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In this article we will discuss about the structure of Sacculina with the help of a diagram.
1. This is a specimen of sacculina—“the sucking root barnacle” an ectoparasite on crab.
2. It is in the form of a flat, fleshy and sac-like structure having only the gonad. It is found attached to the ventral surface of crabs between thorax and abdomen.
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3. The various body divisions (segmentation), almost all appendages, eyes, mouth, anus & alimentary canal etc. are degenerate in adult as a result of parasitic mode of life.
4. There is present a small peduncle below, which sends five highly branched and anastomosing filaments into the body of host to absorb nourishment.
5. It is hermaphrodite and its development is completed through a “nauplius larva” which changes to cypris larva which alone is capable of infesting new hosts.
Note:
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To begin with, a cypris larva of sacculina attaches to a normal crab, discards its shell, penetrates inside and gets converted into a mass of cells and is attached to the intestine of host It remains there till the crab molts next, whence a part of it protrudes out as sac-like structure containing an ovary. The remaining internal parts get branched, filamentous and penetrate into different organs of the host.
