Arthropods II. Insect origins Flashcards
Describe Crustacea
- paraphyletic
- Subphylum in the Phylum Arthropoda
- all Pancrustacea that are not Hexapods
Hexapods
evolved from a crustacean ancestor
Describe the Pancrustacea
Crustaceans and Hexapods together
Hexapoda emerged
~470 mya
Insects emerged
~400 mya
Describe the six major crustacean Classes
- Cephalocarida
- Remipedia
- Malacostraca & Maxillopoda
- Branchiopoda
- Ostracoda
- Maxillopoda
Cephalocarida
e.g. horseshoe shrimp
Malacostraca & Maxillopoda
- crabs
- krill
- woodlice & others
- barnacles
- copepods
Branchiopoda
- fairy shrimp
- water fleas
Ostracoda
seed shrimp
Maxillopoda
- tongue worms
- fish lice
- polyphyletic
Describe Crustacea
- two pairs antennae
- metamorphosis with nauplius larvae
- no general body plan
- at least two body segments
Give some examples of crustacean body plans
- head and trunk
- head, thorax and abdomen
- cephalothorax, pereon and pleon
Generalised crustacean
shrimp
Describe Crustacean diversity
- tagmosis regions
- segment numbers
- segment fusion
Describe Malacostraca
- ~40k species
- tagmosis standardised (H-T-A), with appendages on each
- gastric mill within stomach
Describe Crustacean appendages
- uniramous and biramous appendages
- evolutionary tendency towards fewer appendages and more specialised
Ramus
an article branch
Give some specialisations of crustacean appendages
- defence & predation
- sensory functions
- respiration
- reproduction
- chewing & food manipulation
- locomotion
- multi-functions
Describe Crustacean development
- direct and indirect development
- not all adult segments & appendages present at hatching
- 1st larval stage often nauplius larva with first 3 head segments & associated appendages
- periodic moults add new segments & appendages
Describe indirect Crustacean development
involves a larval stage
Describe direct Crustacean development
hatch with all segments & appendages
Describe Crustacean diversity in development
variation in larval types, stages & no. of moults
Describe a Crustacean nauplius larva
- 1st antenna
- 2nd antenna
- naupliar eye
- labrum
- mandible