Tlalocohyla celeste Varela-Soto, Abarca, Brenes-Mora, Aspinall, Leenders & Shepack, 2022
Tapir Valley Tree Frog
|Species Description: Varela-Soto D, Abarca JG, Brenes-Mora E, Aspinall V, Leenders T and Shepack A. 2022. A new species of brilliant green frog of the genus Tlalocohyla (Anura, Hylidae) hiding between two volcanoes of northern Costa Rica. Zootaxa 5178(6): 501-531.|
Tlalocohyla celeste is a small frog described from three males and one female with the male snout-vent length range being 20.10 - 21.45 mm and the female being 24.55 mm. It has a head length range of 7.55 - 8.35 mm and a head width range of 6.95 - 8.5 mm. In dorsal view, its snout is nearly rounded, and in the profile view, its snout is rounded and protruding. Its rounded nostrils are located dorsolaterally on slightly raised processes, directed laterally. The canthus rosalis is rounded and well defined, and its loreal region is concave. Its internarial distance is slightly smaller than its eye diameter, and its interorbital range is larger than its eye diameter. Its eyes are large and protruberent, and its pupils are horizontally elliptical (Varela-Soto et al. 2022).
Its upper arms and forearms are slender and have the same thickness throughout. There is a small axillary membrane and no ulnar skin fold. There are numerous, tightly packed, and rounded accessory palmar tubercles across the whole palm. The inner metacarpal tubercle is elliptical and large, and the outer metacarpal tubercle is similar to the accessory palmar tubercles. The relative finger length is I < II < IV < III. The finger discs are round, moderately expanded, and similar in size, with the exception of the first finger disc being slightly smaller. There are smooth nuptial pads without epidermal projections that are rounded at the base of the first finger. The subarticular tubercles on fingers I and II are single and rounded, and on fingers III and IV they are large and slightly bifid. The webbing between the first and second finger is vestigial, and the webbing formula is I 3+ – 2- II 2- – 3- III 3- – 2- IV (Varela-Soto et al. 2022).
Its hind limbs are also slender and are slightly larger than its foot length and slightly smaller than its tibia length. The inner metatarsal tubercle is medium-sized and elliptical, and there is no outer metatarsal tubercle. The relative toe length is I < II < III < V < IV and the discs are rounded and expanded. The subarticular tubercles are globular, rounded, and single, and the supernumerary tubercles are small, rounded, and single. The webbing formula is I 2- – 2+ II 1½ – 3+ III 1½ – 3- IV 2+ – 1½ V (Varela-Soto et al. 2022).
Its whole body is covered in smooth skin, and it’s granular in the central region of the venter and on the undersides of the thighs (Varela-Soto et al. 2022).
Tlalcohyla celeste’s most notable difference from other small hylids in Costa Rica is its green coloration and transparent ventral skin. In comparison to Scinax species, T. celeste have a similar profile but are much smaller and have dorsolateral stripes. It is most similar to Boana rufitela juveniles, but these juveniles have a rounder lateral profile and complete white dorsolateral stripes, whereas T. celeste’s white dorsolateral stripes are incomplete. These stripes are also the key difference between T. celeste and glass frogs in the family Centrolenidae because glass frogs do not have dorsolateral stripes (Varela-Soto et al. 2022).
Compared to T. godmani and T. loquax, T. celeste has a much smaller snout-vent length, has transparent ventral skin instead of colored skin, and has a very small axillary membrane. It can be differentiated from T. smithii by its smaller size and bright green color with mahogany spots on its dorsal side in comparison to the bright yellow color of T. smithii. Tlalcohyla celeste also has a sulfur-white dorsolateral stripe with a mahogany stripe above it and a transparent belly in comparison to T. smithii’s white dorsolateral stripe with a brown border and white belly. It differs from T. picta by the coloration of its dorsolateral stripes, dorsal coloration, bone color, and vocal sac color. Tlalcohyla celeste also has different advertisement calls and tadpole morphology (see “Larva” section below) than T. smithii and T. picta (Varela-Soto et al. 2022).
In life, the species displays diurnal and nocturnal coloration. With its nocturnal coloration, it has a yellow-green (#103, numbers following Köhler 2012 method) head, dorsal, and limb color, and its ventral skin is transparent with a small light cyan (#158) axillary membrane. There is an incomplete dorsolateral stripe of sulfur white (#96) that starts at the posterior edge of the orbit and extends over halfway to the start of each hind limb. For its entire length, it is bordered above by a diffuse mahogany red (#34) stripe that extends anteriorly from the orbit to the tip of the snout as well. There are also numerous mahogany red spots evenly dispersed on the head, back, and lower limbs, but not on its lateral sides below the dorsolateral stripes. The upper surfaces of the finger and toe tips are a light greenish yellow (#87). The upper edge of the orbit is a reddish brown (#72) and the rest of the upper eyelid has a slight spectrum yellow (#79) spread over it. The iris is gold with raw umber (#23) reticulations. There is a white line bordering the posterior and anterior edges of the orbit. The vocal sac is yellow-green (#103) when deflated and is turquoise green (#147) when inflated. During the day, the mahogany stripes and splotches are much less noticeable and the frog appears more uniformly green. The eyes also lighten to a sliver-gray color (Varela-Soto et al. 2022).
