The Lesser Protostomes

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The Lesser Protostomes
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The Lesser Protostomes

• Phyla contain few numbers of species
• All phyla are aquatic organisms
• Recorded in the fossil record especially fossil
  beds such as the Burgess shale
• Morphologies are intermediate to the morphologies
  of the major lophotrochozoa phyla Mollusca,
  Annelida and the Ecdyzoa phylum Arthropoda

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Lessor Lophotrochozoan Phyla
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Phylum Gnathostomulida

• 1st discovered 1928, formally described 1956
• 18 genera, 80 species
• 0.5-1mm
• Feed on bacteria, fungal, protozoan cells in
  sediment
• Aceolomic
• Incomplete digestive tract
• Monociliated epidermal cells

Gnathostomula jenneri
Gnathostomula paradoxa
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Phylum Micrognathozoa
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Phylum Micrognathozoa

• 1 species !!!
• 1st discovered 1994, formally described 2000
• 0.1-0.2mm
• Complete gut
• Complex jaw
• Only females found
• Parthenogenetic ?

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Phylum Rotifera

• 2000 species
• Corona of ciliated cells
• Pseudoceolomic
• Central nervous system
• Complete gut
• Many species are female only
• Parthenogenetic

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Phylum Rotifera

• Rotifer YouTube Movie

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Parthenogenetic Reproduction

• Females are diploid
• Amictic eggs
• Produced by mitosis
• Are not fertilized
• Mictic eggs
• Produced by meiosis
• Develop w/o fertilization into haploid male
• Fertilized mictic eggs enter dormancy

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Phylum Acanthocephala
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Phylum Gastrotricha

• 500 species
• 0.06-0.5mm
• Feed on bacteria protozoa
• Hermaphroditic
• Freshwater species parthenogenetic

Chaetonotus simrothi
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Phylum Cycliophora
Simbion pandora

• Discovered 1995
• 0.35-.1mm
• Live on mouthparts of marine decapod crustaceans

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Phylum Phoronida
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Phylum Ectoprocta (Bryozoa)
Electra pilosa
Plumatella repens
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Bryozoan Micrographs
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Ectoprocts (Bryozoans)
Bugula sp
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Phylum Brachiopoda
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Phylum Brachiopoda