As a culture of cells becomes overgrown, the amount of cellular debris in the culture dish increases significantly. The A. P. Mongoose fibroblasts featured in this time-lapse sequence have formed almost a complete monolayer along the bottom of the imaging chamber. Accordingly, the cytoplasmic fragments in the chamber, which can be produced when migrating cells leave behind bits of their contents as they advance along their paths or following cellular apoptosis, are copious. At some points during the high speed playback of the sequence, the debris that flows across the field of view is so heavy that it is reminiscent of a violent snow storm.

The sudden simultaneous appearance of numerous cell fragments is caused by currents in the culture medium. The currents are able to easily sweep along all debris that is not sufficiently connected to the substratum. If entire cells were unable to form strong anchorage points with the culture surface, they would be carried away from the substratum by currents as well. Focal adhesions are generally formed, however, between fibroblasts and culture surfaces, which ensure the cells stay in place or move only via their own directed crawling motions. The focal adhesions formed by the cells are utilized similar to microscopic feet, which remain stationary as the fibroblasts travel over them but are then typically released as they become increasingly distal from the leading cell margin.

A. P. Mongoose fibroblasts exhibit very little contact inhibition of migration. Many of the highly active cells only briefly pause along their paths when they collide with other cells. Early in the time-lapse sequence, a three-way collision in the upper right-hand corner of the field of view causes the two smaller cells involved to alter their courses after they all seem to briefly stick together. Most of the A. P. Mongoose fibroblasts, however, simply crawl over other cells in their way, stretching out and contracting their lamellipodia and filopodia to pull themselves along.