elective paper i: fishery sciences subject code:18mzo14e
TRANSCRIPT
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UNIT – III: SENSE ORGAN AND POISON GLANDS
ELECTIVE PAPER– I: FISHERY SCIENCES
SUBJECT CODE:18MZO14E
SENSE ORGAN IN FISHES
ELECTRIC ORGAN
POISON GLANDS
SOUND PRODUCING ORGAN
BIOLUMINESCENSEDr. A. JEYASANKARAssistant Professor
Department of ZoologyGovernment Arts College (Autonomous)
Coimbatore-18E-mail: [email protected]
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LATERAL LINE• system of tactile sense organs (connected with the sense of touch), unique to
aquatic vertebrates.
• It serves to detect movements and pressure changes in the surrounding water.
• It is made up of a series of mechanoreceptors (a sense organ or cell that respondsto mechanical stimuli such as touch or sound) called neuromasts (lateral lineorgans) arranged in an interconnected network along the head and body.
• This network is typically arranged in rows; however, neuromasts may also beorganized singly.
• At its simplest, rows of neuromasts appear on the surface of the skin; however,for most fishes, they lie embedded in the floor of mucus-filled structurescalled lateral line canals.
• These canals are placed just underneath the skin, and only the receptor portionof each neuromast extends into the canal.
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AMPULLAE of LORENZINI
• In sharks and rays, some neuromasts have been evolutionarily modified to become electroreceptors called ampullae of Lorenzini.
• These receptors are concentrated on the heads of sharks and can detect the minute electrical potentials generated by the muscle contractions of prey.
• Ampullae of Lorenzini can also detect Earth’s electromagnetic field,and sharks apparently use these electroreceptors for homing (returnits territory's) and migration.
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ELECTRIC ORGAN IN FISHES
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cartilaginous skeleton
Bony skeleton
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ELECTRI ORGAN
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Electric Rays
Photo by Philippe Guillaume
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Electric Skates
Photo by Andy Martinez_NOAA
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Electric Stargazers
Photo by Canvasman21 at English Wikipedia
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Electric Catfish
Photo by Stan Shebs
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Knifefish
Photo by Albert Lab Univ Lousiana
Photo by Albert Lab Univ Lousiana
Google Images
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High influx High influx
Low influxLow influx
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DIVISION OF POISONOUS FISHES
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Difference between poisonous and Venomous fishes
• Venom vs. Poison
• The difference is simple: Venom is injected. Poison is ingested.
• Venomous animals often possess a specialized body part, like fangs, spines, stingers, barbs and other generally sharp and unpleasant tools, that allow the animal to puncture the skin of their opponent to inject venom.
• Once the animal breaks the skin, a rush of venom travels from a gland that stores the toxin in a process called envenomation.
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• Poisonous animals, on the other hand, coat part or all of their body in a toxic substance, so they’re harmful to touch or eat.
• Some animals create and secrete their own poison, while others gain their poison by eating toxic prey.
• Many poisonous animals use their toxin for defense rather than offense—it’s a way to dissuade predators from eating them!
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Venomous Ocean Animals
• There are more venomous animals in the ocean
• All octopuses, as well as some cuttlefish and squid, arevenomous, and mostly use their venom to hunt and kill theirprey.
• Jellyfish can also be venomous, and use a harpoon-like stingingcell called a nematocyst to inject their prey.
• The tiny Australian box jellyfish is considered the mostvenomous animal in the sea—their sting can cause cardiacarrest, paralysis, or death in humans in just a few minutes.
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• There are over 1,200 venomous fish in the ocean, too, including stingrays and lionfish.
• Lionfish, and invasive species in the Western Atlantic, Caribbean and Gulf of Mexico, have a series of venomous spines lining their back that can cause pain and swelling upon envenomation.
• Their cousin, the stonefish, is the most venomous fish in the world, and their stings can be fatal if left untreated.
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Poisonous Ocean Animals
• Just like some land animals, some of the most colorful organisms in the sea are poisonous.
• Nudibranchs, often referred to as sea slugs, use their bright colors to warn predators that they should stay away.
• Since nudibranchs lack other defenses (like a shell), some use toxins to avoid being eaten.
• Some produce their own poison, while others consume those of sponges or anemones to use as their own.
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• Puffer fish, also known as blowfish, are also poisonous—but that doesn’t stop humans from eating them.
• Although one puffer fish contains enough tetrodoxin to kill 30 people, the fish is considered a delicacy in Japan.
• Only highly trained chefs who know how to avoid the poison are allowed to prepare the fish.
