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 Post subject: Re: Shark ID (RV)
Unread postPosted: Fri Aug 22, 2008 12:04 am 
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6 catergories of sight, hearing, taste, touch, smell and electroreception.

Smell: sharks possess a pair of nostril-like holes called nares under the snout. Each nare is divided by a nasal flap into two openings. Water passess into the incurrent channel and over the olfactory lamellae and exits through the excurrent channel. Olfactory lamellae are folds inside the olfactory sac - these sacs lead directly into the large olfactory lobe in the fore-brain.
What happens: odours pass over the olfactory lamellae and stimulate the neurosensory cells which then sends a signal to the brain. This is referred to as chemosensory function.
As the snout of the shark passess backwards and forwards through the scent trail it is able to determine the direction from which the odour is coming.

Sight: In most sharks the eyes are well developed, large and complex structures. Most sharks possess excellent vision in low light conditions thanks to the tapetum lucidum. This is a layer composed of mirrored crystals which reflect light back onto the retina amplifying the image.
Sharks cannot identify shapes as there is no lens to focus.

Touch: is split into actual contact and distant touch that is picked up through the lateral line canals.

TO BE CONTINUED........

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Last edited by KampRunner on Fri Aug 22, 2008 8:40 am, edited 1 time in total.

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Fri Aug 22, 2008 8:37 am 
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continued.....

Lateral lines are a series of interconnected canals run back from the head to the upper lobe of the tail in a distinct line.
Infraorbital canal on the head extends from behind the eye along the snout.
Supraorbital canal from above the eye to the snout and connecting with the infraorbital.
Supratemporal canal leads back over the top of the head.
These canals open to the outside skin through tiny pores which allow water in.
How it works:- water displaced by the movement of fish in the area - this creates small waves which pass over the hairs inside the canals - they then send signals to the sharks brain. The sharks own movement also creates waves which bounce off the fish and return to the shark creating a vibration echo map. In this way the shark can detect its prey.
Sharks can also detect temperature change as they have a row of pores around the pectoral fins and gills - called pit organs

Electroreception:The lateral line pores around the snout have modified to respond to fluctations in the electrical fields in the sharks habitat. These sensory organs are calles ampullae of Lorenzini - small gel-filled sacs which have sensory nerve at the base of each pore which transmits the electrical signals put out by the prey to the brain. Actively hunting sharks can have as many as 1500 ampullae around the snout whilst sedentary ones might only have a few hundred. The ampullae are so sensitive thest they can pick up voltage fluctations of just over 10 millionths of a volt!
It appears that when sharks are close to their prey that the electrical sense takes over from sight or smell.

Taste: - is another chemosensory function similar to smell. Gustatory sensory cells are found in small pits lining the mouth and throat - dissolved chemicals from the bitten object attach to these cells which send a signal to the brain. This determines whether the shark will eat or reject the meal.

Hearing:- ears are completely internal embedded within the frontal skull and responsible for balance and equilibrium. The inner ear consists of a series of ducts and sacs filled with endolymph.
Simply put:- the endolymph fluid moves about and sways as the shark banks and this swaying registers on sensory hair cells which send signals to the brain resulting in a sense of imbalance that the shark then corrects.

So to summarise the sensory organs of sharks/rays are:-
Chemoreception - smell & taste
Photoreception - visual
Mechanoreception - touch
Electroreception - electric fields

PHEW......end of Q1 and Q2 :shock:


TO BE CONTINUED......

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Fri Aug 22, 2008 10:11 am 
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Eish KampRunner - you have now made me feel very bad & sad !! :cry: :cry:
I didn't mean for you to go into so much detail with your answer which, by the way, is absolutely brilliant up till now. Please don't spend much more time with the rest of the question :pray: :pray:
Basically for Q1 i was looking for ampullae of Lorenzini & a brief description. Everything else hinged off of Q1.....so not much extra detail required.
I am sorry that i was not more explicit with my question - forgiven ??

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Fri Aug 22, 2008 12:52 pm 
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Personally, I am a little disappointed by the answer! :(

I think for the sake of science and future generations, KampRunner should at least have provided us with a few references ... :huh: :twisted:

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Fri Aug 22, 2008 2:16 pm 
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:imsmilin: Imberbe


The references will be supplied at the end of the task Imberbe :tongue:

@scorpy....you are forgiven (only just) for now :x :lol:
It was great fun researching and I will complete Q4 because its interesting.

