ZOO115 Invertebrate Zoology

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ZOO115 Invertebrate Zoology

• Phylum Onychophora

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Onychophora (Talon bearer)- General
Characteristics

• Common name Velvet worms
• Intermediate between annelids and arthropods
• 110 species
• Fossil records from Early Cambrian period (530
  MYA)
• Terrestrial
• Dark humid tropical regions

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Onychophora - General Characteristics

• Soft-bodied
• Wormlike 5mm-15cm in length
• Segmented with serial repetition of organs

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Onychophora Support

• Body is covered by thin chitinous cuticle
• Similar to arthropods
• Highly permeable
• Flexible
• Accordion-like
• Longitudinal, circular, diagonal and surface
  oblique muscles
• Body wall, other than cuticle, similar to Annelids

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Onychophora - Locomotion

• Trunk bears 13-43 pairs of appendages
• with claws
• Like parapodia of polychaetes
• Operated as part of the hemocoel

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Onychophora - Nutrition

• Carnivores - eat small arthropods
• Secrete jets of slime up to 30 cm to entangle
  prey
• Lacerate prey with mandibles (jaws)
• Secrete saliva with hydrolytic enzymes
• Pharynx pumps liquid food into stomach

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Onychophora - Digestion

• Chitin-lined foregut (pharynx and esophagus
• midgut (intestine digestion and absorption

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Onychophora - Excretion

• Anus for solid waste
• Nephridia - like arthropods

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Onychophora Circulation

• Open system similar to arthropods
• tubular heart with pericardial sinus
• large hemocoel
• Gas exchange
• small openings in each segment Spiracles
• lead to tracheal tubes

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Onychophora - Nervous system

• Ladderlike nervous system - like both annelids
  and arthropods
• Paired ventral nerve cord
• Sensory
• Antennae
• Eyes at base of antennae
• Sensilla on sensory papillae

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Onychophora - Reproduction

• Separate sexes
• Sexually dimorphic
• Males smaller
• Sperm transferred by spermatophore
• In Peripatopsis, spermataphores placed anywhere
  on female, her cuticle temporarily dissolves and
  takes up the sperm.
• Most bear live young