Honduras Spikethumb Frog

Plectrohyla dasypus is a frog with a snout vent length of 31.5 - 44.0 mm for males. It has a short snout (4.0 mm long). The distance from the tip of the snout to the anterior edge of the orbit is 80% the size of the diameter of the eye. From the lateral view, the snout is truncate. From a dorsal view, the snout tapers gradually to a sharp point and lacks a vertical rostral keel. The canthal ridge is thickened and the loreal region is slightly concave. The lips are thickened moderately and barely flare. The nostrils are positioned near the tip of the snout; they are protuberant and are directed towards the dorsolateral. The internarial distance is 3.2 mm and the area is slightly depressed where it converges with the canthal ridges. The top of its head is flat. The interorbital distance is 4.8 mm and the diameter of the eye is 5.0 mm. There are heavy dermal folds that extend posteriorly from the posterior edge of the orbit. This fold barely covers the upper edge of the tympanum, so the rest of the tympanum is distinct. The arms are robust, with the upper arm slightly lighter than the forearm. There is a distinct transverse fold on wrist. It does not have an axillary membrane. The long, slender fingers have vestigial webbing; the relative finger lengths are 1 < 2 < 4 < 3. The subarticular tubercle is large and subconical. The terminal tubercle on the fourth finger is normal. The supernumerary tubercles are in single rows on the proximal segments of the fingers. A prepollex is present that appears small, flat, blunt, non-bifurcated, and for which the bone does not protrude through the skin. The heels overlap slightly when the hind limbs are pressed close. The toes are long and slender; the relative toe lengths are 1 < 2 < 5 < 3 < 4, and the fifth toe is almost as long as the third toe. The discs on the toes are somewhat large. The subarticular tubercles are also somewhat large and are subconical. The supernumerary tubercles are small and are found in a single row on the proximal segment of each digit. Toes are webbed about three-fourths of the way, extending from the base of the penultimate phalanx of the first toe to the penultimate phalanx of the second, and this repeats between the base of the penultimate phalanx of each toe to the penultimate phalanx of the toe next to it. The opening of the anus is posteroventrally at the mid-thigh level. The anal sheath is short and broad. The skin on the dorsal surfaces and throat have some tubercles. Skin on the chest, belly, and ventral surface of the thighs and anus are granular, while the shanks’ ventral surface is smooth (McCranie and Wilson 1981).The tadpoles have a body length of 14.5 - 16.4 mm and a total length of 40.8 - 44 mm. In the dorsal view, the body is ovoid and the snout if bluntly rounded. The eyes are small and are dorsolaterally directed. The nostrils are anterolaterally directed and are slightly closer to the eyes than they are to the tip of the snout. The spiracle is sinistral on the midline on the midlength of its body. The long cloacal tube is dextral. The caudal musculature is moderately robust and extends near to the tip of the tail. The fins are shallow. The caudal musculature is at the midlength of the tail and is deeper than either the ventral or dorsal fins. The dorsal fin does not extend onto the body. The mouth is ventral and at its greatest width is a little over half the width of the body. The oral disc is not notched at the margin. A single row of small papillae completely borders the edge of the oral disc and a row of larger papillae are present along the middle to the fringing row. It has a well-developed beak that has long, pointed serrations equal in length. The V-shaped lower beak is fairly robust (McCranie and Wilson 1981).Plectrohyla dasypus can be differentiated from other frogs of the Plectrohyla genus by its spines that are by its vocal slits. These spines are blunt, short, and prepollical, whereas other Plectrohyla frogs have spines that are long, pointed, and distally curved. It can also be differentiated by the color of its spots that are only found in this species and a few individuals of P. matudai (Duellman and Campbell 1992). P. dasypus lacks a vertical rostral keel that is seen in other species of the Plectrohyla genus. In general, P. dasypus is slightly larger than the other frogs of its genus (McCranie and Wilson 1981).This species has small, scattered black spots with have a lime-green border on a bronze dorsum (Duellman and Campbell 1992). It has a black stripe that follows the canthus above the tympanum to above the arm. The venter and hidden leg areas are dark grey, as is the toe webbing. The eyes are copper and have black reticulations. The chin is grey with a thin bronze layer. In preservative, the dorsum is dark grey with small, scattered black spots and the venter is grey. The tadpole has a creamy tan caudal musculature that has dark brown flecks lengthwise. The fins are translucent and have dark brown spots, with more spots on the dorsal fin (McCranie and Wilson 1981).The forelimbs between individuals may vary with some paratypes having hypertrophied forelimbs while others do not. In preservative, the females have venters that are paler than males (McCranie and Wilson 1981).The species authority is: McCranie and Wilson (1981). ''A new hylid frog of the genus Plectrohyla from a cloud forest in Honduras.'' Occasional Papers of the Museum of Natural History of the University of Kansas, 92, 1-7.The Plectrohyla and Hyla histineta groups are considered to be allopatric ecological counterparts. They share a few synapomorphies with each other: medial ramus of pterygoid that is long and articulates with the otic capsule, thick dorsal skin, fringing papillae that are continuous on the upper lip (Duellman and Campbell 1992). The species name is the generic name of the nine-banded armadillo, Dasypus novemcinctus. The common name of the armadillo is Cusuco, which is the location where P. dasypus is found (McCranie and Wilson 1981).(image, http://amphibiaweb.org/images/amazing/amazing_logo.jpg) Featured in Amazing Amphibians on 11 March 2013 (http://amphibiaweb.org/amazing_amphibians/20130311_Plectrohyla_dasypus.html)

