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CANADIAN WATERS | ![]() |
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![]() Creature Feature!![]()
Invertebrates!
To learn about the Kingdom Metazoa (multicellular animals), follow the link. The Protozoa (Protists): single-celled animalsThere are so many tiny microscopic organisms that play a large part in the Web Of Life. Here are the major groups living in marine environments. All organisms in the Kingdom Protista are single-celled. Their body is therefore one cell that contains different structures called Organelles that carry out daily function much like our organs do. One type of organelle found in many protists is the Chloroplast. Chloroplasts are organelles that produce food for the organism through a process called Photosynthesis. Therefore organisms that have chloroplasts do not ingest their food. Chloroplasts which are also found in plants can be many different colours depending on the type of Pigments that they contain. Single-celled organisms containing chloroplasts are the colour of their chloroplast pigments. Mastigophora (The flagellates)These protists have one or many whip-like structures called flagella sticking out from their bodies which are used for locomotion. Each organism is a single cell with a Nucleus and other organelles that carry out its daily functions. They are either Autotrophic, producing their food internally or Heterotrophic obtaining their food from their environment. These organisms reproduce by splitting in two which is called Binary Fission. We are going to examine four groups of Mastigophorans; euglenoids, volvocids, dinoflagellates and zooflagellates.
The Red Tide Phenomenon or Paralytic Shellfish Poisoning (PSP)Shellfish can become unsuitable for consumption by humans due to two factors: pollution from sewage and PSP.
2. Sarcodina (The Amoebas)What is an amoeba?
These single-celled organisms do not have flagella. They move by using pseudopodia. A pseudopodium (means false foot) is formed when the Protoplasm (fluid that amoebas cells are filled with) flows in one direction to move the animal along. Amoebas also reproduce by binary fission (see description above of the Mastigophora).
An interesting group of amoebas are the Foraminifera. These organisms have a cytoplasm that is enclosed by a test or shell with many chambers. They live in the ocean and they can have many different test structures. Small holes in the test of these organisms are where the pseudopodia protrude for locomotion.
3. ApicomplexaThese protists are parasitic. They penetrate into the cells of other organisms using a structure called and apical complex. An example of this group is the genus Plasmodium that has four species which infect man. The organism is passed from the mosquito and released into the bloodstream of a human. This tiny little organism is the cause of malaria a widespread disease in some areas of the globe. The organism works by attacking the red blood cells of humans. 4. CiliophoraThis group, like the amoebas uses a method other than flagella for locomotion. Instead this group uses cilia which are similar in structure to flagella, but they are much shorter and greater in number. The cells of ciliates have two types of nuclei, a feature which is different from all other protists. Ciliates are heterotrophic.
The Metazoa!The Kingdom Metazoa is very different from the Kingdom Protista. Metazoans are all multicellular (not unicellular), heterotrophic organisms that produce embryos. There are many different types of organisms that are in this group; worms, sponges, crabs, sea anemones, fish, whales and most other animals.
Crustaceans - Crabs, Lobsters, Shrimp & Others!CrabsCrab is the common name for any Arthropod (hard shelled invertebrate) of two crustacean groups:
Both of these groups have a hard shell around their body. It is called an Exoskeleton and it takes the place of bones in vertebrate animals (ie. animals with a backbone). Crustaceans have a very different body shape. The back end is small and their front end has been stretched to get the shape that we see. Most crabs live on the sea floor, but some live in freshwater and on land. Crabs are really neat animals because they can run sideways with the greatest of ease. Their young are called ZOEA larvae and they live under water until they are adult. The ZOEA larvae look like something from outer space. Barnacles are also a type of Crustacean. They are the only sessile crustaceans. Barnacles filter feed using feathery tentacles to trap organic particles in the water. There are approximately 900 species of barnacles found around the world, which are all marine. They can be found on various substrates: rock, shell, drifting wood, the hulls of boats and the skin of animals including whales, turtles and fish.
