P. Nematoda: Enterobius

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P. Nematoda Enterobius

• Pinworms (Enterobius vermicularis)
• most common nematode parasite in the US
• 30 all children, 16 all adults
• causes little disease
• 12 mm
• adults live in large intestine/cecum
• ? migrate to anal region at night/lay eggs
  (Scotch Tape Method)
• itching
• scratching contaminates hands and bedclothes
• eggs develop/become infective w/i 6 hrs at body
  temp.
• ingested, hatch in duodenum, mature in large
  intestine
• haploid ? from unfertilized eggs
• diploid ? come from fertilized eggs
  (haplodiploidy)

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P. Nematoda Filarial Worms

• Filarial worms
• 8 sp. infect humans
• some live in lymphatic system
• cause inflammation/blockage of lymphatics
• ? release live young (microfilariae) into
  blood/lymph
• mosquitoes ingest microfilariae
• worms develop to infective stage
• move into mosquito bite wound when it feeds
• Elephantiasis caused by repeated exposure
• swelling/growth of connective tissue
• dog heartworm (Dirofilaria immitis)
• most common U.S. filarial worm
• transmitted by mosquitoes

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P. Nematomorpha

• Horsehair worms
• 1 m long, 0.5-3.0 mm dia.
• 320 sp.
• Moist habitats worldwide
• Similarities to nematodes
• cuticle
• epidermal cords
• only longitudinal muscles
• nervous system
• Free-living adults, parasitic juveniles
• parasites of arthropods
• Some encyst on vegetation
• eaten by grasshoppers

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P. Nematomorpha Form/Function

• Characteristics
• rounded anterior end
• posterior w/ 2-3 caudal lobes
• lacks lateral hypodermal cords
• ventral nerve cord connected to ventral
  hypodermal cord by nervous lamellae
• Digestive system is vestigial
• larvae absorb food from arthropod hosts
• adults utilize stored nutrients, absorb organic
  molecules via vestigial gut/body wall
• Circulatory/respiratory/excretory systems lacking

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P. Nematomorpha Form/Function

• Reproduction/life cycle
• dioecious
• ? discharge eggs into water
• larvae infect arthropod host by being eaten
• after months in host, mature worm emerges into
  water

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P. Kinorhyncha

• lt 1 mm
• 150 sp.
• Worldwide
• intertidal ? 6000 m deep
• most live in mud
• Feed mainly on diatoms/digesting OM
  from surface of mud
  particles

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P. Kinorhyncha Form/Function

• Characteristics
• body divided into 13 segments w/ spines, no cilia
• retractile head w/ circle of spines/retractile
  proboscis
• cuticle and syncytial epidermis
• circular/longitudinal/diagonal muscles
  anchored in each
  segment
• cannot swim
• anchors in mud burrow w/ spines
• mouth ? proboscis ? pharynx ?
  esophagus ?
  stomach-intestine ? anus
• pseudocoel filled w/ amebocytes and fluid
• eyespots and sensory bristles
• dioecious
• 6 juvenile stages and nonmolting adult

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P. Loricifera

• Discovered 1983 in spaces btwn grains of
  marine gravel
• 10 sp. known
• Widely distributed
• most in coarse sediments at depths of 400 m
• 1 sp. at 8000 m
• Oral spines
• Brain fills head and nerves innervate spines
• Diet unknown (bacteria?)
• Dioecious

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P. Priapulida

• 16 sp.
• Marine, colder waters
• intertidal zones to deep ocean floors
• Some tube dwellers
• burrow by body contractions
• orient mouth at surface
• Feed on detritus
• Eversible proboscis w/ rows of curved
  spines to capture
  prey
• Trunk w/ 30100 superficial rings
  covered w/
  tubercles/spines
• Chitinous cuticle
• Body cavity w/ amebocytes
• Respiratory pigment (hemerythrin)
• Dioecious

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Lophotrochozoa Phyla
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P. Rotifera

• 1800 sp. known
• Worldwide
• Mostly freshwater/marine/terrestrial/parasitic
• Ciliated crown (corona)
• beats like rotating wheel
• Many colors/sizes/shapes
• Some are colonial
• Forms
• floaters are globular
• creepers are elongated
• sessile forms are vase-like
• Cyclomorphosis regular variation in
  body form to accommodate seasonal/food
  change
• Endure dessication/temp. changes by encystment

