CLASSIFICATION OF NAUTILUS

KINGDOM :- ANIMALIA (Multicellular eukaryotic organisms)

PHYLUM :- MOLLUSCA (Unsegmented bilaterally symmetrical and provided with visceral mass, foot and mantle.)

CLASS :- CEPHALOPODA (Head well developed with eyes and radula. Foot represented by arms and tentacles.)

SUB-CLASS :- NAUTILOIDEA OR TETRABRANCHIATA (Gills, kidneys and auricles, 4 each in number)

ORDER :-  NAUTILIDA (Shell and tentacles absent. Arms eight.)

FAMILY :- NAUTILIDAE

GENUS :- Nautilus (The pearly Nautilus)

GEOGRAPHICAL DISTRIBUTION

  • Commonly found in Indian and Pacific oceans.

HABIT AND HABITAT

  • Nautilus is a gregarious, nocturnal deep-sea form crawling over the bottom in troops at night time in search of animal food comprising crabs and shellfish.

NAUTILUS

GENERAL CHARACTERSTICS OF NAUTILUS

  • Commonly known as pearly Nautilus.
  • Body of the animal lies in the flat and spirally coiled shell in one plane and internally divided into various chambers by septa having septal necks. 
  • Shell measures approximately 25 cm. 
  • Shell is differentiated into body chamber containing head, tentacles and several coiled chambers with extension of visceral mass called siphundes. 
  • Periostracum dark brown or black, porcellaneous layer with undulating transverse bands of white and yellowish brown alternately and inner layer pearly. 
  • Body proper is lodged in the largest chamber and the other chambers remain either empty of filled up with gas which helps in floatations. 
  • Internal septa are perforated. It is tetrabranchiate having 4 ctenidia, 4 kidneys and 4 auricles. Ink gland is absent.
  • Sexes are separate. About 60 to 90 prehensile tentacles are radially arranged around the mouth. Siphonal funnel is formed of two separate folds.
  • Eyes are open vesicles without cornea or lens.
  • Ink gland and chromatophores absent.
NAUTILUS

SPECIAL FEATURE

  • Nautilus is the only cephalopod having external shell. It has about 2,000 fossil species which date back to the Cambrian and reaching their maximum in the Silurian and Devonian ages. The body is used for food and the shell is extensively employed for ornamental and useful purposes. Oliver Wendell Holmes in his famous poem, “Chambered Nautilus”, calls it as “The ship of pearl”.

IDENTIFICATION

  • The animal contains spirally coiled shell and all above features, hence it is Nautilus.

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