DEEP SEA FISHES AND THEIR ADAPTATION : MORPHOLOGICAL ,PHYSIOLOGICAL & ANATOMICAL..

2. K.G. ART’S & SCIENCE COLLEGE RAIGARH (C.G.)
SESSION - 2021
DEPARTMENT OF ZOOLOGY & RESEARCH CENTER
SUBJECT :- ICTHIOLOGY .
SEMINAR TOPIC :- DEEP SEA FISHES & THEIR ADAPTATION.
Guided by Submitted by
Prof. Anita Pandey mam. GIRJA PRASAD PATEL
M.Sc. IV Sem. Zoology

3. DEEP SEA FISHES & THEIR ADAPTATION
SYNOPSIS :-
1. INTRODUCTION.
2. WHAT IS ADAPTATION. ??
3. THE DEEP SEA.
4. CHARACTERISTICS OF THE DEEP SEA.
5. EXAMPLES OF DEEP SEA FISHES.
6. ADAPTATION IN DEEP SEA FISHES.
7. CONCLUSION.
8. REFERENCE.

4. DEEP SEA FISHES & THEIR ADAPTATION
1. INTRODUCTION :-
• Deep sea fishes are fishes that live in the darkness below the sunlight surface waters.
• A large number of species of fish inhabit in deep sea.
• We are going to discuss about the adaptation in deep sea fishes. Fishes are the cold
blooded vertebrate that breath through gills and live in water.
• Ocean water is distinguished in different zones. These zones together constitute the
deep sea habitat.
• All fishes are peculiar and possess various kinds of structural features in adaptation to
the ecological condition of their habitat.

5. 2. WHAT IS ADAPTATION.?? :-
• Adaptation may be defined as a process that makes an animal compatible
and fit to its environment.
• According to NEWMAN , the adaptation means the mutual fitness of
organism and environment.
• From the ecology point of view , adaptation of the animals of different
habitats are called ecological adaptation like aquatic adaptation, (fresh
water & marine both) pelagic and deep sea adaptation, cave adaptation etc.
• The adaptation may be morphological or structural , physiological in Deep
sea fishes are considered.

6. 3. THE DEEP SEA :-
• The water of Ocean can be distinguished into two parts :-
The surface water of ocean where sunlight reaches easily is called Epipelagic zone .
The region of the sea below 200 meters depth is usually referred to as the DEEP SEA.
And can be further divided into :-
• Above 200m :- Epipelagic zone.
• Range between 200 – 1000m :- Mesopelagic zone.
• Range below 1000m :- Bathypelagic zone.
• The deepest part :- Benthic zone.
 Sea zone :- Only 2% of known marine species
inhabited the pelagic environment.

7.  Epipelagic zone :-
• The epipelagic zone (0-200m) is the area where light penetrates the water & photosynthesis
occurs.
• This is also known as the Photic zone.
 Mesopelagic zone :-
• The mesopelagic zone is the Disphotic zone, meaning light there is minimal but still
measurable.
• The Oxygen layer exists somewhere between a depth of 700m and 1000m deep depending
on the place in the ocean.
• This area is also where nutrient are most abundant.
 Bathypelagic zone :-
• The bathypelagic & abyssopelagic zones are Aphotic zone, meaning that no light penetrates
this area of the ocean.
• This zones make up about 75% of the inhabitable ocean space.

8. 4. CHARACTERISTICS OF THE DEEP SEA :-
1. Total Darkness.
2. High Pressure.
3. Low temperature ( 1 – 5 ֯C ).
4. Scarcity of food.
5. No water current or wave action.
6. Low O2 content.
7. No seasonal change.

9. Conditions of Deep Sea :-
Physical factors :-
Temperature :- The deep sea is also an extremely hostile environment , with
temperatures that rarely exceed 3°C (37.4 °) & fall as low as -1.8°(28.76°) 4-8°C.
Light :- Completely absent.
Pressure :- Because pressure in the ocean increases by about 1 atmosphere for every
10meters of depth (760mmHg).
Chemical factors :-
Salinity :- Does not much variation, at about 35 parts per thousand.
Dissolved Oxygen.
Biological factors :-
Predation, Competition, & Scarcity of food.

10. 5. EXAMPLES OF DEEP SEA FISHES :-
i. Eurypharynx pelecanoides. (Gulper)
ii. Linophryne Lucifer (Angler) :- The fin rays have phosphorescent organs.
iii. Polycanthonotus. (Notocanth).
iv. Bassogigas. (7cm. Long deepest known fish).
v. Lepidion (Gadoid).
vi. Bathypterois (Benthic tripod fish).
vii. Hariotta (Holocephali).
viii. Idiacanthus ferox (Highly fragile).
ix. Malacosteus indicus (Wide mouthed).
x. Chiasmodon niger (Great swallower).
xi. Saccopharynx ampullaceus (Gulper).
xii. Photocorynusspiniceps (Ceratoid angler fish).

