Adaptations in deep sea fishes

BIOLOGY

1. Department of zoology Govt. Dungar Collage DR. ANU KUMAR SHARMA ASSOCIATE PROFESSOR

2. Adaptations in Deep-sea Fishes

3. Contents : Adaptation. What is deep – sea ? Problems faced by deep- sea fishes. Adaptation shown by deep sea- fishes. Examples of deep – sea fishes.

4. What is Adaptation ? Adaptation  is the evolutionary process where an organism becomes better suited to its habitat. This process takes place over many generations. It is one of the basic phenomena of biology. When people speak about  adaptation , they often mean a 'feature' (a trait) which helps an animal or plant survive.

5. What is a Deep- sea ?

6. Zones of an ocean

7. Problems faced by deep-sea fishes

8. Absence of light : Light is virtually absent in the deep ocean, which means that deep-sea organisms cannot rely on vision for feeding, avoiding being eaten, or mating and photosynthesis. Low temperature and high pressure : As we travel from the surface of the ocean downward to the seafloor, water pressure increases by one atmosphere (or 14 pounds per square inch) for every 10 meters (32.8 feet) of depth. O cean waters have an average temperature of only 4°C (39°F). Scarcity of food : Plants are absent due to absence of light . Phytoplankton are also absent , so the fishes are depended on dead plants and animals falling from surface water but due to limiting amount it leads to competition. 4. Low oxygen and high salinity : Oxygen acts as limiting factor as it is about 5 ppm below 1000 m depth. Salinity doesn't have much affect on distribution or activity of fishes.

9. Adaptations shown by Deep – sea fishes

10. Food and feeding habits : Deep sea fishes are generally predators and carnivorous due to scarcity of food .e.g., Gstrostomias Some species are scavengers feeding on the dead plants and animal falling from the above surface . Mesopelagic fishes migrate to the surface water at night to fed on planktons and animals. Large teeth and well developed dentition :– allow capture and killing of prey much larger than normally possible size . Distandable stomach and long alimentary canal :– digest prey much larger than normally possible over a long period of time.

11. Linophryne Chiasmodon niger Saccopharynx

12. Eyes: Enlarged and Specialized eyes : some species have retina having large numbers of rods. Telescopic eyes : species like Gigantura , have tubular eyes for better telescopic vision in dim ocean light . Upward pointing eyes : this helps the fishes to see the silhouette of the fish swimming in above surfaces. While some bathypelagic fishes have non functional eyes or are completely blind. Agryropeleus (Hatch fish)

13. Sensory Organs : Fin rays and feelers : In some benthic fishes feelers are stiff and enable the fishes to stand in the bottom. And in Bathypelagic fishes like angler fish first ray of dorsal fin is modified into tentacle , helps them to lure the prey. Well developed olfactory organs and lateral –line system ,so that the fish can detect the slightest movement of water in its neighbourhood . Bathypterois ( Tripod fish )

14. For maintaining Buoyancy: Deep sea fishes are adapted to high pressure by developing bodies with no excess cavities , such a swim bladder , that would collapsed under heavy pressure If they have bladders they have filled of Lipids instead of gases to avoid collapsing . The flash and bones of deep sea fishes are soft and flabby.

15. Bioluminescence: The production of living lights is called bioluminescence. Fishes bears a organ called Phototrops for production of light. These organs are located on the head and along the ventral or lateral sides of body as in Gastrostomias and Photostomias . The lantern fish Linophryne has luminescent organ on fin rays while some angler fishes have light organ on the tip of movable lure.

16. Uses of Bioluminescence : To aid vision in abyssal darkness. To identify and attract the mate. To lure the pray. To drive away the enemies.

17. For reproduction and mating: Sexual adaptation : In some cases males are found attaches to female, becoming a complete parasite . Some fishes also become hermaphrodite . Sex recognition : It is helped by luminescent organs . Some angler fishes also produce pheromones to attract mate. Fecundity : The deep sea fishes adapted mass spawning and produce a large no. of epipelagic eggs which hatch in water . Larva : The deep fishes shave epipelagic larva who feeds on zooplankton. The larva are transparent to avoid predatory animals.

18. Larva of anglerfish

19. Examples of Deep – Sea Fishes :   Alepisaurus (Lancet fish ) Cetomimus (whale fish) Bathysaurus (Lizard fish)

20. References : -A Textbook of FISH BIOLOGY and fisheries by S.S. Khanna and H.R. Singh. -Fish and Fisheries by Pandey and Shukla . Website : - Biologydiscussion.com