Flashcards in Lecture 5 RH Deck (94)
What is so special about arthropods?
First animals to colonize land
They are the most diverse animal phylum (900000 species)
What are the key features of arthropods?
Metameric, heteronomous, tagmatisation
Paired, jointed appendages
Most are highly cephalised
Most reproduce by internal fertilization
What are ecdysozoan protostomes?
Protostomes that molt and dont undergo spiral cleavage
What is heteronomous segmentation?
Segments are different
What is homonomous segmentation?
All segments are the same
What is tagmatisation?
Multiple segments fused into distinct body regions.
Why is tagmatisation significant?
Allows specialization of segments for different purposes
What is the exoskeleton of arthropods made of?
chitin in some species of crustaceons it is reinforced with calcium or wax layer
What is the function of the arthropod exoskeleton?
Protection against predators and dessication
Where do legs arise from in arthropods?
Paired jointed appendages are modified as legs
How is the exoskeleton's rigidity overcome in arthropods when growing?
What kind of muscles do arthropod limbs have?
What is the problem with molting?
Molting is an energy and time consuming process which can get an arthropod killed
What are tracheae?
Hollow internal tubes and invaginations of cuticle
What is the function of tracheae?
Deliver oxygen to tissues
How is water loss reduced in arthropods?
Spiracles are closed by valves in some species to reduce water loss
What are wings made from?
Evaginations of cuticle
What are some features of the head of highly cephalised arthropods?
Well-developed central ganglia
Image-forming eyes (Compound eyes with units called ommatidia)
Antennae and antennules form mecahanosensory organs and chemosensory organs
What are the subphyla of arthropods?
Crustacea: crabs, lobsters, shrimp, barnacles
Chelicerata: Horseshoe crabs, spiders, scorpions, ticks, mites
Myriapoda: centipedes, millipedes, pauropods, symphylans
Hexapoda: insects, collembolans, proturans
What are the anatomical features of trilobites?
Biramous appendages, 1 pair of antennae
What are the anatomical features of crustaceons?
Biramous appendages, 2 pairs of antennae, naupilius larvae
What are the anatomical features of chelicerata?
uniramous appendages and no antennae
What are the anatomical features of myriapodae?
uniramous appendages 1 pair of antennae
What are the anatomical features of Hexapodae?
Uniramous appendages, 1 pair of antennae, no abdominal appendages
Which group of arthropods is most diverse?
Insects followed by chelicerates
What are the features of subphylum crustacea?
45000 described species
Great diversity in body forms and ecological niches
Mostly aquatic, some terrestrial
Display all types of feeding modes (predator, scavenger, herbivore, suspension feeder, deposit feeder) life styles
An important food group for humans
What are the traits of a generalized crustacean?
3 tagmata, or can have fused cephalothorax
What are the typical crustacean head appendages?
What are the typical thorax appendages in crustaceanss?
up to 3 pairs of maxillipedes
Often 5 pairs of pereopods
What are the typical abdominal appendages?
6 pairs of pleopods
Telson and uropods
What are pereopods functional for?
What are maxillipeds?
Important limbs for manipulating food
What are pleopods functional for?
Where do claws arise from?
What are telson and uropods required for?
What are the appendage rami of crustaceans?
Where are the gills typically located on sea dwelling crustaceans?
What is autonomising the leg?
Dropping the leg off in reaction to predator grasping it
What body systems does a crustacean have?
Complete digestive tract with gastric mill (teeth like structures at the opening of the stomach)
Open circulatory system: hemocoels (reduced coelom), heart ostia
Excretory system (metanephridia in head aka green glands)
Nervous system with brain and segmental ganglia
*muscles and exoskeleton inside the stomach to assist digestion
Where is the anus located in crustaceans?
The very posterior end
What is a hemocoel?
remnant of coelom which has blood accumulating forming sinuses
Where are gills located in crustaceans?
on legs outside of the body
How do crustaceans sense balance?
Statocysts on uropods
Do crustaceans have compound eyes?
How do crustaceans reproduce?
Internal fertilization (often with gonopod but highly variable)
Fertilized eggs are often brooded by females
Are crustaceans mono or dio ecious?
What larva do crustaceans produce?
nauplius (free swimming or in egg)
then the following can be the next stages:
Zoea (crabs and other decapods)
Megalopa (crabs and other decapods)
What is the life cycle of a prawn?
1) Fertilized eggs are released offshore
2) Nauplius stage followed by protozoea and mysis
3) Juveniles return to inshore nursery areas
4) Adults then go offshore to lay their eggs
What are the classes of crustaceans?
Class malacostraca (includes decapoda, euphausiacea, stomatopoda, amphipoda, and isopoda)
Class Branchiopoda (contains fairy shrimp, water fleas, tadpole, and clam shrimp)
Class Maxillopoda (Contains Barnacles, tongue worms, ostracods, seed shrimp)
What are the features of decapods?
2 tagmata (cephalothorax + abdomen)
5 Pereopods (first 3 can chelate)
Pleopods are variable
Serial homology: Body segments are homologous
Occupy all habitats and feeding modes (deposit feeder, suspension feeder, predator, herbivore, scavenger)
What are the sexual dimorphisms in crabs?
Males have a narrow abdomen and pleopods modified as gonopods
Females have a wide abdomen and pleopods used to carry fertilized eggs
What are the features of subclass cirripedia (barnacles)?
All marine and sessile
Free-living species are filter feeders
6 pairs of thoracic cirri.
Reduced body (uncephalised and no abdomen)
What is the life cycle of barnacles like?
1) Sexual reproduction results in nauplius larva which becomes a cyprid larva and loses antennae.
2) Cyprid larvae finds a rock and attaches to surface
3) Cyprid larva metamorphoses and produces a shell around it
Are barnacles hermaphrodites?
Are barnacles mono or dio ecious?
What do barnacles do to mate considering that they are sessile?
They have an extensible penis which can grow to reach the female.
What are the features of parasitic crustaceans?
Most show greatly reduced body form
They parasitise a wide range of animals including other crustaceans
All have typical crustacean larva
What is a defining feature of crustaceans?
The nauplius larval stage
How do the limbs adapt to the different environments crustaceans live in?
Different crustaceans use different specialized limbs to swim around
What are crustacean adaptations to allow walking?
Pereopods with varying degrees of specialization
What are crustacean adaptations to allow burrowing?
Amphipod can create a specialized limb out of their amphipod or their uropod in order to burrow
How do suspension feeders modify their limbs for feeding?
In copepods: Maxilliped and 2nd maxilla are specialized for feeding.
In Decapods: 2nd antennae
Euphasids and branchiopods use pereopods
How are limbs adapted to swimming?
In fairy shrimp and euphasid: Pereopods or pleopods move in waves of power and recovery strokes
In decapods: 5th pereopods form swimming legs and in some cases uropods form flippers
Copepods flick antennae
What is modified for scavengind and deposit feeding?
Pereopods in some decapods
2nd antennae in gnathopods
Specialized stabbing pereopods in some
What are the characteristics of the phylum hexapoda?
1 pair of antennae
3 pairs of legs on thorax
Various head appendages
abdominal appendages are mostly absent
Tracheae for gas exchange
malpighian tubules for excretion
How do insects excrete their wastes?
What are chelipods?
Crab claws which are modified pereopods
What are the main physiological adaptations to life on land in insects?
Malphigian tubes with efficient resorption of water
Tracheae which deliver oxygen directly to muscles
Valves in tracheae which close to reduce water loss.
What are chewing mouthparts?
Strong mandibles with toothed plates
Maxillae to manipulate food
What are chewing mouthparts needed for?
Predation, herbivory, or scavenging
Which insects typically have chewing mouthparts?
How do piercing and sucking mouthparts work?
Needle-like labium or stylet modified from maxillae and mandibles.
Tubular labrum for sucking while saliva flows out through hypopharynx
Used to pierce flesh or plant cells
Which animals typically have piercing and sucking mouthparts?
How do sucking mouthparts work?
Feed on energy rich liquids (eg nectar)
They are long and just suck
Which insects have sucking mouthparts?
Butterflies and moths have no mandibles
Honey bees use labial palps and maxillae
How do lapping mouthparts work?
Labium is modified into absorptive pads
Used for scavenging on any liquids
Biting flies use mandibles to cut flesh and make it bleed before lapping it up.
What are some leg modifications in insects?
Hair on bee legs collect pollen
Mole cricket can dig with legs
Grasshopper has strong legs for jumping very high
What are some antennae modifications in insects?
Some are modified for sensing chemicals, vibrations, air currents, surfaces
What are some wing modifications in insects?
Most insects have 2 pairs of wings
Beetle have wing covered by a pair of elytra
Flies have wings and halteres
What are the features of wings of insects?
They are formed by the evagination of cuticle with top and bottom membrane
Veins move to alter shape of wing
Wings pivot on side plate of exoskeleton
Compression of thorax causes wings to flap
Elasticity of exoskeleton can be used to increase beat frequency.
What is a hemimetabolous life cycle?
Gradual change between instars
What is holometabolism?
Why is it advantagous for separate stages of a lifecycle in insects?
Each stage of the life cycle specializes for a certain function.
At what taxonomic level are insects separated?
Which orders are most commonly used by biologists?
Coleoptera (beetles, fireflies, weevils)
Diptera (flies, mosquitos)
Hymenoptera (ants, bees, wasps)
Lepidoptera (Butterflies, moths)
What is happening to pollinating insect populations?
They have been declining in numbers causing a decline in number of plants that depend on these insects
What is causing colony collapse disorder?
Common pesticides are causing brain damage to bees and this disrupts their function.
What are the features of myriapods?
1 pair of antennae
Tracheae, spiracles cannot be closed
What do malpighian tubules do?
Help them produce highly concentrated excretions
What are the features of chilopoda (centipedes)?
1 pair of legs per segment
Last pair of legs is sensory or defensive
Maxilliped on 1st trunk segment has forciple
What is a maxilliped?
Maxillae like legs for manipulating food
What is a forcipule?
What are repugnatorial glands?
Defensive glands that secrete a chemical that is caustic