Florida is home to a wide variety of native plant, animal and fungus species which make up the biosphere. These lifeforms exist collectively and, with the aid of the weather, balance their respective populations by way of utilizing the other species and their byproducts.
The introduction of invasive species from other parts of the world have altered, in extreme cases eliminated, the balance. The local species have little or no way to adapt to these environmental interlopers.
A common trait of exotic invasive species is they leave a visible trail of change and destruction. It is easy to see the results of their presence, in most cases.
One exception to the trait of obvious visible presence and damage is the hammerhead flatworm. Classified as a land planarian, Bipalium kewense Moseley, as it is scientifically known, is making its presence felt out of the sight of most terrestrial residents.
Land planarians, the exotic carnivorous flatworms native to southeast Asia, are easy to identify by their shovel shaped head.
Land planarians are carnivorous and most species are active predators, with a few species acting mostly as scavengers of recently deceased target invertebrates. In their home ranges, the land planarians’ presence and activity are considered a measure for overall environmental health.
There are over 830 known species, most being found in tropical forests. These settings provide the flatworms plenty to eat and adequate moisture to flourish.
Unfortunately, the international plant trade is thought to have relocated enough of these simple creatures to parts of the world where they are becoming a problem for native species. They are frequently found in and around potted plants which have rich soil and earthworms.
The hammerhead flatworms found in panhandle Florida can track their prey, in particular earthworms. Their slow pace and obvious trail easily leads the faster exotic flatworm to its target.
Once the planarian captures the earthworm it uses the muscles in its body, as well as sticky secretions, to prevent escape. The secretions also contain a neurotoxin, tetrodotoxin, employed to subdue its prey.
Unique to land planarians, they propel themselves with what has been described as a creeping sole on their underside. The result is they glide smoothly with a motion similar to many native snakes, and for which they are occasionally mistaken.
Bipalium kewense can be identified by its dusky pale color, a dark line in the center of its back and running the length of its body and a distinctive shovel shaped head. This species may reach lengths up to five inches.
Land planarians are usually found in dark, cool, moist areas and under objects such as rocks, logs, in leaf litter or under shrubs. They will be seen on the soil’s surface only after heavy rains.
Most of their movement and feeding occurs at night. High humidity is essential to their survival, but they can survive water loss if it does not exceed 45 percent of their body weight.
As with most exotic invasive animals few, if any, local creatures will eat them. In this case it is believed their taste is too offensive for even the most indiscriminate native to consider them a menu selection.
In a twist of irony, there is one group of creatures which will eat land planarians, and that is other land planarians. Hopefully, their appetite for the familiar will only intensify.
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