Lecture #19

Question 1

What are the three Whale Fall stages, and what are the main organisms in each of them?

Answer 1

• Stage 1: Mobile-scavenger stage (sharks, invertebrates, rat-tails, hagfish)
• Stage 2: Enrichment opportunist stage (crustaceans, mollusks, polychaete worms)
• Stage 3: Sulphophilic (sulphur-loving) stage (Sulphur-producing lipid degrading bacteria, Chemoautotrophic bacteria, Mussels, tube worms, calms bristle worms, limpets, fish)

Question 2

Explain “sexual dimorphism” in Osedax.

Answer 2

• in most species of osedax, there are large females and microscopic males
• main purpose of the male is to release sperm to fertilize the eggs
• one exception, similar sized genders with internal fertilization

Question 3

Discuss Osedax eggs buoyancy in relation to their ecological niche.

Answer 3

• eggs are neutrally or negatively buoyant

- need to settle on a substrate, so more logical to not float

Question 4

What are the different body parts of Osedax?

Answer 4

• top is palps/crown: gills of the organism
• attached to trunk
• attached to roots, which burrow into the bone

Question 5

Describe the three-step process for Osedax nutrition. How do they dissolve the bone? How do they take up collagen, amino acids, and lipids? How do they digest these compounds?

Answer 5

• excrete acid to dissolve bone calcium phosphate, and proteases to release collagen and lipids
• absorb nutrients and transport to bacteria
• transport collagen and lipids in vesicle (transcytosis), amino acids are transported using amino acid transporters
• has trophosome which contains symbiotic heterotrophic bacteria
• bacteria produce more diverse metabolites, which are transferred back to worm
• osedax also digests bacteria

Question 6

Why do Osedax roots require an abundant oxygen supply to be able to excrete acid and dissolve bones?

Answer 6

-O2 used for production of CO2 and excretion of acid

Question 7

Acid secretion for bone dissolution is associated with the absorption of bicarbonate. What type of acid-base disturbance is it?

Answer 7

-metabolic alkalosis (caused by addition of HCO3-(e.g. post-feeding))

Question 8

What other cell types and organisms use an acid-excreting mechanism that is similar to that in Osedax root cells?

Answer 8

-giant clams secrete acid to bore into coral reefs

Question 9

Describe how (and where) the giant clam uses some cellular mechanisms that are similar to coral, and other that are similar to Osedax.

Answer 9

• VHA in the siphonal mantle of giant clams and the coral symbiosome promotes algal photosynthesis by keeping low pH for contained symbionts
• VHA in pedal mantle of giant clams and osedax root both secrete acid