• Bonus: Blue ringed octopuses are overachievers—they’re both venomous and poisonous! Its venom is 1,000 times more powerful than cyanide, and this golf-ball sized powerhouse packs enough venom to kill 26 humans within minutes. Also, they’re poisonous if eaten.
• Best to avoid those guys altogether.
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Venom apparatus• The venom apparatus of fishes typically consists of venom glands
located in paired anterolateral grooves on either side of sharp spines,
with the spine and venom gland complex covered by an integumentary
sheath.
• The venomous spines are most often found in association with the
dorsal fin, but pelvic, anal, and pectoral spines are also common.
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• Some species, notably stargazers, toadfish, and weeverfish, possess venomous opercular spines on either side of their heads.
• In addition to opercular spines, toadfish and weeverfish also maintain venomous dorsal spines.
• In venomous toadfish, the glandular venom tissue sits at the base of these spines.
• Stingrays lack all of these and instead produce serrated spines in their caudal region.
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Representative
venomous fishes.
Venomous spines on fish
are colored in red.
(A)Chimaera and
serrated dorsal spine;
(B) Stingray and serrated
caudal spine;
(C) Catfish and serrated
pectoral spine;
(D) Fang blenny and
canine tooth with
venom gland;
(E) Toadfish and
opercular spine with
venom gland;
(F) Weeverfish;
(G) Gurnard Perch;
(H) Stonefish and dorsal
spine with venom
gland.
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Red tide is a phenomenon caused by
algal blooms (Wikipedia definition) during
which algae become so numerous that
they discolor coastal waters (hence the
name "red tide"). The algal bloom may
also deplete oxygen in the waters and/or
release toxins that may cause illness in
humans and other animals.
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SOUND PRODUCING ORGANS IN FISHES
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Fishes produce different types of sounds using different mechanisms and for different
reasons.
Sounds (vocalizations) may be intentionally produced as signals to predators or competitors,
to attract mates, or as a fright response.
Sounds are also produced unintentionally including those made as a by-product of feeding
or swimming.
The three main ways fishes produce sounds are by using sonic muscles that are located on
or near their swim bladder (drumming); striking or rubbing together skeletal components
(stridulation); and by quickly changing speed and direction while swimming
(hydrodynamics).
The majority of sounds produced by fishes are of low frequency, typically less than 1000
Hz
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Hydrodynamic Sound
• Hydrodynamic Sound Hydrodynamic sound production occurs when afish quickly changes direction and/or velocity.
• These sounds are extremely low frequency.
• These sounds are simply a by-product of swimming.
• It is possible that hydrodynamic sounds may be important topredator and prey interactions and communication.
• For example, it has been postulated that sharks can detect the lowfrequency hydrodynamic sounds emitted by smaller fishes.
• Therefore, schooling fishes may inadvertently attract a shark simplyby the sounds produced during swimming.
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Stridulation (Producing sound by rubbing together certain body parts)
Stridulatory sounds are produced when hard skeletal parts or teeth are rubbed together,
like the method used by crickets to make sounds.
In fishes, stridulation often occurs during feeding when jaw teeth or pharyngeal teeth
are gnashed together.
Stridulation may be used intentionally to produce sound as a fright response or
territorial display.
Stridulatory sounds may be modified or amplified by the swim bladder.
Stridulatory sounds influenced by the swim bladder have predominant frequencies well
below 1000 Hz.
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SIGNIFICANCES:
• Calling behavior in fishes
• Sound as communication between the fishes
• Foraging as well as social interactions in fishes
• Increased visual signaling –nearby predators
• Sound is play an important role in successful mating
• It might convey the information of value to other fish of the same
species including both male and female
• Protection of spawning (Laying eggs) behavior from unwanted
disturbances
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Schematic representation of the general
structure of light organs in fishes.
External side with light emission and internal
side with blood capillaries and nerve supply.
Matrix represents the space between the
photogenic chamber and other structures.
The right half of the photogenic chamber
represents an intrinsic light organ with
photocytes.
The left half of the photogenic chamber
represents a symbiotic light organ with
transverse section of tubules filled with
luminous bacteria.
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Bioluminescence plays an important role in the ecology of the ocean.
The function of bioluminescence in the oceans is more clearly understood in the context of the
essentially dark environment below about 200 m.
The functions of bioluminescence are for:
Defense
Schooling of fish (group is swimming in the same direction in a coordinated manner)
Luminous lure (To attract prey)
Feeding
Communication (in the dark)
Mating
Camouflage
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