Lecture 6 Arthropod A

ARTHROPODA

5 Interesting Facts about Arthropoda • Making up more than 80% of all animals; • When a tarantula is angry, it will pull off some of its hairs and throws them to its prey; • A cockroach can live for 5 days after its head is removed; • A dragonfly is able to fly at a speed of 30 mph; • Total weight of arthropoda is more than the other animals combined.

ARTHROPODA - GENERAL • • • •

The name means jointed legs; Most successful of all animals; Represents 80% of all animals; > 1 million spp. Already identified (estimate 6 – 9 million); • Habitat: deep oceans – highest mountains; • Size: – Biggest: ‘king crab’ (12 feet including legs) – Small: example: copepoda

ARTHROPODA - CHARACTERISTICS – –

Bilateral symmetry; Body divided into 3 sections; • • •

head (made up of 6 segments) thorax abdomen some groups: (eg prawn with cephalothorax)

– –

Outer segmentation only (no septa) Jointed appendages • • •

1 or 2 pairs per segment, Sometimes modified for specific task Joints allow easier and faster movements.

ARTHROPODA – CHARACTERISTICS(cont) – Exoskeleton made of chitin • • •

Terrestrial sp: exoskeleton layered with wax – protection from dehydration Removed from time to time; Disadvantage – heavy – modified in flying spp.

– Molting • • •

New exoskeleton formed prior to molting; During molting, abdominal muscle contracts and fluid moves to the anterior region; Head expand, causing exoskeleton to split.

ARTHROPODA – CHARACTERISTICS (cont) –

True coelom reduced during adult stage; •

– – – –

During adult stage almost entire body cavity becomes a hemoecel filled with blood;

Complete digestive system: mouth, enteron and anus; Open circulatory system : dorsal heart, artery and messenchyma blood cavity (sinus) Respiration by absorption (body surface), trachea (air tubes), book lungs, gills; Excretory system – green gland (crayfish) or Malphigian tubules (Insecta)

CIRCULATORY SYSTEM – LOBSTER

Respiratory System of Prawn

TRACHEAL SYSTEM - Insecta

Trachea - grasshopper

Green Gland of Crayfish - excretion

EXCRETION IN INSECTA • Malphigian Tubule – Folding of intestine forming a pouch; – Pouch bathed with blood in hemoecel – Waste materials absorbed and moved into pouch and removed through intestine

• Waste Material – uric acid

ARTHROPODA – Classification • Subphylum Trilobita • Subphylum Chelicerata Class Merostomata (horse-shoe crab) Class Arachnida (spiders) • Subphylum Mandibulata – – – –

Class Crustacea (shrimp, copepoda) Class Diplopoda (eg millipedes) Class Chilopoda (eg centipedes) Class Insecta (insects)

ARTHROPODA – Classification (cont) • Subphylum Trilobita - extinct

ARTHROPODA – Classification (cont) • Subphylum Chelicerata – First pair of appendages – celicera (with claws) – Second pair – padipalp – No antenna

Class Merostomata (horse-shoe crabs) Class Arachnida (spiders)

Subphylum: Chelicerata

Class Merostomata (horse-shoe crabs) - 5 spp. still exist; - marine animal - Hard shell to protect cephalothorax; - feed on small invertebrates; - second pair appendages resemble legs - respiration – book lung

Subphylum: Chelicerata Class Arachnida

-

Spider (Araneae)

Scorpion (Scorpionida)

Tick (Acari)

Subphylum: Chelicerata Class Arachnida - almost 100,000 spp identified spider (50,000) ticks and mites (48,000) scorpion

- respiration – trachea, book lung

Subphylum: Mandibulata – Class Crustacea (shrimps, crabs, copepoda) – Class Diplopoda (millipedes) – Class Chilopoda (centipedes) – Class Insecta (insects)

CLASS CRUSTACEA

• • • • • • • • •

Estimated 30,000 sp Most aquatic (especially marine) 2 pairs of antennae 1 pair of mandible 1 pair of compound eyes 1 pair appendages per segment Most body – head, thorax, abdomen Repiration: gills Exoskeleton : hard but flexible

Class Crustacea Sub-class: copepoda branchiopoda ostrocoda branchiura thecostraca malacostraca

Sub-Class Malacostraca Phyllocarida (sea fleas)

Stomatopoda Decapoda (crab, shrimp/prawn)

Peracarida (amphipod, isopod, mysids)

Euphausiacea

Class Diplopoda (millipede) about 8000 spp Head a pair of antennae a pair of mendible

Respiration – trachea Feeding – herbivours, scavenger

Many with poison gland

CHILOPODA (Centipede) • • • • •

About 5000 sp Terrestrial Carnivour/predator Food: small arthropods A pair of antennae and mandibles • A pair of legs per segment • With poison gland

CLASS INSECTA (INSECTS) - Characteristics • • • • • • • • • • • •

1 million spp identified (estimate few millions) Most successful group Habitat: almost all terrestrial and fresh water A few marine spp Body: 3 tagmata – head, thorax and abdomen Big compound eyes A pair of antennae 2 pairs of wings 3 pairs of legs (for walking) Mouth parts (depending on food) Respiratoion: trachea, gills Excretion: Malphighian tubule

CLASS INSECTA (INSECTS) – Charact (cont) • Reproduction: – Separate sex – Fertilization only once (sperm stored by female) – Use pheromone

• Growth – Special characteristics – Some: egg juvenile (resemble adultl) molting grow adult – Most: egg

larva

pupa

adult

INSECTA SUBCLASS APERYGOTA (No wings) Order Thysanura – silverfish

INSECTA SUBKELAS PERYGOTA (with wings) SUPERORDER EXOPTERYGOTA (incomplete metamorphosis)

• • • •

Order Isoptera (white ants) Order Odonata (dragonfly) Order Blattaria (cockroach) Orthoptera (grasshopper) Order Mantodea (praying mantis)

INSECTA SUBCLASS PERYGOTA (with wings) SUPERORDER ENDOPTERYGOTA (complete metamorphosis) • • • •

Order Lepidoptera (butterfly) Order Diptera (house fly, mosquito) Order Coleoptera (beetle) Order Hymenoptera (ants, bees)

SUPERORDER EXOPTERYGOTA (incomplete metamorphosis) Odonata - dragonfly

Orthoptera -grasshopper

SUPERORDER EXOPTERYGOTA

Mantodea – praying mantis

Blattaria – cockroach

SUPERORDER ENDOPTERYGOTA – complete metamorphosis Hymenoptera – ants, bees, and hornets - Membranous wings; - 2 pairs of wings

SUPERORDER ENDOPTERYGOTA Diptera – housefly - a pair of wings - second pair much reduced

SUPERORDER ENDOPTERYGOTA • Coleoptera – (sheath) •

Hard front wing pair

• Lepidoptera – scaly wings