Class Cephalopoda Flashcards

Class Cephalopoda Overview

• Includes cuttlefish, squid, and octopus.
• Recognized as the most advanced group within the mollusks.

Distinctive Features of Cephalopoda

• Possess a chambered shell (if present) and tentacles surrounding the mouth.
• Features a radula and beak, along with a closed circulatory system.
• Highly developed neural organization (cephalization) and image-forming eyes.
• Contains a large mantle cavity with a muscular funnel (siphon).
• Typically features 1-2 pairs of ctenidia (gills) and nephridia (excretory organs).
• Carnivorous lifestyle, exhibiting gonochoristic reproduction (separate sexes).

Circulatory System

• Cephalopoda have a closed circulatory system enabling faster movement.

Subclass Nautioidea

• Solecephalopods with an external chambered shell.
• Have pinhole eyes without cornea or lens, and possess 80-90 suckerless tentacles.
• Lack chromatophores and ink sac; regarded as "living fossils."

Siphuncles

• Structures that connect shell chambers, allowing adjustment of buoyancy by manipulating water and gas content.

Subclass Ammonoidea

• Extinct cephalopods that coexisted with dinosaurs and serve as significant index fossils.
• Present sexual dimorphism complicates species determination.

Subclass Coleoidea

• Comprises cuttlefish, octopuses, and squid, known for advanced adaptations.

Characteristics of Coleoidea

• Equipped with 8-10 prehensile arms covered with suckers.
• Possess a pair of ctenidia and nephridia; internal shells may be vestigial or absent.
• Have well-developed eyes with cornea and lens, along with chromatophores and an ink sac for defense and communication.

Chromatophores

• Composed of specialized cells (chromatophore, iridophore, muscle, nerve, and glial cells) for rapid color change via neural control.
• Produce colors such as brown, yellow, and other shades by contracting and expanding.

Order Sepiodea

• Represents cuttlefish, characterized by a dorsally flattened body, lateral fins, and unique feeding adaptations.

Sepiodea Features

• Possess 8 short arms and 2 long feeding tentacles without hooks, targeting fish and crustaceans.
• Cuttlefish bones are hollow, with internal chambers aiding in buoyancy control.

Order Teuthoida

• Known as squid; recognized for their streamlined body designed for speed.

Teuthoida Characteristics

• Comprising 8 short arms and 2 long non-retractable tentacles; possess a vestigial internal shell called the gladius.
• Adaptations for pelagic life, with suckers often reinforced with hooks.

Teuthoida Adaptations

• Utilize a siphon to propulse and navigate swiftly in water.

Order Octopoda

• Represent octopuses, which are recognizable for their unique body structure.

Octopoda Characteristics

• Lack a shell, exhibit 8 arms, and typically occupy benthic marine environments.
• Primary prey includes mollusks and crustaceans.

Notable Species

• The Dumbo octopus thrives in deep-sea habitats, exemplifying cephalopod diversity.

Reproductive Biology

• Cephalopods possess separate sexes and are not hermaphroditic, reflecting varied reproductive strategies.