Who would ever imagine spiders living underwater on an oyster reef? Believe it or not, they do. The tremendous productivity of our Gulf coastal waters has made them important to humans throughout history. Bivalves such as scallops, clams and oysters have always been key elements in the human connection to these habitats. Oysters in particular are important in many human cultures around the world but even the most astute consumers of these delectable shellfish typically have no idea about the multitude of organisms that live with oysters beneath the waves. The labyrinth of nooks and crannies created by the structure of oyster shells provides the perfect ingredients for a thriving community in our bays and tidal creeks. Many a student of coastal ecology has been utterly amazed at the personal discovery of the tiny creatures that lead very interesting lives among the shells of the oyster reef.
When students from local schools near Apalachicola Bay began noticing the occasional tiny spider crawling on the oyster shells that they were studying during their field trips with me, a few spider specimens were collected and sent to the University of Florida arthropod ID lab in Gainesville. I had assumed that the spiders had fallen into the student’s buckets from the tree canopy above so when the lab experts replied with a positive I.D. of Paratheuma insulana, the oyster spider, I was shocked. There was actually a spider that could live underwater. The lab scientists were also excited by the fact that this was a new county record in Florida for the diminutive, 2mm-long spider species. Apparently, these tiny, reddish-brown spiders are able to trap air on the tiny hairs that cover their bodies and subsequently breathe through their exoskeleton. Wow, SCUBA without air tanks and regulators!
Oyster spiders feed on another very unique inhabitant of the reef called the oyster springtail. Springtails are tiny insects that have a projection that folds under their body and allows them to “spring” into action when disturbed. There are many species of terrestrial springtails but one type actually lives underwater on the oyster reef along with the spiders. The tiny, black springtails feed on detritus trapped among the shells and in turn are an important prey for the spiders. A perfect example of the WEB of life; get it? (I couldn’t resist).
If these two strange creatures weren’t enough to peak your interest, there is an assortment of odd-looking polychaete (many bristled) segmented worms that slither among the shells as well. Commonly called bristleworms, they are part of the complex food web on the oyster reef. There are over 10,000 species of polychaetes described by scientists and some are red while others are bright green. Often their translucent bodies allow you to actually see the blood flowing through their circulatory system. One species is called the polydora worm and it has the capability to bore through oyster shells, creating what are commonly called “mud blisters.”
Most folks have no idea about the amazing diversity of species that occur at this micro-level in the ecosystem. From the oyster flatworm, with its distinctive rows of eye spots on the head, to a scuba diving oyster spider, it is a true adventure every time you look into the clusters of an oyster reef. A small field microscope of about 20 power is useful for observing these typically unseen creatures of our coastal estuaries. When you have the opportunity to explore an oyster reef on a low tide just remember two things. The closer you look…the more you’ll see. And, oysters are sharp, so protect yourself with some gloves and a sturdy pair of close-toed wading shoes! Happy hunting.
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