What are osedax spp called?
Bone-eating worms
What are 2 characteristics of osedax spp?
- colonize bones of dead whales
- no mouth/gut, are gelatinous tubes
How are whale skeletons dissolved to release the organic molecules?
Oxidative phosphorylation releases CO2 and water. These are substrates for carbonic anhydrase, which converts them to H+ ions and carbonic ions to make the water acidic and dissolve the bones
How are root epidermal cells in bone eating worms involved with feeding?
Root epidermis secretes enzymes to degrade biomineral/organic matrix, and have transporters to facilitate nutrient uptake
What are osedax larvae similar to? How are they similar
Trochophore larvae of annelids
-have girdle of long cilia around middle to swim
What do xylotrophic bacteria utilize as their energy/carbon source?
Cellulose/lignin in wood
What are the 2 clades of shipworms?
Pholadidae (deep ocean)
Teredinidae (shallow marine)
How are the shell valves of shipworms modified?
Have file-like areas to carve out wood, creating sawdust that worm eats
How do shipworms breathe? How do they close off this opening?
Siphons at opening of burrow. One draws water in, other pushes water out.
Pallets close off opening
What are characteristics of the teredinidae? (5)
- elongate, worm-shaped body plan
- viscera shifted posteriorly; not encased by shell valves
- shell valves as specialized cutting tools
- elongate body lines burrow with calcareous coating
- expanded space for gills
‘pallets’ to seal opening in burrow
What are the similarities between wood-boring bivalves due to?
Shared ancestry-ancestor likely emerged in deep ocean and migrated upwards
What part of a shipworm stores the sawdust?
Caecum
What is the largest part of the shipworm?
The ctenidia, make up 2/3 of mantle epithelium
Where are the xylotrophic bacteria found?
endosymbiotic xylotrophic bacteria are within cells (bacteriocytes) of ctenidia
What type of enzymes do xylotrophic bacteria secrete?
cellulolytic enzymes
So if enzymes produced in caecum, how do worms digest sawdust?
A substantial amount of lignocellulases are produced endogenously within the shipworm’s digestive gland (worms themselves are able to do some degradation of cellulose, but prob not all of it)
What are 2 important components of the shipworm digestive gland?
- lots of rough endoplasmic reticulum for protein synthesis
- active golgi bodies to package and secrete these proteins
What is another role that xylotrophic bacteria play?
There is evidence that they fix N
How does reproduction work in teredinidae?
- mature 6 weeks post settlement
- females take up sperm, fertilization takes place in mantle cavity
- initial brooding on gills
- 2-4 week feeding phase for veliger larvae before settlement
How do teredinidae acquire xylotrophic bacteria? How was this proved?
Via vertical transmission from mothers.
-proved using primers to amplify symbiont rDNA in target tissues (ovary, eggs)
What is unique about giant shipworms?
thiotrophic (sulfur oxidizing) bacteria have replaced xylotrophic bacteria (live in mangrove swamps that are rich in sulfur)
What symbiotic relationship occurs in Hawaiian bobtail squid (incl name of symbiont)?
-have light organ on ventral side that is populated by bioluminescent bacteria (vibrio fischeri)
What is the light organ made of?
mantle epithelium on ventral side
What does the light organ look like?
- anterior and posterior appendages “horns” that are ciliated
- three pores extend from base of those to antechamber
- these lead to crypts where bacteria reside