Hermit CrabsThese creatures are great at hiding themselves. They put their abdomen into gastropod mollusc shell which they carry on their back for protection. When a hermit crab grows larger it must leave its shell and find a larger one. During this period it is very vulnerable to being eaten by larger marine animals because the part of their body usually hid by the shell does not have a hard Exoskeleton like other crustaceans such as crabs and lobsters. Lobsters
Jellyfish & Sea Anemones (Cnidarians)JellyfishJellyfish, like the other animals in their family are made up of two jelly-like layers called an ectoderm and an endoderm. The only features that they have in common with humans are a stomach and a mouth. Sea Anemones
Sea Anemones are very strange creatures that look like underwater flowers. Don't be fooled though, they attack other marine invertebrates and small fish to eat them. Their bodies are shaped like a vase, with tentacles at the top and a mouth in the middle of their tentacles. The tentacles have a stinging material used to stick to prey and digest it. The young of many sea anemones are tiny jellyfish that float and swim for large distances until they settle to the sea floor where they become adult sea anemones.
Marine Worms (Annelids, Nematodes & more)!There are too many types ot marine worms to mention them all. They consist of parasites, surface-dwelling predators, tube-dwelling predators, scavengers, omnivores and substrate feeders. Tube-dwelling worms such as Amphitrite sp. wait in their tubes until they sense vibrations above them. The tube worm then uses its "tentacles" or parapodia to help its Proboscis get hold of its prey. Tube worms can also pull back into their burrow quickly if they sense a vibration in the water that might constitute a predator. Marine "Insects"!The only group of insects that are strictly marine are the Pycnogonids or Sea Spiders. There are approximately 1000 species of pycnogonids in the world ranging from a size of 1 to 10 mm. Pycnogonids are botton-dwelling creatures most of which are carnivores feeding on bryozoans, soft corals, hydroids, sea anemones and sponges. Some species feed on algae or microorganisms. Marine Molluscs!
Certain members in this group do not have a shell or have a reduced shell inside their body. These species are known as the octopods and include, cuttlefish, squid, nautiluses and octopuses. These molluscs have a foot modified into prehensile tentacles and a muscular funnel. The tentacles spread around the head of the animal with the mouth at the center. Octopuses are bottom-dwelling organisms, with a rounded body and no fins. Each individual octopus dies after one breeding season. Sea Urchins, Starfish & More (Echinoderms)!Echinoderms are a colourful and unique group of invertebrates. They include starfish/seastars, sea urchins, sea cucumbers, sand dollars, brittle stars and others. There are 6000 species of echinoderms worldwide. All of the members of this group locomote using tube feet and some use secondary methods as well.
StarfishStarfish as you can imagine are star-shaped with five legs. They are however not fish, which are vertebrates. These invertebrates love to eat clams, scallops and coral. The Crown of Thorns starfish near Australia was once responsible for the decimation of coral reefs. This organism goes in a natural cycle of huge population growth and then normal growth. Sea UrchinsSea urchings are very healthy eaters. They only eat plants, mainly different types of algae or seaweed that live near them on the sea floor. Sea CucumbersBe careful, don't try to eat a sea cucumber. They are definitly not as tasty as a real cucumber. The cucumber we eat at home is a green vegetable, a type of plant. Sea cucumbers are actually living animals and not plants. Sponges (Porifera)!Sponges have an interesting body structure. Their body has some properties like a colonial protozoan (below) and some of a true multicellular animal with tissues. There are three types of sponges: Asconoid, Syconoid and Leuconoid. The inner cavity of the sponge is called the Atrium or spongocoel. The cells that line the atrium are called Choanocytes that have flagella (below). The outside of a sponges body is covered by flat cells called pinacocytes. Between the outer and inner layers is a mesohyl layer that contains amoebocytes which float around. The body wall is made stronger by a skeleton of inorganic spicules and hollow cells called porocytes that open to draw water through the porocytes into the atrium which is pushed out a main osculum. More complex sponges have tubes and chambers lined with flagellated choanocytes. The increased complexity has allowed sponges to get larger in size.
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Created: 2001-06-08 Updated: 2005-01-27 Reviewed: 2003-09-03 |