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P. Rotifera Form/Function

• Characteristics
• ciliated corona surrounds nonciliated central
  area w/ sensory bristles and mouth
• cilia func. in feeding/locomotion.
• some w/ cuticle
• subepidermal muscle
• all w/ fibrous epidermis layer
• pseudocoel w/ mesenchymal ameboid cells
• narrow retractile foot w/ 1-4 toes
• attaches w/ pedal glands that secrete adhesive

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P. Rotifera Form/Function

• Digestion
• coronal cilia sort out larger unsuitable
  particles
• mastax muscular pharynx w/ hard jaws (trophi)
• trappers have funnel-shaped area around mouth
• side lobes fold inward to trap prey
• hunters project trophi to seize prey
• salivary and gastric glands secrete
  enzymes for
  extracellular digestion
• stomach absorbs nutrients
• Nervous/sensory system
• bilobed brain dorsal to mastax w/
  paired nerves
  leading to organs
• sensory organs include eyespots,
  sensory bristles
  and papillae,
  ciliated pits and dorsal antennae

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P. Rotifera Form/Function

• Reproduction
• dioecious
• ? smaller than ?
• some classes, ? unknown
• others, ? occur only briefly
• other ? produce 2 types eggs
• 2n amictic eggs (not mixed w/ ?)
  that
  form 2n ?
• 1n mictic eggs that become 1n ?
  if not
  fertilized
• parthenogenetic produce 2n eggs
  that hatch into
  2n ?
• mating is by hypodermic penetration
• sperm injected into ? pseudocoel at
  any
  location on body

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P. Acanthocephala

• Spiny-headed worms
• 500 sp. known
• Worldwide
• Parasites in fish/bird/vertebrate intestines
• larvae develop in crustaceans or insects
• Highly derived class of rotifers
• Proboscis of recurved spines penetrate/rupture
  host intestines
• can be inverted into proboscis receptacle
• Characteristics
• flattened body
• both longitudinal/circular
  body
  wall muscles
• syncytial body wall
• minute crypts ? SA

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P. Acanthocephala Form/Function

• 80 of tegument is lacunar system of
  fluid-filled canals
• distribute nutrients/remove wastes from muscles
• lack heart/respiratory system/digestive tract
• absorb all nutrients across the tegument
• some have protonephridia w/ flame cells

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P. Acanthocephala Form/Function

• reproduction
• ? have pair of testes
• sperm ejected into vagina, travel to pseudocoel
• ? produce ovarian balls that rupture/float free
  in pseudocoel
• uterine bell receives shelled embryos, pass to
  uterus
• shelled embryos discharged in feces
• hatch when eaten by intermediate host (grub)
• larvae burrow through beetle intestine
• develop into juvenile
• cystacanths in insect hemocoel

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P. Gastrotricha

• 800 sp.
• Freshwater/marine
• Live in interstitial spaces btwn benthic sediment
• lt1 mm
• Similar to rotifers but ventrally flattened/lack
  corona/ lack mastax/bristly or
  scaly
• Body plan
• elongated w/ dorsal surface/pattern
  of
  bristles/spines/scales
• ventral surface is flattened/ciliated
• head is lobed/ciliated
• tail may be forked
• Glide on plant or animal substrates using ventral
  cilia

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P. Gastrotricha Form/Function

• Syncytial epidermis, cuticle
• Adhesive tubes secrete substances for attachment
• No body cavity
• Digestive system
• mouth ? pharynx ? stomach-intestine ? anus
• extracellular digestion
• algae/protozoa/detritus
• Nervous/sensory systems similar to
  rotifers except no
  eyespots
• Reproduction
• hermaphroditic
• thin-walled eggs develop rapidly develop
• thick-shelled eggs for dormancy
• Development is direct

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P. Entoprocta

• 150 sp.
• Usually marine
• lt5 mm
• Resemble hydroid cnidarians
• Cup-shaped calyx bears circular crown of ciliated
  tentacles
• Attaches by stalk w/ adhesive glands
• Tentacles and stalk are continuations of the body
  wall
• 830 ciliate tentacles on lateral and inner
  surfaces
• roll inward
• cannot retract into calyx
• Long cilia maintain current
• brings in particles
• Short cilia capture food/direct it to mouth

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P. Entoprocta

• U-shaped gut w/ mouth/anus openings w/i circle of
  tentacles
• Body wall w/ cuticle/epidermis/longitudinal
  muscles
• Well-developed nerve ganglion on ventral side
• No circulatory/respiratory organs
• Monoecious/dioecious
• some protandric
• Fertilized eggs develop in brood
  pouch btwn
  gonopore/anus