Some data on the structure of pelagospheres — Sipunculid larvae

Pelagosphaera, the larvae of Sipunculids (probably, of the genus Sipunculus) were collected during the expedition of the r/s «A. Kovalevsky» in the Aden Gulf in the upper 100—0 m layer over the depths of 70—2445 m and of the r/s «Vitiaz» in the North-West Pacific in the 500—0 m layer over the depth reaching 6810 m. Pelagosphaera of the Aden Gulf were investigated and drawn when vital with fully spread metatroch. This made it possible to show the details of their morphology and anatomy, especially the structure of the metatroch. The larvae of the Aden Gulf probably present two close stages of the same species. All the Pacific larvae are at the same developmental stage. Comparing the geographical and bathymetrical distribution of the larvae and adults of the genus Sipunculus, are supposed Pelagosphaera of the Aden Gulf to be the larvae of Sipunculus aequabilis, while Pelagosphaera of the Pacific are supposed to be the larvae of S. norvegicus