20. Small Phyla Nov 9

20. Small Phyla Nov 9 - Phylum Onychophora Phylum...

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1 Phylum Phylum Onychophora Onychophora Velvet worms Affinities not clear Have many Annelid-like characteristics and Many Arthropod-like characteristics Some unique characteristics LOOK AT THESE IN LAB! World distribution of two families of onycophorans Peripatus most common genus Current distribution wide, but discontinuous All extant onychophorans are terrestrial But, many fossil marine species esp. in Burgess Shale Now all terrestrial - only phylum Range in size from a few to > 15 cm Cuticle Cuticle Thin, flexible Molted Not desiccation proof live in very humid places Head - Antenna Oral papillae Slime glands - Slime used for defense, prey capture Slicing jaws and teeth
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2 Paired appendages - segmental only external evidence of segmentation Appendages - lobopods Outpockets of body wall (like annelids) Claws at end Internal segmentation Coelomic sacs Ducts Nephridia Hemocoel Major body cavity, similar to arthropods Muscles form interior partitions Coelom reduced - around excretory organs - Nephridia - segmental Respiration Tracheal tubes , air filled, over all of body Deliver oxygen directly to tissues Spiracles - open outside of body Excretory system Segmental paired Nephridia ciliated sac coelomic derivative most glands modified from nephridia Nervous system segmental paired ventral nerve cords Reproduction Separate sexes, sexually dimorphic 1 pr. Gonads, derived from coelom ciliated oviducts Internal fertilization, spermatophores Early cleavage similar to arthropods - not spiral Live young (ovoviviparous) or produced eggs (oviparous) Direct development Cross Section of an onychophran What similarities does it have with Annelids? with Arthropods? Make a table of all characteristics of onychophorans that are: shared with Annelids shared with Arthropods unique to this group
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Phylum Tardigrada (waterbears) Coelomate Coelomate Phylum Tardigrada (waterbears) Tiny largest ~1.5 mm Live in moist areas leaves moss Or are aquatic Evolutionary position not clear ~800 known species Some similarities with arthropods Many similarities with pseudocoelomates Small size, simple body Stylet sucking phrynx - Triradiate simple gut Herbivores - pierce plant cells and suck contents Cuticle – layered, chitinous, molted to grow Muscles – strands, smooth Body Cavity = Hemocoel Coelom - remains around gonads - ?true coelom? Brain, sensory organs, paired segmental ganglia
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This note was uploaded on 01/27/2010 for the course BIO 37282 taught by Professor Padilla during the Fall '10 term at SUNY Stony Brook.

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20. Small Phyla Nov 9 - Phylum Onychophora Phylum...

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