Creature Feature!

 Cetaceans (Dolphins, Whales & Porpoises)
Pinnipeds and Others (Seals, Sea Lions, Walruses and the Sea Otter)
Reptiles - The Sea Turtles
Fish
Invertebrates
Birds

Invertebrates!

• Protozoa (Creatures under a microscope)
• Crustaceans (Crabs, Lobsters)
• Cnidarians (Sea anemones and Jellyfish)
• Marine Worms
• Insects
• Molluscs (Snails, Clams, Scallops, Squid)
• Echinoderms (Sea Urchins, Starfish)
• Porifera (Sponges)

To learn about the Kingdom Metazoa (multicellular animals), follow the link.

The Protozoa (Protists): single-celled animals

There 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.

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• Euglenoids have green chloroplasts and one flagellum for locomotion. They are mostly found in freshwater.
  
• Volvocids are mostly colonial organisms which means that they are formed when single cells group together to form a colony. Some species however are Unicellular. These protists are usually red, green or yellow due to the pigmentation of their chloroplasts. A few species do not use chloroplasts to obtain nutrition. Instead these species are heterotrophic. Each individual volvocid in a colony is called a "zooid". Zooids have two to four flagella and their bodies are covered by a gelatinous substance.
  
• The dinoflagellates are often a nuisance for seafood lovers. These unicellular organisms are responsible for a lot of Primary Production in marine and freshwater systems. Some dinoflagellates secrete toxins which get absorbed by shellfish and are in turn eaten by fish. When people eat contaminated shellfish or fish they get sick. There are different types of sicknesses associated with this phenomenon often referred to as "red tide". Each dinoflagellate has two flagella, chloroplasts and Cellulose plates covering their body.
  
• Zooflagellates are protists with flagella and no chloroplasts. They are Symbiotic organisms which means that they live in association with a host organism. The relationship between symbiont and host can be of three types; parasitic, commensal or mutualistic. Here are some examples of the different symbiotic relationships:

1. Parasitism

   Parasitism refers to a symbiotic relationship where the symbiont receives some benefit from the host (a place to live , nutrition from the hosts tissues etc...) and the host is harmed in some way by the association.

   Example: The zooflagellate Trypanosoma gambiense is responsible for the african sleeping sickness.

2. Commensalism

   Commensalism occurs when the symbiont benefits from the host organism, but no harm comes to the host.

   Example: Opalinid flagellates such as the genus Opalina live in the gut of animals such as frogs. These organisms are not essential for the hosts survival but the frog is not harmed.

3. Mutualism

   A mutualistic symbiotic relationship occurs when both the host and symbiont receive some benefit from the association and neither is harmed.

   Example: The genus Trichonympha lives in the hind gut of termites. These zooflagellates digest the cellulose in the plant/wood material that the termites feed on. Termites cannot digest cellulose and the zooflagellates break it down for them into substances that they can digest. The zooflagellates receive nutrition from the cellulose digestion process and the termites in turn get the plant material that they can receive nutrition from. Without the zooflagellates, the termites would die.

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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.

1. Animals that have been polluted have a high content of bacteria inside their bodies. These bacteria could cause sickness in humans and therefore some harvesting closures occur around coastal regions that are adjacent to urban areas. The mollusc tissues and the water quality are monitored regularly to prevent harvesting of polluted animals. Molluscs can also clean themselves quickly when placed or surrounded by clean water.
   
2. PSP is also referred to as "red tide" due to the colouring of the pigments in the organisms that cause them. The microscopic, single-celled dinoflagellates can cause PSP. When these organisms are present in large numbers (high densities are called blooms) they can discolour the water. Some species of dinoflagellates are harmless, some kill marine organisms and others affect mammals without affecting marine organisms.

   Two species which often occur in blooms on the West Coast are: Gymnodium splendors and Noctiluca scintillans, which are harmless. Toxic species include Protogonyaulax acatenella and Protogonyaulax cantenella, which normally occur in small quantities. A bloom of the toxic species can be caused by a biological, hydrological or meteorological factor, usually in the summer.

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).

Amoebae can be naked or have an external covering called a test. The test or "shell" can be made of many substances such as chitin which is a component of the hard Exoskeleton of insects.

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.

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3. Apicomplexa

These 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. Ciliophora

This 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.

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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!

Crabs

Crab is the common name for any Arthropod (hard shelled invertebrate) of two crustacean groups:

1. Hermit crabs and others closely related species (approximately 1400 species).

2. True crabs (about 4500 species).

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.

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Hermit Crabs

These 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

There are three species of true lobsters. In Canada, they can grow to a length of 25 centimetres and they can live up to 15 years. The American lobster, Homarus americanus lives on the east coast of North America, from Labrador, Canada to North Carolina in the United States. Lobsters live at depths of 3 metres to as deep as 180 metres. An average weight for the american lobster is about 0.9 to 2.2 kg (2 to 5 lb).

Did You Know?... The largest lobster of this species was recorded at 20 kg (45 lbs).

Jellyfish & Sea Anemones (Cnidarians)

Jellyfish

Jellyfish, 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.

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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!

The mollusca is a group of hard-shelled invertebrates of which many have commercial importance. These "shellfish" as they are known include abalone, clams, oysters, mussels, snails and squid. Non commercially important members of this group include chitons, limpets and octopuses. Many of the hard-shelled species have a muscular "foot" that extends out of the shell. The foot is used for locomotion, attaching to substrates and for burrowing.

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.

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Starfish

Starfish 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 Urchins

Sea 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 Cucumbers

Be 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.

Links

Education Planet - Marine Invertebrates Page
http://www.educationplanet.com/search/Environment/Animals/Marine_Invertebrates

Gander Academy's Marine Invertebrates
http://www.stemnet.nf.ca/CITE/marinver.htm

Marine Invertebrates of Canada
http://www.aquatic.uoguelph.ca/inverts/

References

Barnes, Robert D. 1987. Invertebrate Zoology. Fifth Edition. Saunders College Publishing, Toronto. 893pp.

Microsoft Encarta 96 Encyclopedia. Microsoft Corporation.

New Webster's Dictionary and Thesaurus. 1992. Lexicon Publications, Inc., Danbury, CT

Artwork:
Clipart by the Corel Corporation
Original Art by Jennifer Lalonde