Pseu oelomate Animals

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					    Chapter 9
Protostome Animals
                     Protostome Animals
Spiral cleavage
Blastopore forms Mouth
Mosaic Embryo

Many Phyla

2 subgroups
   Ecdyozoa (9 phyla)
      shed Cuticle
   Lophotrochozoa (17 phyla)
      ciliated tentacles / band of cilia in larval stage
        Lophotrocochozoan Pseudocoelomates

•   False body cavity not lined with mesoderm
•   Bilateral symmetry, triploblastic
•   Epidermis (often syncytial).
•   Muscles surround pseudocoel (Longitudinal)
•   Digestive, excretory and reproductive systems
•   Perivisceral fluid—Hydrostatic skeleton
•   Simple circulation
•   Storage for waste
•   Complete digestive tract (exception acanthocephala)
•   Eutely in some species
    Phylum Rotifera—”Wheel bearer”

~ 2000 spp. Cosmopolitan

Some Epizoic and Parasitic

Body consist of Head, Trunk and Foot

Corona and Mastax

Germovitellaria produce yolk and oocytes

Cloacal bladder- Pair of Protonephridial
tubules with flame bulbs

1 to 4 toes—Pedal glands
Phylum Rotifera—Reproduction

Asexual and Sexual Repr.

Males not known in many spp.

Amictic eggs (2n) only

Other species produce
Amictic AND Mictic (n) eggs

Mixis stimulus

        Phylum Acanthocephala—Spiny Headed Worms

~ 1100 spp. Cosmopolitan. 2 mm to 1 m !!! Ouch! 

Adults endoparasites of vertebrates

Molecular evidence—highly modified rotifers!

Proboscis with recurved spines
Proboscis receptacle

No digestive tract

Syncytial tegument with crypts
Lacunar system—distribution of nutrients?

Excretion across tegument
Phylum Acanthocephala—Reproduction

internal Fertilization

Protrusible penis
Copulatory bursa
Cement glands
Copulatory plug

Zygote develop into acanthor larvae

Cystacanth larvae infective to def. host

Parasite induced changes in Host behavior
         Phylum Gastrotricha—”Belly Hair Worms”

~ 460 spp. FW and Marine

Bristly or scaly

Glide on cilia


Marine spp.
Protandrous hermaphrodites

FW spp.
Male system non-functional

                  Phylum Entoprocta—“Within Anus”

~ 100 spp. Most Marine

Coelomate animals

Stalked and sessile
Colonial or solitary

Body is cup shaped with ciliated tentacles

Ciliary feeders

Mouth and Anus within “cup

Monoecious, dioecious, or protandrous herm.
                       Ecdyozoan Protostomes
                   Phylum Nematoda—Roundworms
~ 12,000 described spp. estimate: ~500,000 spp

Cosmopolitan, all habitat and climatic regions

Free living or parasites of animals and plants

Non living Cuticle (growth via molting)

No cilia or flagella

Most dioecious, internal fertilization
Sperm lack flagella !!! WHAT???

Excretory System
Gland cells &/or Canal system. NO flame cells

                                                  N.C., circa 1913
Complete digestive system with Muscular pharynx
              Phylum Nematoda—Form and Function
Digestive and Reproductive systems
in fluid filled pseudocoel

High hydrostatic pressure

Cuticle primarily collagen secreted by

Below Hypodermis, longitudinal muscles only

Cephalization near Pharynx

2 nerve chords (ventral/dorsal)
           Some interesting (i.e. parasitic) nematodes
           Ascaris lumbricoides, Human roundworm

Found in 20% of the world’s pop.
Females--200,000 eggs/day

                                  Juveniles— Pneumonia
                                  Adults— Abdominal problems, blockage
                                  What can you do?
Unblock it!!!!
Necator americanus--Hookworm

Adults in small intestine (12-20 mm)
Feed on blood!!
Eggs passed in feces hatch in the soil
Rahbditiform Larvae (feed on bacteria)
Filariform Juveniles burrow through skin
Migration--blood-lungs-intestine           Copulatory bursa

Mental retardation in children
              Enterobius vermicularis--Pinworms
Most common helminth parasite in the U.S. (30% in children)
Bulbous Pharynx
Live in large intestine and cecum
Females migrate to the anus to lay eggs



     Bulbous pharynx
                            Filarial Nematodes
Females release live microfilariae in blood and lymph
8 species of filarial worms known to parasitize humans (tropics)
Insect vectors
Ex. Wuchereria bancrofti causes Elephantiasis
Adults in lymphatic system cause its inflammation and obstruction
Microfilariae picked up by mosquito with blood meal, develop and infect
new host when mosquito bites uninfected individual
          Dirofilaria immitis—Dog Heart Worm

Most common filarial nematode in the U.S.
Insect vector = mosquito
       Phylum Nematomorpha—Horse Hair Worms
~250 spp. Worldwide
Free living as adults
Parasitic as juveniles in arthropods
Emerge from arthropod only near water !
                     Other Ecdysozoa Phyla
All marine dioecious worms

Phylum Kinorhyncha
  ~179 spp., < 1 mm, mud dwellers

Phylum Priapulida
  ~9 spp., 12-15 cm, predators

Phylum Loricifera
  ~100 spp., live in marine gravel

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