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: dr.a.jeyasankar@gmail.com

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.

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.

ELECTRIC ORGAN IN FISHES

cartilaginous skeleton

Bony skeleton

ELECTRI ORGAN

Electric Rays

Photo by Philippe Guillaume

Electric Skates

Photo by Andy Martinez_NOAA

Electric Stargazers

Photo by Canvasman21 at English Wikipedia

Electric Catfish

Photo by Stan Shebs

Knifefish

Photo by Albert Lab Univ Lousiana

Photo by Albert Lab Univ Lousiana

Google Images

High influx High influx

Low influxLow influx

DIVISION OF POISONOUS FISHES

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.

• 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!

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.

• 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.

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.

• 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.

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.

• 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.

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.

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.

SOUND PRODUCING ORGANS IN FISHES

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

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.

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.

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

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.

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