Bolitoglossa chiquitica, Arias & Chaves & Kubicki & Parra-Olea, 2024

Arias, Erick, Chaves, Gerardo, Kubicki, Brian & Parra-Olea, Gabriela, 2024, Taxonomic assessment of the Bolitoglossa (Eladinea) subgenus (Caudata: Plethodontidae) with the description of two new species from the Cordillera de Talamanca, Costa Rica, Zootaxa 5537 (2), pp. 211-233 : 220-224

Bolitoglossa chiquitica sp. nov.

http://zoobank.org/ urn:lsid:zoobank.org:act:13B37240-3F5F-4028-B2DC-61504085B0C8

Costa Rican Miniaturized Salamander

( Figures 5–7 )

Holotype. UCR22420 ( Fig. 5 ), an adult male from Costa Rica: Provincia de Limón: Cantón de Talamanca: Distrito de Talamanca: the Caribbean slope of Cerro Utyum , Parque Internacional La Amistad , (9.3484º N, - 83.1725º W, 2595 m elevation), collected by Erick Arias, Gerardo Chaves, and Omar Zúñiga on 13 July 2013.

Paratopotypes. UCR22416, an adult male; UCR22417, a subadult male; and UCR22419, a juvenile; same data as holotype.

Generic Placement. Assigned to the genus Bolitoglossa due to having fewer than 14 costal grooves and lacking a sublingual fold and to the subgenus Eladinea based on the molecular evidence presented herein.

Diagnosis. The combination of the following characteristics can be used to distinguish Bolitoglossa chiquitica from the other described species of the genus Bolitoglossa (1) very small body (25.2–28.3 mm in adult males) with limbs relatively long and slender; (2) having hands and feet greatly webbed, less than one phalanx of the longest digits free of webbing; (3) dorsal coloration of yellowish cream to dark brown with a well-defined dark post-ocular stripe that cross the neck and reaches the pectoral shoulder; (4) 16S and cyt b mtDNA distances.

Comparisons. Bolitoglossa chiquitica is differentiated from members of the subgenus Eladinea by its 16S and cyt b mtDNA distances. Since B. chiquitica is only known to occur in Costa Rica and molecular evidence strongly supports it forming part of the Bolitoglossa diminuta species group within the subgenus Eladinea , phenotypic comparisons are presented here only concerning to members of that clade (i.e., B. aurae , B. aureogularis , B. diminuta , B. jugivagans , and B. pygmaea ), which are endemic to mountain ranges of Costa Rica and western Panama. In addition, we compare with B. robinsoni due the geographic proximity and the lack of information about the phylogenetic position of the last species.

Contrasting characteristics for Bolitoglossa chiquitica are presented in parentheses. Bolitoglossa aurae Kubicki & Arias 2016 can be distinguished from B. chiquitica by having unique dorsal coloration of pale yellow with a dark brown middorsal stripe on the head and body (dorsal color yellowish cream to dark brown uniform); tail longer, TL/SL = 1.37 (TL/SL = 0.92); adult larger, SL = 40.5 mm (SL = 25.2–28.3 mm in adult males). Bolitoglossa aureogularis Boza-Oviedo et al. 2012 has limbs relatively short, LI = 3.5 (limbs longer, LI of 2.0–2.5); bright yellow gular and yellow-brown chest regions (gular and chest regions cream with numerous dark spots); adult larger, SL = 48.8 mm (SL = 25.2–28.3 mm in adult males). Bolitoglossa diminuta Robinson 1976 by having dorsal coloration brown with a pair of dark brown bands running from eye to tail base (dorsal color yellowish cream to dark brown uniform); tail long TL/SL = 1.14 (tail shorter, TL/SL = 0.92); adult larger, SL = 31.1 mm (SL = 25.2–28.8 mm in adult males). Bolitoglossa jugivagans Hertz et al. 2013 has relatively short limbs, LI = 4 (limbs longer, LI = 2.0–2.5); tail long TL/SL = 1.24 (tail shorter, TL/SL = 0.92); a dorsolateral line running from eye to groin (dorsum and flanks uniform); adult larger, SL = 31.2 mm (SL = 25.2–28.8 mm in adult males). Bolitoglossa pygmaea Bolaños & Wake 2009 ( Fig. 6D–F ; Fig. 7 ) by having dorsal coloration variable from pale orange to dark brown with large black patches (dorsal color yellowish cream to dark brown uniform); loreal region, upper lips, and lower lips with few melanophores (loreal region, upper lips, and lower lips strongly pigmented with melanophores); head rounded in profile (head truncated in profile); snout raised anterodorsally, internarial and interorbital regions strongly concave (snout relatively truncate anterodorsally, internarial and interorbital area relatively flat); nostrils large, LNH 9–10 % of HeW, RNW 8–9 % of HeW (nostrils small, LNH 6 % of HeW, RNW 4% of HeW); restricted to Páramo rainforest habitat, in moss-mass and under rocks, above 3100 m a.s.l. (restricted to Montane rain forest, in bromeliads, below 2600 m a.s.l.). Bolitoglossa silentium sp. nov. has hands and feet with little webbing, fewer than two phalanges of the longest digits free of webbing (hands and feet are greatly webbed, less than one phalanx of the longest digits free of webbing); extensive black pigment on the dorsum and costal grooves (dorsum and costal grooves yellowish cream to dark brown but not black); adult larger, SL = 41.1–55.6 mm (SL = 25.2–28.8 mm in adult males). Bolitoglossa robinsoni Bolaños and Wake 2009 has hands and feet with little webbing, fewer than two phalanges of the longest digits free of webbing (hands and feet are greatly webbed, less than one phalanx of the longest digits free of webbing); extensive black pigment on the dorsum and costal grooves (dorsum and costal grooves yellowish cream to dark brown but not black); adult larger, SL = 46.22–64.17 mm (SL = 25.2–28.8 mm in adult males).

Description of holotype. Adult male having an SL of 28.3 mm ( Fig. 5 ). Head relatively well-differentiated from the trunk (HeW 5.0 mm, NeW 4.2 mm, ShW 3.9 mm), with the greatest width of the head transversally crossing at the eyes; head rounded in dorsal outline and rounded to truncate in profile; snout moderate (SnL 2.0 mm, 6.7 % of SL), with nearly terminal small nostrils (LNH 0.3 mm, RNW 0.3 mm) directed anterolaterally; internarial area slightly convex in dorsal outline. Snout protruding beyond the anterior margin of the lower lip in lateral view. Eyes large and prominent (EW = 109.5 % of SnL), weakly protruding beyond the dorsal and ventral outline of the head, directed anterolaterally, with a distinct suborbital groove. Teeth are numerous. There are 3 premaxillary teeth, 34 maxillary teeth, and 17 vomerine teeth. Well-defined superior eyelids, higher than the top of head in the interorbital area ( Fig. 6C ). Top of head flat and smooth, tapering slightly toward anterior terminus, lacking contrasting interorbital or other dermal structures. Canthus rostralis weakly rounded; intercanthal area flat to slightly convex; and loreal region flat. Evident cirri (nasolabial protuberances) on tip of snout; nasolabial grooves start at ventrolateral margins of nares and terminate in a cirrus. Gular fold is well-defined, starting on the dorsolateral portion of the neck, below the postorbital groove. Mental gland is not visible under the skin.

Arms relatively short and slender (FLL = 6.4 mm, 22.6 % of SL), without noticeable hypertrophied forearm compared to the upper arm. Hands relatively large and broad (HaL = 2.4 mm, 33.3 % of VGS; HaW = 2.5 mm, 50 % of HeW; Fig. 6A ). Finger I is embedded in the webbing tissue; the tip of Fingers II and IV slightly protrude freely; two phalanges protrude free beyond interdigital tissue margin in Finger III. Tip of fingers rounded; no terminal pads discernible on the ventral surface of fingers. Relative lengths of fingers on the right hand I <IV <II <III.

