Description

Diagnosis: Small reddish-brown tree frog (SVL 30-37 mm) with numerous white tubercles covering the body; cranial and supratympanic crests; slender body and limbs (Alcala and Brown 1998).

Description: Nyctixalus spinosus is a small tree frog (SVL 30-37 mm) with a slender body and limbs. The head is longer than wide and bears cranial as well as supratympanic crests. Skin of the anterior of the head is co-ossified to the skull. The snout is truncated and high, sloping down and back toward the mouth and projecting over lower jaw. A distinct and prominent canthus rostralis is present. The canthi continue posteriorly as bony ridges from the anterior of the orbit along to the occipital region. The snout is slightly narrower behind the nostrils and is concave between the eye and nostril. The loreal region is concave. The nostrils are located very near the tip of the snout. No vomerine teeth are present. Choanae are large and elongated. The tongue is elongate and divided at the posterior with two small rounded "horns" present. No papilla is present. The interorbital region is depressed. Tympanum is distinct, lying very close to the eye and measuring about four-fifths the diameter of the eye. Large adhesive toe and finger discs are present, along with intercalary cartilage between the distal and penultimate phalanges. Fingers lack webbing and have distinct transversely widened discs. Terminal phalanges are bifurcate (shape intermediate between a Y and a T). Each disc has a distinct circummarginal groove, continuous with a transverse groove crossing near the middle of the ventral surface of the disc. Finger lengths are III>IV>II>I. Toes are about one-third to one-half webbed, with third and fifth toes of unequal length. The discs on toes are smaller than those of the fingers. Subarticular tubercles are well developed. There is a prominent inner metatarsal tubercle and a small outer metatarsal tubercle. Tibiotarsal articulation extends slightly beyond the tip of the snout. The eye is large with its diameter about equal to its distance from the nostril. Pupils are horizontal and the iris color is gold. Eyelids are extremely rugose. Dorsal surfaces are reddish brown with numerous whitish and pointy tubercles on rough and granular skin. These tubercles are present on upper surface of limbs and fingers, on the side of the head, and even under digits. Belly is granulate and inner aspect of thighs and tibia are smooth. No specimens were noted with vocal sacs (Taylor 1920; Alcala and Brown 1998).

Nyctixalus spinosus has a brownish dorsum with scattered lemon yellow to orange spots. The anterior part of the head is darker brown. Interscapular region has two prominent orange spots with darker margins present, above and slightly behind the tympanum. Smaller yellow spots are found on the superciliary region as well as along the lip and canthus rostralis, below the tympanum and along each side of the back. Snout tip has a small prominent spot. Limbs have brownish dorsal surfaces, plus reddish orange on anterior and posterior surfaces. Arms also have two yellow spots with darker margins, and legs also have larger yellow spots. The belly, sides, and undersides of limbs are orange-yellow. Fingers and toes have yellow spots (Taylor 1920).

Variation: Basilan specimens had orange bellies (rather than the orange-yellow seen in the Bunawan, Mindanao specimens), with many large yellowish-white spots on the chin and sides of the belly; yellowish spiny granules on the heels and below the vent; and Toes III and V of equal to nearly equal length (vs. Toe III > Toe V in the type specimen, from Mindanao); variable number of dorsal yellow spots; nares closer to the snout tip.

Similar species: N. pictus is also found in the Philippines (on Palawan). It occurs at a lower elevation (150-300 m) and can be distinguished by its darker body color (cinnamon brown to chocolate), fewer tubercles (numerous in N. spinosus, and lack of cranial and supratympanic crests (present in N. spinosus) (Alcala and Brown 1998).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Philippines

View distribution map in BerkeleyMapper.

Nyctixalus spinosus is endemic to the Philippines and is native to Mindanao, Leyte, Bohol and Basilan Islands, with an altitudinal range of 500-1,100 m above sea level (Alcala and Brown 1998; Stuart et al. 2008). It probably occurs more widely than current records suggest, especially in areas between known sites (Stuart et al. 2008). N. spinosus inhabits the forest floor litter of mountain and lowland rainforests (Alcala and Brown 1998), as well as submontane dipterocarp forest (Nuñeza et al. 2009). It lays its eggs in tree holes (Alcala and Brown 1998).

Life History, Abundance, Activity, and Special Behaviors
N. spinosus is arboreal and nocturnal. This species is oviparous and lays around 30-40 eggs that are probably attached to the walls of tree holes (Alcala and Brown 1998). Tadpoles of this species have been found in tree holes that develop when tree limbs have been broken off and adjacent tissue has decayed, forming tanks from anastomosed trunk buttresses (Taylor 1962, cited in Wassersug et al. 1981). Taylor (1920) also noted that he found both adults and tadpoles at the bottom of a tree hole filled with both water and rotting leaves, in a tree trunk about 0.5 meters above the forest floor. Adults are very active and are fast jumpers (Taylor 1920). They feed largely on ants, according to Taylor (1920), who also noted high numbers of "aquatic" ants among leaves and detritus in the water.

Larva
Tadpole body length is one and a half times the width and much shorter than the tail. Nostrils are much nearer to the tip of the snout than the eye. Eyes are dorsal. The interorbital distance equals the distance between the eyes and the nostrils. The upper beak is very slightly curved and the lower beak is V-shaped. The specimens examined by Taylor (1920) were not well preserved, and he was unable to determine the tooth row formula. Tadpole color in life is dark brown to black with a lighter venter. Older tadpoles have tiny yellow spots. Shoulder spots are visible by the time the anterior limbs have emerged.

Tadpoles appear phytotelmic although no detailed development are documented yet (Wassersug et al. 1981).

Trends and Threats
This species is rare (Alcala and Brown 1998). A major threat is the loss of the species' habitat, the lower montane and lowland rainforest, due to agricultural development and human settlement (Nuñeza et al. 2009).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Intensified agriculture or grazing

Comments
This species was originally described by Taylor (1920).

References

Alcala, A. C. and Brown, W. C. (1998). Philippine Amphibians: Illustrated Field Guide. Bookmark, Inc., Philippines.

Brown, R. M. (2007). ''Introduction to Robert F. Inger's Systematics and Zoogeography of Philippine Amphibia.'' In R. F. Inger (Ed.), 1954. Systematics and Zoogeography of Philippine Amphibia. Natural History Publications, Kota Kinabalu, Malaysia.

Nuñeza, O. M., Ates, F., and Alicante, A. (2009). ''Distribution of endemic and threatened herpetofauna in Mt. Malindang, Mindanao, Philippines.'' Biodiversity and Conservation, 19, 503-518.

Stuart, S., Hoffmann, M., Chanson, J., Cox, N., Berridge, R., Ramani, P., Young, B. (eds) (2008). Threatened Amphibians of the World. Lynx Edicions, IUCN, and Conservation International, Barcelona, Spain; Gland, Switzerland; and Arlington, Virginia, USA.

Taylor, E. H. (1920). ''Philippine amphibia.'' The Philippine Journal of Science, 16, 213-360.

Taylor, E.H. (1962). ''The amphibian fauna of Thailand.'' University of Kansas Scientific Bulletin, 43(8), 265-599.

Wassersug, R. J., Frogner, K. J., and Inger, R. F. (1981). ''Adaptations for life in tree holes by rhacophorid tadpoles from Thailand.'' Journal of Herpetology, 15(1), 41-52.

Species Account Citation: AmphibiaWeb 2022 Nyctixalus spinosum: Spiny Tree Frog <https://amphibiaweb.org/species/4381> University of California, Berkeley, CA, USA. Accessed Dec 28, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 28 Dec 2024.

AmphibiaWeb's policy on data use.