In this article we will discuss about the structure of lata fish. This will also help you to draw the structure and diagram of lata fish.
The Lata fish (Ophicephalus punctatus) it easily available all over India and Bangladesh throughout the year. Anatomical peculiarities of the Lata fish are therefore represented diagrammatically (Fig. 133) for the guidance of the students in their practical work along with a few important systems. Its generic name has now been changed to Channa.
The Lata or Murrel or Goroi is a fresh water fish and is found in ponds, ditches, jheel etc. They are very common in West Bengal, and Bangladesh. Being a carnivorous fish it takes smaller fish and aquatic animals as food. Because of the presence of accessory respiratory organs it can live outside water for a considerable period.
The body is spindle shaped and laterally compressed. A full grown fish is 15-18 cm in length. The colour of the dorsal surface is blackish grey while the ventral surface in yellowish grey. Above and below the lateral line sense organ are found eight alternate patches.
The body is covered with scales. The scales are of two types—Ctenoid and Cycloid. The body is divided into three regions—Head, Trunk and Tail (Fig- 133.). The dorsal side of the head is flat and the scales here are large and plate like. The dorsal fin is broad and undivided, the anal fin is extended. The tail fin looks like that of Bhetki. The lateral line is interrupted at frequent intervals. The other structural aspects resemble that of Bhetki.
It consists of the following parts—Mouth. The mouth aperture is wide and terminal. It is bound by upper and lower jaws. The jaws are lined with sharp and conical teeth. Mouth leads to the Buccal cavity. The floor of the buccal cavity is provided with a tongue which is devoid of muscles.
It leads to the Pharynx. The lateral walls of the pharynx bear 4 gill-slits in line as rows on either side. The pharynx leads to the stomach via a short oesophagus. A sphincter is present between oesophagus and stomach. The cardiac and pyloric part of the stomach is identifiable. (Fig. 134).
The pyloric part continues as intestine. The intestine is a coiled tube. At the line of demarkation between the pylorus and intestine there is present a pair of finger dike projections called Pyloric Caeca. The posterior portion of the intestine is inflated’ and forms the Rectum. The rectum opens to the outside through the Anus located at the posterior ventral end of the trunk.
Liver is the largest digestive gland. The reddish brown liver is located beneath the heart. It is made up of two distinct lobes— left and right. Liver secrets bile. The bile remains stored in a gall bladder located in a notch on the right lobe of the liver. A Bile duct arises from the gall bladder and opens into the intestine through an aperture close to the pyloric caecum.
Lata being aquatic takes oxygen that remains dissolved in water. The respiratory organs are Gills. There are two gill chamber one on either side of the pharynx. Each chamber bears 4 gills arranged along the anteroposterior axis of the body. Each chamber is covered by operculum. The mechanism of respiration resembles that of Bhetki.
Lata can remain alive for some time on land and by using aerial oxygen with the help of its Accessory respiratory organ. The accessory respiratory organ is a sac-like structure derived by the out pushing of the pharynx. On the dorsal side of each gill chamber is located one such organ. The internal lining of the organ being highly vascular acts as respiratory surface.
The heart is composed of a thin-walled sinus venosus, an oval muscular ventricle and an auricle. The conus arteriosus is absent and this region, like that of Bhetki, is marked by the presence of a pair of valves guarding the entrance of the bulbus aorta. The bulbus aorta is non-contractile and represents the dilated base of the ventral aorta. The bulbus aorta and the ventral aorta are covered by a tough membrane.
Afferent Branchial System:
The deoxygenated blood from the ventricular cavity is conveyed through a stout median ventral aorta to the gills for aeration by four pairs of afferent branchial arteries. All the four pairs of the afferent branchial arteries have independent origin from the ventral aorta.
The first and second pairs of the afferent branchial arteries are simple straight arteries leading to the corresponding pairs of gills. While the third and fourth afferent branchial arteries of each side cross each other forming a loop after their origin from the ventral aorta (Fig. 135).
Efferent Branchial System:
The efferent branchial arterial system is peculiar. The first and second pairs of efferent branchial arteries are lacking (Fig. 136.). The third efferent branchial artery on each side receives oxygenated blood from the third gill of that side and gives off a cephalic artery. This artery runs forward and bifurcates into an external carotid artery and an internal carotid artery.
A transverse artery acts as a connecting bridge between the third and fourth efferent branchial arteries of the two sides. The left fourth efferent branchial artery gives origin to the dorsal aorta. The coeliacomesenteric artery originates from the point of union of the transverse artery and the right fourth efferent branchial artery.
Two subclavian arteries arise independently on the two sides and each divides into two arteries— the pectoral artery supplying the pectoral fin and a pelvic artery to the pelvic fin. The dorsal aorta occupies a mid-dorsal position and runs posteriorly up to the tail as caudal artery. Along its course it gives off paired segmental arteries, gonadal arteries and renal arteries (Fig. 136).
The absence of first and second pairs of efferent branchial arteries in Lata is difficult to interpret. The oxygenated blood from the first two pairs of the gills is possibly drained into the supra-branchial cavity directly through some sort of capillary networks. These capillary networks together with that of the supra- branchial cavity unite to form an artery which joins with the cephalic arteries.