Legs short and slender (HLL 6.6 mm, 23.3 % of SL). Feet small and slender (FoL 2.8 mm, 38.9 % of VGS; FoW 2.7 mm, 56 % of HeW; Fig. 6B ). Toes II, III, IV, and V protrude freely beyond interdigital tissue margin (LT2 1.3 mm; LT3 1.6 mm), Toe I with minimal indentation at interdigital spaces. Toe III is most free of interdigital tissue, with about the entire distal phalanx protruding. Tips of toes rounded; terminal pads weakly discernible on ventral distal surface of toes. Relative lengths of toes on the right foot I <V <II <IV <III.

Body subcylindrical (slightly wider than high) in cross-section, and slender (TW = 4.3 mm; TW = 15.2 % of AGL). The skin on the head, body, limbs, and tail surfaces is smooth. Eleven costal grooves are visible between the axilla and groin, 13 if counting axillary and inguinal grooves; costal grooves are most visible on ventral and lateral portions of the body. Adpressed limbs separated by 1.5 costal folds; 12 costal folds total between axilla and groin. Tail short (TL = 26. 1 mm), cylindrical in cross-section, with an evident constriction at the base and some caudal grooves discernible on the anterior portion of the tail.

Coloration in life. The ground color of the dorsal surfaces of the head, trunk, tail, hind limbs, and forelimbs is dark brown to tan with numerous, uniformly distributed pale specks. This coloration extends to the lateral midline, where pale specks become much less numerous and the background paler. Tip of head and upper eyelids brown blackish, darker than the top of head and trunk. Pale specks form a paler ring surrounding the upper eyelids. A pair of thin lateral blackish-brown stripes from the posterior margin of the eye to the gular fold. The iris is bright dark bronze with a dark brownish-black reticulation. The upper surfaces of the arms and legs are similar to the color of the trunk; the distal portion of the hands and feet is paler, pinkish brown. The tip of the tail and dorsal midline of the proximal portion of the tail are paler, pale brown.

The trunk’s ventral surface was paler than the dorsal surface, tan cream with numerous dark spots. The chest was paler than the surrounding areas, almost without dark melanophores. The gular surface is darker than the belly, with numerous dark melanophores. The ventral surface of the tail was similar to the dorsal surface, dark brown. The cloaca was darker than the surrounding areas. The ventral surfaces of the arms and legs were paler than the dorsal surfaces. The palmar and plantar surfaces were pale brown with black chromatophores.

Coloration in ethanol ( Fig. 5 ). After eight years in ethanol (70%), the overall coloration of the holotype is paler throughout and contains a principal brown to dark brown tone.

Measurements (in mm), limb interval, and percentages of the holotype. SL 28.3; TL 26.1; ShW 3.9; HeW 5.0; NeW 4.2; EW 2.3; SnL 2.1; JSL 5.4; LGFS 7.4; LNH 0.3; RNW 0.3; IND 1.8; NLP 0.6; ICD 2.6; HLL 6.6; FLL 6.4; TW 4.3; VGS 7.2; FSL 9.9; UHL 4.4; AGL 13.2; VL 3.3; HaW 2.5; HaL 2.4; LF2 1.2; LF3 1.5; WF3 0.7; FoW 2.7; FoL 2.8; LT2 1.3; LT3 1.6; WT3 0.7. Limb interval 1.5. Measurements in related percentages: VGS/SL 25.4 %; IND/HeW 36 %; AGL/SL 46.6 %; HeW/SL 17.7 %; HeW/AGL 37.9 %; SnL/ HeW 42 %; LNH/HeW 6 %; LNH/SL 1.1 %; RNW/HeW 6 %; RNW/SL 1.1 %; HLL/SL 23.3 %; FLL/SL 22.6 %; HaL/VGS 33.3 %; FoL/VGS 38.9 %; HaW/HeW 50 %; FoW/HeW 54 %; LT2/FoL 46.4 %; LF2/HaL 50 %; WT3/FoW 25.9 %; WF3/HaW 28 %. Number of teeth: PMT 3, MT 34, VT 17.

