Shellfish Breeding and Hatchery Management (2+1)

21.1.3 Developmental stages of Perna indica (Mussel)

The fecundity of mussels is 0.5-10 million. Following external fertilization through cleavage & gastrulation, embryo becomes first larval stage, viz, trochophore which is then transformed to veliger. All embryonic developments take 4 hours after fertilization (Morula stage – 58-60 um).

The shell gland of veliger secretes larval shell, i.e., Prodissconch I which subsequently attains straight hinge or ‘D” shaped stage. The straight to hinge larva measures 70-76 um. This stage is reached in 17-10 hours.

The development of straight hinge larvae to umbo stage is reached on 7^th day. At this stage, larva measures 120-140 um. Eye spot stage is reached on13^th to 14^th day when the larval second larval shell, Prodissoconch II with the help of mantle becomes “Veliconcha’. In pediveliger stage the foot is developed on 16^th day at size of 280-320 mm. At this stage the larva is in crawling stage and sinks down & attaches a suitable substratum in a bottom on 20^th day after fertilization by developing Byssus threads.

After complete metamorphosis, larva acquires adult characteristics and becomes ‘plantigrade’ (or) “spat”. The spat attains a maximum length of 2.7 mm by 32^nd day. It look line a true mussel.