A series of still images from a representative time-lapse sequence show the progression of encapsulation of a glochidium of Ulterbackia imbecillis on a live fin of a bluegill (Fig.
Additionally, fibrous material was regularly observed on the cells composing the collars or the completed cysts, but not on areas of the fin distant from an attached glochidium.
undulatus, and the glochidium was completely encapsulated in 260 min (Fig.
The new shape of the cells may be more effective than the native shape for migration over new or exposed surfaces (e.g., the surface of a wound or the shell of glochidia) and may aid them in crawling or rolling as they cover the glochidium.
What initiates the rapid onset of cyst formation once a glochidium attaches to a fish is unknown.
The larval shell of the glochidium is ornamented with sharp hooks ("hooked" glochidia; Arey, 1921; Jeong, 1989; Jeong et al., 1993; Kwon et al., 1993; Pekkarinen, 1996) or small teeth ("hookless" glochidia; Arey, 1921; Nezlin et al., 1994) that are utilized to adhere to the surface of a potential host.
This idea is embodied in the hypothesis that a "factor" secreted by a glochidium initiates or influences migration of the epithelial cells of the host (Lefevre and Curtis, 1912; Arey, 1921; