What are the major Characteristics of Molluscs?
- Unsegmented soft body.
- Most have an internal or external shell.
- Have a mantle – a fold in the body wall that secretes the hard protective shell.
- Muscular foot and/or tentacles.
- Have a radula – a toothed structure used to
- Two pairs of gills except in pulmonate snails.
Anatomy of a Sea Slug
What is seen in this picture ?
The Nudibranchs is a multiple colored sea slug out of its shell. After their larval stage, these slugs shed their shells. This species Nembrotha
Another Nudibranch species is shown to the right and is identified as Triopha catalinae.
Both Nudibranchs are from the same species but as shown vary quite a bit from being in different environments. Their skin is altered in order to be better adapted to each respected niche.
Observing Bivalve shells …..
This image depicts the labeled sections of a bivalve shell from the top view.
What does Bivalve mean ?
What substance are all of the Mollusc shells made of?
Mollusk shells are made of a chalky material called calcium carbonate. The shell has three layers for extra strength: a tough outer layer, a chalky middle layer, and a shiny inner layer, next to the animal’s skin.
Anatomy of a Clam
Label the function of the “mantle”, “adductor muscle”, and “foot”.
Adductor Muscle: Scallops and clams
Foot: The foot in a clam is the mechanism the organism uses to burrow itself into the sand to hide from
Observing the preserved Squid, Octopus, and cuttlefish.
The head is located a the top of the tentacles that are protruding from the rest of the body this houses the mouth and brain of the cuttlefish. The eyes are located mid level on the head they are a yellow tone with a black slit in between the layers. Finally, the arms/tentacles are again protruding from the head of the cuttlefish.
How are Squids, Octopus and cuttlefish still related to Bivalve’s ?
The cephalopods appear to be very different from other mollusks, but physiologically they are similar. Cephalopods, like most mollusks, have a mantle, a mantle cavity, a radula, and a U-shaped digestive tract. Cephalopods have two kidneys and three hearts, which pump blue blood. They are carnivores that feed on fish, shrimp, crabs and other cephalopods.
The most obvious difference between most cephalopods and other mollusks is the apparent lack of a shell. Octopuses do not have shells at all, while squids have a small internal shell. (Nautiluses, which are found in the South Pacific and Indian oceans, are the only cephalopods with an external shell. They are also the only cephalopods with four gills instead of two.)
Name the major characteristics of Echinoderms
Echinoderms in Latin is “spiny skinned” organisms. These include but are not limited to as Sea stars, Brittle stars, Sea Urchins, Sea Cucumbers, Feather stars.
The characteristics of a Echinoderms :
Body consisted of 5 equal segments
They have no heart, brain, nor eyes
Mouth is located on the underside and the anus on top.
What is the function of the tube feet?
Tube feet function in locomotion, feeding, and respiration. The tube feet in a starfish are arranged in grooves along the arms. They operate through hydraulic pressure. They are used to pass food to the oral mouth at the center, and can attach to surfaces.
<Observing the live Sea Urchin, and the Urchin and sand dollar skeletons >
What Composes all these Skeletons of these organisms ?
The skeletons are made up of a water vascular system. Their spherical shape is typically small, ranging from about 3 cm to 10 cm in diameter, and their bodies are covered with a spiny shell. The skeleton of a sea urchin is also known as the test.
How is a sea cucumber similar to and different from a sea star?
They are similar in structure and movement is limited. They are different in a few ways as the sea cucumber eject a toxin if they are threatened which the sea star lacks.
How does a Sea Cucumber feed?
Sea Cucumbers are scavengers that feed on small food items in the benthic zone (seafloor), as well as plankton floating in the water column. Algae, aquatic invertebrates, and waste particles make up their diet. They eat with tube feet that surround their mouths.
What are the four basic structures that are diagnostic or characteristic of the Phylum Chordata?
A dorsal hollow nerve cord,
A post-anal tail.