Photo courtesy of Kate GardinePhoto courtesy of Kate GardineClose up of a Bighead:  Photo courtesy of Kate Gardiner



If there is one thing for certain about Bighead carp it is their large desire to feed!

Close-up of Carp Mouth - Photo courtesy of GLFCThe Bighead carp is classified as heterotrophic, which basically means that they must consume another organism in order to obtain nutrients and energy.  If you would like to see an example of a heterotrophic organism click here.  The most common organisms that are eaten by by the Bighead carp are zooplankton and  algae.  They are also known to feed on aquatic insects and other larval forms of organisms.  One common type of algae that they are well known for feeding on is the blue-green algae. 

Want to see an example of blue-green algae?  Click here to find out!  Photo courtesy of Kate Gardiner

How do Bighead carp acquire these tiny forms of food?  These fish have exploited the methods known as filter feeding in order to obtain their food.  Filter feeding is the straining of water in order to obtain tiny organisms to consume.  In order to filter the zooplankton and algae Bighead carp will use gill rakers.  Gill rakers are very long and condensed comb-like structures which allow water to pass through, but still trap the food source to be eaten.  Bighead carp have a large appetite and must take in many of these small organisms.  They must expend some energy in order to obtain food, but lucky for Bighead carp it is fairly easy to filter feed.  Once food is captured what happens next?  These fish do the common procedure of ingest and then digest.  This species have a straight through digestive tract. 

Lake Calumet, IL - Photo courtesy of Asian Carp Regional Coordinating CommitteeThere is one thing unique to this digestive tract though.  Bighead carp do not have a true stomach so digestion and intake occurs in the intestines.  The lack of a stomach prevents efficient digestion so much of the food source taken in is not actually absorbed.  This is why the Bighead carp is always eating, so there is a  constant flow of food for the fish to digest to compensate for inefficiency in nutrient uptake.  This explains why Bighead carp appear to have such large appetites and "out-eat" other aquatic organisms competing with them.

Photo copyright 2012 Minnesota DNRAn issue that Bighead carp and many other multicellular organisms need to overcome is the supply and demand of cells in a large volume.  As an effect of having larger volume, these organisms must have a system to transport nutrients, gas, and waste products between cells.  This system is known as the circulatory system.  The circulatory system in Bighead carp is classified as a closed system, where blood never leaves the circuit.  The advantage to a closed system is a faster and more efficient exchange.  What makes up this organisms circulatory system?  In Bighead carp, like other fish, a two-chambered heart pumps the blood to the gills where oxygen diffuses into the blood, then the oxygenated blood is taken to the rest of the cells of the body, and finally the deoxygenated blood continues back to the heart to be pumped through the single circuit again.  The two-chamber Photo courtesy of T. Lawrence, GLFCheart is made up of an atrium and ventricle where blood at low pressure enters through the atrium of the heart and is pumped out of the ventricle at high pressure.  There is another important part to the closed system; the capillaries.  Capillaries are  no larger than the size of a red blood cell and have ultra thin walls to allow for diffusion of oxygen.  This enables body cells to supplied with extreme precision. 

There is an adaptation allowing for improved gas exchange in Bighead carp and many other fish.  This adaptation in the gills is known as countercurrent exchange.  Countercurrent exchange is where water flows across the gills in one direction, as blood moves through the gills in the opposite direction.  This countercurrent flow creates a diffusion gradient where the gas exchange is maximized.  As you know gas will move from an area of high concentration to low concentration.  In the case of the fish gills the water has a high concentration of oxygen and the blood moving through the capillaries in the gills has a low concentration.  This countercurrent flow will always have a higher concentration of oxygen in water than in the blood of the fish so the diffusion of oxygen is maximized.  See the graph below to visualize this.

Photo courtesy of Joe, Wikimedia

Example of Concurrent Vs. Countercurrent Exchange

Now that you know how Bighead carp obtain nutrients, click here to learn about their reproduction.

Top of page