Chacophrys pierottii (Vellard, 1948)
Chaco Horned Frog, Chacoan Burrowing Frog, Escuercito chaqueÃ±o
|Species Description: Vellard, J. (1948). "Batracios del chaco argentino." Acta Zoologica Lilloana, 5, 137-174.|
© 2004 Dr. Rafael I. Marquez (1 of 1)
Chacophrys pierottii is a relatively small fossorial frog within the Ceratophyridae family, described by adult specimens with snout-vent lengths ranging from 45.2 - 65.57 mm. Females obtain larger sizes than males (Vellard 1948; Lescano 2011; Quinzio and Reiss 2017; Marangoni et al. 2018). The head of C. pierottii is large and thick, with head length ranging from 20 - 24 mm, head width ranging 19.16 - 29 mm, and head height ranging from 15 - 17 mm (Vellard 1948; Marangoni et al. 2018). This massive head size encompasses roughly half of the frog’s total body length. Parotoid glands are absent from the head. The profile of the head is strongly convex until the snout, and compressed in front of the eyes. The lateral parts of the head behind the eyes are similarly convex. From a frontal view, the snout creates a barely protruding triangle below the nostrils, which are observable on either side of the median line. The lateral sides of the head adjacent to the snout are strongly depressed. In addition, the lower jaw of the snout is strong, with curved spiniform extensions. The nostrils themselves are closer to each other (4 - 5 mm), than to the eyes (5 - 6 mm) or the tip of the snout (6 - 7 mm). In addition, the skin of the head is co-ossified with the skull. The prominent eyes of C. pierottii have a diameter ranging from 5 - 7 mm, with a narrow, depressed inter-orbital distance ranging from 3 - 5 mm. The upper eyelids are without fringes, instead having free, straight edges, and a width ranging from 5 - 6 mm. The adjacent tympanum is distinct and half the size of an eye (Vellard 1948).
Chacophrys pierottii has a thick, short body with very short forelimbs and hind limbs, similar to an Odontophrynus. The forelimbs range from 10 - 13 mm. The palm has two tubercles, a heart or oval shaped one near the base of the thumb, and a smaller, narrower oval one. The fingers are free and feature a medial subarticular tubercle at their base. The 1st finger is quite long, roughly twice the length of the 2nd and barely reaching the 3rd. The tibio-tarsal articulation just reaches the shoulder. On the foot, there is no tarsal fold, but a distinct, singular, huge, and spade-shaped metatarsal tubercle is present. The 1st and 2nd toes are greatly reduced in length. The webbing reaches the base of the 3rd toe’s final phalanx and the base of the 4th toe, but is absent between the 4th and 5th toe. The subarticular tubercles are indistinct or completely absent (Vellard 1948).
Small granulations cover the dorsal skin of the body. Between the borders of the eyes in the front and behind the brown interocular band, two lines of granulations are present. Several rows of granulations on the upper eyelids, which have no skin appendages, are also present. A glandular cord stretches from the eye, over the tympanum, and to the shoulder. The throat is smooth, like the lower surface of the limbs, while the chest, belly, upper surface of the limbs, and outer lateral region of the tibiae are grainy. Lastly, the anal region of C. pierottii is strongly granular (Vellard 1948).
Regarding the juvenile stage, Pueta and Perotti (2013), as well as Quinzio and Reiss (2017), determined juveniles have a snout-vent length ranging from 24.4 - 44.2 mm, a jaw width 11.9 - 20.7 mm, and a jaw length 9.5 - 16.2 mm. Additionally, in a study done by Faivovich and Carrizo (1992), metamorphs, captured as larvae, measured approximately 20 mm.
As 2022, Chacophrys pierottii is the only species in its genus (Faivovich et al. 2014). Vellard (1948) determined that a lack of parotids, unique sternum shape, small size, narrower and taller head shape, as well as proportion of head to body differentiated C. pierottii from the genus Odontophrynus. Vellard, however, placed these Chacoan frogs in the Ceratophyrs genus. Lynch (1971) later concluded that numerous osteological factors reflecting reduced ossification, in addition to chromosome number, separated C. pierottii from the Ceratophyrs genus.
