Lecture 19 Flashcards
internal phylogeny of arthropoda
until recently hexapods and myriapods considered sister taxa, recently hexapods nested within crustaceans
pancrustacea
new crustacean clade to include hexapods
3 arthropod tagmata
- head (eating and sensing)
- thorax (locomotion)
- abdomen (digestion and reproduction)
cephalothorax
head and thorax combined in some taxa
trilobita
extinct in End-Permian (280 MYA), 4000, 1 pair antennae and compound eyes many pairs of biramous limbs
biramous
2 branched
“crustacea”
crabs, lobsters, shrimp, 50 000, most marine some freshwater/terrestrial
crustacean morphology
- 2 pairs antennae
- biramous limbs
- compound eyes (often on stalks)
- cephalothorax, usually covered by carapace
- mouthparts are mandibles
- appendages guide food
- thoracic limbs for locomotion
- abdominal limbs for swimming, filter feeding, eggs
- exoskeleton strengthened with calcium carbonate
- exchange gases through gills (aquatic/semiterrestrial species) or tracheae (true terrestrial)
carapace
shield that covers dorsal and lateral sides, sometimes also abdomen
mandibles
single-segmented biting/chewing mouthparts
crustacean reproduction
- separate sexes (barnacles are hermaphrodites)
- sperm transfer via copulation, intromission, or spermatophore deposited outside on female’s genital opening
- females brood eggs until they hatch
- most have larval stages, some direct development (freshwater/terrestrial) start out with 6-limbed nauplius larva
copulation
male places sperm on or in the female’s sperm receiving structure
crustacean feeding
filter feed, scavenge, prey on fish, commensals/parasites of vertebrates/invertebrates
bottom-trawling
for prawns/shrimp, destroys benthic habitat, > 75% bycatch discarded
hexapoda
insects and springtails, 6-legged, most terrestrial some freshwater few marine, important in pollination
myriapoda
centipedes and millipedes, all terrestrial, oldest terrestrial fossils, direct development
hexapods and myriapods 4 shared characteristics
- 1 pair antennae
- mandibles for mouthparts
- tracheae (respiratory tubes) for gas exchange
- uniramous limbs
clade Mandibulata
pancrustaceans and myriapods, all have mandibles
2 classes of hexapoda
- Insecta (most diverse and species rich)
2. Collembola (springtails)
hexapod morphology
- 3 tagmata
- entognathous (Collembola) or ectognathous (Insecta)
- Collembola have forked terminal appendage used for jumping, collophore, and ocelli
- Insecta have compound eyes and often ocelli, most have wings as adults (clade Pterygota) some apterygote
3 hexapod tagmata
- head (1 pair antennae)
- thorax (3 pairs jointed legs)
- abdomen (without paired jointed appendages)
entognathous
mandibles enclosed by cheeks
ectognathous
mandibles not enclosed
collophore
ventral tube used for water and ion regulation in collembola, produces sticky substance
ocelli
simple single-lensed eyes
3 types of hexapod lifestyle
- ametaboly
- hemimetaboly
- holometaboly
ametaboly
primitively wingless groups, juveniles look exactly like small adults except have no genitalia
hemimetaboly
wings develop slowly over several moults (as wing pads), juveniles may share morphology and habitat of
adult or different, juvenile often called a nymph
holometaboly
wings develop all at once in a special stage
called a pupa, juvenile always has different morphology and ecology than adult, juvenile properly termed ‘larva
hexapod reproduction
- separate sexes
2. indirect sperm transfer in collembolans and apterygotes, pterygotes copulate
indirect sperm transfer
spermatophore (encapsulated package of sperm) placed on a substrate
entomology
main reason is economic importance of hexapods
colony-collapse disorder
viewed as disaster, cause unclear
myriapoda morphology
- more than 3 pairs of legs
2. less tagmatized - head (ocelli, mandibles, 1 pair antennae) and trunk (9-325 pairs jointed legs)
2 classes myriapoda
- diplopoda (10 000)
2. chilopoda (2500)
class diplopoda
millipedes, two pairs of legs and two stigmata per segment
diplosegments
result of fusing of adjacent pairs of segments
class chilopoda
centipedes, 1 pair of legs per segment, 1 pair of modified legs behind mouthparts, poison claws to subdue prey and fight predators
chelicerata
horseshoe crabs, scorpions, spiders
chelicerata morphology
- lack antennae
- chelicerae as main mouthparts
- 2 tagmata - cephalothorax (carapace, 6 pairs limbs, eyes) abdomen (may or may not bear appendages, contains gut and reproductive organs)
chelicerae
3 segmented pincer mouthparts, some species reduced to 2 segmented stabber
6 pairs chelicerata limbs
chelicerae, pedipalps, 4 pairs legs
2 classes chelicerata
- xiphosura (4)
2. arachnida (90 000)
class xiphosura
horseshoe crabs, marine, compound eyes, book gills, long terminal spine, ingest particles, planktonic larvae
book gills
many flat plates look like pages of book
class arachnida
spiders, mites, scorpions, most terrestrial few aquatic mites, ocelli, are fluid-feeding predators, separate sexes
3 main orders arachnida
- araneae (48 000)
- scorpiones (1200)
- acari (54 000)
araneae
spiders, tight constriction between cephalothorax and abdomen, 2-segmented chelicerae, spinnerets, exchange gases through tracheae or book lungs, all fluid-feeding predators, poison glands empty through fangs of chelicerae, some use silk to capture prey, maternal care of eggs sometimes young
spinnerets
abdominal appendages for spinning silk
book lungs
look like book gills that have been enfolded by abdomen
araneae sperm transfer
- male deposits sperm blob on small web
- sucks up sperm in modified pedipalp
- inserts into female’s genital opening
scorpiones
scorpions, desert or rainforest, pedipalps modified as grasping pincers, abdomen clearly segmented, terminates in poisonous sting
acari
mites including ticks, do everything live everywhere, most fluid-feeders many detritivores ingest solid particles, young hatch with only 3 pairs of legs called larvae, most economically important arachnids,
