Brachiopods

Brachiopod

The conserved remains of the plants, animals and the other living organisms of the bygone eras of the geological past, mostly older than 10,000 years are known as Fossils.  These fossils are obtained inadvertently or excavated by digging, and preserved for prosperity for research. There are mainly two kinds of fossils, body fossils, which retain the remains of the body parts of the animals or organisms that lived in the past, and the trace fossils that include only the traces or signs of the organism that lived in the past, like footprints, burrows and tracks.

The Brachiopod belongs to the Brachiopoda phylum and consists of about 300 different species in that family. It is a marine organism with a hard shell in the upper and lower portion unlike the valve arranged on left and right side in Bivalves. It is very rarely encountered, but it doesn't mean that it is very extinct. It prefers cold water and can be seen in the deep ocean habitat of the polar region.  It has a feeding organ in a coiled shape known as Lophophore which is protected by the shells. In the Brachiopod, you have 2 divisions known as Articulate and Inarticulate Brachiopod.

History

The Brachiopod has a long history similar to the Bivalve. The word Brachiopod is acquired from a Greek word which means "arm" and "foot". It is also referred to as "Lamp shells" because of its shape that resembled the Roman lamps of ancient times. Around 500 to 550 million years ago, this organism inhabited the Earth. The Caribbean Explosion led to the appearance of its fossilized forms near the rocky places. It was found in abundance from the Ordovician Period throughout the Permian age. It was the most abundant species during the Paleozoic Era, which became extinct after the Permian period. It was the most common fossil found on the rocks during those periods.

Reproduction

In the Brachiopod species, there are separate sexes, except 3 species belonging to this genus. The funnel shaped excretory organ known as Neprhridia on both sides of the Brachiopod'smouth discharge the sperms and eggs into the mantle cavity. Usually the fertilization process takes place outside the valves, but in some cases, the young ones develop in the brood pouches present in the female Brachiopods. The fossils of Brachiopods are often seen with internal cavities, which seem to be the brood chambers present in the living Brachiopods. The eggs, thus discharged settle down to the bottom, and transforms into a free-flowing larva. This stage in Articulate Brachioppod continues only for a few days, whereas in the Inarticulate Brachipod, the free-flowing larva stage continues for more than 6 weeks and forms a new Brachiopod.

Habitat

The Brachiopods are usually found in the cold polar marine regions.  There are around 300 species of Brachiopod and is widespread in the deep seas and oceans. It is the highest populated organism in the Antartica region. It is also commonly found in the South Australian, Japanese and New Zealand waters.  Some rare species of Brachiopod have also been found on the South African coast proving its presence in the Indian Ocean. Around 12 types of species are found in the West Indian and Caribbean waters. The other common places where the Brachiopods are found is the east and west coast of the Atlantic Oceans, British Isles, Mediterranean sea, Hawaii and the west coast of America. The largest species of Brachipod is found on the coast of Argentina and Chile.

Features

The Brachiopod can be seen in many sizes and forms those changes according to the change in habitat. Most of the species of the Brachiopod are too small in length and width. Some can be found about  1 inch long, whereas some are minute creatures measuring to 1 mm. Fossils of giant Brachiopod are also found which measured about 15 inches in width. Now, as the specie is getting extinct, the variety is also diminishing but in the past, a wide variety of physical properties could be found in the Brachiopod specie. Still, there are some tongue shaped and lengthwise oval shaped Bradhiopods. Some varieties have a soft and spiny surface, whereas some have rigid textures. The recently found Brachiopods are white or light yellowish in color but exhibit red spots or stripes over it. It is also found in dark green, pink and brown colors. The Brachiopod found in the tongue-shaped structure has a brown shade with green splotches over it.

Feeding Mechanism

The anterior portion of the valves consists of the Lophophore which looks like a circle bordering  the mouth with small tentacles. The tentacles consist of small cilia, which help to draw the food from the surroundings by beating and creating a water flow towards the mouth. This causes the plankton to reach the Lophophore and once it gets caught inside the Lophophore, then it easily passes through a special groove which directly reaches the mouth. From the mouth, the food reaches the stomach and then the intestine. Other than food, the water current also provides oxygen for the organism to breathe. But oxygen use of Brachiopods is comparatively lesser than the Bivalves.

Circulation and Respiration

The Braciopod consist of mantle and Lophophore for the purpose of respiration. They carry out the process of oxygen intake and exhale carbon-dioxide. The fluids present in the coelom are the carrier of oxygen to all the body parts. When the coelom contracts, the fluid starts moving through the mantle. It is also driven by the beating of the small cilia. Some species possess the Respiratory Pigment Hemerythrin which helps partially to supply the oxygen into the coelomocyte cells. Usually the oxygen intake of the Brachiopods is very low compared to the bivalve species.

Fossil Records

Till date, fossils of the Brachiopod, counting to around 12,000 have been found, which is classified into about 5000 genera. Some modern fossils are found that have 100 mm length and some had 200 mm width. The fossils found in the Caribbean areas were first seen to comprise of the inarticulate Brachiopod, and later, the articulate Brachiopod started to emerge. Researchers used the Brachiopod to predict the climatic changes that took place in the era of the Paleozoic.  During the Ordovician period, the global temperature reduced and it caused a tremendous difference of temperature between the poles and the equators which led to the creation of different varieties of Brachiopod, which was revealed from the fossils collected at different altitudes. Similarly warmer periods led to very minute changes and almost the same species of Brachiopod fossils were acquired from the Silurian period.