IMAGE: ISKANDAR ET AL., 2014, PLOS ONEMost frog and toad species reproduce via external fertilization: males bathe extruded eggs with sperm as they grip females’ bodies to encourage them to mate. A few species employ internal fertilization. Some of these amphibious innovators give birth to fully formed froglets. Now scientists have discovered a new frog species that fertilizes eggs internally, with females birthing tadpoles that will later metamorphose into frogs. Announcing their findings in PLOS ONE last week (December 31), researchers working on the Indonesian island of Sulawesi described the unique reproductive strategy of a new fanged frog species, Limnonectes larvaepartus.
The researchers who described the new frog species also observed live tadpoles in the oviducts of females while preparing specimens for study, and on one occasion, they saw a gravid female extrude tadpoles in-hand when she was captured. “In total, we have either observed tadpoles in the oviducts or direct-birth of tadpoles on 19 occasions,” the authors wrote. Although they found evidence to suggest that the frogs were letting tadpoles metamorphose in the oviducts before birthing froglets, the scientists concluded that it was more likely that they were giving birth to tadpoles that would undergo metamorphoses outside their mother’s body. They found free-living tadpoles during their collecting, and never collected a gravid female with froglets inside her oviducts.
(Hat tip: National Geographic’s Laelaps)