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Fri Aug 22, 2008 4:03 pm 
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:funny:
@ Imberbe - methinx thou art somewhat of a stirrer. :wink: :naughty: You may just get me into trouble with the :angel:s

@ KampRunner...i'm glad that you have enjoyed the question - i also am fascinated by this super-sixth-sense that sharks have. i must say that reading your info has expanded on what i had read (& expected as an answer) :clap: :thumbs_up:

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Fri Aug 22, 2008 11:56 pm 
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And finally......
Man uses the sharks ability to sense electric fields to protect bathers.
A magnetic barrier almost like an electronic wave is set up in the water - this causes an unpleasant sensation picked up through Ampullae of Lorenzini - and the shark moves away.
Ref:- elasmodiver.com

Thats it folks :whistle: ..... over and out :wink:

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Sat Aug 23, 2008 12:16 pm 
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A Great Answer, KampRunner. :clap: :clap: :dance: :clap: :clap:
You went wa-a-a-a-ay past the call of duty there. :thumbs_up:
Your prize : YOU are now in the Hot Seat !!!

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Sat Aug 23, 2008 7:01 pm 
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:tongue: @ scorpy

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Sat Aug 23, 2008 8:43 pm 
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What is the common name for cephalofoil


What is its purpose?

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Mon Aug 25, 2008 11:48 am 
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Hi KampRunner
Nice interesting question. I Will try my best to answer by Thursday 'cos i won't be here for the weekend :whistle: will be @ the place we all love !! :wink:
It would be great if some other people with an interest in the marine world joined in...it isn't very difficult, but extremely interesting (& Google provides all the answers). What do you think?

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Mon Sep 08, 2008 9:50 am 
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Question 1
The cephalofoil is commonly known as the “hammerhead” as found in the eight species of hammerhead sharks. These are among the most easily recognizable visual features found within the shark kingdom. All hammerheads are, to some extent, characterized by unique lateral expansions of the nasal and orbital chondrocranium area, which takes the form of a distinctive double-bladed cephalofoil.

Question 2
There are a number of hypotheses surrounding the evolution of the sphyrnid cephalofoil over the last 20 to 25 million years, but few have been empirically tested or proven.
Some of these hypotheses include the following ;-

1) increasing electro sensitive acuity - All shark species have hundreds of minute dark pores on their heads--the open ends of electrically sensitive organs known as ampullae of Lorenzini. Each ampulla, or vesicle, is filled with conductive gel. Highly sensitive neurons project into the gel, firing at rates proportional to the current passing through it. These ampullae could detect the electric field from a 1.5 volt AA battery at about ten yards (hammerheads' prey, however, create electric fields far weaker than would a battery adrift in the sea). The sharks hunt for their most common quarry--animals that are cryptic, often buried, unmoving, nearly scentless, and quite invisible--by sensing two kinds of electric fields: the DC field that results from the osmotic potential between the prey's body tissue and seawater, and the AC fields generated by the contraction of the prey's muscles.

2) increasing scent-tracking efficiency – for similar reasons stated in Point 1 above, hammerheads have a far greater sense of smell than other sharks which enables them to track the almost negligible scents given off by most of its prey.

3) increasing maneuverability – tests conducted by various scientific specialist in shark behavior have indicated that some of the species of hammerhead (specifically scalloped & giant hammerheads) turn more sharply and more often than other reef sharks do when presented with electric fields .

4) increasing lift – the “hammer” is believed to enable the hammerhead shark to make exceptionally fast turns when pursuing prey or fleeing from danger due to its ability to tilt its head in order to exert huge turning force on its body. This led aeronautical engineers to incorporate small wings at the front of some advanced fighter jets. The forward “control surfaces” replace the larger ones that are necessary when control is behind the main wing. This enabled the plane to turn faster with less drag.

There are a number of other hypotheses surrounding the mystery of the cephalofoil of hammerhead sharks which could explain some of the unique behavior and abilities of these creatures in the wild.

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Mon Sep 08, 2008 8:14 pm 
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Geez Scorpy.....brilliant answer as ever. :dance: :dance: Worth waiting for :D

It looks as if you are the IT man again.....I'm off to KNP tomorrow so will be away gathering quiz material :twisted: for 2 weeks.

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Mon Sep 08, 2008 11:58 pm 
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Thanx KampRunner - you are too kind :redface:
I hope you have a great trip to KNP & get to see mega sightings and enjoy all the other good things Kruger has to offer. :mrgreen:
Take care & enjoy !!

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 Post subject: Re: Shark ID (RV)
Unread postPosted: Wed Sep 10, 2008 10:48 am 
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Image

1. ID this shark
2. State the areas where it is predominantly found
3. What do they typically feed on?
4. Describe the function of the elongated snout
5. This shark closely resembles another species of fish (not a shark). Name this fish and give 3 features that differentiate between them.

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