Molluscs ​, Echinoderms, Invertebrate Chordates

What are the major Characteristics of Molluscs?

Anatomy of a Sea Slug

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Image source:
This image depicts what the overall anatomy of the Chiton (sea slug) appear like.
It also has two overlapping layers for protection.

Observing Nudibranchs

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Image :

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 cristata is found primarily in Indonesia. The colors on the sea slugs vary depending on abiotic factors in their given niche that allow them to be most productive.

Triopha catalinae 1.jpg
Image : Wiki

Another Nudibranch species is shown to the right and is identified as Triopha catalinae.

The Triopha catalinae is commonly referred to as the Sea Clown Tripoha. This species is found in Northern California coastline.

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 …..

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Image : Wiki

This image depicts the labeled sections of a bivalve shell from the top view.

What does Bivalve mean ?

An aquatic mollusk that has a compressed body enclosed within a hinged shell, such as oysters, clams, mussels, and scallops.

Image : Taken by myself

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

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Image: Wiki

Label the function of the “mantle”, “adductor muscle”, and “foot”.

Mantle : The mantle’s fuction in mollusks that have shells, such as clams, mussels, and snails, the mantle is what secretes calcium carbonate and a matrix to form the mollusk’s shell.

Adductor Muscle:  Scallops and clams canswim by opening and closing their valves rapidly by alternatingly contracting and relaxing their adductor muscles; water is ejected on either side of the hinge area and they move with the flapping valves in front.

Foot: The foot in a clam is the mechanism the organism uses to burrow itself into the sand to hide from predators .

Observing the preserved Squid, Octopus, and cuttlefish.

Image From myself
Depicted is a gulf squid in preservatives
Image from myself
Depicted a octopus in presevatives
File:Cuttlefish komodo large.jpg
Image from : Wiki
Image depicting a cuttlefish in the wild.

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 :

Radical Symmetry

Several arms

Body consisted of 5 equal segments

They have no heart, brain, nor eyes

Mouth is located on the underside and the anus on top.

Image : Taken by myself
This depicts a dried sea star from an aerial view.
Image : Taken by myself
This image shows the mouth of a sea star located in the center of the body on the underneath side.

Name the phylum ?

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 >

Image : Taken by myself and depicts a sea urchin under a micro scope showing its mouth.
Image : Taken by myself
Depicts a live sea urchin in a glass vial.
Image: Taken by myself .
Depicts a whole body of a skeleton of a Sea Urchin
Image : Taken by myself and depicts a Sea Dollar skeleton

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.

Image : Taken by myself
Depicts a Sea cucumber in preservatives.

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 notochord,

A dorsal hollow nerve cord,

Pharyngeal slits

A post-anal tail.

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