This species is native to Honduras. It is found in Parque Nacional Cusuco (Cusuco National Park) in the Sierra de Omoa, Departamento de Cortes, north-western Honduras. It can be found at an elevation between 1,410 and 1,990 above sea level (Cruz et al. 2010). Plectrohyla dasypus can be found along stream in a hardwood cloud forest (McCranie and Wilson 1981).

The canopy trees in Cusuco National Park contain a lot of epiphytes, such as bromeliads, where some individuals are found during the day. Other individuals have been observed swimming in the stream during the day or in the vegetation along the stream. They will come out of the stream at night to forage (McCranie and Wilson 1981). They also use this stream to breed. Because of this, it is likely that males are more territorial of the stream. While there have not been studies done specifically for P. dasypus on this matter, this pattern is seen in other species of the Plectrohyla genus. No studies have been done on the reproductive behavior of this species, but studies on other species of the Plectrohyla have suggested that females reproduce continuously throughout the year, so this inference may be made for P. dasypus (Duellman and Campbell 1992).

This species has suffered a rapid decline due to Batrachochytrium dendrobatidis (Bd), the amphibian fungal pathogen that results in chytridiomycosis. Bd causes behavioral symptoms such as lethargy and the loss of righting reflex immediately prior to death. In 2007, the presence of Bd was confirmed in P. dasypus’s habitat, and 78% of the population displayed symptoms of Bd infection. This pathogen appears to be the cause of a drastic population decline, with about 80% of the population disappearing within the last ten years. This rapid decline is one of the reasons why it is currently listed as Critically Endangered by the IUCN (Cruz et al. 2010). There is a correlation between oral defects in larvae and Bd infection, so it is possible that the defects are a result of infection. The oral defects included abnormal jaw sheaths and tooth row formations that were reduced, disrupted, or missing entirely. The presence of Bd in Cusuco National Park can be dated back to 1996, but the population of P. dasypus began to decline around 1994, so it is possible Bd has played a role in the decline since the beginning. There has also been habitat degradation and agricultural practices in Cusuco National Park that may have an impact on the environment. These environmental stressors may have an impact on P. dasypus’s health, making them more susceptible to Bd (Kolby 2009; Kolby 2010).

Plectrohyla dasypus (common name: Honduras spikethumb frog) is a species of frog in the family Hylidae. It is endemic to the Sierra de Omoa in the Cortés Department of northwestern Honduras. The species range is within the Cusuco National Park.

Natural habitats of Plectrohyla dasypus are lower montane wet forests. They are found on low vegetation along streams and in arboreal bromeliads, and breed in streams. Once moderately common, the species has undergone a dramatic decline that is attributed to chytridiomycosis.