Intro to Ecdysozoa Lecture 13

Question 1

support structure in Ecdysozoans

Answer 1

Exoskeleton

Question 2

why is exoskeleton important

Answer 2

• barrier to desiccation
  protection
  shape of animal
  frame for muscle attachment

Question 3

features of Ecdysozoa

Answer 3

periodic molting (Ecdysis)
three layered cuticle
lack cilia for locomotion
amoebid sperm

Question 4

Cycloneuralia (5) within Ecdysozoans

Answer 4

Priapulida
Kinorhyncha
Loricifera 
Nematomorpha
Nematoda 
(named for position of brain around the pharynx)

Question 5

Molting (Ecdysis)

Answer 5

periodic replacement of exoskeleton (believed to have only evolved once)

Question 6

cuticle layers (3)

Answer 6

epicuticle (outside)- thin protein
exocuticle- protein, calcium, chitin
endocuticle (inside)- thick calcium, thick membranous layer
(secreted by epidermis)

Question 7

Process of Ecdysis (3 steps)

Answer 7

1. epidermis undergoes round of cell division and separates from exoskeleton (apolysis)
2. new exoskeleton is secreted by epidermis, remains soft until old cuticle is shed
3. new cuticle expands and hardens

Question 8

Cycloneuralia also known as Introverta

Answer 8

spiny retractable proboscis (introvert) present in all phyla

Question 9

Nematoida

Answer 9

Nematoda and Nematomorpha

Question 10

traits of Nematoida

Answer 10

cuticle made of collagen
reduction of circular muscles
epidermal longitudinal nerve cords
amoebid sperm (tailless)

Question 11

Nematodes

Answer 11

ecto and endoparasites of crops, animals and humans

impermeable cuticles good for parasitic nematodes

Question 12

most common nematode parasite?

Answer 12

Pinworm

Question 13

Cryptobiosis

Answer 13

Suspension of life processes in situations of unfavorable conditions into resistant states (nematodes, rotifers and tardigrades)

Question 14

The model Nematode?

Answer 14

C. elegans

• soils, in temperate regions
• first multi-celled animal to have its genome completely sequenced

Question 15

Nematode bauplan

Answer 15

adult nematodes have 1,000 somatic cells
tube within a tube (mouth at anterior extends back to the anus)
lack circulatory or respiratory systems

Question 16

free-living vs parasitic forms

Answer 16

4 molts of the cuticle during growth

complicated lifestyle, usually with several different hosts

Question 17

Human diseases caused by Nematodes

Answer 17

Elephantiasis (filarial nematodes)
African river blindness
Hook worms and Whip worms

Question 18

One host parasites

Answer 18

Intestinal roundworm
Hook worm
Whipworm

Question 19

Two host parasites

Answer 19

Blood-sucking insect acts as intermediate host
Heartworm
Guinea worm

Question 20

How to get rid of parasites?

Answer 20

Finding out the specifics of the different molting processes in the parasitic nematodes and disrupting some stage of molting

Question 21

molting in nematodes

Answer 21

Relatively little is known about molting in nematodes, but making comparisons to molting in Arthropods may uncover aspects that constrain molting

Question 22

Difficulties in Nematodes and Arthropods

Answer 22

hard to connect similar underlying control of molting in both
Nematodes lack key enzymes (sterols)
cuticle is collagen rather than chitin
enzymatic cascade that mediates release of exoskeleton in nematodes may be distinct from arthropods

Question 23

Altering molting

Answer 23

Determine what genes are responsible for molting and inactivate them, killing the parasite and not affecting the host (RNA interference)

Question 24

Regulation of molting in Nematodes and Arthropods

Answer 24

Master regulators of molting may function in similar systems between the two
regulation of molting is conserved in Arthropods
(supports hyp that molting only evolved once)

Question 25

Nematomorpha

Answer 25

horsetail worms 
very long and slender
terrestrial and fw
single pseudocoelom
lack of circular muscles 
Semi-parasitic (Larvae parasitic in insects, adults free-living in fw)

Question 26

Scalidophora or Cephalorhyncha

Answer 26

Kinorhyncha
Priapulida
Loricifera

Question 27

Priapulida

Answer 27

• bottom dwelling, predatory worm
  large spiny eversible head end (introvert)
  distinctive plumose caudal appendage in some
  few species, but common in Cambrian Sea and fossils well known
  Large pseudocoelom

Question 28

Loricifera

Answer 28

recently discovered
occupy interstitial marine shell gravel, and deeper sediments (annoxic environments)
very tiny

Question 29

Bauplan of Loricifera

Answer 29

Head region
Trunk region (6 plates that compose lorica)
Neck region (between head and trunk)
withdraw head into neck and both into trunk

Question 30

Scalids

Answer 30

spine on the head region that stick out protectively when head is extended and face outwards when head is withdrawn

Question 31

Kinorhyncha

Answer 31

sediment dwellers in global oceans
head, neck and trunk
Trunk has 11 segments called (zonites) with a single dorsal plate (tergite) and two ventral plates (sternites)
head retracted into trunk (introvert)
mouth surrounded by spines called stylets