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External Morphology of Labeo rohita | Rohu | Diagram

In this article we will learn about the external morphology of Labeo rohita or rohu fish. Labeo rohita is a very common fish in South Asia, especially in India, Bangladesh, and Myanmar. It is a carp fish and it has so much demand in the local market because of its taste. The common name of Labeo rohita is Rohu / Rui.

Systematic Position/Classification

Phylum: Chordata

    Sub-Phylum: Vertebrata

            Class: Actinopterygii

                Order: Cypriniformes

                    Family: Cyprinidae

                       Genus: Labeo

                           Species: Labeo rohita

 

Labeo rohita (Rohu) Diagram

Labeo rohita

Fig: External morphology of Rohu/Rui

External Morphology of Labeo rohita (Rohu)

1. Shape, Size, and Color

      • Spindle-shaped body. 
      • The color is greyish or blackish on the back, and silvery-white or pale on the two sides and belly.
      • Full-grown individual measures 1 meter in length.
      • A full-grown individual measures 20 – 25 kg in weight.
      • The body is divided into a head, trunk, and tail.

2. Head

      • The Head extends from the tip of the snout to the hind edge of the operculum.
      • The snout is depressed, short and obtuse.
      • A pair of external nostrils are present on the dorsal surface of the snout. 
      • The mouth is subterminal; it is the large transverse aperture, bounded by thick and fleshy lips.
      • Two small, thread-like, sensory maxillary barbels are present at the corners of the mouth. Rostral barbels are absent.
      • Teeth and tongue are lacking.
      • The eyes are large and located on each lateral side of the head.
      • The eyes on the head are without eyelids but are protected by a transparent protective membrane.
      • Behind the eye, on either side, there is a large movable bony gill cover or operculum present. 
      • The branchiostegal membrane is attached to each operculum posteriorly.
      • Beneath each operculum, there are four comb-like gills in a branchial/gill chamber.

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3. Trunk

      • It is the thick middle part of the body.
      • The trunk is elongated and oval in cross-section.
      • It is wide in the middle and narrow towards the dorsal and ventral sides.
      • It is covered over by thin, overlapping cycloid scales.
      • On either side of the trunk extending from the back of the operculum up to the tail, there is a dark line on the mid-ventral portion of the body called, the lateral line.
      • Fins are well-developed and supported by bony fin rays.
      • In the trunk region, there found three kinds of fins e.g. dorsal fins, pectoral fins, and pelvic fins. 
      • On the back of the middle of the trunk, there is a single large somewhat rhomboidal fin called the dorsal fin.
      • Just behind the operculum, there is a pair of fins on either side of the body called the pectoral fins.
      • Behind the pectoral fins, on the ventral side of the trunk, there is a pair of fins on either side called pelvic fins.
      • Three kinds of apertures are found in the trunk region. They are found mid-ventrally at the posterior end of the trunk. The anterior aperture is the anus, the middle is the genital, and the posterior is the urinary aperture.

4. Tail

      • It comprises about one-third posterior part of the body.
      • It is laterally compressed and narrower behind.
      • At the end of the tail, there is a large caudal fin.
      • On the ventral side of the tail region, there is a median anal fin lying just posterior to the urinary aperture.
      • The tail is the principal locomotor organ.

 

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The external Morphology of Labeo rohita is fully explained above. If you love our articles, consider visiting our other articles. We always try to write updated and informative articles for the students. Thank you!

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