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In this article we will discuss about Bugula:- 1. Habit and Habitat of Bugula 2. External Structures of Bugula 3. Body Wall 4. Coelom 5. Digestive System 6. Circulatory System 7. Excretory System 8. Nervous System 9. Reproductive System 10. Development.
Contents:
- Habit and Habitat of Bugula
- External Structures of Bugula
- Body Wall of Bugula
- Coelom of Bugula
- Digestive System of Bugula
- Circulatory System of Bugula
- Excretory System of Bugula
- Nervous System of Bugula
- Reproductive System of Bugula
- Development of Bugula
1. Habit and Habitat of Bugula:
Bugula is a marine dichotomously branched colonial ectoproct. It is a benthonic animal and remains fixed on any foreign body by its slender root filaments. The colony of Bugula may reach the height of several inches. It is a ciliary feeder and lives on micro-organisms, specially the diatoms.
2. External Structures of Bugula:
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The colony of Bugula consists of a number of units called zooids. The form of a complete colony of Bugula is called zoarium. The feeding zooid of such a polymorphic colony is called auto-zooid. The colony communicates with the exterior through an orifice which is devoid of a lid, called operculum. The zooids are cylindrical in shape and have a wide crescentlc mouth at the terminal end (Fig. 20.3).
The zooids have chitinous wall. The ventral side of the wall has a very thin cuticle. The cuticle together with the underlying body wall constitutes a thin chitinous membrane, called the frontal membrane.
The other walls become much thickened. The living parts of the zooids remain immovably attached to the inner side of the zoecia. The living parts consist of two portions, an anterior protrusible and movable part called introvert and the posterior trunk which is attached inside to the inner-side of the zooecium.
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The introvert bears a lophophore having 14 long filiform tentacles. The tentacles are hollow and contain coelomic cavities. The zooids exhibit polymorphism. The colony has some peculiar pedunculate appendages called avicularia (plural of avicularium), resembling closely the miniature head of birds. These are defensive organs.
3. Body Wall of Bugula:
The body wall of Bugula consists of an outer chitinous cuticle called zooecium, an underlying epidermis and an inner peritoneal layer. Muscle layer is absent in this genus.
4. Coelom of Bugula:
The coelom is quite extensive and is incompletely divided into two parts by an incomplete septum. The anterior coelom is small and called ring coelom. The ring coelom is situated at the base of the lophophore and extends to the tentacles.
The trunk coelom is large and occupies the space between the body wall and the alimentary canal. The trunk coelom is traversed by 20-40 pairs of muscle fibres which are regarded as the displaced muscles of the body wall. The coelom also contains funicular cords which suspend the alimentary canal.
5. Digestive System of Bugula:
The alimentary canal is a U-shaped tube. The mouth is situated at the centre of the lophophore. The mouth leads into a spacious pharynx which passes into the oesophagus. The pharynx has an internal ciliated lining.
The inner lining of the oesophagus is non- ciliated. The oesophagus leads into stomach from where projects a conical caecum. The caecum is attached with the body wall by funiculus. The intestine terminates in a round anus situated near the mouth.
6. Circulatory System of Bugula:
There is no blood vessel in ectoprocts and the circulatory system is wanting.
7. Excretory System of Bugula:
Definite excretory organs are lacking in ectoprocts. By introducing vital dyes, it is observed that the coelomocytes, funicular tissues, tentacles and caecum of the alimentary canal help in eliminating the waste products.
8. Nervous System of Bugula:
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The nervous system comprises of a nerve centre in the form of a small ganglion situated in the ring coelom. Nerves are given to the various parts of the body from this ganglion.
The ganglion is continuous with a nerve ring surrounding the pharynx. The nerve ring gives two ganglionated motor and sensory nerve fibres to each tentacle. In this genus, the tentacular nerves form an anastomosis with the nerve ring. Special sense organs are absent.
9. Reproductive System of Bugula:
Asexual reproduction by budding is occasionally found in Bugula. But sexual reproduction is a most common occurrence. It is hermaphrodite. Gonoducts are absent. The ovary is an aggregation of ovocytes and remains enveloped by a thin peritoneal wall.
The testis is located at the proximal end of the body and it may be divided into three or four bunches. It exhibits different stages of spermatogenesis. Development takes place in brood chamber which is produced as an outgrowth of the zooecium called ovicell or oecium.
10. Development of Bugula:
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Self-fertilization has been observed in Bugula. The fertilized egg undergoes holoblastic cleavage and the cleavage plane is of biradial type.
The coeloblastula is formed which eventually transforms into a gastrula by the process of delamination. During the process of production of 64-128 blastomeres, 4 elongated cells become cut off and enter into the blastocoel. These are actually endomesodermal cells which give endoderm and mesenchyme.
The larva is lecithotrophic and called Cyphonautes (Fig. 20.5). The cyphonautes larva in Bugula shows few specialised features, viz., shape is oval, absence of shell, absence of alimentary canal, delimitation of the apical organ by a circular groove.