11. 6. ADAPTATION IN DEEP SEA FISHES :-
• The deep sea fishes show various peculiar adaptation features.
• The deep sea fauna including fishes are subjected to an ecological principle called as
“ Thiemann's principle “.
• According to this principle , if a biotope is one sided and specialized , it will have fewer
species but individuals with many peculiar characters.
• True to the principle many deep sea fishes show a number of peculiar adaptation listed.
1.) Predatory Habit :-
• The deep sea zone is away from the reach of suns rays and thus , it is a pitch dark
environment .
• The absence of light of show the growth of vegetation and photosynthetic organism .
• EXA . :- Gastrostomias .

12. 2.) Scavengerous Feeding :-
• Deep sea fishes feed on the falling bodies from surface that sink to the bottom.
• As the low temperature prevails in deep sea , the decomposition of bodies falling from
above is much slower , therefore, fishes of this zone enjoy an almost fresh diet.
• The food missed by the deep sea fishes accumulate at the bottom constituting the food
supply of deep sea sedimentary forms such as echinoderms and foraminiforms.
Fig. :- Gastrostomias, a deep sea fish with predatory habit.

13. 3.) Large mouth , powerful dentation and distensible stomach :-
• Deep sea fishes are equipped with large mouth , wide buccal cavity , well developed
dentition and distensible gastro-intestinal tract.
• These features help the deep sea fishes to sallow larger preys.
• EXA. :- Chiasmodon niger (Great swallower) & Saccopharynx ampullaceus (Gupler) have
distensible stomach and Linophryne has a powerful dentition.
A.) Chiasmodon niger having large
mouth and distensible stomach.
B.) Saccopharynx having
distensible stomach
C.) Linophryne having powerful
dentition

14. 4.) Weak Endoskeleton :-
• In deep sea fishes, the endoskeleton is fragile, weak, light and flexible. This
is due to the uncalcified or weakly calcified skeletal system.
• This is caused by the low temperature prevailing in the deep sea.
• EXA. :- Chimaera.
Fig. :- Chimaera having weak endoskeleton

16. 5.) Decreased size and Weight :-
• The size and weight of the fishes to decreases with increase in the depth.
• 10m depth in sea water 2atm.
• 20m depth in sea water 3atm
• This relates to ambient pressure of water column lying above them, availability of food
materials and to the problem of sinking.
• By reducing the size as in Idiacanthus, a lesser part of the body is exposed to ambient
pressure working on it and by reducing their weight, the total density of the fish is
reduced to counter the gravity.
• Fishes living in deeper waters have lesser amount of red muscles and so they are less
active than those living in depths above them.
Fig. :- Small body size of Idiacanthus.

17. 6.) Well – developed lateral line system :-
• Lateral line system is well developed in all deep sea fishes.
• This sense organ enables the deep sea fishes to live successfully depending
on the system of echolocation in the lightless environment inspite of the
absence of eyes.

19. 7.) Muciferous System :-
• The muciferous system of many deep sea fishes is developed to an extra ordinary degree.
• They have the ability to secrete large amount of mucus.
• The entire body is covered with layer of mucus viz. in Macruridae.
• The exact physiological role of this secretion is unknown, but it has been observed, but it
has been observed to have phosphorescent properties.
8.) Eyes :-
• Eyes are very well developed in some deep sea fishes.
• In the darker water of the deep sea eyes have very little role.
• These fishes are, therefore, either blind or have eyes of varied dimensions. The shape and
size of the eyes of deep sea fishes are, however, determined by the depth in which the
fishes inhabit.
• The eyes of Mesopelagic fishes viz; Electrona, Bonaparyia, Alepisaurus, Paralepis, etc. are
usually larger and adapted to vision in dim light.

20. • They often have large pupils to absorb a maximum amount of light.
• The retina has a high concentration of visual pigments and increased number of rods to
accommodate them.
• It is capable of absorbing about 95% of light that is likely to it.
• The eyes of some mesopelagic like Gigantura chuni fishes are shaped like tubes to enlarge
the field of vision.
• Their eyes may be said telescopic eyes with enlarged lens. EXA. :- Electrona (Myclophid).
• Eyes of certain other fishes are more like a concave mirror to maximize the amount of light
entering to them.
• Bathypelagic fishes living in the complete darkness of the sea, have reduced eyes but
those of benthic fishes vary in size.
• Their occurrence relate to the detection of bioluminescence and in part to the recognition
of the sex.
• Their reduced size is probably related to the limited energy whuch the fish can manage to
spend.

21. • Many deep sea fishes are completely blind. To compensate the loss of vision, they are well
equipped with the lateral line system , tactile organs and other sensory structure.
• One common feature of the eyes of deep sea fishes is either the reduction or absence of
cones.
• The number of rods in the retina increased in respond to faint light.
• Some deep sea fishes have very much reduced eyes and others are blind.
Fig. :- Mesopelagic fishes showing moderate size of eyes.