In addition, C. pierottii can be distinguished by its advertisement call of higher dominant frequency (4109.7 - 5060.1 Hz) and lower number of pulses per note (49 - 108), in comparison to Ceratophyr species, which have a dominant frequency ranging from 1250 - 1886.1 Hz and pulses per note ranging from 59 - 107. Chacophrys pierottii, furthermore, is capable of emitting a higher pitch sound in comparison to Ceratophyrs and Lepidobatrachus (Lescano 2011).
The general dominance of prey items (bees, coleopterans, and anurans) in the diet of C. pierottii also distinguishes the frog from Lepidobatrachus llanensis, which generally consumes aquatic invertebrates and other anurans, Ceratophrys ornata, which selectively eats other anurans, Ceratophrys cornuta, which mainly consume Orthopterans and ants, and Ceratophrys cranwelli, which mainly eats other anurans (Pueta and Perotti 2013).
In life, the adult stage of C. pierottii is dorsally light green with chestnut spots bordered, on either side, arranged in a regular light net, which is reminiscent of C. ornata. A green stripe stretches from the anal region to the nape of the neck, at which it bifurcates to reach the posterior half of the upper eyelids. Two fragmented longitudinal bands run along the sides of the back and flanks, one formed by lateral spots and the other by smaller and more irregular spots. A white-bordered, V-shaped, brown band is visible between the eyes, covering the anterior half of the eyelids and pointing posteriorly. A band of similar nature runs from the inner angle of the eye, running along the canthus, and reaching the end of the snout. Three or four irregular bands, the median one most developed, run vertically up the sides of the snout but do not reach the canthus. The limbs of C. pierottii are green, with the brown streaks running along the dorsal surface of the forearms, tibiae, and tarsi; meanwhile, the palms and soles are gray. The throat is yellow in shade, with irregular, elongated, brown spots, which can form zig-zag bands to the chest. The belly and ventral surfaces of the limbs are a uniform yellow-white (Vellard 1948).
In life, the juvenile stage of C. pierottii is an ochraceous brown. Small reddish spots are scattered across the body, especially on the rostral canthus, snout, and limbs, which themselves are brown with black glandular flanges and bordered by yellow. Two scapular spots, a V-shaped interocular spot, and two lumbar spots are also well-defined. After many weeks, coloration becomes a uniform light green, with three longitudinal purple spots visible on the throat.
Males have a vocal slit in the floor of their mouth and are generally smaller in size than females (Marangoni et al. 2018).
Distribution and Habitat
Country distribution from AmphibiaWeb's database: Argentina, Bolivia
Chacophrys pierottii is endemic to the semi-arid and arid regions of the Gran Chaco in Northern Argentina, southern Bolivia, and western Paraguay (Alto Paraguay, Boqureon, and Presidente Hayes), which are generally 70 - 200 m above sea level (Faivovich et al. 2014; Marangoni et al. 2018; IUCN 2021) . The Chaco regions are approximately 1,141,000 km2 of flood plains, full of low forests, savanas, and two rivers (Fabrezi and Cruz 2014). This region has strong seasonality, with wet summers and dry winters. Rainfall is concentrated from October to April, filling the lagoons temporarily, as they dry up in winter (Vellard 1948; Cei 1968; Marangoni et al. 2018)
Life History, Abundance, Activity, and Special Behaviors
Chacophrys pierottii has adapted to their environment by having a fossorial, nocturnal lifestyle and an explosive reproductive nature (Cei 1968; Faivovich et al. 2014; Quinzio and Reiss 2017). The species is also short-lived, likely having a maximum life-span of 5 years (Marangoni et al. 2018). The terrestrial adults burrow underground, not feeding nor molting, during the cold, dry season. To further prevent water loss, a cocoon of dead skin forms over the adults (Cei 1968; Faivovich et al. 2014; Quinzio and Reiss 2017). During the rainy season, especially during January, the frogs become more active as the ephemeral lagoons form (Vellard 1948). Adults participate in a maximum of four reproductive events during their short reproductive lifespan, all within a temporary breeding pool on clay soil. These explosive breeding events result in the larger females laying large clutches of eggs on the muddy bottom of the pools (Cei 1968; Marangoni et al. 2018)
The males use an advertisement call to attract females, usually around after 60 mm of rain, from near the edge of the ephemeral ponds, and under bushes by Lescano (2011). The call is similar to a cricket call with 3 - 12 high-pitched, repetitive notes in a pulsed structure that begin suddenly, hold stable amplitude, then abruptly descend. These notes last between 499 - 1056 ms and are emitted at a rate ranging from 46.2 - 66.6 notes/min. Pulse duration ranges from 3 - 9 ms and pulse rate ranges from 81.8 - 111.7 pulses/s. The dominant frequency is high, ranging from 4109.7 - 5060.1 Hz. Lastly, secondary harmonics range from 8953 - 9150 Hz. Some males have slight variation in call, but they did not result in any male-female interactions. Both sexes use a distress call when they are threatened, in addition to sudden movements and mouth-gaping to broadcast the signal and potentially bite aggressors. The distress call ranges from 33.6 - 81.6 pulses with a duration ranging from 233 - 1074 ms. In comparison to the advertisement call, its dominant frequency is lower (2518.56 - 3473.96 Hz) and has poorly defined energy bands at higher frequencies (Lescano 2011).
