Bi 212, Lecture 5 Phylum Arthropoda

Phylum Arthropoda: “jointed foot”

Evolutionary relationships and HOX genes

Basic Arthropod Features  Paired, jointed appendages  Functions: Locomotion; feeding; protection  joints allow for flexibility  Segmentation  Some: segments all similar  Most: segments combined into specialized body regions  Example: Insects have 3 regions: head, thorax and abdomen  Exoskeleton  Key material: chitin  Same materials also in mouthparts, wings, eye lens  Key function of exoskeleton?  Exoskeleton is molted

Focus on Molting  Function: growth  New exoskeleton built under old  How is this possible, since new exoskeleton is larger than the old one?  Risks  Strategy of female crabs to reduce risk…  Some arthropods continue to molt and grow throughout their lives.

Subphylum Crustacea  Lobsters, crabs, shrimp, barnacles, copepods, etc..

Subphylum Crustacea  Antennae  How many pairs?  Body regions  Cephalothorax & abdomen  Calcium carbonate in exoskeleton  Gills  Compound eyes  Feeding modes  Lobsters and crabs  Barnacles  Krill!

Antarctic krill Euphausia superba

Subphylum Unirama (Hexapoda & Myriapoda)  Insects, centipedes, millipedes   Three distinct body regions  Name them!   Head capsule   Single pair of antennae   Compound eyes   Feeding modes (examples)  Chewing (wasp)  Piercing/sucking (giant water bug) Dennis KunkelPhotos:

Subphylum Chelicerata (Cheliceriformes)  Spiders, mites, scorpions, horseshoe crabs   Antennae  How many pairs?   Body regions  Cephalothorax & abdomen   Eyes: type?   Specialized feeding structures  Pedipalps  Chelicerae  Sucking stomach

Body plan  Feeding/Digestive system  Modes of feeding in different groups (already discussed)  Complete  Circulation/gas exchange  Open circulatory system  Respiration structures and systems  Crustacea: gills  Uniramia: tracheal system. CARRIES OXYGEN AND CO 2  Chelicerata: tracheal system, book gills and book lungs

 Water/ion balance and ammonia excretion  Crustacea: gills and antennal (or “green”) glands  Uniramia and Chelicerata: Malpighian tubules  Nervous system  Brain (=cerebral ganglia)  Ventral nerve cord (paired, fused)  Ganglia: one per segment or fewer (consolidated) Body plan

 Reproductive systems  Usually internal fertilization  Spermatophores  Sperm storage Body plan

Reproduction  Internal fertilization (many)  Spermatophores  Sperm storage Photo: