Last week, we undertook a sea star hunt at Sanibel Sea School. Our survey team counted 158 sea stars along a short section of San Carlos Bay; we will keep these counts to compare with future observations on the health and dynamics of our marine environments. Perhaps just as importantly, we will also keep the memories of our experiences of sea star hunts along cool clear waters of San Carlos Bay. Collectively we took a small step towards our role as stewards of this marine planet – and we had a lot of fun doing it.
For most of us old enough to vote, we know these creatures as star fish, but new generations of ocean lovers know them as sea stars. We call them sea stars now to avoid confusing them with fish. They are animals that belong to the phylum Echinodermata, along with the brittle stars, sea urchins, sand dollars and sea cucumbers. The name Echinodermata is derived from the Greek echinos (spiny) and derma (skin) – they are the spiny skinned animals.
They are one of a very few groups of animals that are exclusively marine – that is, they’re found only in the oceans. Although they are invertebrate animals (not having a backbone), the echinoderms are fairly close relatives to vertebrate animals (those of us with backbones). One of the characteristics they share with us vertebrates is that they have skin covering their hard parts; they do not have an external skeleton like that found in mollusks or crabs.
Echinoderms also have a unique and quite fascinating hydraulic system in which they use water to pressurize a system of tubes which protrude from their body. This hydraulic system is known as the water vascular system and allows them to crawl along the bottom of the sea on a cushion of numerous “tube feet”.
The most common sea star in San Carlos Bay is the Orange Sea Star which is in the genus Echinaster. There may be as many as six separate species in our area, but like many of our marine animals little is known about them. These sea stars appear not to feed on bivalve mollusks like many other sea stars do. But rather, they feed on sponges and can also ingest dead organic matter which accumulates on the sea floor. Their recent abundance is likely another part of the cycle in our ocean’s dynamics related to nutrient inputs from land-based sources.
Whatever the cause of their recent abundance, enjoy these stars of the sea, but please remember that like mollusks, they are protected by Florida State law in Lee County and collecting live specimens is prohibited.