Regarding diet, C. pierottii is an opportunistic, generalist predator, mainly feeding on bees, coleopterans, and anurans; the juveniles are ambush generalist foragers. There is no significant correlation between prey size and predator size, indicative of the explosive behavior of C. pierottii, as the frogs exploit what scarce, temporary resources they have to survive and breed (Wells 2007; Pueta and Perotti 2013).
Chacophrys pierottii larvae are Orton type IV larvae (thus having a singular, asymmetrical spiracle that drains both gill chambers and labial teeth in singular rows) with keratinized mouthparts to scrape food from substrates (Orton 1953; Quinzio and Reiss 2017).
Quinzio and Reiss (2017) determined that at Stage 38, the snout-vent length ranges from 33 - 42 mm. Quinzio et al. (2006) mainly described larvae at stage 37, but larval stages 28 - 36 can be found in their work as well. Meanwhile, Faivovich and Carrizo (1992) observed larvae at Stage 38 - 39 then let the larvae metamorphosis in captivity to correctly identify them as C. pierottii. The eyes of C. pierottii larvae are dorsolateral, with diameter increasing and interocular distance decreasing from Stage 37 to 38. At Stage 37, the snout gently curves laterally and is rounded dorsally, but by Stage 38, the snout narrows dorsally, and a central, upward-pointing appendage is present halfway between the nostrils and the snout’s end. This appendage is longer than it is wide, flattened, and slightly inclined backwards. Dorsolateral and rounded nostrils reduce in diameter and internarial distance from Stage 37 to 38, in addition to becoming flared (Faivovich and Carrizo 1992; Quinzio et al. 2006). At Stage 37, the oral disc is anteroventral and notched, with its anterior labium visible dorsally. The oral disc is surrounded by a single, continuous row of well-separated marginal papillae, which have wide bases and rounded tips, and a small number of submarginal papillae are visible in the lateroventral constriction area (Quinzio et al. 2006). By Stage 38, the oral disc becomes intra-angular at the margins and is visible ventrally, but not dorsally. Its frontal region has a single row of marginal papillae and a double row of papillae at the ends. Its upper lateral region has a double row of papillae, while the lower lateral region a single row of papillae (Faivovich and Carrizo 1992). At both stages, the jaws are keratinized, pigmented, serrated, and feature an arched-shaped upper jaw. Stage 37’s lower jaw is V-shaped with more serrations than the upper jaw, while Stage 38’s is semicircular with a central notch, free margins, and serrations like supraostodont. Stage 38’s upper jaw also has free margins and large triangular serrations (Faivovich and Carrizo 1992; Quinzio et al. 2006). The labial teeth of Stage 37 are curved, long, and hook-shaped on the distal tips, with a labial tooth row formula of 1 (1+1)/(1+1) 2 (Quinzio et al. 2006). The keratodonts of Stage 38 are longer than they are wide, rod-shape, and large, curving towards the mouth. Their disposition corresponds to the labial tooth row formula 1/(1+1), thus the supra-angular row is half of the frontal infra-angular row. Notably, such a dental system indicates the larvae is carnivorous, but in captivity, the larvae only ate food for tropical fish instead of live food (Faivovich and Carrizo 1992).
