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Bi 212, Lecture 5Phylum Arthropoda
Phylum Arthropoda:jointed foot
Evolutionary relationshipsand HOX genes
Basic Arthropod FeaturesPaired, jointed appendagesFunctions: Locomotion; feeding; protectionjoints allow for flexibility
SegmentationSome: segments all similarMost: segments combined into specialized body regionsExample: Insects have 3 regions: head, thorax and abdomen
ExoskeletonKey material: chitinSame materials also in mouthparts, wings, eye lens Key function of exoskeleton?Exoskeleton is molted
Focus on MoltingFunction: growthNew exoskeleton built under oldHow is this possible, since new exoskeleton is larger than the old one?RisksStrategy of female crabs to reduce riskSome arthropods continue to molt and grow throughout their lives.
Subphylum CrustaceaLobsters, crabs, shrimp, barnacles, copepods, etc..
Subphylum CrustaceaAntennaeHow many pairs?Body regionsCephalothorax & abdomenCalcium carbonate in exoskeletonGillsCompound eyes Feeding modesLobsters and crabsBarnaclesKrill!
Antarctic krillEuphausia superba
Subphylum Unirama(Hexapoda & Myriapoda)Insects, centipedes, millipedesThree distinct body regionsName them!Head capsuleSingle pair of antennaeCompound eyesFeeding modes (examples)Chewing (wasp)Piercing/sucking (giant water bug)
Dennis Kunkel Photos: www.microscopy-uk.org
Subphylum Chelicerata (Cheliceriformes)Spiders, mites, scorpions, horseshoe crabsAntennaeHow many pairs?Body regions Cephalothorax & abdomenEyes: type?Specialized feeding structuresPedipalpsCheliceraeSucking stomach
Body planFeeding/Digestive systemModes of feeding in different groups (already discussed)CompleteCirculation/gas exchangeOpen circulatory systemRespiration structures and systems Crustacea: gillsUniramia: tracheal system. CARRIES OXYGEN AND CO2Chelicerata: tracheal system, book gills and book lungs
Water/ion balance and ammonia excretionCrustacea: gills and antennal (or green) glandsUniramia and Chelicerata: Malpighian tubulesNervous systemBrain (=cerebral ganglia)Ventral nerve cord (paired, fused)Ganglia: one per segment or fewer (consolidated)Body plan
Body planReproductive systems Usually internal fertilizationSpermatophoresSperm storage
ReproductionInternal fertilization (many)SpermatophoresSperm storagePhoto: www.guclehmann.dewww.livescience.com