Lecture 15 Flashcards
Sub Phylums in Phylum Arthropoda
- Subphylum Chelicerata
- spiders, ticks and mites, horseshoe crabs, scorpions, etc…
- Subphylum Myriapoda
- millipedes, centipedes
• Subphylum Crustacea
• lobsters, crayfishes, shrimp, crabs, water fleas, copepods, and
barnacles
- Subphylum Hexapoda
- Mainly insects: butterflies, bees, wasps, flies, beetles, moths, etc…
Phylum Arthropoda characteristics
3 germ layers coelomate or eucoelomate protostomia, scdysozoa blastopore--> mouth complete gut mostly sexual reproduction bilateral symmetry
Adaptations of Arthropods (6)
- Versatile exoskeleton
- Segmentation and specialized appendages
- Air piped directly to cells
- Highly developed sensory organs
- Complex behaviours
- Trophic breadth through metamorphosis
Exoskeleton
- Exoskeleton = external skeleton
- called the cuticle in arthropods and nematodes
- Cuticle is secreted by the underlying epidermis
- The cuticle contains chitin, a nitrogenous polysaccharide
The cuticle is….
• heavy
limits body size
• hard and waterproof
great protection
• Thin and flexible between segments
permits free movement of jointsMolting
• Exoskeleton doesn’t expand
• To increase body size, arthropods must molt
• Molt = shed old feathers, hair, skin, or shell, to make way for new growth
• Ecdysis = shedding of outer cuticle, as in insects or crustaceans
a more specific term than moult
Defining feature of the clade ecdysozoa
metamerism in arthropods
=segmentation
- Segments often combined or fused into functional groups, called tagmata (sing. tagma)
- Appendages are also often differentiated (swimming, walking, etc)
Tagmata types
- Head
- Thorax (chest)
- Cephalothorax (head + thorax)
- Abdomen
- trunk
Subphylum Hexapoda visual caracteristics
3 pairs of legs
1 pair antennae
3 body parts (head, thorax, abdomen)
sub phylum chelicerata visual caracteristics
4 pairs legs
no antennae
2 bpdy parts (cephalothorax, abdomen)
sub phylum crustacea visual characteristics
8+ legs
2 pairs of antennae
variable body parts
sub phylum myriapoda visual characteristics
18+ legs
1 pair antennae
2 body parts (head, segmented trunk)
Subphylum Hexapoda Classes
Class Entognatha
• Small class, e.g.springtails
• Wingless
• Base of mouth parts enclosed
Class Insecta • Enormous group • Base of mouth parts visible • Usually two pairs of wings on thorax • e.g.butterflies,bees,wasps,flies,beetles,moths...
Chelicerata cephalothoracic appendages
Most have 6 pairs
• 1 Pair of chelicerae (mouthparts)
• 1 Pair of pedipalps (second pair of appendages)
• 4 pairs of walking legs
Types of Circulatory Systems
• Closed circulatory system
Blood is contained within vessels
Vertebrates and some invertebrates
• Open circulatory system
Blood is confined to vessels in only a
portion of circuit through body
Blood mixes with interstitial fluids (i.e. fluids between cells) in the hemocoel
Because it is mixed with fluid, it is properly called hemolymph
Arthropods and some molluscs
Respiration for arthropods
Most land arthropods (e.g. insects) use a system of air tubes called tracheae for gas exchange
!!!! hemolymph does not carry oxygen in these species!!!!
oxygen directly to tissues and cells through holes or valves
Aquatic arthropods breathe mainly through gills
Developed sensory organs in arthropods
• Compound eye
• Some have antennae
• Keenly alert to environmental stimuli…
Touch, Smell, Hearing, Balance, Chemical reception
Arthopods behaviours
• Simple behaviours
E.g. orientation of a moth towards light
• Complex behaviours
E.g. female potter wasp
• scoops up clay into pellets
• Lays eggs in each pot
• Hunts and paralyzes a number of caterpillars
• Seals the opening with clay
• Eggs hatch to find food waiting
Where does arthropod behaviour come from?
• Most behaviour is innate (unlearned)
• Many arthropods also demonstrate learned behaviours
E.g. the potter wasp must remember (learn) where she has left
her pots
• Social insects (e.g. bees, termites) are capable of most basic forms of learning used by mammals, but not of insight learning
Insight learning = when faced with a new problem, can
organize memories to construct a new response
Metamorphosis in arthropods
- Occurs in any species with indirect development (i.e. a larval stage)
- e.g. most arthropods, cnidarians, molluscs, amphibians
- Particularly striking in insects
- Larval and adult forms live in different niches; have difference sources of food, experience different selective pressures
Metamorphosis definition
sharp change in form during postembryonic
development – for example, tadpole to frog, or larval insect to adult
Direct development in arthropods
- Ametabolous
- Young or juveniles are similar to adults except in size and sexual maturation
- A few (primarily wingless) insects exhibit this type of development (Also mammals, species with telolecithal eggs)
- Stages: egg, juvenile, adult
Indirect Development in arthropods
- Hemimetabolous or Holometabolous
- Passes through larval stage capable of feeding itself
- Undergoes metamorphosis to reach adult stage
Hemimetbolous
- (incomplete) metamorphosis
- Wings develop externally as budlike growths
- Nymph resembles adult in form and eating habits
- Nymph differs from adult in size, body proportion, and colour pattern • E.g. Grasshoppers, cicadas, mantids, dragonflies
- Stages: egg, nymph, adult
Holometabolous
- (complete) metamorphosis
- Approximately 88% of insects undergo holometabolous metamorphosis
- Separate stages for growth (larva), differentiation (pupa), and reproduction (adult)
- Larva are wormlike (e.g. caterpillar)
- Pupae are usually inactive (nonfeeding) and enveloped by a case
- No further molting occurs in adult stage
- E.g. beetles, butterflies and moths, flies, wasps
- Stages: egg, larva, pupa, adult
