Individual migration of mesentodermal cells in the early embryo of the squid Loligo vulgaris: in vivo recordings combined with observations with TEM and SEM.

Abstract

In the translucent preorganogenetic embryo of the squid Loligo vulgaris a population of single cells between the ectodermal layer and the yolk syncytium can be studied continuously in vivo during migration to the vegetal hemisphere of the egg. The results from 2 different preparations are reported: 1. An intact embryo served to view locomotive cell behavior through the translucent ectoderm with undisturbed cell-substrate interactions. 2. In an embryo a patch of ectoderm was microsurgically removed thereby exposing migrating cells to direct observation and experimental manipulation. In vivo time lapse microcinematographic recordings for 22 h (in 1.) and 10 h (in 2.) revealed the following: cell migration is neither directional nor dependent on the presence of the ectodermal layer (in 2.). Although the migrating cells primarily use the syncytial surface as a substrate for locomotion, under natural conditions they also adhere to the basal ectodermal surface as revealed by TEM and SEM. Migration rates were 18.3 +/- 12.6 mu/h in 1. Locally directed cell migration was observed in a group of cells in 1. which were involved in a process of aggregation, the latter being probably related to precocious formation of organ primordia. A preliminary note has appeared previously (Segmüller and Marthy, 1984).