What is common in the diet of lancelets and mollusks: a comparative characteristic

In this article you will find answers to questions about how mollusks feed on what is common in feeding lancelets and mollusks. These organisms are not compared by chance. They have many similarities in common, many of which relate to physiological processes.

Lancets and mollusks: aquatic inhabitants

Lancetnik is the most primitive animal of the Chordovye type . But his position in the system of the organic world was not easy to determine. Scientists took him for a clam and called a lancet-like slug. Only 60 years after the discovery of this animal, it became known that they are a representative of a completely different type. Indeed, the appearance of lancelets and mollusks is very easy to confuse. They have a soft body that is not segmented. But the lancelet has an axial skeleton inside it, called a chorda. Molluscs are deprived of it.

What is common in feeding mollusks and lancelets? First of all, this is the common habitat in which they extract it. These organisms live in water. The lancet prefers the shallow waters of the seas. He leads a semi-mobile lifestyle, one end of the body buried in the sand.

Depending on the species mollusks can live in the seas, fresh water bodies, on land. For example, a grape snail, which is a representative of the class of gastropods, can be found on the forest litter. But the cephalopods live exclusively in the seas and oceans. Bivalves include bezbuki, perlovitsy, dreiseny, mussels, oysters, shipworms, tridacty. They live only in water.

What is common in feeding mollusks and lancelets

Lancetta on the method of nutrition has the most similar features with representatives of bivalve mollusks. Gastropods scrape off the algae from the substrate. They do this with a grater, a tongue covered with horny denticles. But cephalopods are active predators. They attack fish and crustaceans.

Primitive chordates are not adapted to this. What is common in the diet of lancelets and bivalves? They are all heterotrophs, which absorb suspended organic matter from water. Similar ones are called filters.

Structure of the digestive system

To find out what is common in the diet of lancelets and mollusks, it is necessary to consider the structure of the digestive system. It is an end-to-end type. In the lancelet, the digestive system is represented by a through intestine, which forms a hepatic outgrowth. It begins with a mouth opening surrounded by tentacles. The next section is the pharynx, permeated with gill slits.

In mollusks, the digestive system also begins with the mouth, and ends with the anal. The latter opens into the mantle cavity. The middle section of the intestine forms an extension called the stomach. Another example, which shows that common in the diet of lancelets and mollusks, is the presence of specialized glands. In the first they are represented only by the liver. And mollusks also have salivary glands, the ducts of which open into the pharynx. The composition of this substance in different classes may differ. For example, in cephalopods, in addition to enzymes, in the saliva there are toxins that kill prey.

Source of power

What else is common in feeding lancelets and bivalves? This is the food itself. As it enters the body through filtration, it includes microorganisms, blue-green algae, infusoria, small crustaceans, eggs and larvae of other animals. They all form the basis of zooplankton and phytoplankton. Mineral substances that are dissolved in water are also absorbed by organisms. This way of feeding is passive. In many ways it was he who determined the sedentary lifestyle of the lancelet and bivalve mollusks.

Filters

The most important feature, which determines what is common in the diet of lancelets and mollusks, is, of course, filtration. For its implementation, shellfish have siphons. These are two openings in the back of the body that open into the mantle cavity. Through the bottom siphon, water enters it with the particles of food suspended in it. And through the top is already released in pure form.

The filtration in the lancelet is closely related to breathing. Cilia, located in the pharynx and on the septum between the gill slits, create a constant current of water. Here, gas exchange takes place.

So, we examined what is common in the diet of lancelets and mollusks. These animals have a similarity in the general plan of the structure of the digestive system. It is an end-to-end type. It includes a tubular differentiated intestine, as well as digestive glands. The organisms that we have considered in our article are heterotrophic filterers. They feed on the water-weighed organisms that they pass through themselves. Such a method is passive, causing a sedentary lifestyle of these animals.