What is the Difference Between Leeches and Bloodsuckers

The main difference between leeches and bloodsuckers is that leeches are free-living worms that are hematophagous whereas bloodsuckers are the animals that practice hematophagy, feeding on blood. Furthermore, around 75% of all species of leeches are hematophagous while some mammals, birds, fish, nematodes, and arthropods are bloodsuckers. 

Leeches and bloodsuckers are two types of creatures that practice hematophagy. Generally, blood is a fluid tissue rich in proteins and lipids. Blood can be taken from an organism without great effort. 

Key Areas Covered 

1. Leeches
     – Taxonomy, Anatomical Features, Importance
2. Bloodsuckers
     – Taxonomy, Anatomical Features, Types, Importance
3. What are the Similarities Between Leeches and Bloodsuckers
     – Outline of Common Features
4. What is the Difference Between Leeches and Bloodsuckers
     – Comparison of Key Differences

Key Terms 

Annelids, Bloodsuckers, Hermaphrodite, Hirudin, Leeches, Pharynx, Proboscis

Leeches – Taxonomy, Anatomical Features, Importance 

Leeches are segmented worms or annelids of the subclass Hirudinea. They are free-living and can be either parasitic or predatory. Generally, leeches have soft, muscular bodies, which can lengthen and contract. Most leeches live in freshwater habitats, but, some also live in terrestrial and marine habitats. Moreover, they are hermaphrodites, having male reproductive organs mature first and female reproductive organs mature later.

Figure 1: Leech

Furthermore, the two main types of mouthparts found in bloodsucking leeches are the protrusible pharynx (a proboscis) or a non-protrusible pharynx. The non-protrusible pharynx may or may not contain jaws. In leeches with a proboscis, there are three blades, which leave a Y-shaped incision on the skin of the host. Their mouth occurs behind these blades. Moreover, these leeches secrete a protein called hirudin prior to the sucking of blood. Generally, hirudin occurs in the saliva and serves as an anticoagulant, preventing blood coagulation. For instance,  Hirudo medicinalis is a medicinal leech used in the treatment of joint diseases as well as the extremity vein diseases. However, it can only feed on twice a year and it takes months to digest blood.  

Bloodsuckers – Taxonomy, Anatomical Features, Types, Importance 

Bloodsuckers are animals that practice hematophagy. As they are hematophagous animals, they feed on blood. Moreover, blood is rich in nutrients and also, it is easy to take up blood from the body. Generally, hematophagy is a preferred form of feeding mechanism in worms and arthropods. Therefore, some intestinal nematodes and most leeches that are free-living are hematophagous. Moreover, insects including sandfly, blackfly, tsetse fly, bedbug, assassin bug, mosquito, tick, louse, mite, midge, and flea are examples of bloodsuckers. Some arachnids are also bloodsuckers. On the other hand, some mammals including vampire bats, some birds including vampire finches, hood mockingbirds, and Tristan thrush, and some fish including lampreys and candirus are bloodsuckers.

Figure 2: Bedbug – Cimex lectularius

Moreover, bloodsuckers have especial mouthparts and biochemical solutions to facilitate their action. Here, the main type of mouth part is the proboscis, which is a fine, hollow, needle-like structure. Some bloodsuckers such as vampire bats have incisor teeth to cut the skin. Generally, bloodsuckers take blood either directly from veins or capillaries. Moreover, they have specific biochemical solutions in their saliva. These solutions may either serve as anesthesia, which reduces pain sensation in the host or anticoagulants, which prevent blood coagulation. Also, some of these chemicals may induce vasodilation and prevent inflammation. 

Figure 3: Arran brown (Erebia ligea) and Water ringlet (Erebia pronoe) – Bloodsucking Butterflies

Bloodsuckers – Classification

Bloodsuckers can be divided into two groups based on their behavior of sucking blood. That means; some bloodsuckers are obligatory hematophagous animals while others are facultative hematophagous animals. Obligatory hematophagous animals do not survive on any food other than blood. For example, leeches and human bed bug are obligatory hematophagous animals. On the other hand, facultative hematophagous animals are one of the sexually mature forms depending on other sources of food than blood. For example, only female mosquitoes feed on the blood of vertebrates. Significantly, these bloodsuckers can serve as intermediate hosts for the transmission of vector-borne diseases as well. 

Similarities Between Leeches and Bloodsuckers 

• Leeches and bloodsuckers are animals or some primitive animals that feed on the blood of different host animals. 
• Generally, this process is known as hematophagy. 
• Those hematophagous animals have either mouthparts or chemical agents to penetrate the vascular structure of the host animal. 
• Moreover, their saliva contains hembiochemical solutions to overcome natural hemostasis (blood coagulation), vasoconstriction, inflammation, and pain sensation in the host.  
• Additionally, they have complementary biological adaptations to locate their host including special physical or chemical detectors for sweat components, CO2, heat, light, movement, etc.  

Difference Between Leeches and Bloodsuckers 

Definition 

Leeches refer to the segmented worms of the subclass Hirudinea, and they are either parasitic or predatory, while bloodsuckers refer to the animals that practice hematophagy. Hence, this is the main difference between leeches and bloodsuckers.

Types 

Around 75% of all species of leeches are hematophagous, while some mammals, birds, fish, nematodes, and arthropods are bloodsuckers. 

MouthParts 

Moreover, leeches have either protrusible pharynx or non-protrusible pharynx, while bloodsuckers have either proboscis or sharp incisor teeth to suck blood. Thus, this is also an important difference between leeches and bloodsuckers.

Preventing Blood Coagulation 

Another difference between leeches and bloodsuckers is that leeches use a protein called hirudin as an anticoagulant, while bloodsuckers have hembiochemical solutions to prevent blood coagulation. 

Obligatory or Facultative Hematophagy 

Besides, while leeches are obligatory hematophagous animals, bloodsuckers can be either obligatory or facultative hematophagous animals. 

Conclusion 

Leeches are the obligatory hematophagous animals that suck blood. Moreover, they are segmented worms classified under the subclass Hirudinea. They often have proboscis to suck blood from its host. On the other hand, bloodsuckers are animals that practice hematophagy. They include mammals, birds, fish, arthropods, and nematodes. Also, they have different mechanisms and biochemical solutions to suck blood while preventing other biochemical reactions in the host. However, some bloodsuckers are obligatory while others are facultative. Therefore, the main difference between leeches and bloodsuckers is the type of animal and other features of hematophagy. 

References:

1. “Leech.” Encyclopædia Britannica, Encyclopædia Britannica, Inc., 4 July 2011, Available Here.
2. “Hematophagy.” Wikipedia, Wikimedia Foundation, 7 Apr. 2019, Available Here.

Image Courtesy:

1. “Sucking leech” By GlebK – Own work (CC BY-SA 3.0) via Commons Wikimedia   
2. “Cimex lectularius” By “CDC/ Donated by the World Health Organization, Geneva, Switzerland.” (Public Domain) via Commons Wikimedia   
3. “Blood feeding butterflies 5362” By © Túrelio , 2007 (CC BY-SA 3.0 de) via Commons Wikimedia