The strawberry poison frog, strawberry poison-dart frog or blue jeans poison frog (Oophaga pumilio, formerly Dendrobates pumilio) is a species of small poison dart frog found in Central America. It is common throughout its range, which extends from eastern central Nicaragua through Costa Rica and northwestern Panamá. The species is often found in humid lowlands and premontane forest, but large populations are also found in disturbed areas such as plantations. The strawberry poison frog is perhaps most famous for its widespread variation in coloration, comprising approximately 15–30 color morphs, most of which are presumed to be true-breeding. O. pumilio, while not the most poisonous of the dendrobatids, is the most toxic member of its genus.
Diet
The diet of O. pumilio causes the skin of the amphibian to become toxic in nature when certain subspecies of mites and ants are ingested very similar to many other poison dart frogs. Alkaloid toxins are organic in nature and contain nitrogenous bases that react with carbon and hydrogen groups. Pumiliotoxin 251D is the specialized toxin that is sequestered by this species of frog. This toxin has a negative stimulating effect on cardiac function and is a severe disruptor of the sodium potassium ion channels within cells. Upon ingestion of Pumiliotoxin 251D, organisms preying on O. pumilio experience convulsions, paralysis, and death.
It has been found that once O.pumilio reaches sexual maturity, their granular glands significantly increase in size and their diet shifts. In females, it is common to find about 53% more alkaloids than adult males.
Oribatida mites belonging to the glandulate suborder Brachypylina are an important origin of pumiliotoxins in O. pumilio. Hexane-extraction techniques indicate presence of alkaloid toxins in Brachypylina. Toxins appear to be biosynthesized in adult mites, as nymph and larval stages of the arachnid do not carry the toxins. Experimental analysis of this species of mite show alkaloid toxins are found almost exclusively in the opisthonotal glands of mites of the Scheloribatidae. Oil glands of the mite contain the toxins and are then released internally as the amphibian digests the arthropod.
O. pumilio can also attribute its cutaneous toxicity to its rich diet of formicinae ants. Species of the formicine genus Brachymyrmex contain pumiliotoxins which the frogs incorporate and accumulate poison from. There is a variability of alkaloid profiles among populations and individuals of O. pumilio, which is indicative of varying levels of available prey within their infraspecific habitats. Research and physical analysis reveal that maternally derived alkaloids exist in young tadpoles. The increase in alkaloids in tadpoles suggests that the females are providing more chemical defenses to their more vulnerable young. This being one of the first found examples of provisioning that occurs after hatching. During tadpole-rearing, mother frogs feed their young an unfertilized egg from their ovaries after dropping each individual tadpole into a repository of water usually found in a bromeliad. Tadpoles lacking the obligate nutritive egg diet do not contain the alkaloid. This step is crucial for the tadpoles to sequester the alkaloid from their mother; without such, young tadpoles become susceptible to predation by arthropods and other frogs.
Behavior
Oophaga pumilio is diurnal and primarily terrestrial, and can often be found in leaf litter in both forested and disturbed areas. Studies have shown that the optimal habitat is determined by the male, considering the resource benefits and defense costs. Males tend to expend more energy defending smaller but higher quality areas. There has also been evidence that the better competitors and fighters are the males guarding smaller sites with higher female density. In most Anura the louder the vocalization when competing usually means they are larger in size and in better health. However, in the O. pumilio species researchers have determined that these frogs call out at a lower rate to limit their energetic expenditures. Females, on the other hand, simply distribute themselves according to tadpole rearing sites.
Though brightly colored and toxic, these frogs are relatively small, growing to approximately in standard length.