Sex differentiation and gametogenesis in Boneilia viridis Solando

Large numbers of trochophore larvae of Bonellia viridis (Echiurida) were cultivated either in pure sea water (‘Glaszuchten’) or in sea water containing an intact or fragmented proboscis of an adult female RüsselzuchtenThe ability of these larvae to differentiate into males or females was investigated.

Sex determination for the majority (43–83 %) is metagamic and phenotypic. These findings therefore confirm the results of Baltzer and disprove those of Wilczynski.

When larvae are exposed to the action of the female proboscis, 76 % become males. The sensitive period during which this determination can take place lasts from day 3 to day 16 of larval life. Exceptions to this rule are discussed.

The gametogenesis of Boneilia viridis has been investigated by electron microscopical methods.

In early stages the oogonia of the ovary are already in syncytial contact with the nurse cells. The possible functions of the nurse cells and follicle cells are discussed. Electron micrographs failed to reveal two types of eggs (male- and female-determined eggs, according to Wilczynski).

Spermiogenesis in Boneilia is described. The spermatogonia are situated in paired clusters in the coelomic cavity, and form a syncytial complex. After completion of spermiogenesis, the spermatozoa abandon their syncytial contact.

The fine structure of ripe spermatozoa is described and discussed.

You do not currently have access to this content.