The Velar Ciliature in the Brooded Larva of the Chilean Oyster Ostrea chilensis (Philippi, 1845).

Abstract

The Chilean oyster (Ostrea chilensis) broods its offspring almost to the settlement stage (about 8 weeks). Larvae are maintained inside the infrabranchial chamber of the female. Samples from all embryo and larval developmental stages were obtained from mantle cavities of brooding females and analyzed by scanning electron microscopy, with particular attention to the velar structures. All embryos and the earliest veliger stages of O. chilensis are devoid of cilia. Cilia first appear when shell length reaches 290-300 {mu}m, and the first cilia to grow on the velum form the outer preoral cilia. In larvae 340 {mu}m long, all the ciliary rings on the velum can be distinguished. These are the apical cilia (AC), inner preoral cilia (IPC), outer preoral cilia (OPC), and adoral cilia (AOC). The absence of the apical tuft in both O. chilensis and the closely related species O. edulis represents an adaptation to brooding by the embryos and larvae, but the lack of the postoral cilia (POC) in O. chilensis and the lack of cilia in the embryonic and early veliger stages are associated with an extreme brooding condition in this species.