At Stages 37 - 38, the larvae’s body is slightly depressed and roughly half of the larvae’s total length. The body is dorsally heart-shaped, longer than it is wide, and wider than it is tall at Stage 37, while at Stage 38, the body is ovoid. The internal organs are ventrally visible at both stages, and a short spiracle is sinistrally and anteriorly positioned (Faivovich and Carrizo 1992; Quinzio et al. 2006). Furthermore, Quinzio et al. (2006) determined that under magnification, lateral line systems are visible. Both stages features a short, cylindrical, and medial vent tube, separated by the abdominal skin through a fold. From Stage 37 to 38, the tail length roughly doubles and changes from a rounded tip to a sharp tip (Faivovich and Carrizo 1992; Quinzio et al. 2006; Quinzio and Reiss 2017). Both stages have a dorsal fin starting slightly before the tail-body junction and a ventral fin that begins at the hypaxial musculature. The fins are roughly symmetrical at Stage 37, but the dorsal fin is slightly taller than the ventral fin at Stage 38 (Faivovich and Carrizo 1992; Quinzio et al. 2006). Quinzio et al. (2006) found that at Stage 37, the tail’s musculature has poorly defined myotomes.
In life, the tadpoles have brownish-gray dorsums and unpigmented bellies. Their eyes have yellowish irises with dark spots surrounding rhomboidal pupils. A dark pigmentation surrounds the nostrils as well (Faivovich and Carrizo 1992; Quinzio et al. 2006). Quinzio et al. (2006) noted that at Stage 37, the caudal epaxial musculature is densely pigmented, and the inferior border of the hypaxial musculature has stellate melanophores. The transparent dorsal and ventral fins have some isolated melanophores as well. Meanwhile, Faivovich and Carrizo (1992) determined that at Stage 38, the musculature of the tail is densely pigmented in the upper half and the lower edge, with a white irregular strip between them. Caudal fins are sparsely pigmented as well. Furthermore, pigmentation of the back decreases to the sides and the intraocular region is reddish.
In preservation, any pigmented areas are darker (Quinzio et al. 2006). The labial tooth row formulas are different, as well as a respectively absence and presence of a nasal appendix. Quinzio et al. (2006) has no explanation for these differences.
Faivovich and Carrizo (1992) collected the larvae in a 15 cm deep and 3 meters wide muddy pond; Lepidobatrachus laevis and Leptodactylus cf. bufonius were also found in the waters. The water temperature was 32 degrees Celsius, and aquatic ferns, of the genus Marisilia, were observed in the water. Quinzio et al. (2006) collected the larvae in temporary ponds formed by rainfall, 1 m in depth and featuring submerged vegetation of Allenrolfea vaginata and A. patagonica.
Before metamorphosis, the larvae are suspension feeding omnivores, with smaller larvae feeding on detritus (shrimp eyes, insect pieces, wood) and large larvae feeding on macerated soft food (such as shrimp) and algae (Fabrezi and Cruz 2014; Fabrezi and Cruz 2020). The larvae of C. pierottii grow intensively and complete metamorphosis in 2 weeks. Such rapid development is influenced by competition, desiccation, and food resources (Fabrezi and Cruz 2014; Fabrezi and Cruz 2020). Metamorphosis occurs when the vent tube is lost and forelimbs emerge. There is a cessation of feeding, evident by an empty gastrointestinal tract and loss of keratinized mouthparts by Stage 42 (Fabrezi and Cruz 2020). Quinzio and Reiss (2017) also determined that the olfactory eminence develops during metamorphosis.
A well studied aspect of C. pierottii is their heterochrony, or timing of development. It is proposed to be influenced by the ontogeny of the thyroid gland, which supplements thyroid hormones. Starting at Stage 27, thyroid glands are small masses anterior to the musculus geniohyoideus origin; by Stage 35, premetamorphosis, C. pierottii has compact, cordiform glands with distinct and numerous follicles; by Stages 37 - 39, prometamorphosis, the follicle number increases and glands become longer, bigger, and lose their cordiform shape; by Stage 41, postmetamorphosis, glands are cylindrical. It is a possibility that the multiple heterotopic follicles support rapid metamorphosis due to further secretion of thyroid hormones. In addition, a diet that provides exogenous thyroid hormones (such as through protein from shrimp) supports the rapid growth and development of the larvae. Notably, at Stage 37, C. pierottii has the largest thyroid glands, when compared to Lepidobatrachus laevis, Lepidobatrachus llanensis, and Ceratophrys cranwelli (Fabrezi and Cruz 2014).
