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. The term external morphology of Rohu, the external structure of Rohu or the external features of Rohu are similar.
Systematic Position / Classification
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Actinopterygii |
| Order: | Cypriniformes |
| Family: | Cyprinidae |
| Subfamily: | Labeoninae |
| Genus: | Labeo |
| Species: |
Labeo rohita
|
Habit and Habitat of Labeo rohita
- Rohu is an herbivorous fish species.
- Its chief food is various phytoplankton, zooplankton, and aquatic plants.
- It is a fast-growing fish species that can attain a maximum length of up to 1.5 meters and a weight of up to 25 kg.
- Rohu is a diurnal fish species that is active during the day and rests at night.
- Rohu is a bottom-dwelling fish species that is typically found in freshwater habitats with slow to moderate water flow.
- It prefers deep pools and runs of rivers, and can also be found in lakes, ponds, and reservoirs.
- Rohu is tolerant to a wide range of water conditions, including temperatures ranging from 25°C to 32°C, pH ranging from 6.5 to 8.5, and dissolved oxygen levels ranging from 3 to 6 ppm.
Labeo rohita (Rohu) Labeled Diagram
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.
-
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.
-
Frequently Asked Questions (FAQs)
1. Do teeth and tongue present in Labeo rohita?
Ans: No, teeth and tongue are lacking in Labeo rohita.
2. Do eyelids present in the eyes of Labeo rohita?
Ans: No. The eyes on the head are without eyelids but are protected by a transparent protective membrane.
—————-THE END—————–
Learn more:
- Digestive System of Labeo rohita | Rohu | Diagram
- Urinogenital System of Labeo rohita | Rohu | Diagram
- Respiratory System of Labeo rohita with Diagram | Rohu
- Labeo rohita – Rohu / Rui
- General Characters of All Classes of Vertebrates.
Reference: