Lophotrochozoans Flashcards
(25 cards)
Characteristics of bilaterians?
- bilateral symmetry, triploblastic
- muscle tissues + organs from mesoderm
- protostomes and deuterostomes
- possess coelom and complete digestive tract
- differentiated along posterior-anterior axis
Features of differentiation in bilaterians?
- cephalization (sensory structures concentrated at anterior)
- directional motility
- concentration of neural ganglia
- reproductive + digestive structures discahrge posteriorly
- regulated by Hox genes
What is phylum acoela?
Basal to the 3 bilaterian clades, these marine worms are simple scavengers.
What are the 5 phylum in Lophotrochozoa?
Platyhelminthes, Ectoprocta, Brachiopoda, Mollusca, Annelida
Features of Platyhelminthes?
- flatworms that live in moist areas or water
- triboplastic but no coelom
- mouth and gut cavity but no anus
- no circulatory or gas exchange system (diffusion due to flat body shape)
Characteristics of free-living Rhabditophora?
- prey on small organisms in freshwater
- anterior cephalization with eye spots
- centralized nerve net
- gastrovascular cavity with one opening
- hermaphrodites, sexual/asexual
Characteristics of parasitic Rhabtidophores? What are the two types?
- suckers or hooks for host attachment
- tough, outer covering
- definitive host where it sexually reproduces
Trematodes, Tapeworms
What are tapeworms?
- endoparasitic in digestive system of animals, absorb nutrients from hosts intestines
- long chain of proglottids containing sex organs
- hermaphrodites
Tapeworm lifecycle?
- fertilized eggs consumed by host 1
- larvae encyst in tissues of host 1
- host 1 eaten by host 2
- Larvae develop into tapeworms in gut of host 2, sexual reproduction occurs
- fertilized eggs eit body via feces
What are Catenulida?
low diversity flatworms, free-living, reproduce via budding
What are the 2 lophophorates and features of lophophorates?
Ectoprocta, Brachiopoda
- lophophore - feeding structure with a fan of ciliated tentacles around the mouth
- sessile, aquatic, coelomates
- planktonic larval stage
Characteristics of Ectoprocta?
- sessile colonial animals resembling coral
- form colonies in calcium carbonate skeleton
- hermaphrodites and budding
- suspension feeders using retractable lophophore
- U-shaped gut, anal opening outside lophophore
Characteristics of Brachipoda?
- resemble molluscs
- attached to sea floor by a stalk
- suspension feeders using paired lophophores
- complete gut (anus optional)
What are the 2 trochozoans and features of trochozoans?
Mollusca and Annelida
- motile trochophore larvae
- planktonic larvae with 2 cilia bands that facilitate movement and guide food to mouth
- sensory plate with eye spot above cilia bands
Body plan of Mollusca?
1) Muscular ventral foot used for locomotion
2) Visceral mass above foot with internal organs
- reduced coelom, hemocoel
3) Mantle secretes shell
- involved in respiration and secretion
Segmented? Gills? Feeding? Circulation? Sex? Life cycle?
No
Located in mantle cavity for gas exchange or feeding
Rasp-like radula
Open circulatory system using hemolymph
separate sexes, gonads in visceral mass
ciliated trochophore larval stage
Class Polyplachophora features?
chitons: oval-shaped, protective shell with 8 dorsal plates
- use foot as a suction cup to adhere to rocks
- radula scrapes algae
Class Gastropoda features?
slugs + snails
- only aquatic have trochophore stage
- may have shell secreted by mantle
- terrestrial lost gills, mantle cavity developed into simple lung
- move using ventral foot or cilia action
- cephalization; antenna, eyes, ganglia, mouth
Class bivalvia features?
- shell divided in 2 halves drawn together via adductor muscles
- may have eyes + tentacles at edge of mantle
- suspension feeders using gills in mantle cavity
- no cephalization; no head or radula
Class Cephalopoda characteristics?
- no external shell except nautiluses
- may have gas-filled internal shell for buoyancy control
- long tentacles around mouth evolved from foot
- modified radula as a biting beak
- immobilize prey with poisonous saliva
- siphon (fused mantle tube) for jet propulsion
- closed circulatory system supporting active lifestyle
- direct development, no trochophore larvae
2 clades of Annelida and features?
Errantia, Sedentaria
- segmented worms with fused rings called annuli
- segments separated by septa
- coelom lined with mesodermally-derived tissues and acts as hydrostatic skeleton
- cephalization; mouth and ganglia
- complete digestive system
- closed circulatory system
Features of Errantia?
predatory, mobile with parapodia on each segment
- parapodium has chaetae and chitin bristles
- external gills, free-spawning
- cephalization; sensory antennae and eyes
- external fertilization, hatch into trochophore larvae
Features of Sedentaria?
less mobile
- may burrow into substrate and ingest substrate
- may live in tubes; elaborate gill/tentacles for suspension feeding
- no parapodia, reduced cephalization
- may undergo direct development
Features of leeches?
- no parapodia or chaetae
- predeators/parasites
- hermaphrodites, reproduce through reciprocal fertilization
- direct development