In regards to development and internal morphology, during larvae development, fat bodies are absent and gonads are undifferentiated. From stages 27 - 41, the coiled gut is visible ventrally, while the liver and pancreas are visible dorsally on the right side of the gastroduodenal loop (which is positioned anteriorly). The loop separates the esophagus and maniccotto glandulare, the cranial segment of the gut, from the long, double-coiled intestines. During limb bud stages, the lungs are well-developed and inflated and the gut begins to differentiate. The intestinal tract empties, the diameter and length of the intestine decreases (Stages 42 - 43), the stomach differentiates (Stage 44), and the rectum expands, forming the ampulla. At a microscopic level, the fundic region of the gastrointestinal tract, glandularae manicotto, which is composed of many tubular glands, undergoes transformation during larvae development. The submucosa and external musculature thicken, the gastric folds deepen, and the number and type of gastric glands increases. These glands differentiate at the end or after metamorphosis (Fabrezi and Cruz 2020).
Trends and Threats
Chacophrys pierottii is listed as “Least Concerned” in the IUCN, but the species is still threatened by destruction to its habitat. The Gran Chaco region is subject to global deforestation to create farmland or pastures for livestock, such as cattle, in addition to agrochemical runoff pollution. Chacophrys pierottii itself is threatened by an illegal pet trade as the frogs are collected to be sold during explosive breeding events (Vellard 1948; Marangoni et al. 2018; IUCN 2021). Road development in Paraguay has also led to habitat loss (IUCN 2021).
In effort to conserve the species, C. pierottii is protected in Argentina’s Chancani Provincial Nature Park and Natural Forest Reserve, Reserva Natural Formosa, Teuquito Multiple Use Reserve, Paraguay’s Parque Nacional Defensores del Chaco and Reserva Natural Cañada del Carmen, and Bolivia’s Kaa-lya (IUCN 2021).
Relation to Humans
Chacophrys pierottii is caught for the illegal pet trade, prevalent during its breeding season (Marangoni et al. 2018; IUCN 2021).
Based on osteology and chromosome number, Lynch (1971) concluded C. pierottii is not apart of the Ceratophyrs genus. Maxon and Ruibal (1988) used albumin protein analysis to further determine that C. pierottii is a sister group to Lepidobatrachus and Ceratophrys. Later, Faivovich et al. (2014) used seven mitochondrial and six nuclear gene sequences, in addition to ploidy levels and the adaptation of a cocoon mechanism, to support this position; however, the analyses provide poor support.
The position of C. pierottii as a sister taxon to Lepidobatrachus is supported through the ontogeny of the olfactory system and tadpole development ((Quinzio and Reiss 2017; Fabrezi and Crus 2020).
Originally known as Ceratophyrs pierotti, Chacophyrs was distinguished through a variety of osteological factors (Reig and Limeses 1963; Lynch 1971).
Chacophrys pierottii is a diploid species with a karyotype (Faivovich et al. 2014).
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Originally submitted by: Hong Nguyen (2023-02-14)
Description by: Hong Nguyen (updated 2023-02-14)
Distribution by: Hong Nguyen (updated 2023-02-14)
Life history by: Hong Nguyen (updated 2023-02-14)
Larva by: Hong Nguyen (updated 2023-02-14)
Trends and threats by: Hong Nguyen (updated 2023-02-14)
Relation to humans by: Hong Nguyen (updated 2023-02-14)
Comments by: Hong Nguyen (updated 2023-02-14)
Edited by: Ann T. Chang (2023-02-14)
Species Account Citation: AmphibiaWeb 2023 Chacophrys pierottii: Chaco Horned Frog <https://amphibiaweb.org/species/5726> University of California, Berkeley, CA, USA. Accessed Mar 20, 2023.
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Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 20 Mar 2023.
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