BIO2231 Lecture Notes - Lecture 10: Mandibulata, Osmoregulation, Neoptera
30 May 2018
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Phylum Arthropoda
• Triploblastic, coelomate, protostome, bilateral, hard cuticle and moulting, animals with jointed
legs
• Biggest phylum
• General body plan; box (cuticle); tergite (top plate), sternite (bottom plate), pleurite (side plates
that hold appendages)
- heart is usually dorsal vessel (contractile vessel rather than
round shape
- open circulatory system
- 2 nerve cords running front to back + ganglia
• Reasons for success; 1. Cuticle (exoskeleton); chitin and protein, protective but flexible, chemical
barrier, muscle attachment, dessication
prevention
- procuticle; where mix is solidified, crosslinking
embedding of calcium salts (crustaceans)
- epicuticle; chemical barrier, mix of proteins
and wax waterproofing
- epidermis secretes cuticle, sensory structures
have to pass through cuticle (which itself is dead)
usually in form of hair.
- large metabolic investment
- calcium salts are reabsorbed (recycled)
- reorganise body
- secrete molting fluid, enzymes eat up cuticle ->
new cuticle
2. Segmentation and tagmata; eg head and trunk (dedicated to particular
function
3. Jointed appendages; increase precision in movement
- no circular muscles, muscle bands instead
- joints move in one plane
- branching; uniramous (hexapods and chelicerates)
or biramous (crustaceans and trilobites)
find more resources at oneclass.com
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4. Air piped directly to cells; spiracles (openings)
- absent in aquatic insects; have external
gills, highly branched
5. Cephalization; clearly defined head, concentration of ganglia (brain)
- sensory systems highly developed, compound eyes,
palps and antennae, chemosensitive setae
6. Complex social behaviour patterns; simple and complex responses
7. Metamorphosis; reduces competitions between life stages
• Subphylum Trilobita
• Suphylum Chelicerata; Class Arachnida (spiders, scorpions, mites), Class Merostomata
(horseshoe crabs)
• Subphylum Myriapoda; Class Chilopoda (centipede), Class Diplopoda (millipede)
• Subphylum Crustacea; Class Branchiopoda (tadpole shrimps, water fleas), Class Malacostraca
(crabs, shrimp, crayfish, amphipods, slaters),
• Subphylum Hexapods; Class Insecta (flies)
Subphylum Trilobita
• Trilobed body in cross-section, abundant during Cambrian, extinct over 250 MYA
• Three tagmata; head, trunk, pygidium
• Highly developed compound eyes
• Biramous with gills, no mouth parts
Subphylum Crustacea
• Appendages typically biramous (2 branches)
-often has epipod (feathery like), acts as gills
• Two pairs of antennae
• One pair of mandibles, two pairs of maxillae
• Two tagmata; cephalothorax and abdomen
-abdomen has 6 segments
• Respiration via external gills
• Carapace; dorsal cuticle of head may extend
posteriorly and around sides of animal to cover
thoracic and abdominal somites (covers head and thorax/cephalothorax)
• Coxa is embedded in base of body, gills in between carapace and body, blood pumped into gills
travels dorsally and heart pumps to rest of body
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• Have compound eyes
• Mouth part has flaps that moves water into chamber of gills
• Lacks waxy waterproofing
• Bears pigmented and calcified layer
• B-crustacyanin, bluish colour, red when denatured
• Not well adapted to terrestrial
• Moulting -> initiated by environmental -> perceived by CNS -> decreases moult-inhibiting
hormone from x-organ in brain -> drop in MIH releases moulting hormone from Y-organ near
mandibles ; tightly regulated
• Coelom is reduced (pretty much gone), main body cavity is haemocoel, body fluid around organs
in midsection is haemolymph
• Open system
• Blood pigments; haemoglobin and haemocyanin
• Smaller species lack respiratory organs (eg plankton), larger have thoracic gills, few terrestrial
have lungs
• Digestive system; one way tubular gut, complex stomach in some
• Excretory and osmoregulatory organs in crustaceans are paired gland located in their head, with
excretory pores opening at the base of either the antennae or maxillae
• Excretory; paired nephridia in head, excreted waste in form of ammonia
• Life cycle (metamorphosis);
• Nauplius; planktonic larval forms
• Some have direct development
• Most morphologically diverse
• Most marine, few freshwater and terrestrial
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Phylum arthropoda: triploblastic, coelomate, protostome, bilateral, hard cuticle and moulting, animals with jointed legs, biggest phylum, general body plan; box (cuticle); tergite (top plate), sternite (bottom plate), pleurite (side plates that hold appendages) Heart is usually dorsal vessel (contractile vessel rather than round shape. 2 nerve cords running front to back + ganglia: reasons for success; 1. Cuticle (exoskeleton); chitin and protein, protective but flexible, chemical barrier, muscle attachment, dessication prevention. Procuticle; where mix is solidified, crosslinking embedding of calcium salts (crustaceans) Epicuticle; chemical barrier, mix of proteins and wax waterproofing. Epidermis secretes cuticle, sensory structures have to pass through cuticle (which itself is dead) usually in form of hair. Secrete molting fluid, enzymes eat up cuticle -> new cuticle. Segmentation and tagmata; eg head and trunk (dedicated to particular function. Branching; uniramous (hexapods and chelicerates) or biramous (crustaceans and trilobites) Absent in aquatic insects; have external gills, highly branched. Cephalization; clearly defined head, concentration of ganglia (brain)
