Our world is filled with an amazing diversity of creatures, and ecosystems! Many of these are hidden from human eyes because they are in the ocean. Visiting an aquarium, or tide pool is a great way to connect with these important ecosystems. Tide pools, coral reefs and kelp forests are very diverse with high numbers of plant and animal species. Diversity in these places can be comparable to diversity in rain forests (California Water Monitoring Council, 2013). Additionally, healthy near shore ecosystems can provide shoreline stability, healthy fisheries, and beautiful places to explore.
This activity will explore diversity of marine invertebrates. Each of these animals are important to ecology, some as the base of the food chain, while others are top carnivores. Energy produced in rocky intertidal habitats can also be exported to the open ocean or onto land when terrestrial predators eat tide pool animals (California Water Monitoring Council, 2013).
Although many people think of animals as only those that have backbones such as fish, birds, reptiles, and mammals, over 95% of the world’s animals are invertebrates, which lack backbones. These are things such as insects, arachnids, and sponges. Invertebrates were the first animals on the planet, with fossil evidence showing their existence for at least 600 million years. Vertebrates evolved from these animals. There is tremendous invertebrate diversity, but for the purpose of this activity, we will focus on four types of marine invertebrates that can be seen in most aquariums and tide pools: Cnidarians, Mollusks, Echinoderms, and Arthropods. (Commonwealth Scientific and Industrial Research Organization, 2008).
Cnidarians include jellyfish, corals, sea anemones, and hydroids. These animals obtain their food by using stinging structures in their tentacles to capture prey. Cnidarians have what is called an incomplete digestive tract with only one opening to both take in food and expel waste. Cnidarians are able to absorb oxygen from the water around them directly through their skin and expel carbon dioxide the same way (National Zoo, 2015).
Echinoderms include sea stars, brittle stars, sea cucumbers, and sea urchins. All echinoderms have a water vascular system with fluid-filled tube feet, which help them move, feed, and respire. They can be spotted easily because of their 5-point radial symmetry. (National Zoo, 2015)
Arthropods includes crustaceans, arachnids, centipedes, millipedes, and insects. Crustaceans respire with gills that obtain oxygen from the water around them. Crustaceans use many feeding strategies including filter feeding, scavenging, and hunting. They all have a complete digestive tract with two openings. (National Zoo, 2015)
Mollusks are extremely diverse and includes clams, snails, squids, and octopuses. Mollusks have a soft body that sometimes has tentacles, but they have never have articulated legs. Mollusks capture food in a variety of ways including filter feeding like clams, scraping algae off rocks like limpets, and stunning prey with poison like cone snails. Like arthropods, mollusks have a complete digestive system with two openings. (National Zoo, 2015)