Posted by: floridanature | August 8, 2008

The Apple Snail: The Ecology of Mollusk Zen

I saw my first clutch of apple snail eggs on Juniper Spring Run years ago. They were clumped together on the green stem of a flowering pickerel weed, and each was the size of a fat bb. A friend insisted they were “lizard eggs.” That seemed plausible at the time, although I had trouble picturing terrestrial reptiles skipping over the water to lay their eggs on an aquatic plant. But Florida was a peculiar place, so I figured most anything was possible.

Not long afterwards, I started paddling the Wekiva and found scads of similar eggs along the river. Some of the clutches were white while others were pink. I thumbed through a zoology text this time and discovered the eggs belonged to an aquatic mollusk, the Florida apple snail (Pomacea paludosa). I also learned the eggs were laid on stems of plants just above the water for a reason: They were high enough up so the egg would not drown, but not so high that the newly-hatched baby snails would have trouble reaching the water.

This was a key part of my information gathering—of learning the right name, and the right behavior.

I also found Pomacea was the largest freshwater snail in the world, that there were over 100 species, and its range was almost entirely subtropical. The Florida version could grow to two inches in shell diameter; its South American cousins could grow twice that.

Florida Apple snails graze on algae mats attached to underwater plants like eel grass, a plant that needs clean, clear water to thrive. The grass does well in healthy lakes rimmed with wetlands and spring-fed rivers like the Wekiva.

Once when I was out paddling by myself in the scarlet glow of twilight, I saw a limpkin pecking at a live apple snail with her curved beak. Sweetgum draped with moss sagged overhead, and cypress knees lined the soggy river bank, creating a moment that was heartbreakingly timeless and rare. The limpkins, the wading bird with the plumage reminiscent of a deer fawn, was becoming scarce. Wildlife biologists had figured a mainstay of the bird’s diet was the apple snail. But, the snail’s own fodder—the eel grass-algae—was declining because its habitat was in trouble. As the apple snail goes, so goes the limpkin. This lesson was about ecology.

I learned of a decade-old study in the spring-fed Wakulla River of north Florida. It revealed that nutrients from an upland spray field for wastewater from the city of Tallahassee had once emerged from the deep, powerful head spring. Until the spraying was halted, elgrass died and apple snails disappeared from the spring run. The limpkin population was diminished by almost half. Back home, our own Wekiva was facing similar dilemmas and I wondered when the limpkins here would also began to disappear.

This part of my learning was the most disturbing: Putting waste into the ground takes it out of sight, but it doesn’t take it out of mind. This is especially true in Florida where the limestone under our earth is so porous. Protecting a spring extends far outside the basin of its run, deep into the labyrinthic limestone of the aquifer—miles upstream of where the spring emerges from the ground. Thus, the apple snail has meaning far beyond its own life and death, and it often extends down to the deep, hidden aquifer that feeds the springs of our landscape.

Once, I seined an apple snail from a wild stream. I put it into my office aquarium, which is populated with native plants and fish. The snail set about its tiny business, moving about with its stoic mollusk determination. Over the log, up the glass, down the glass. One day, I lifted the plastic tank lid to scatter food and found a clutch of pink eggs on the underside. Unlike many hermaphodictic snails, the Apple Snail is distinctly male or female, and I had a momma.

The eggs would hatch in two weeks or so, and tiny little apple snails would tumble out of each. I was delighted about witnessing the genesis of life. But there was another lesson to be learned.

The snail, pulled from its home and living in a sort of aquatic zoo, still wanted to propagate. Although it is near the bottom of the food chain, the animal showed a unity of purpose often foreign to humans.

When we kill our springs and lakes and rivers, we kill something in ourselves—something that nestles deep inside the spirit. Surely, we will live on in some form, but at what price?

A future without the enchantment of natural places is not one most sane humans would consciously choose. Instead, it is being chosen for us by powerful growth-obsessed zealots who live in a sort of fantasy-land of denial. Florida is losing its natural lands at a rate of 20 acres an hour and there’s no sign of it slowing down. Despite our human cleverness, we still haven’t figured out a way to balance growth with environmental sustainability.

A snail egg isn’t laid by a lizard, no matter how much we might think so. And the natural landscape of Florida isn’t infinite. Its intricacies are complex and finely geared to inextricable ecological rhythms.

Having bogarted our way to the top of the food chain in a heartbeat of time, we are just now facing the accountability that comes with the job. The apple snail, for whom all of life may be a single zen moment of being, might have some answers for us.

But we have to stop rushing about, listen closely and pay attention to the details. Especially when they come to us in a whisper of tiny pink eggs.

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Responses

  1. Great article. I am finishing up a research/field technician position up here in Gainesville. We monitor vegetation that is used by the snail kite. We work down in the Everglades and the Kissimmee Chain of Lakes(Greater Everglades Ecosystem). The apple snail is an important food source for the snail kite. Have you heard about the exotic apple snails that are found in Florida?

  2. Thanks, much. Good luck on your work with the snail kite!
    Yes, have seen the exotic apple snail and its eggs, which are pretty easy to spot. Not yet on the Wekiva, but have seen on Withlachochee and some isolated lakes.


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