Question

notes on sacculina in detail

Answer 1

i) Delage (1884) carried out many re­searches on Sacculina carcina.

(ii) Among others, Smith (1906), Boschema (1931) worked on parasitic cirripeds.

(iii) Smith (1910-1911) and Giard (1911- 1913) have shown that gonadial tissues of a male crab undergo drastic change while females remain unchanged.

(iv) Day (1935) was the first man reported the life history of Sacculina. Later Foxon (1940) elaborated the observation of Day.

Systematic Position:

Phylum – Arthropoda (Gk. arthron = joint, podos, genitive of pous = foot)

Class – Crustacea (L. crusta = a hard shell)

Subclass – Cirripedia (L. cirrus = curled; pedis – foot)

Order – Rhizocephala (Gk. Rhizo. Pre­fix from Greek rhiza – a root, kephale = head)

Genus – Sacculina (L. Sacculus = a small bag) [Gk. = Greek, L. = Latin]

Life History of Sacculina: 

Sacculina lives as a parasite on crab and commonly known as root-headed barcle. The parasitic habit has caused much degen­eracy of different structures in the adult.

The different structures like mouth and anus are absent. It is seen like a soft round tumour on the abdomen of the crab. From this tumour numerous branched filaments are ramified in all the parts of the body of the host except the heart and the gills which are used as nutrient absorbing root-like system from the crab.

The adult Sacculina (Sacculina externa) is characterised by:

1. Loss of segmentation and appendages.

2. All the organ systems are degenerated except the reproductive organs.

3. There is a pair of elongated testes and a pair of ovaries with accessory geni­tal glands, genital atrium and collaterial glands.

4. There is a single nerve ganglion.

5. Sacculina is hermaphrodite.

6. An adult female produces numerous eggs.

7. The mechanism of fertilization is not actually known.

8. There are diverse opinions regarding the process of fertilization. Fertiliza­tion in Sacculina, in all probabilities, is internal.

The adult Sacculina is difficult to recog­nise as an arthropod. The study of its devel­opmental history justifies its inclusion as a crustacean. The life history of Sacculina is extremely interesting (Fig. 18.30).