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Shark adaptations to the marine environment
Transcript of Shark adaptations to the marine environment
of Sharks in Response to The Marine Environment. Daniel Davies
Student Number 12829470 The Marine Environment SHARKS Apex marine predators
Subclass: Elasmobranchs 470 species arranged over
8 orders. Have been around for between 375-400 million years. Sea-water is an ionic solution which is much
denser than air. Distributed throughout the worlds oceans and seas. Restricts the passage
of light. Restricts the passage
of the shark. Improves the passage
of sound and vibrations. Improves the passage
of electricity. Sensory perception Sharks have seven
separate senses Sight Lateral line Electroreception The lateral line is a fluid filled chamber that runs the length of a sharks body.
This sensory organ only functions within the aquatic environment
It is connected to the outside environment by small pores.
Vibrations and movement in the water are transferred via the small pores into the lateral line where they trigger hair receptor cells which in turn actuate a nervous response. Due to the scattering and absorptive
abilities of water light does not travel far in water.
The tapetum lucidum is a reflective membrane which aids to concentrate any light that passes the lens.
The receptive layer in a sharks retina accounts for approximately 50% of the retina, against 30% in most vertebrates
Rod cells = 100000-300000/mm
Cone cells = 1000-3000/mm 2 2 Hydrodynamic body shape Dermal Denticles Movement Through Water The Ampullae of Lorenzini is a sensory organ used in the detection of bio-electric fields.
A system of gel filled channels, each connected to six aveoli.
The gel consists of a mucopolysaccharide that maintains ionic and conductive properties very similar to sea water.
Capable of detecting the nervous impulses of their prey. Minute voltages, less than 0.05x10 mV/cm.
Longer channels improve the sensitivity to uniform fields, while a range of channel lengths and orientations aids in the detection of local variations.
The electric current passes passively down the channel and triggers a non-motile hair cell affecting a nervous response.
This sense is highly efficient in an ionic solution, such as sea water. -3 The fusiform (tapered at both ends)structure of the shark is an incredibly hydrodynamic shape.
The hydrodynamic shape requires less energy to propel the shark through the water.
The tapered head improves the sharks agility, allowing for quicker turns and changes of direction.
The agility and efficiency of movement are further improved by the flexible, lightweight nature of their cartilaginous skeletons. Dermal Denticles are tiny teeth like scales that reduce the drag of the shark.
They work by directing the flow of water long the sharks body and by reducing the vortices and turbulence created by the sharks passage.
The dermal denticles that cover a sharks body reduce the energy required to propel the shark through the water. Predator Avoidance in Embryonic Sharks Oviparous sharks lay eggs that take on average between 7-15 months to hatch, depending on the species and conditions
After internal fertilisation the maternal shark will deposit the egg within the benthic region, where the egg will develop independent of its mother.
During the later stages of its development the embryonic shark utilises its tail to pump clean oxygenated sea water through the egg.
Once the ampullae of lorenzini have developed, the embryonic shark will use electroreception to detect the approach of potential predators.
If a predator comes to close, to reduce the risk of predation the embryonic shark will stop beating its tail and curl into a ball within the egg. Some species will also reduce both their heart and breathing rate until the threat has passed. Swimming Techniques of a Shark By actively altering the stiffness and physical shape of the caudal fin at different stages of its stroke, a shark produces a dual linked vortex ring with every half stroke.
The dual linked vortex rings are laterally and downward facing and effectively improve the forward and upward momentum of the shark.
This behavioral pattern is linked to another behavioral pattern of pelagic sharks, known as yo-yo swimming, where sharks constantly move up and down through the water column.
Yo-yo swimming may infer various adaptive advantages, these include;
Increasing body temperature in the warm surface waters after swimming in the cooler deep waters
Swimming over various depths improves the directional information and localisation of chemo-reception.
When descending into deeper water the earths magnetic field becomes more perceivable, and so it may be used for navigation during migration. References Figure 1.
Dermal denticles of a shark viewed with a (SEM) Figure 2.
Oceanic Blue Sharks
display a highly hydrodynamic
form. Figure 3.
A labeled diagram
of a sharks eye Figure 4.
Depicts the location of the lateral line on the body of a shark Figure 5.
A sensory pore from the
ampullae of lorenzini Figure 6.
A Banded cat shark Embryo held within its eggcase. Figure 7.
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