Remarkable variation. In coloration, this species is very uniform, the two-adult male paratypes are paler than the holotype, but the pattern is the same. These two males were found without the tail. The juvenile paratype is paler than the holotype suggesting a possible ontogenetical variation. Despite the color variation, the three paratypes show the characteristic dark post-ocular stripe that crosses the neck and reaches the pectoral shoulder. In one paratype, the number of costal interspaces between adpressed limbs was 1, differing from the holotype (1.5). The three paratypes lack the band formed by paler-colored specks surrounding the upper eyelids in the holotype.

Measurements (in mm), limb intervals, and percentages of the paratypes. SL 25.2–27.8; ShW 3.4–4.2; HeW 4.4–4.8; NeW 4–4.1; EW 1.9–2.2; SnL 2–2.1; JSL 4.9–5.3; LGFS 6.9–7.8; IND 1.8; NLP 0.5; ICD 2.7; HLL 6.2– 6.6; FLL 6.1–6.5; TW 3.7–3.8; VGS 7–7.3; FSL 9.1–9.2; UHL 4.3–4.7; AGL 11.8–14.3; VL 3.6–3.2; HaW 2.1–2.3; HaL 1.9–2.3; FoW 2.5–3.1; FoL 2.5–2.9. Limb intervals 1–1.5. Measurements in related percentages: VGS/SL 26.3–27.8 %; IND/HeW 37.4–40.9 %; AGL/SL 46.8–51.4 %; HeW/SL 17.2–17.4 %; HeW/AGL 33.6–37.3 %; SnL/HeW 41.7–47.8 %; HLL/SL 24.1–26.2 %; FLL/SL 23.4–24.2 %; HaL/VGS 27.1–31.5 %; FoL/VGS 35.7–39.7 %; HaW/HeW 47.7–47.9 %; FoW/HeW 56.8–64.6 %. Number of teeth: PMT 3–4, MT 30, VT 16–19.

Etymology. The specific epithet is a noun in apposition, it is from the Spanish word “chiquitica ”, a popular diminutive used by Costa Rican people to refer to especially small things or animals. This name is given in reference to the small size of this species and its restricted distribution to Costa Rica.

Habitat and natural history observations. The habitat of Bolitoglossa chiquitica is a mature cloud forest dominated by Quercus covered in moss, with a great abundance of bryophytes and epiphytes. All specimens were found within bromeliads previously cut off of a tree from between 5 to 7 meters above the ground. This site was surround by a sphagnum swamp. The type locality occurs in the Montane rain forest ( Holdridge 1967; Bolaños et al. 2005), characterized by a very short dry season (one to two months), annual precipitation range between 2200 to 4500 mm, and annual temperature between 6 to 12 ºC.

Distribution. This species is known only from the type locality in the Caribbean slope of the Cerro Utyum to 2595 m a.s.l. ( Fig. 1 ). This species was found in the primary forest within the protected area of La Amistad International Park.

Figures

FIGURE 1.A) Map of the Cordillera de Talamanca in the Costa Rica-Panamá border-line region showing all known populations of the seven species within the Bolitoglossa diminuta Species Group. B) Map showing the localities for B. bramei, B. pygmaea, B. robinsoni, and B. silentium sp. nov. on the Fábregas and Echandi massifs. The open shape indicates the historical data and the solid shape indicates the localities with molecular data included herein.

FIGURE 5. Dorsal and ventral views of the body of the holotype of Bolitoglossa chiquitica sp. nov. (UCR22420) in preservation. Photograph by E.A.

FIGURE 6. Ventral views of the hand and foot and detail of the face of the holotype of (A-C) Bolitoglossa chiquitica sp. nov. (UCR22420) and (D-F) B. pygmaea in preservation. Photographs by EA.

FIGURE 7. Detail of the face of (A-D) Bolitoglossa chiquitica sp. nov. and (E-T) B. pygmaea in preservation. Photographs by EA.UCR vouchers:A:22416, B:22417, C:22419, D:22420 (holotype), E:11788 (holotype). F:11789. G:11790, H:11791, I:11792, J:11793, K:11794, L:11795, M:11796, N:11797. O:11798, P:11799, Q:22718, R:22720, S:22724, and T:23697. Specimens A-D from Utyum, Costa Rica, E-P and T from Fábregas, Panama, and Q-S from Echandi, Costa Rica.