EARTHWORM

Earthworms are ecosystem engineers whose impact on soil carbon dynamics is critical to understanding how forest soils can act as carbon sinks or sources of CO2 emissions. Using their digestive enzymes, earthworms breakdown the organic layer of forest soils and transport plant-derived carbon into deeper soil layers. They emit CO2, but they can also help to stabilise carbon by forming protected clusters of carbon. There is no agreement on whether earthworms mineralize or stabilise a greater amount of carbon than other organisms. There has been little research into how earthworms affect carbon dynamics in forests, and there is a need for more research in this area.

Morphology of Earthworm

• They have a tube-like structure or a cylindrical shape, and their bodies are reddish-brown in colour with reddish-brown segments. 
• The body has been separated into small parts for ease of movement. The dorsal side of the body is distinguished by a dark line of blood veins, while the ventral side is distinguished by the presence of genital holes. 
• The anterior end is distinguished by the presence of the mouth and the prostomium (an organ that aids in digging).
• The glandular tissue known as clitellum is present in segments 14-16 of a grown earthworm, and it is this tissue that allows us to distinguish between the mouth and tail ends. With respect to the clitellum, the body is split into three segments: the preclitellar segment, the clitellar segment, and the postclitellar segment.
• Earthworms are hermaphrodites, which means that they have both male and female sex organs in their bodies. Segments 5-9 are responsible for accommodating four pairs of spermathecal apertures each. 
• The female genital pore is located at the 14th segment, and a pair of male genital pores are located at the 18th segment of the genital pore segment. 
• The earthworm’s body is made up of S-shaped setae, which aid in its propulsion and movement. Setae can be found in every segment, with the exception of the first, final, and clitellum segments.

Anatomy of Earthworm

The earthworm’s body wall is covered by a thin, non-cellular cuticle on the outside of its body. A layer of epidermis is sheathed beneath the cuticle, which is followed by two muscle layers and the coelomic epithelium (inner layer) before the cuticle is shed again. There is a single layer of glandular columnar epithelium that makes up the epithelium of the mouth.

Digestive System

The alimentary canal is a long tube that connects the first to the last section of the body’s digestive system. Earthworms eat the leaves and decaying organic matter that has been mixed with the soil as their food source.

The alimentary canal and its secretion differ from those of other creatures in that they are influenced by the type of diet consumed. This canal begins at the mouth (buccal or oral cavity) and extends via the pharynx, oesophagus (5-7 segments), muscle gizzards (8-9 segments), stomach (9-14 segments), intestines, and ultimately finishes at the anus. During their journey through the alimentary canal, the food particles are gradually digested as they pass through the numerous compartments.

The soil particles and other debris are ground down by the muscular gizzards, and the humic acid in the hummus is neutralised by the calciferous glands that are located in the gizzards and the stomach. The presence of typhlosole (26-35 segments) in the gut increases the amount of surface area available for absorption.

Earthworms have a closed circulatory system that is composed of a heart, blood arteries, and capillaries. The segments 4-6 of the circulatory system are made up of blood glands that aid in the formation of blood cells and haemoglobin.

Earthworms do not have a well-developed respiratory system because they do not breathe through their skin. Diffusion is the mechanism through which they breathe through their damp skin.  

Excretory System

The excretory system in earthworms is made up of coiled tubules that govern the volume and composition of the bodily fluids and, as a result, serve as the excretory organ for the creatures. Nephridia are divided into three groups: septal nephridia (15-last segments), integumentary nephridia (3-last segments), and pharyngeal nephridia (final segments) (4-6 segments). Wastes and excess fluid are delivered to the nephridia and expelled by the digestive tube, which is attached to the funnel.

System Nervous System

Control of sensory input and muscle reactions is exercised over an organism’s ganglia, which are organised in a segmented fashion throughout. The earthworm’s nervous system is composed of these ganglia, which are located on the paired nerve cord.

Sensory System Although earthworms do not have eyes, they do have specialised receptor cells that allow them to detect changes in their environment. Sensory organs and chemoreceptors that are specifically designed for them allow them to respond flawlessly to stimuli. The earthworm’s sensory system is located in the front region of the body. Earthworms are nocturnal creatures. 

Reproductive System

Earthworms are bisexual in their reproductive system. As a result, each human possesses both the male and female reproductive systems within themselves.

The male reproductive system is made up of two pairs of testicles (10-11 segments each), a vasa deferentia (which extends till the 18th segment), and two pairs of accessory glands (which are located on either side of the testicles) (17th and 19th segments). A pair of male genital holes allow for the opening of the prostate and spermatic ducts (18th segment). Each of the four pairs of spermathecae is responsible for storing the spermatozoa (6-9 segments).

It is made up of a single pair of ovaries and an oviduct in the female reproductive system. A funnel-shaped ovarian funnel runs below the ovaries and connects to the oviduct, which then opens at the female vaginal hole to allow for fertilisation (14thsegment).

CONCLUSION

Earthworms are useful for a variety of purposes other than as fish bait. They are the most important contributors to enriching and improving soil for the benefit of plants, animals, and humans alike. Burrowing earthworms form tunnels in the soil, which aerates the soil and allows air, water, and nutrients to penetrate deeper into the soil. Earthworms are beneficial to the environment because they help to keep the soil healthy. Earthworms devour organic stuff in the soil, such as rotting vegetation or leaves, which they find in the soil. Plants are unable to directly utilise this organic stuff. Following the digestion of organic materials, the earthworm excretes waste from their bodies, which are known as castings. There are numerous nutrients in the castings that the plant can utilise.