Table 1 Timing of developmental stages of Gibbula varia (at 22°C); different stages of larval development and metamorphosis of G. varia inside the gelatinous egg capsules before hatching.
Name of stage and approximate time of development (hpf) | Brief description of main features |
|---|---|
Early Trochophore Larva (12 hpf) | The pretrochal cells are smaller than the posttrochal cells; prototroch starts to form by cilliation of trochoblasts; shell gland starts to evaginate; foot rudiment and stomodaeum are not completely formed. |
Late Trochophore Larva (18-24 hpf) | The larva comprises a prototroch, shell field surrounded by mantle edge, a pedal rudiment, and stomodaeum. |
Pretorsional veliger larva (36-48 hpf) | The mantle and mantle cavity form. The larva has a velum, apical organ marked by apical cilia, mouth opening, and pedal rudiment with anlage of operculum. |
Post-torsional veliger larva (60 hpf) | The mantle lies over the back of the head and the velum gradually splits ventrally, the operculum apears. |
Metamorphotic (competence) stage (72 hpf) | Eye rudiments and cephalic tentacles begin to form in the prevelar area. The anlage of the radula becomes visible. |
Encapsulated juvenile | Velum is completely lost; eyes and cerebral tentacles are formed. |
Hatchling (96 hpf) | The encapsulated juvenile hatches and shell mineralization begins. |