Compare hagfish osmoregulation to marine invertebrates, elasmobranch and bony fish
- osmoconformers, like marine invertebrates
- similar levels of solutes to elasmobranchs bc of buffering with TMAO and urea
- nearly twice as much solutes as bony fish
- buffer intracellular fluids with amino acids, which they take up from the gills
What is knotting and what does hagfish use it for?
- the hagfish ties itself in a knot and pulls it tight
- can remove extra slime
- allows them to take a bite without a lower jaw
Mention four characteristics found inside a decomposing whale carcass
- low oxygen
- high CO2
- low pH
- high dissolved nutrients
What are hagfish strategies for dealing with low Oxygen levels?
- Low metabolic rate
- Relatively high capacity for anaerobic metabolism
- Some capacity for O2uptake across the skin
- Large volume of blood
What is the implication of hagfish having high plasma [Cl-] for acid/base regulation?
- recovery from acidification depends on H+ secretion and HCO3- accumulation
- if they accumulate HCO3-, they need to get rid of another negative ion: Cl-
- high amounts of Cl- in the plasma allows them to get rid of the Cl- and replace it with HCO3- that they’re accumulating while still maintaining the charge balance
What are hagfish three ways of feeding?
- eating the flesh and organs of dead animals
- absorbing amino acids across gills and skin (similar to invertebrates)
- active predation
Explain the experiments that established that hagfish can take up amino acids across the gill epithelium. What are the proteins involved and where they are located in the gill cells? How do they interact with each other via secondary active transport? How can you tell that the amino acids are taken up via active transport and not by simple diffusion?
- secured hagfish skin over the open end of a vial and placed that end in filtered seawater with 3H labelled amino acids
- more amino acids were taken up in gills than across skin, but there was uptake in both locations
- NKA on basolateral side and transporter that brings in both Na+ and amino acids on the apical membrane
- the NKA keeps the concentration of Na+ very low in the cell, making it favorable for the other transporter to bring in Na+ and amino acids with it
- Kinetic curve reaches a plateau as external amino acid concentration is increased, indicating active transport rather than simple diffusion: the amino acid transporters have become saturated and they cannot transport amino acids any faster, even if there are more amino acids in seawater
What are the similarities and differences between hagfish gills and the gills from other fishes?
- hagfish have gill pouches instead of gill arches (many more than other fish)
- other fish’s gill arches are all open to an operculum while the gill pouches are connected to the pharynx
- both types of gills have filaments with lamellae to increase surface area
What are the two cells found in the hagfish slime gland that are essential for slime production?
- thread Cells
- mucus cells with mucin vesicles
What type of protein makes the coiled structure in thread cells?
-proteins from the “Intermediate Filament” Family, present in cell cytoskeleton and in mammalian alpha-keratins (hair, horns, nail, hooves)
Describe step by step how hagfish slime is produced and how it helps protect against predators
- pressure from a predator’s bite triggers the contraction of the slime gland muscle
- the thread is held together by a “glue protein that dissolves in contact with seawater
- mucin vesicles burst in contact with seawater
- thread unravels
- mucin swells and attaches to thread proteins
- movement further pulls thread, more mucin attaches => slime
- it clogs the gills of predators, they must spit out the hagfish to try to dislodge it
How long does it take to refill each slime gland? Does this mean that the hagfish is totally defenseless during this period? Why or why not?
- 30 days
- no, glands are not fully discharged and wouldn’t all be empty at once so there will still be slime present at all times
What are potential industrial uses of hagfish slime? What are its advantages compared to synthetic and other biological polymers?
- high performance (10x the strength of nylon)
- environmentally sustainable materials (not made from petroleum)
- may be able to be produced in bacteria
- impart flexibility and strength without adding weight
- safety helmets bulletproof vests, car parts, human tendons
