Crustacea 1 Flashcards
Introduction
Key characteristics
Body structure
Locomotion
Gas exchange
Feeding
Reproduction and development
Moulting
.
Introduction
- Large degree of morphological diversity
- Essentially marine, though some freshwater and terrestrial species
- Dominant in plankton
- Important component of the benthos
Classification
Kingdom: metazoa
Phylum: Arthropoda
Sub-phylum: Crustacea
Class: 10
Focus: Cirripedia, Malacostraca
Key characteristics
10 points
- Bilaterally symmetrical
- Body more than two cell layers thick
Tissues, organs and circulatory system - Nervous system
- Body comprised of a five-segmented cephalon (with compound eyes), thorax and abdomen
Cephalic shield or carapace present - Jointed, biramous appendages
- Three pairs of mouthparts
- Through, straight gut with digestive ceca
- Gas exchange by aqueous diffusion across specialised branchial surfaces
- Separate sexes or hermaphrodites
- Nauplius larva
[the use of the appendages of the head (the antennae) for swimming. The nauplius is also the stage at which a simple, unpaired eye first appears.]
definitions
Cephalon – ‘head’, derived from Greek ‘cephale’
Thorax = chest/breastplate
Carapace = dorsal (upper) section of exoskeleton
Biramous = appendage branching in two, each branch
has a segments attached end to end.
Note: Uniramous = limb comprising series of single
segments attached end to end.
Body structure
4 points
- The cephalothorax, comprises the head and the thorax fused together, and is distinct from the abdomen behind.
- Number of segments can differ among species.
- Pereon is thoracic segments not incorporated into the cephalothorax.
- Very well developed pereopods.
Locomotion
4 points
- Mobile crustaceans move primarily by use of limbs
Sedentary parasites
Sessile cirripedes
- Swimming
- Crawling
- Walking
Gas Exchange
7 points
- Most posses distinct gills
- Require continuous flow of water
- Branchial chambers
Present in many decapods - Formed between carapace and body wall
- Provide protection from damage
- Small openings restrict flow of water
Gill bailers create ventilating currents - Always remain moist
Not necessarily always underwater
Survive in intertidal
Feeding
8 points
- Suspension feeders
- Filter feeders
- Deposit feeders
- Predators
- Scavengers
- Herbivores
- Detritivores
- Parasites
Reproduction
5 points
- Dioecious
- Sexual reproduction
- Copulation and internal fertilisation
- Egg brooding
- Hermaphrodites
Development
2 points
- Characteristic larval stage
Nauplius larva - Two types of development
Direct development
Embryos hatch as juveniles
Mixed development
Embryos brooded and then hatched
Moulting
- Grow by periodic shedding of exoskeleton
Moulting - Regulated by the hormone ecdysone
Three main stages of moulting
- Tissue growth during intermoult stages
Increase in size by 15-25 % with each moult - Premoult
Old cuticle loosened and new cuticle begins to form - Postmoult
Absorption of water and hardening of new cuticle
