Nemertea and intro to Mollusca

Question 1

What are the basic features about Phylum gnathostomulida?

Answer 1

• veriform worms with turbellarian-like characteristics
• acoelomate, ciliated epidermis, incomplete gut, etc

Question 2

What are the main features of Phylum Micrognathozoa?

Answer 2

• very small
• complex jaws
• only females

Question 3

What are Phylum nemertea? its defining characteristic?

Answer 3

• “ribbon” worms
• Rhynchocoel is defining characteristic

Question 4

What is the Rhynchocoel in Phylum Nemertea?

Answer 4

• “nose’ coelom, meaning it is at the anterior end
• it is the space surrounding the proboscis
• used as a hydrostatic skeleton and its primary function is for prey capturing

Question 5

What acts as a hydrostatic skeleton in Phylum Nemertea?

Answer 5

the Rhynchocoel

Question 6

How is Nemertea NOT like turbellaria?

Answer 6

• has a complete gut and circulatory system
• much larger

Question 7

What is the proboscis ejection process like?

Answer 7

1. proboscis is inverted within the head, the sphincter muscles are contracted to prevent release of pressure
2. circular muscles contract, which builds up pressure in the rhynchocoel
3. prey is detected, nemertine aims and relaxes sphincter muscles, release of pressure allow proboscis to evert rapidly
4. system resets

Question 8

What are the three defining characteristics of Phylum Mollusca?

Answer 8

1. Mantle
2. Radula
3. foot

Question 9

What is the mantle in mollusca?

Answer 9

• dorsal tissue that secretes shell/spicules
• also used for protection, and to localized chemical defenses
• also can be used for gas exchange

Question 10

What are radula in molluscs?

Answer 10

• protein and chitin covered epidermal tissue near mouth “teeth”
• can be used to graze on algae, drill into other prey

Question 11

What is the foot in molluscs?

Answer 11

• ventral body wall muscle, used for crawling, grasping, swimming

Question 12

Molluscs have a coelomae, but also have a ……

Answer 12

secondary space called the haemocoel (blood cavity)

Question 13

Shell material has three layers…

Answer 13

1. outermost: Periostracum
2. middle: prismatic
3. innermost: Nacreous

Question 14

the two shell layers that are inorganic are _____ and ______while the organic layer is the ______

Answer 14

the two shell layers that are inorganic are PRISMATIC and NACREOUS while the organic layer is the PERIOSTRACUM