LARVAE OF PORIFERA, COELENTERATA AND PLATY HELMENTHES

Published in Zoology
Tuesday, 27 June 2017 13:26
LARVAE OF PORIFERA
 
1. Parenchymula (Stereo- gastrula) - Leucosolenia
2. Rhagon - Higher sponges
3. Amphiblastula - Sycon
 
Sycon thumb15

LARVAE OF COELENTERATA
 
1. Planula - Obelia, Sea Anemone
 
Obelia planula larva thumb9
 
2. Ephyra - Aurelia (Jelly fish)
 
ephyra larvae thumb15
 
3. Actinula - Some hydrozoan
4. Anthocynathus - Coral fungia
 
Coral fungia thumb15
 
5. Conaria - Velella
6. Hydratubia - Aurelia
 
Aurelia ephyra larvae thumb11
 
LARVAE OF PLATYHELMENTHES
 
1. Muller’s Larva - Polycladida of Turbellaria
2. Liverfiuke (Fasciola) Miracidium - L Platyhelminths
3. Redia - Liverfiuke (Fasciola)
4. Sporocyst - Liverfiuke (Fasciola)
5. Cercaria - Liverfiuke (Fasciola)

PORIFERA LARVA – PARENCHYMA AND AMPHIBLASTULA LARVA

Published in Zoology
Monday, 17 April 2017 20:49
Parenchyma Larva:
 
Parenchyma Larva is seen in the life history of Leucosolenia. The life history of Leucosolenia was described by Metchnikoff in 1879 and Minchin in 1896.
 
The fertilisation is internal. Zygote undergoes holoblastic cleavage and develops into coeloblastula. It shows a hollow cavity covered by a single layer of cells.
 
Many amoeboid cells enter the central cavity and it becomes   parenchymuia larva (or) stereogastrula.
 
This larva shows an outer layer of flagellated cells and a mass of internal amoeboid cells. At the posterior and non-flagellated cells are present called archaeocytes. This larva swims in the water for sometime. Then attaches to a suitable substratum.
 
Parenchyma Larva-Metamorphosis: The amoeboid ceils from interior will come outside and give dermal layer and mesenchyme. The flagellated cells will surround the inner spongocoel. At its apex an osculum is formed. It grows into adult sponge.
 
Amphiblastula Larva:
 
Amphiblastula larva is a typical free swimming larva formed in Sycon sponge reproduction. 
  1. It is ova! in shape.
  2. It shows small micromeres with flagella on one side.
  3. The other half of the larva shows large macromeres.
  4. The larva comes out of the sponge through osculum.
  5. It swims in the water for some time with the help of flagella.
Amphiblastula  undergoes metamorphosis. The macromeres will overgrow the micromeres and gastruiation takes place. Because of which flagel­lated cells become internal Then it attaches to a substratum. It becomes small individual.

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