In preservative, the dorsal green coloring turns a pale greenish white (#97) and the mahogany markings turn into a pale vinaceous (#247) color. The iris turns black and the hands, feet, and tips of digits become creamy-white. The ventral skin becomes semi-transparent in preservative (Varela-Soto et al. 2022).
Tlalcohyla celeste displays sexual dipmorphism as well as differences in coloration throughout development stages and time of day. Female T. celeste are bigger than the males and don’t have a vocal sac, vocal slits, or nuptial pads. The diurnal and nocturnal coloration differs quite a bit with the mahogany markings in particular. During early development stages, small juveniles have a lighter green dorsal color and do not have the dorsolateral stripes. However, they do have clusters of mahogany splotches most commonly anteriorly and there is a short, dark stripe from the posterior edge of the eye orbit along with a broad, dark canthal stripe (Varela-Soto et al. 2022).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Costa Rica
At the time of the species description, T. celeste was only known from the type locality, which is in a wetland habitat in the Tapir Valley Nature Reserve at an elevation of 660 m asl. The reserve is classified as Tropical Premontane Wet Forest and Tropical Moist Forest. There is no marked dry season, the mean annual precipitation is 3,500 mm, and the monthly temperature range is 20 - 33 ºC (Varela-Soto et al. 2022).
The frogs live in an 8-hectare marshland with a permanent water level that is continually fed by a small tributary of rainwater from the hillsides and groundwater. The water moves slowly through the wetland because of a small discharge channel. The shallow area of the marsh mainly has the grass Rhynchospora corymbosa but vegetation becomes more diverse in the riparian zone, away from the water, where it turns into shrubs and trees that connect to the forest in the higher elevation areas (Varela-Soto et al. 2022).
Life History, Abundance, Activity, and Special Behaviors
Tlalcohyla celeste has three distinct calls. Call type I is made up of trill notes and has an average duration of 0.34 s emitted at intervals of 2 - 10 s and has an average call repetition rate of 12 calls/minute. The pulse rate is 30 - 50 pulses per note, and the frequency ranges from 3.80 - 4.30 kHz. Call type II has one to three squeak-like, pulsating notes. Each note has an average duration of 0.08 s and the frequency range is 4.00 - 4.40 kHz. Call type II usually is emitted 0.17 - 0.21 s after the first call. Call type III is a croak of 3 - 5 pulsating notes that lasts on average 0.29 s with each note lasting on average 0.03 s, and it is emitted at 0.35 - 1.61 s intervals with a repetition rate of 23 calls/s. The pulse rate per note is 60 - 90. The frequency range is 3.70 - 4.10 kHz (Varela-Soto et al. 2022).
Tlalcohyla celeste males emit these calls year-round, but particularly during high rains. They start calling at 16:00 h and continue until sunrise. During heavy rainfall, individuals can also be heard during the day. Males tend to call near the water’s edge and the density of the males increases the farther into the wetland it is. They call while on vegetation, mainly the surrounding grasses, in head-up, horizontal, or head-down positions. Usually, the males are quite near each other while calling and range from 0.1 - 3 m off of the ground (Varela-Soto et al. 2022).
Satellite male behavior has been observed in T. celeste. The females are most often observed on the edge of the wetland and sometimes even in the edge of the forest about 20 m away from the water’s edge (Varela-Soto et al. 2022).
This species exhibits axillary amplexus, and gravid females have been observed from June through September. Amplectant pairs are observed at night and in pre-dawn morning hours, and they separate immediately after oviposition. During each breeding cycle, females can engage in multiple oviposition events (Varela-Soto et al. 2022).
Egg masses are found on the tip of drooping edges of leaves above the water from June to November, indicating that the eggs hatch into exotrophic tadpoles and drop into the still fresh water below. They have about 20 - 61 unpigmented eggs per egg mass that have a longer length than width. Eggs are about 2.0 mm in diameter. Tadpoles hatch ten days after oviposition, and embryos start to have clear developmental signs after five days where they slowly turn light brown with black spots (Varela-Soto et al. 2022).
Individuals have been observed catching micro moths and small flies, and its diet most likely consists of small vertebrates. There have been no observations of predation, but there are snakes and ctenid spiders, both of which are known frog predators, in the wetland. Opilionid arachnids were seen scavenging a dead frog, and wasps were seen attacking T. celeste eggs and developing larvae (Varela-Soto et al. 2022).
