Aboral End

Introduction

Symmetry describes the harmony or agreement between an organism's dimensions. Since most living species share the form of symmetry they exhibit with their most recent common ancestor, symmetry is employed in the animal kingdom to both classify organisms and identify their common ancestors.

Animal Characterization Using Body Symmetry

Based on the symmetry of their bodies, animals and plants can be categorized. The term "symmetry" specifically refers to a correspondence of bodily components on either side of a dividing line or dispersed around a central point or axis that are similar in size, shape, and relative location.

True animals can be roughly categorized into three groups at the most fundamental level, according to the degree of symmetry in their body plans: radially symmetrical, bilaterally symmetrical, and asymmetrical.

The three basic body symmetries are −

• Radial

• Bilateral, and

• Asymmetry

Radial Symmetry

When body parts are arranged around a central axis, they are said to be in radial symmetry. The distinct requirements of each type of symmetry are perfectly matched to an animal's individual lifestyle. Animals and plants with radial symmetry have top and bottom surfaces but no left or right sides, front, or rear.

The "oral side" and the "aboral side" are two terms that can be used to distinguish between the two sides of an animal that is radially symmetric. Radial symmetry is a rare trait among animal groupings, while phylum Porifera (sponges) is the only one with it. Animals in the phylum Ctenophora (comb jellies) and Cnidaria have body designs that exhibit this type of symmetry (corals, sea anemones, and other jellies). These aquatic organisms, which may be stationary or merely capable of slow movement or floating, can perceive the surroundings equally from all angles because to radial symmetry.

The body's components are evenly distributed around a central axis in radial symmetry. The main axis is heteropolar, meaning that it has opposing ends, one of which is called the oral end or anterior end and contains the mouth, while the other is called the aboral end or posterior end and forms the animal's back end and may carry the anus. The top and bottom of the body are formed by this type of symmetry. The human body does not have left or right sides.

Alternatively known as the oral and aboral ends, the top and bottom sides of the body are both sides of the mouth. The echinoderms and cnidarians (which include jellyfish, sea anemones, and coral) have radial symmetry (such as sea urchins, brittle stars, and sea stars). The excretory opening for removing waste from the body is located on the aboral end of these organisms. In addition to excretory structures, these creatures' aboral ends have additional characteristics. These structures may take the shape of statocysts, which serve a protective purpose.

Bilateral Symmetry

Bilaterally symmetrical organisms have nearly identical left and right sides. A butterfly, crab, or the human body are examples of animals that exhibit bilateral symmetry because they are divided into two mirror-image, right and left halves along a sagittal plane. The "head" and "tail" (anterior vs. posterior), front and back (dorsal vs. ventral), and right and left sides are all present in animals with bilateral symmetry.

Cephalization, which refers to the accumulation of an organized nerve system at the animal's anterior end, was made possible by the evolution of bilateral symmetry and the resulting construction of anterior and posterior (head and tail) ends. Except for those with radial symmetry, all true animals are bilaterally symmetrical.

Bilateral symmetry is exhibited by all vertebrates. The following animals have bilateral symmetry −

• Insects

• Fish

• Humans

• Dogs

• Lampreys

• Worms

• Amphibians.

Bilateral symmetry permits streamlined and directional motion, in contrast to radial symmetry, which is better suited for lifestyles that involve little or no movement. In terms of evolution, this basic kind of symmetry encouraged active movement and raised the intricacy of resource-seeking and predator-prey relationships.

Sea stars, sand dollars, and sea urchins are examples of Echinodermata animals, which have bilateral symmetry as larvae but exhibit radial symmetry as adults. Secondary radial symmetry describes this. They are regarded as having bilaterally symmetrical characteristics since it is thought that they descended from creatures with this trait.

Asymmetry

An organism that is considered to have asymmetry has no symmetry at all, regardless of how it would look cut on any axis or plane. These organisms do not have separate compartments to perform their body functions. Some species of sponges, which are among the most rudimentary creatures in the animal realm, are asymmetrical.

An organism that is considered to have asymmetry has no symmetry at all, regardless of how it would look cut on any axis or plane. These organisms do not have separate compartments to perform their body functions. Some species of sponges, which are among the most rudimentary creatures in the animal realm, are asymmetrical.

Flounders and hermit crabs are two examples of animals that exhibit asymmetry. The eyes of adult flounders are on the same side. Hermit crabs have a sizable claw on one side. The Thanksgiving Cactus which contains flowers, has asymmetrical, erratic blooms.

What is Aboral End in Organisms?

The side of the body that is opposite the mouth of the same body is referred to as the aboral end. The mouth signifies the oral end and the anus indicates the aboral end in organisms that have both.

Examples of Organisms with Aboral Ends

Aboral End of Ctenophora

Ctenophores, also referred to as comb jellies, are small, transparent, and predominately pelagic marine predators. Only marine environments—from arctic to tropical, on land or at sea, and from very shallow to extremely deep ocean depths—are home to ctenophores. There are probably between 100 and 150 different species of ctenophores in the oceans of the world.

They have three layers, oral-aboral axis of symmetry, and biradial symmetry. Comb jellies are gelatinous zooplankton that looks a lot like jellyfish but are different from them in a number of significant ways.

These bioluminescent aquatic organisms have openings at both ends of the gut (oral and aboral) and digestion is intracellular. The gut is separated into digestive and distributive areas. Cilia are well developed and have several uses. They are responsible for locomotion and play a role in sensory reception as well.

Aboral End of Cnidaria

The phylum Cnidaria includes sea anemones, jellyfish, coral, hydra, and others. These species have radial symmetry. The gastrovascular cavity's oral end is where the mouth opens. The aboral end is the opposite end. However, the aboral end lacks an anus. The axis of symmetry centers the radial symmetry of cnidarians and connects the oral and aboral poles.

Tentacles encircle the area of the mouth. The presence of nematocysts is one of these creatures' distinguishing characteristics. The Cnidaria often have two forms throughout their whole life cycle − sessile and motile polyp.

The sessile polyp has a cylinder-shaped anchor at its aboral end, which gives it stability. The motile form, also known as the medusa form, features tentacles at the sides of the body and an upward-facing convex aboral end and a bottom-facing concave oral end.

Aboral End of Starfish

Echinoderm is the phylum to which the starfish belongs. At the opposite end of the mouth is the starfish's aboral surface. It is located at the top of the body. On the underside of the body is the oral surface, which includes the mouth.

The following elements make up the starfish's body.

• Five eyespots are present.

• Each of the five rays of the starfish has one of these eyespots.

• Tube feet, or podia, are seen on the underside of the body. These podia assist starfish in moving from one location to another.

• The starfish has five to ten rays, roughly. If accidentally lost, these rays can be regenerated.

• The anus is a last component of the starfish's digestive system. The anus expels the waste material. However, the body absorbs the majority of the waste product. The aboral end only removes a minor portion of the waste.

FAQs

Qns 1. What are aboral surfaces?

Ans. Surfaces away from or opposite the mouth are referred to as aboral surfaces.

Qns 2. What is the function of the aboral end?

Ans. The excretory opening for removing waste from the body is located on the aboral end of these organisms. The aboral end of these creatures also has other characteristics in addition to the excretory structures. Statocysts, which serve a protective purpose, can be one of these structures.

Qns 3. Does a starfish have an aboral surface? Where is it located?

Ans. The starfish's aboral surface is at the other end of its mouth. It is positioned at the top of the body.