Lecture 3 Flashcards
The blood and other tissue of sharks and Chondrichthyes in general is isotonic. What does this mean?
The blood and other tissue is the same or similar salt concentration (so same osmotic pressure pretty much) to their marine environments
What allows sharks and Chondrichthyes to be in osmotic balance with the seawater? What does this adaptation prevent?
Due to the high concentration of urea and trimethylamine N-oxide (TMAO) stabilises the proteins present in the urea, allowing them to be in osmotic balance with the seawater.
This adaptation prevents most sharks from surviving in fresh water
Which shark is the exception in being able to survive in fresh water and why?
The bull shark. It has developed a way to change its kidney function to excrete large amounts of urea and allow it to move far up in rivers
Most sharks are ectotherms, which family are not and are endotherms?
The family Lamnidae
What is unique about sharks which are members of the family Lamnidae, such as the shortfin mako shark and the great white shark? Give a feature of these sharks
They are endothermic and maintain a higher body temperature than the surrounding water (only certain areas of the body are maintained at a higher temperature compared to that of he environment). These kind of sharks tend to be the long distance movers/ travelling vast distances, the ones that are constantly swimming
Describe what happens during shark copulation
. During copulation sharks meet face to face
. The male inserts one of his claspers into the cloaca of the female
. Sperm contained within spermatophore are delivered to the female via a groove in the clasper
. The spermatophore are forcefully ejected by contracting organs known as siphon sacs which use seawater to carry the spermatophores
When is photo-id a useful technique for studying sharks? Give an example
For species such as the mantaray with individuals that have distinctive patterns
Give an example of a shark that has very limited distribution (vertically stay in the same place)
Northern river shark (a species of requiem shark found in tidal rivers in northern Australia)
Give the Latin name for a northern river shark
Glyphis garricki
Give examples of sharks that travel vast distances
Whale, basking, blue, salmon, great white sharks
What is morphometrics?
Some skeleton structure that is selected for and show measurable differences between non-interbreeding populations
When are morphometrics useful?
Useful in size of the animals as the size of these animals is almost directly linked to its age
Can also identify sub-populations from these morphometric features
How are genetics and DNA forensics used to investigate population structure?
. Using polymerase chain reaction (PCR) amplification of mitochondrial (mtDNA) and nuclear DNA followed by restriction enzyme analysis to generate a form of DNA fingerprint (for species, populations or individuals)
. Using a combination of direct sequence comparison and clustering approach to determine similarities between DNA sequences from sample of unknown origin to reference species (phylogenetic approach)
What determines or limits a species abundance?
Prey availability, mortality (predators and anthropogenic- linked to their age range- how long they take to become sexually mature) and life history characteristics
How long do most sharks live?
20-30 years
Which shark lives the longest?
Greenland shark (392y)
How long to spiny dogfish and whale sharks live?
70-100y
Unlike most bony fishes sharks are k-selected reproducers. What does this mean?
That they produce a small number of well-developed young, so they have a lot of resources put into them- so the chances of that offspring surviving is quite high, as opposed to a large number of poorly developed young
What is fecundity?
The number of eggs or young produced by an individual
What is the fecundity range of sharks per reproductive cycle?
Ranges from 2-over 100 per reproductive cycle (every 1-3y)
When do lemon sharks become sexually mature? What is the problem with this?
They become sexually mature at 13-15 years. This is a problem if things like fishing increase mortality, especially before they get to sexual maturity, can have huge impacts on the population of the species
What is an issue with being a K-selected species and increased mortality?
Population increase is very slow and therefore impacts will have a more long term effect
What is the annual rate of increase in shark populations? Give examples of ones at either end of the spectrum
Between <1-30%
thresher sharks at the lower end and blue shark in the North Atlantic at the higher end
What percentage of sharks are classed as threatened to some extent according to the the global scale evolution (finished jan 2014)?
77%