The tadpoles in Gosner stages 34 - 44 are ovoid in both dorsal and lateral views and their snout is rounded. Their total length is 26.1 - 29.7 mm, and their body length is greater than their body width. The rounded nostrils are halfway between the eyes and the tip of the snout, are dorsally directed, and located with well-developed fleshy flanges on the marginal rim. Their eyes are medium-sized and laterally-located. The oral disc is small, not emarginated, and located anteroventrally. There is a single row of short marginal papillae that has an anterior gap. There are also randomly distributed submarginal papillae positioned laterally. The jaw sheaths are less than half the length of the oral disc and are finely serrated. The anterior jaw sheath is rounded and the posterior jaw sheath has a shallow V-shape. There are two anterior keradont rows, with the posterior one having a small gap in the middle, and they are both equal in length. There are three posterior keradont rows, and the most posterior one is much smaller than the other two. The spiracle is sinistrally located on the posterior third of the tadpole, is directed posterodorsally, and has a small opening. The cloacal tube has a triangular apex and is short and dextral. Their tail length is 14.9 - 21.0 mm, and the tail musculature is taller than it is wide. The maximum tail height is 4.53 - 5.68 mm. The dorsal fin is higher than the ventral fin, and it originates slightly anteriorly to the base of the tail and reaches its maximum height at its midpoint. The ventral fin starts anteriorly to the cloaca tube and is a consistent height throughout (Varela-Soto et al. 2022).
In comparison to other tadpoles in the genus, such as T. godmani, T. loquax, and T. picta, the dorsal fin of T. celeste originates at the base of the tail instead of anterior to the location of the spiracle or at the level of it. Tlalcohyla celeste tadpoles differ from T. smithii tadpoles in their tail height and coloration, where T. smithii tadpoles have a consistent tail height until it tapers to a tip and the posterior third of the tail is black and T. celeste tails increase in height for a maximum height in the middle until it tapers to a tip and does not have a black tail tip (Varela-Soto et al. 2022).
In life, the tadpole’s head is yellow ochre (#14) to tawny olive (#17) dorsally with evenly spaced and distinct spots of mahogany red (#34) to warm sepia (#40). The lateral surfaces are lighter in color. There is a vague warm sepia stripe from the posterior edge of the eye orbit and it continues indistinctly down the body. The iris is gold with a warm sepia spot both anteriorly and posteriorly. The ventral skin is clear and there is a reddish coloration anteriorly with cream white (#52) coloration at the intestines. The tails fins are transparent with irregular splotches of black and raw umber (#23), and the tail musculature is yellow ochre (#14) with black and warm sepia spots. There is sometimes a fine medial black line that can be interrupted on the tail musculature as well. In 10% formalin preservative, the tadpole becomes pale greenish white (#97) and all of the spots and markings turn black (Varela-Soto et al. 2022).
The egg masses are found on leaves above the wetland water and when they hatch 10 days after oviposition, they drop into the water below. The embryos show development after five days and their coloration turns to light brown with black spots. The tadpoles most likely develop in the lentic water of the wetland from where they hatched and dropped into the water (Varela-Soto et al. 2022).
Tlalcohyla celeste larvae have been observed from November to June and develop quite slowly. Tadpoles have remained at Gosner stages 36 - 39 for three months after hatching. Throughout development, the cream white color of the intestines darkens to black (Varela-Soto et al. 2022).
Trends and Threats
Currently, the conservation status is unknown for T. celeste. Its habitat, the Tapir Valley Nature Reserve, used to be intensively grazed pasture land, and only with recently conservation efforts has it returned to the wetland that T. celeste lives in. This indicates that all the species in the wetland, T. celeste included, have significant adaptability and resistance (Varela-Soto et al. 2022).
Possible reasons for amphibian decline
General habitat alteration and loss
Based on a Bayesian phylogenetic tree using 12S and 16S mitochondrial DNA, the clade composed of T. godmani and T. loquax is sister to the T. celeste clade. Together they are sister to the clade composed of T. picta and T. smithii (Varela-Soto et al. 2022).
The species epithet “celeste” comes from the Spanish word for light blue or sky-blue and refers to their ventral skin coloration. It was also chosen in honor of the Río Celeste, which is both the same color and feeds the wetland where T. celeste lives (Varela-Soto et al. 2022).
Köhler, G. (2012). Color Catalogue for Field Biologists. Herpeton, Offenbach, Germany.
Varela-Soto, D, Abarca, JG, Brenes-Mora, E, Aspinall, V, Leenders, T, Shepack, A (2022). "A new species of brilliant green frog of the genus Tlalocohyla (Anura, Hylidae) hiding between two volcanoes of northern Costa Rica." Zootaxa, 6, 501-531. [link]
Originally submitted by: Nessa Kmetec (2022-10-10)
Description by: Nessa Kmetec (updated 2022-10-10)
Distribution by: Nessa Kmetec (updated 2022-10-10)
Life history by: Nessa Kmetec (updated 2022-10-10)
Larva by: Nessa Kmetec (updated 2022-10-10)
Trends and threats by: Nessa Kmetec (updated 2022-10-10)
Comments by: Nessa Kmetec (updated 2022-10-10)
Edited by: Ann T. Chang (2022-10-10)
Species Account Citation: AmphibiaWeb 2022 Tlalocohyla celeste: Tapir Valley Tree Frog <https://amphibiaweb.org/species/9562> University of California, Berkeley, CA, USA. Accessed Dec 3, 2022.
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Citation: AmphibiaWeb. 2022. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 3 Dec 2022.
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