Chapter 15: Gnathiferans and smaller lophotrocozoans

Question 1

Clade Gnathifera

Answer 1

Gnathostomulida
Micrognathozoa
rotifera
Acanthocephala

Question 2

Phylum Gnathostomulida

Answer 2

Greek - gnathos (mouth) and stoma (opening)
- small delicate wormlike animals
- can glide and swim
- have monociliated epidermal cells
- acoelomate, no circulatory system
- jaws -> simple blind gut
- internal, cross fetilization

Question 3

Phylum Micrognathozoa

Answer 3

Monotypic, limnognathia maerski
- discovered in 1994, described in 2000
- three pairs of jaws
- only female reproductive organs
- move by cilia, unique ventral ciliary pad that produces glue
- live in sediment`

Question 4

Phylum rotifera

Answer 4

Latin - rota (wheel) and fera (bearing)
- unique organ called the corona or wheel organ
- lots of variation in life history traits
- some can dessicate and live for years

Question 5

external features of roifers

Answer 5

• ciliated corona, body non ciluiated
• cuticle = fibrous layer forming lorica
• foot is narrow and has 1-4 toes
• contains pedal glands that secrete adhesive
• move by creeping, swimming with coronal cilia or both

Question 6

internal features of rotifers

Answer 6

• synctial epidermis (underneath cuticle)
• large fluid filled psedocoel
• digestive system complete (mastax with hard jaws called trophi, salivary and gastric glands)
• protonephridial tubules with plame cells that empty into a bladder then to cloaca
• bilobed brains, paired eyespots, sensory bristles, ciliated pits, dorsal antennae

Question 7

rotifer reproduction

Answer 7

rotifers are dioecious (only one gender)
- no males in class Bdelloidea, in monogonata they only occur a few weeks in the year
High levels of reproductive variation
hypodermic impregnation through copulation

Question 8

rotifer taxnomic classes

Answer 8

seisonidea
bdelloidea
monogonata

Question 9

seisonidea

Answer 9

marine, elongate, cornoa vestigial, sexes similar

Question 10

bdelloidea

Answer 10

swimming or creeping, anterior end retractile, corona with two trochal disks, makes unknown, parthenogenetic

Question 11

monogonata

Answer 11

swimming or sessile
single gemovitellarium
males reduced in size
three types of eggs (amictic, mictic, dormant)

Question 12

Phylum Acanthocephala

Answer 12

Greek - akantha (spine/ thorm) and kephale (head)
- Cylindrical, invaginable, proboscis with rows of spines for attachment in the intestine of the host
- cosmopolitan, lots of species, all parasitic

Question 13

acanthocephalan form and function

Answer 13

body somewhat flattened, body wall synctial, lots of trenches to increase surface area, most substances cross body wall by diffusion
- proboscis can be retracted inside body
- very reduced nervous system and sense organs, no digestive tract
- dioecious
- larvae called acanthors develop into juveniles called cystacanths in insect, ingested by final host. ( can cause perforation of intestine)

Question 14

Clade polyzoa

Answer 14

phylum cycliophora

Question 15

Phylum cycliophora

Answer 15

• discovered in 1995
• live on mouthparts of decapod crustaceans
• eat bacterial or bits of dropped food
• acoelomate with a u-shaped, complete gut
• sexual and asexual phases, chordoid larvae which can swim to a new host

Question 16

phylum gastrotricha

Answer 16

greek - gaster/gastros (stomach) and thrix/trichos (hair)
- small, dorsoventrally flattened, less than 3 mm in length
- aquatic (fresh,brackish,salt) glide on substrate or live in interstial spaces

Question 17

gastrotricha form and function

Answer 17

-elongate with spines or bristles, ciliated venter
- partially synctial epidermis, longitudinal muscles better developed than circular ones
- no circulatory or respiratory system (gas exchange via diffusion)
- complete digestive system (feed on detritus, bacteria, algae, and protozoa)
- solenocytes rather than flame cells
- technically hermaphroditic, function as parthogentic females
-eggs can survive harsh conditions and dormancy for years

Question 18

solenocytes

Answer 18

single flagellum enclosed in a cylinder of cytoplasmic rods

Question 19

Phylum Entoprocta

Answer 19

greek - entos (within) and proktos (anus)
- resemble cnidarians but have ciliated tentacles
- sessile, most microscopic, all stalked, ciliary feeders
- most marine, some commensals on marine annelids

Question 20

entoprocta form and function

Answer 20

• calyx is cup shaped with crown of ciliated tentacles
• longitudinal muscles only
• tentacles can roll inwars but cannot be retracted
• digestion in stomach and intestine
• have a fluid filled pseudocoelom
• nerve ganglion on side of stomach
• no circulatory or respiratory system
• both asexual and sexual reporduction

Question 21

three phyla within lophophora

Answer 21

• very controversial phylogenetic placement
  (unsuure if protostomes or deuterostomes)
• all possess lophophores
  gut ushaped, anus opens outside the mouth ring

Question 22

lophophore

Answer 22

unique arrangement of ciliated tentacles on body ridge
feeding and gas exchange

Question 23

phylum ectoprocta

Answer 23

greek - ektos (outside) and proktos (anus)
- usually sessile colony builders, individuals called zooids
- extend lophophores to filter feed
- exoskeleteon construction variable called a zoecium
- used to be called a bryozoa “moss animals”

Question 24

ectoprocta form and function

Answer 24

each zooid has a feeding polypide and a case froming cystid (body wall)
- polypides come out to feed but retreat behind a trapdoor whenever distrubed
- cilia draw water into mouth funnel and out between the tentacles
- digestion is extracellular in stomach but intra in intestine
- most hermaphroditic some brood eggs
- sometimes multiple embryos asexually from one embryo called poly embryony
- most colonies start from one zooid called the ancestrula from asexual budding

Question 25

phylum brachiopoda

Answer 25

greek - brachion (arm) and pous/podos (foot)
“lamp shells”
- sessile marine animals, resemble bivalve molluscs
- attach to substrate directly or with a stalk called a pedicel
- filter feeders
- open circulatory system with a contractile heart
- separate sexes with external fertilization
- juveniles resemble adults, pedicel attaches, adult existence begins

Question 26

phylum phoronida

Answer 26

latin - phronis
small wormlike animals
- secretes a tube, lives there entire life
- u shaped gut, feed through cilia on lophophore
- contractile blood vessels but not a closed circulatory system (no heart)
- mostly monoecious free swimming ciliated larvae called an actinotroch secretes a tube becomes sessile