Phylum Rotifera - Faculty€¦ · Phylum Rotifera • Freshwater, freeliving (most), few marine • Linked to Lophotrochozoa • Many habitats and shapes • Many interstitial •

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Phylum Rotifera• Freshwater, freeliving (most), few

marine• Linked to Lophotrochozoa• Many habitats and shapes• Many interstitial• Roto-feeders• Telescopic; semi-flexible• Protonephridia and diffusion• Reproduction: parthenogenesis

General Body Plan

Ciliated Head= Corona

Often a ringed cuticle to allow for contraction (antenna)

Jawed Mastax for chewing

Flame cells and bladder

movie

Rotifer Reproduction

•Most Dioecious

•Some parthenogenetic

heavy-shelled dormant egg, much yolk; dormant egg survives the winter

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Lophophorates

• Ciliated Lophophore- feeding structure• Hollow lophophore tentacles are projections of

the coelom (respiratory)• Surrounds mouth

Phylum Bryozoa

• “Ectoprocta”• 4000 species, both

FW and Marine• Colonial-

– Zoecium– Jack-in-the-box– operculum

Phylum Brachiopoda• 325 extant, 12,000 extinct• Two calcareous shells: Top/bottom, not right/left

Phylum Mollusca: snails, slugs, chitons, clams, octopus and squid

• Trend toward rounder body: low SA/vol ratio• Lack of segmentation (except Neopilina)• Hypothetical Molluscan ancestor

– Mantle and mantle cavity, shell– Muscular foot: sensory and locomotory– Visceral Mass

• Cephalization: sensory and feeding• Gills (most)• Complete GI w/ glands, radula• Open circ. system*: heart and haemocoel• Metanephridium• Separate sexes

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“HAM”The trochophore larva

2nd larval stage-Veliger larva of snail

Shell and Mantle 3 layers

1. Periostracum

2. Prismatic

3. Nacreous

Radula

Class ScaphopodaClass Monoplacophora

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Class Polyplacophora: chitons• 600 living species, mostly intertidal• Most similar to ancestral mollusc• Broad-footed herbivores• 8 overlapping plates• Very little cephalization: no eyes or tentacles,

small head w/ radula

Cryptochiton stelleri- Gumboot Chiton

Class Gastropoda: snails, slugs, limpets

• Largest molluscan class, 40,000 species• Mobile: Herbivores and Carnivores

• 3 important changes from ancestral mollusc– Greater cephalization: affects sensory and locomotion

– Asymmetrical spiral shell: portable protection– Torsion: realignment of body with shell

• Feeding strategies and specializations• Gills or “lungs”

Torsion- do you see a problem?(and de-torsion)

Pulmonate gastropods-mantle cavity modified into lung

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Class Bivalvia: clams

• Laterally compressed w/dorsal hinge• Very large mantle cavity: use of gills for

respiration and suspension (filter) feeding– Incurrent and excurrent siphons

• No radula or distinct head present• Pearls: require inner nacreous

layer

CtenidiaHighly modified for respiration AND feeding

Water/Food path

Internal Anatomy Burrowing LocomotionBurrowing Locomotion

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Cl. Cephalopoda: nautilus, squid, octopus• 650 species, extinct members include Ammonites (65

mya)• Predators• Swimming lifestyle: jet propulsion• Reduced or absent shell• Closed circulatory system• Cephalization: sensory, movement, learning• Foot gives rise to funnel• Arms that are probably derived from the molluscan head • Chitinous beaks• Direct development (larvae?)• Cephalopod eye: convergence

Squid Internal Anatomy

DosidicusDosidicus gigasgigas-- Humboldt SquidHumboldt Squid Giant Squids

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Architeuthis