Pseudocoelomates:
Gnathifera
= more vermiform animals,
pseudocoelomate this time…..
Advantages of a Body Cavity
Advantages of body cavity, pseudocoel
or coelom,
– freedom of movement.
– organ system development
– circulation
– storage
– skeleton
Common Features of all
Pseudocoelomates
1. body wall (epidermis, dermis, and muscles)
2. complete digestive tract
3. epidermis secretes cuticle with bristles & spines.
1
Pseudocoelomates do not form a clade.
Some are part of superphylum
Lophotrochozoa, others are in superphylum
Ecdysozoa.
All share the pseudocoelomate body plan.
Lophotrochozoa
Ecdysozoa
2
Clade Gnathifera
small cuticular jaws with a homologous microstructure.
numbers of pairs of jaws vary
Gnathostomulida, Micrognathozoa, and Rotifera are tiny
Acanthocephalans are worm-like endoparasites
Phylum Gnathostomulida
= includes the jaw worms.
!Very small - <3mm.
!Live in interstitial spaces of
fine coastal sediments.
!Can endure low O2.
!Feeding = scraping
!Internal fertilization
Phylum Micrognathozoa
tiny animals (100-300µm)
live interstitially
two-part head, thorax, and abdomen with tail
movement = cilia, ciliary adhesive pad that produces glue
complex jaws
simple gut
reproduction = female organs, parthenogenesis,
development
3
pseudocoelomate
Phylum Rotifera
three embryonic germ
layers (triploblastic)
marine or freshwater,
interstitial
free-living
complete digestive system
corona
Lifestyle and Form
range of colors and shapes
- Shape correspond to lifestyle
(floaters, swimmers, sessile)
- individual or colonial
- mostly freshwater
General Body Plan
Digestive tract a continuous tube
Grinding mastax
Toes for attachment
http://www.youtube.com/watch?v=49RROi71bbA
&NR=1&feature=fvwp
http://www.youtube.com/watch?v=fRBc3kk
ya7w&feature=related
4
Reproduction
Dioecious
some species parthenogenetic
some are parthenogenetic during
part of the year
= eggs are thick shelled
Phylum Acanthocephala
parasites = fish, birds, and mammals, rarely humans
1100 species known
No digestive system, circulation, respiration = absorption
protonephridia
Syncytial epidermis
Proboscis
Phylum Gastrotricha
• appear similar to rotifers
• Triploblastic
• Complete digestive system
• Hermaphroditic or
parthenogenetic
http://www.youtube.com/watch?v=Vrf977j-gbI
5