Questions and Answers
What are the characteristics of Mandibulata?
Presence of mandibles on the third segment of head, designed for chewing.
Which of the following statements is true regarding the superclass Crustacea?
What are the defining features of Crustacea?
Body divided into three tagmata: cephalon, thorax, abdomen.
What is the structure of the cephalon in Crustacea?
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What regulates ecdysis in crustaceans?
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What are phyllopodous appendages?
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Describe stenopodous limbs.
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What is unique about the muscular structure of crustacean limbs?
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How do smaller and larger crustaceans respire?
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What are the components of the cuticle of a crustacean?
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What types of excretory organs do crustaceans possess?
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All crustaceans are dioecious and must copulate.
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What is the digestive process in crustaceans?
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Which class of crustaceans includes crabs, shrimp, and lobsters?
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What type of crab larvae do most crabs hatch as?
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How is water circulated to the gills in crabs?
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What are raptorial appendages in mantis shrimp used for?
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Amphipods possess a carapace.
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Isopods respire using gills in terrestrial environments.
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What is the notable classification characteristic of the Remipedia subclass?
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Study Notes
Mandibulata Characteristics
- Mandibulata characterized by mandibles on the third segment of the head, adapted for chewing.
Superclass Crustacea
- Comprises approximately 65,000 species, showcasing significant variation among arthropods.
- Exclusively aquatic among major arthropod groups, emphasizing its specialization within the ecosystem.
- Economic significance in fisheries, essential for commercial shrimp mariculture.
- Plays critical ecological roles as filter feeders, suspension feeders, and deposit feeders.
Defining Features of Crustacea
- Body segmented into three tagmata: cephalon, thorax, and abdomen.
- Cephalon consists of five segments, each with a pair of appendages.
- Includes two pairs of antennae and three pairs of feeding appendages (mandibles, 1st and 2nd maxillae).
Additional Features of Crustacea
- Primitively possesses a cephalic shield covering head segments.
- Most species have compound eyes and a nauplius larval stage.
- Equipped with antennal or maxillary glands for excretion and gills for respiration.
Ecdysis Regulation Mechanism
- G2 gland hormone inhibits ecdysteroid production by G1, preventing molting.
- When G2 is inactive, brain hormones stimulate G1, facilitating molting.
- Ecdysteroid hormones govern the molting process, with G2 suppressing G1 hormone production.
Phyllopodous Appendages
- Primitive small crustaceans feature broad, leafy limbs.
- Functions include locomotion and respiration.
Stenopodous Limb
- Larger, derived groups possess stout or slender limbs for walking and grasping.
- Limbs can be biramous (two branches) or secondarily uniramous (one branch).
Crustacean Limb Anatomy
- Muscle bundles originate and insert between segments, supported by flexible membranes.
- Marked reduction of circular musculature, with hardened procuticle at all joints except where flexibility is required.
Respiration in Crustaceans
- Smaller crustaceans rely on diffusion through articular membranes.
- Larger species utilize gills or modified epipods that extend from walking legs for gas exchange.
Structure of Crustacean Cuticle
- Composed of four layers: epicuticle, various layers of procuticle (pigmented, calcified, uncalcified), epidermis, and basement membrane.
Excretory Organs
- Small crustaceans diffuse ammonia through gills.
- Larger crustaceans possess antennal glands located at the base of the second antenna for excretion.
Reproductive Traits
- Most crustaceans are dioecious, requiring copulation for reproduction.
- Sperm is amoeboid, with internal fertilization.
- Young are typically brooded until they hatch as nauplii, progressing to metanauplius upon developing five appendages.
Digestive System Pathway
- Digestion follows: esophagus → Cardiac Chamber (grinding ossicles) → gastric mill (grinding teeth) → Pyloric Chamber → midgut.
Taxonomy of Mandibulata
- Comprises 11 classes, with five classes exhibiting more than 1,000 species.
- Key classes include:
- Malacostraca: includes crabs, shrimp, lobsters, and amphipods.
- Cirripedia: includes barnacles.
- Copepoda: comprised of copepods.
- Ostracoda: encompasses ostracods.
- Branchiopoda: includes brine shrimp, water fleas, and fairy shrimp.
Class Malacostraca
- Represents 60% of described crustacean species.
- Thorax consists of 8 segments, abdomen has 6-7 segments, ending with a telson.
- Anterior thoracic segments fuse with the head to create a cephalothorax, with maxilliped appendages.
Order Decapoda
- Includes commercially significant species like banded coral shrimp, ghost crabs, spiny lobsters, and mud crabs.
Crab Anatomy
- Defines main organs specific to crab anatomy (details unspecified).
Larval Stages of Crabs
- Two key larval stages: Zoea and Megalopa; crabs typically hatch from eggs as Zoea after passing the nauplius stage.
Cheliped Formation
- The specific limb type modified to form the cheliped is undefined.
Water Circulation Around the Carapace
- Mechanisms for water circulation to gills around the crab carapace are unspecified.
Order Stomatopoda
- Comprises mantis shrimp, a burrow-dwelling group characterized by raptorial appendages adapted for hunting.
Order Amphipoda
- Includes amphipods, with prominent lateral compression and absence of carapace.
Order Isopoda
- Isopods lack a carapace and have a dorsally compressed body.
- Terrestrial isopods (like pillbugs) respire using tracheae, contrasting with marine relatives that use gills.
- Example of convergent evolution within different environments.
Remipedia Sub-class
- Contains 24 living species, discovered in 1981 within caves.
- Exhibits primitive characteristics, with a pair of antennae and appendages resembling ancestral forms.
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Description
Explore the fascinating world of the Super-class Crustacea with these informative flashcards. Learn about their key characteristics, ecological significance, and economic importance. Perfect for students and enthusiasts wanting to deepen their understanding of this remarkable group of arthropods.
