Gnathifera: Rotifera

Question 1

4 Gnathifera Spiralians

Answer 1

Rotifera, Acanthocephala, Micrognathozoa, Gnathostomulida

Question 2

Gnathifera Structure

Answer 2

1 mm most

Pseudocoelomate (not bound by mesodermal epithelium, bound by thin layer of mesenchyme under epidermis)

Question 3

Rotifera (3 Classes)

Answer 3

1. Monogononta (1000s)
2. Bdelloidea (100s)
3. Seisonidea (dozens)

Question 4

Rotifer Lifestyle

Answer 4

Free living, feed in planktonic habitat, all three groups are epibenthic that attach to substrate by pair of toes

Some benthic rotifers live in tubes attached to substrate; protonaceous sclerotized tubes, made from mucous (polysaccharide), or made from found materials like sediment or poo

Question 5

Rotifer Anatomy

Answer 5

• Gut is straight to anus, pharynx is elaborate muscular and secretory
• Protonephridia and pair of gonads
• Pseudocoelomate
• Epidermis and gonads are syncytial (fusion of epidermal cells); cuticle secreted within syncytium, not outer surface

Question 6

What is the corona?

Answer 6

Corona: crown of ciliated epithelial cells (homologous to trochophore bands of cilia); common in bilaterians with small body

Question 7

What is the Trophus?

Answer 7

Jaws secreted in pharynx; Mastax is the muscular part of pharynx that moves and holds jaws

Trophi shape differentiate Monogononta and Bdelloidea

Question 8

Acanthocephala (spiny-headed rotifers), sister group to Seisonidea

Answer 8

• Endoparasites, mm to 10s ofcms in length
• Dioecious; females mate promiscuously, males compete intensively
• No corona, evertable pharynx attaches themselves to host, no gut, one large gonad

Question 9

Gnathostomulida (Chewing mini Rotifers)

Answer 9

<1mm

• Benthic grazers, interstitial organisms in course sediments
• No corona, not suspension feeders or grazers
• Develop secreted suticular structures in pharynx with spines and roots with muscular attachments to pharynx wall (probs should be called Trophi)

Question 10

Cycliophora: modified Rotifers?

Answer 10

One genus: Symbion
Ectoparasites on mouthparts of crustaceans
Internal body is like benthic rotifer
- Corona, protonephridia, pseudocoelomic body cavity, big gonad, suspension feeders, parthenogenetic and sexual, no trophi

Question 11

Gastrotricha

Answer 11

100s um in body length, benthic, active crawlers on ventral surface with adhesive toes, sensory cilia around mouth, gut, gonad, protonephridia, but no coelom of BVS