22. 9.) Sensory Organs :-
• In deep sea fishes, sensory organs are well developed to compensate the loss of eyes.
• Their fin rays are considerably elongated. In Bathypterois, one fin ray of the pectoral fin is
produced into a sensory filament.
• In Stylophorus paradoxus, the caudal fin is produced into a long filament.
• These structures are sensory to touch and perceive the disturbances in the surrounding
water.
10.) Colouration :-
• Deep sea fishes have a riot of colours though red colour seems to
predominate over.
• The most deep sea fishes are black or silvery with counter shading as means
of concealment and protection from the predators.
• In addition, dark, violet, black, or brown are quite common.
• Colouration in deep sea fishes may be attributed to attraction of the preys.

23. 11.) Hydrostatic Pressure :-
• Actually the hydrostatic pressure in the sea increases by one atmosphere for
every 10 metres depth.
• But the deep sea fishes are unaffected by the enormous pressure acting upon
them in the great depths of the sea for their tissue possess the same pressure
of the surroundings.
12.) Swim Bladder :-
• In many deep sea fishes, swim bladder is lacking. This is just to escape the
high stress of pressure that may be experienced with depth increase.
• However, some species of gonostomatidae possess well developed bladders.
• In such fishes special structure like retia mirabilia capable of secreting gas are
found attached to the swim bladder.

25. 13.) Bioluminescence :-
• The production of living light by the deep sea fishes is called Bioluminiscence. It is common
in deep sea fishes.
• Fishes bearing photophores produce cold light of blue or green colour.
• The photophores are located in some parts of the body or all over the body.
• The blue light is one of the transmission rate through the sea water.
• However, Malacosteus & Pachystomius , produce red light to illuminate the prey which are
incapable to perceive blue or green light.
• The light may be emanated in three ways, namely intracellular production , extracellular
production and production through bacterial action.
• Photoblepharon has a light organ under the eyes. The Lantern fish Linophryne has fin rays
studded with luminescent organ.
• Gastrostomias has two longitudinal rows of photophores where as Photostomias has four
longitudinal rows of luminiescent organ.
• In angler fishes such as Lophius & Linophryne, the light organ is located at the tip of
movable lure and the lure can be used to draw the prey towards the mouth.

26. • The main function of bioluminescence is to aid vision in the abyssal darkness. It is also
applied to identify the mate and attract the prey.
• Many deep sea fishes utilize this cold light to drive away enemies by sudden flash of light.
A.) Photostomias having and longitudinal rows of bioluminescent.
B.) Lophius having bioluminescent lure.

27. 14.) Abundance :-
• The number & diversity of deep sea fishes decrease with the increase in
depth.
• This is because the quality of food gradually diminishes towards the bottom.
15.) Sexual adaptation :-
• In the deep sea, it is difficult to get a mate because of the absence of light and
of thin population.
• Hence, in some cases the male is found attached to the body of the female.
• An interesting example of sexual adaptation is seen in Endriolynchus. In this
fish the attachment between the male & female is so close that tissues and
blood vessels are interconnected.

28. Fig, :- Photocorynus male permanently attached with female

29. 16.) Sex recognition :-
• Sex recognition in deep sea fishes is helped by species specific
bioluminescence coupled with the sex pheromones usually produced by the
females.
• Olfactory organs of male fishes are generally larger to sense specific odour
(smell) of their mate.
17.) Fecundity :-
• The deep sea fishes spawn at a depth in which they live, but their eggs always
rise to the surface.
• The fecundity is high to increase chances of survival , and are neutrally
buoyant.
• The eggs of viviparous squalids contain aqualene that makes them neutrally
buoyant .

30. 18.) Larva :-
• The larvae of deep sea fishes hatch in surface productive zone (within 30m.
depth), where they get enough food to grow until the metamorphosis is
completed.
• After metamorphosis, the youngs move down to the habitat of their parents.
• They are transparent to minimize detection by surface feeders and posses
well developed teeth as they feed upon copepods.
• Their skin may swell in the shape of balloons to reduce density and the rate of
sinking.

31. 7. CONCLUSION :-
• In authors view (Pandey & Shukla) – “the adjustments made by animals in response to
specific or even general environment conditions may be referred to as adaptation.
• The region of the sea below 200meters depth is usually called the deep sea.
• So we concluded that the deep sea has different environment condition. But the fish of
deep sea have evolved various adaptation to survive in this region.
• They are able to live in this (Deep sea) region.
8. REFERENCE :-
 FISH & FISHERIES :- PANDEY & SHUKLA (3rd revised edition).
 AN INTRODUCTION TO FISHES :- S.S. KHANNA.
BY INTERNET.