Marine Biology: Nautilus Internal Structure

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Questions and Answers

What is the function of the venom duct in the process of vermivorous feeding?

To release pheromones for mating

To exhibit torsion

To release toxin in the harpoon (correct)

To secrete a pigment for camouflaging

What is the main characteristic of the subclass Opisthobranchia?

Presence of a shell

Highly reduced or lost shells (correct)

Presence of gills in front of the heart

Absence of chemosensory organ

What is the function of the rhinophore in Opisthobranchia?

To release toxins for defense

To sense the environment through chemosensory function (correct)

To aid in torsion

To secrete a pigment for camouflage

What is the term for the rotation of the visceral mass, mantle, and shell 180˚ with respect to the head and foot of the gastropod?

Torsion Signup and view all the answers

What is the term for the process of eating worms?

Vermivorous feeding Signup and view all the answers

What is the characteristic of Aplysia californica?

It is a species of Opisthobranchia Signup and view all the answers

What is the term for the sense organ that helps Opisthobranchia detect smells?

Rhinophore Signup and view all the answers

What is the external appearance of a doridacean nudibranch?

It lacks a shell Signup and view all the answers

What is the characteristic feature of the subclass Pteriormophia?

Having lamellibranch gills Signup and view all the answers

Which of the following is NOT a characteristic of the subclass Pteriormophia?

With radula dentition Signup and view all the answers

What is the sister group of Mytilida?

Arcida Signup and view all the answers

Which of the following is an example of Pectinida?

Perna viridis Signup and view all the answers

What is the characteristic feature of the order Ostreida?

With central adductors like scallops Signup and view all the answers

Which of the following is closely related to Arcida?

Mytilida Signup and view all the answers

What is unique about the mollusca class mentioned in the content?

They are the only group with no radula or head. Signup and view all the answers

What is the function of the byssal thread in certain mollusks?

It attaches them to surfaces. Signup and view all the answers

What is the term used to describe the process of attaching to hard substances using calcium carbonate?

Cementation Signup and view all the answers

What is the term used to describe the larval stage of certain mollusks?

Veliger Signup and view all the answers

What is the structure derived from the ciliary ring of the prototroch?

Velum Signup and view all the answers

Which type of mollusk is highly mobile and can swim by clapping?

Scallops Signup and view all the answers

What is the function of the siphuncle in the nautilus shell?

To suck water inside for movement Signup and view all the answers

What is unique about the tusks shells of scaphopods?

They are open at both ends and have different diameters Signup and view all the answers

What is the main difference between the habitat of nautiluses and scaphopods?

Nautiluses are free-swimming, while scaphopods are burrowers Signup and view all the answers

What is common between nautiluses and squid?

They are both classed as Cephalopoda Signup and view all the answers

What is the function of the narrow portion of the scaphopod shell?

To anchor the animal in the substrate Signup and view all the answers

What is unique about the eyes of nautiluses?

They are highly developed Signup and view all the answers

What is the primary function of the aragonitic sclerites in Aplacophora?

To support the structure of the cuticle Signup and view all the answers

Which of the following is a characteristic of Neomeniomorpha?

Feed on small cnidarians Signup and view all the answers

What is the function of the lateral teeth in Pteriomorphia?

To make the valves fit and lock in with each other for protection Signup and view all the answers

Which of the following is a characteristic of Chaetodermomorpha?

Deep-water species that borrow food Signup and view all the answers

What is the purpose of the adductor muscles in Pteriomorphia?

To bring the two parts of the shell together Signup and view all the answers

What is the primary component of the aragonitic sclerites in Aplacophora?

Calcium carbonate Signup and view all the answers

Which of the following is NOT a characteristic of Aplacophora?

Have a hard, calcareous shell Signup and view all the answers

Which of the following is a basis for classification in Pteriomorphia?

The type of teeth they have Signup and view all the answers

Study Notes

Nautilus

Has a huge, chambered (septate), and buoyant shell
Shell has a structure called a siphuncle, which helps in buoyancy
Has tentacles and highly developed eyes
Moves using the siphuncle, which sucks water inside and helps the animal move in a smaller chamber

Tusk Shell or Scaphopoda

Shell is open at both ends, elongated, and has different diameters (left is wider than the right)
Has a narrow portion of the shell in water, and the rest of the shell/animal is buried in the substrate
Moves using the structure inside the shell called the siphuncle

Squid

Divided into classes such as Protobranchia, Pteriomorphia, Palaeoheterodonta, Heterodonta, and Anomalodesmata (based on dentition or teeth)

Aplacophora

Worm-like, absent of shell
Cuticle is covered with calcareous spicules called aragonitic sclerites made of calcium carbonate
Has two subclasses: Chaetodermomorpha and Neomeniomorpha
Chaetodermomorpha are deep-water species, usually borrowers, and detritivores
Neomeniomorpha feed on small cnidarians

Polyplacophora and Monoplacophora

No additional information provided

Opisthobranchia

Members have highly reduced shells
Have a chemosensory organ called a rhinophore
Exhibit detorsion; reduction or loss of shell; gills located behind the heart; hermaphroditic; mostly marine

Anatomy of an Opisthobranch

External appearance of a doridacean nudibranch
Has rinophores, mantle, gills, food, and mouth
Colorful appearance, lacks shells and radula

Mollusks

Capable of secreting a pigment for camouflaging or evading predators
Exhibit torsion, the rotation of the visceral mass, mantle, and shell 180˚ with respect to the head and foot of the gastropod

Bivalves

Foot adapted for burrowing (in soft substrates e.g., muddy or purely sandy)
Some are attached to surfaces via byssal thread (byssus), or by cementing themselves to hard substances through production of calcium carbonate on their shell’s lower part
Scallops (highly mobile) can swim by clapping their shells

Phylogeny of Pteriormphia

Pectinida are closely related to Limida (not that common); sister group to Arcida
Pteriida and Ostreida are closely related; sister group to Mytilida

Subclass Pteriormphia (Bivalves)

Epibenthic (not infanual); most are attached by byssus threads; with lamellibranch gills
Includes economically important mussels, scallops, clams, and oysters
Comprises the following orders: Mytilida (mussels), Pteriida (pearl oysters and winged oysters), Ostreida (true oysters; edible; with central adductors like scallops), Arcadia (ark clams, taxodont dentition), Limida (file shells), and Pectinida (scallops)

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Description

This quiz covers the internal structure of Nautilus, a type of cephalopod, including its shell and buoyant properties.