirty year old alkaloid fraction could only detect a trace amount of one of these compounds, which proved to be an artifact, namely 2-benzothazolyl-N,N-dimethyl dithiocarbamate (John W. Daly, in litt. 6 April 2006). The molecular ion was at m/z 254 (C10H10N2S3)+ with the only major fragment ion at m/z 88 (C3H6NS)+ (for presence of this compound in rubber-based vial closures see Kapp & Vetter 2006).

Larvae: The single stage 25 larva AMNH 104374 was taken from the back of male nurse frog AMNH 104369 (additional tadpoles were observed on this frog but were lost when catching it in dense grass). Body oval, slightly compressed anterior to intestine; length 4.1 mm; maximum width 2.9 mm; maximum height 2.0 mm. Eyes positioned dorsally, oriented dorsolaterally; interorbital distance 1.3 mm. Internarial distance 1.1 mm. Lateral line stitches absent. Spiracle sinistral. Vent tube dextral. Center of intestinal coil sinistral, ventrolateral. Tail tip broadly rounded; length 7.9 mm; maximum height 2.0 mm. Tail muscle width 0.9 mm and height 1.4 mm. Oral disc emarginate, positioned anteroventrally; width 1.0 mm. Anterior labium bearing broad dorsal gap. Marginal papillae of anterior and posterior labia uniserial, marginal papillae conical, short. Labial labial tooth row formula 1/3; only A-1 and P-1 with any degree of keratinization; A-1 complete (i.e., lacking gap), no additional anterior tooth ridges present. Upper and lower jaw sheaths serrated, narrowly keratinized upper jaw sheath gently curved, not pointed or notched. Tail (including both fins) and body with sparse, irregular brown stippling on cream ground, lacking conspicuous markings.

Distribution and natural history: Colostethus ucumari is known from cloud forest localities in the Cordillera Central at approximately 2100–2500 m above sea level. It is a riparian species not known to occur more than a few meters (<3 m) from the water’s edge. Specimens were taken in grassy vegetation and on and beneath rocks along streams and pools, in both primary forest (i.e., unmodified forest of> 20 m height) and in or at the edge of forest clearings, such as pastures and grassy roadside drainage ditches. Most specimens were taken during diurnal collecting, but the holotype and topoparatypes were recorded as being collected while active at night (specific time not reported, but collecting activities and other species obtained suggest it was nocturnal, not crepuscular).

Figures

FIGURE 1. Colostethus ucumari new species adult male AMNH 104369 in life, SVL = 24.0 mm. Photograph by Charles W. Myers.

FIGURE 2. Colostethus ucumari new species adult male holotype ICN 28598, SVL = 22.1 mm. (A) Ventral view. (B) Dorsal view. (C) Lateral view.

FIGURE 3. Cloacal tubercles of Colostethus ucumari new species (ICN 28600).

FIGURE 4. Hand morphology of Colostethus ucumari new species. (A) Left hand of adult male holotype ICN 28598. Hand length = 6.5 mm. Note the swelling along the preaxial side of Finger III. (B) Left hand of adult female paratype ICN 38766. Hand length = 7.7 mm. Finger III is not swollen.

FIGURE 5. Foot morphology of Colostethus ucumari new species (ICN 38769). Foot length = 10.6 mm.

FIGURE 6. Variation in ventral coloration of male Colostethus ucumari new species. Left to right: ICN 38769 (SVL = 27.0 mm), ICN 28556 (SVL = 22.5 mm), ICN 28575 (SVL = 22.1 mm), ICN 38768 (SVL = 22.6 mm).

FIGURE 7. Variation in ventral coloration of female Colostethus ucumari new species. Left to right: ICN 15636 (SVL = 30.0 mm), ICN 38767 (SVL = 29.8 mm), ICN 28600 (SVL = 30.0 mm).

FIGURE 8. Ventral coloration of Colostethus ucumari new species in life. (A) Adult male AMNH 104369 (SVL = 24.0 mm). (B) Adult female AMNH 104371 (SVL = 25.4 mm). Photographs by Charles W. Myers.