The strong-haired frog, also known as the strong-knot frog, the fractured frog, and the hairy frog, belongs to the sectional frog family, in the genus Monotyped frog. Its common name derives from the hair-like structure on the trunk and thighs of male strong-haired frogs during the breeding season.
It is found mainly in Cameroon, the Democratic Republic of the Congo, Equatorial Guinea, Gabon, Nigeria, Angola and the Republic of the Congo. Its natural habitat is mainly in subtropical or tropical low-altitude rainforests, rivers, arable land, plantations and heavily degraded forests, while its larvae tadpoles live in rapids or at the foot of waterfalls.
The strong-haired frog is about 9-13 cm long from the end of the snout to the tail, and can generally reach 13 cm in males and 9 cm in females and weigh about 80 g.
The head of the strong-haired frog is large, the head width is larger than the head length, the snout end is short and round, the nostrils are closer to the eye, farther away from the snout, the pupils are erect, the tongue has grooves, and the two rows of plough bone teeth are located between the relatively large inner nostrils, and the eardrum is obvious, about half the size of the eye diameter.
The back is yellowish brown with yellow spots and dark black stripes between the eyes and back, but is less pronounced in darker-colored strong-haired frogs. The male frog is significantly larger than the female frog, the male frog has a pair of vocal sacs in the body, the front of the front paws first toe segment has a short ridge of three black thorns, two longitudinal, one transverse, the hind legs are very strong, with a strong ability to expand and shrink.
Only male frogs have narrow lung diverticules on their tails, while breeding male strong-haired frogs also develop hairy dermal papillae on their flanks and hind legs. These hair-like mastoids contain many linear arteries that increase the oxygen uptake of the epidermis when resocied, acting like gills in aquatic habitats.
Females lay their eggs in water, and for some time afterwards, the males stay with the eggs to protect them, and this special structure of the epidermal papillae helps the males to live better during this period of time when they are caring for their eggs and tadpoles.
The base of the thumb of the forelimbs of male strong frogs, like other tailless species, has a brown-black protrusion called a marriage tumor, which is conducive to the male frog lying on the back of the female frog when hugging the pair, hugging the female frog's wet and slippery body, because the female frog will lay eggs near the front legs, this position is conducive to the male frog to discharge semen directly on the egg, which will increase the fertilization rate of the egg.
For most of the year, the main task of the growing frog is to forage around in the forest. When the rainy season comes, their attention turns to mating activities. Male frogs usually enter rapids in streams or rivers, but they tend to wait in places where the flow is gentler in these streams or rivers. After a few days, the female will come out of the forest to hug the male.
After the female frog lays her eggs underwater, the male takes care of the eggs. Male frogs need to stay underwater, and the folds on their skin come into play because the water contains oxygen, and these wrinkles can store this oxygen, so that the male frog can stay underwater for a long time without floating on the surface to breathe.
After hatching into tadpoles, the eggs live in place for a period of time, sometimes in rapids at the foot of waterfalls, and the suction cups in their abdomen allow them to grasp the surface of rocks and other objects, after which they grow into young frogs and crawl to the ground to live.
The tadpole of the strong-haired frog is strong and carnivorous, and is notable by the growth of multiple rows of horn-like teeth. Adult frogs feed on slugs, polypods, spiders, beetles, and grasshoppers. The lifespan of the strong-haired frog can reach 5 years.
The strong-haired frog is known for having retractable "claws", but these claws are not real claws made of keratin, but bones. In case of danger, the strong-haired frog will break the bone, after which the sharp "claw" will pierce the toe pad and grow from the fracture. In addition, the researchers also found small bone nodules in the outer tissues of the toes of frogs. Each claw is immobilized in a bone nodule by a tough collagen filament.
According to the first-hand discovery of naturalist Gerald Darrell: when strong-haired frogs are captured or attacked, they will forcefully contract the muscles of the soles of their feet, the sharp bone claws will break the nodules and separate from the bones, the piercing toe pads will be exposed, and when the muscles relax, the claws will automatically retract.
The unique ability of the strong-haired frog can be regarded as a defensive behavior, but the mechanism of its claw expansion and contraction is still unknown, and it is generally speculated that the damaged tissue will regenerate after the danger has passed, and then the claw will naturally retract.
David Wecker, a biologist and amphibian researcher at the University of California, Berkeley, said the weapons appear to be endemic to the animal kingdom, but David Canatella, a reptile scholar at the University of Texas at Austin, questioned whether bone protrusions were used for defense, saying that "[the claws] of the strong-haired frogs can make them grip rocks more firmly."
The strong-haired frog is threatened by habitat loss and poor habitat water quality, but is currently not an endangered species. However, in areas where the hunt for strong frogs is more frequent, strong frogs are rare. In Cameroon, the locals use the brood frog as a delicacy, so the frog is often hunted and roasted, and hunters generally use a spear or machete to prevent it from being harmed by the claws of the frog.
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