Elasmobranch Diversity And Adaptations Flashcards
What is the ampullae of Lorenzini?
Small vesicles and pores (electro receptors) that are found around the head and appear as dark spots
Who first described the ampullae of Lorenzini?
Stefano Lorenzini 1678
What is the function of the ampullae?
They detect weak magnetic fields produced by other fishes
Describe the structure of the ampullae of Lorenzini
Contain multiple nerve fibres that are enclosed in a gel-filled tubule which has a direct opening to the pore
What is the function of the lateral line?
They detect movement by particle movement or sound rather than electrical signals
Describe the structure of the lateral line
Consist of structures called neuromasts, which are located in canals that lie just below the surface of the skin
How do sharks hear?
Through a small opening on each side of their head that leads directly into the inner ear through a thin channel
How do sharks smell?
Sophisticated olfactory senses, located in the short duct between the anterior and posterior nasal openings
What are the two hypotheses for why hammerhead sharks have a hammerhead?
- Hydrodynamic lift
2. Sensory enhancement
How do sharks make their blood isotonic?
Have a high concentration of urea and TMAO in their blood
How do bull sharks live in freshwater?
Kidneys excrete large amounts of urea
What is the daily urine production of a saw fish?
250ml
20x more than a typical elasmobranch
What family of sharks are endothermic?
Lamnidae
Includes mako sharks and great whites
How do some sharks maintain endothermy?
A strip of aerobic red muscle generates the heat
The body retains the heat via a counter-current exchange by a system of blood vessels called the rete mirable
How are males sexually different to females?
Males have pelvic claspers which are modified pelvic fins used for sperm delivery, and paired testes
Females have no claspers but have a cloaca and two paired ovaries
How can you access data from sharks?
Samples from dead animals, such as fossils, fisheries and by-catch
What methods can be used to measure distribution?
Mark recapture with id tags, photo id and various radio satellite or acoustic tags
What age do most elasmobranchs live to?
20-30yrs
What has the longest lifespan for an elasmobranch?
Greenland shark
272yrs
What is the estimated number of sharks killed each year?
40-100 million
What happens to the ecosystem when and if you remove large scale apex predators?
Lack of prey regulation
Ecosystem shift
Possible cascading effects
Loss of important indicator species on the health of the marine system
