Trochozoa: Annelids (Polychaetes)

Question 1

Embryonic Development: Annelid Cleavage and Formation

Answer 1

Annelids: Spiral Cleavage forms Mesentoblast

Question 2

What do annelids’ mesoderm form?

Answer 2

Coelom, mesenchyme, nephridia, muscle, skin cells

Question 3

What is a trochophore?

Answer 3

Planktonic larva

Question 4

Anterior vs Posterior cells/cilia of a Trochophore are

Answer 4

Anterior: Prototroch (beat down for propulsion
Posterior: Metatroch (beat up for swimming and trapping food particles)

Question 5

Development of the Mesentoblast

Answer 5

Mesentoblast migrate and descendants proliferate in blastocoelic space; schizocoely

Question 6

Mesentoblast goes through Teloblastic Growth; what is that?

Answer 6

Development of a series of pairs of coelomic spaces; shared in common with arthropods; newest segments are posterior in front of pygidium

Question 7

Two parts of Annelid Head

Answer 7

Before mouth: Prostomium

Post mouth: Peristomium

Question 8

What is the Pygidium?

Answer 8

Posterior part of trochophore; has mesodermal stem cells that give rise to segments but does not contain coeloms itself

Question 9

What is the Cuticle?

Answer 9

Extracellular matrix secretions over the apical side of ectodermally derived epithelial cells

Question 10

What are Parapodia

Answer 10

A characteristic of annelid body wall; the extension of the body wall and its connective tissue to make limbs (may be homologous to arthropod limbs

Question 11

Parapodia epidermal cells secrete Chitinous Cuticles in 2 ways:

Answer 11

1. Aciculae: internal skeletal rod of chitin for cuticular specialization
2. Chaetae: diverse in form, rod shape secretions that have many functions

Question 12

What forms the palps?

Answer 12

Extension of the prostomium

Question 13

What form the tentacles?

Answer 13

Body wall extensions from the peristomium

Question 14

What are septae?

Answer 14

Pair of epithelia perforated by the gut that separates segments

Question 15

Blood Flow in Annelids

Answer 15

Tubular spaces from blastocoelic lining (posterior to anterior in major dorsal vessel)

Question 16

Nerves in more Bilaterians

Answer 16

Masses of nerve cells (called Ganglia) make ventral nerve cord; anterior part splits around pharynx to form dorsal ganglionic masses

Question 17

Sinusoidal Locomotion

Answer 17

Contract left and right longitudinal masses

Question 18

Peristaltic Locomotion

Answer 18

Alternating contractions of either all longitudinal muscles or circular musculature in some segments (common in burrowers)

Question 19

Protonephridia (1. Structure 2. How it works 3. Filtration)

Answer 19

1. Invagination of epidermis grows in connective tissue layer to meet with nephridial cell
2. Motion of flagella of flame cell allows the excretory system to push fluid to the excretory tubule
3. Basal lamina as filtration surface (material goes through podocytes)

Question 20

Metanephridia (1. What does it lose/ keep from protonephridia? 2. How does it pressurize fluid?)

Answer 20

Not via ciliary motion, no flame cell but has the collecting nephridial tubule
Musculature as pumping power (creates greater hydrostatic pressure through podocytes and basal lamina for better filtration)

Question 21

What is a Nephrostome?

Answer 21

Nephrostome (opening into nephridial tubule and into next anterior coelomic space of following segment) - most often, gametes spawn out of tubule but sometimes spawn out of separate coelomiduct

Question 22

What is an Epitoke?

Answer 22

Specialized segment of body generated by asexual budding or cloning and develop functional specializations for swimming and sexual reproduction

Question 23

Lifestyles of the Wet and Slimy (Reproduction, Specialization, Structure)

Answer 23

Reproduction of parapodia and setae (burrowing)
Tagmatization of groups of segments
Perforation and loss of septae/segments

Skeletal elements: Heavy chitin, calcium carbonate, gelatinous mucous, sediment

Question 24

Lifestyle of the Barely Damp

Answer 24

Reproduction of parapodia and setae

Tagmatization, perforation and loss of setae and segments

Question 25

Lifestyle of Sedentary Annelids

Answer 25

Suspension feeders, elaborate head appendages (parapodia of peristomium into large structures with extenstions of BVS and fine branching, secrete mucous sheet and spits of balls of mucous called Radiole)

Question 26

Sister Group to the rest of the Annelids:

Answer 26

Chaetopteridae

• specialized morphologies of polychaetes
• permanent burrow
• suspension feeders
• water current by parapodia, anterior parapodia secrete mucous for filtration to trap particles and ingest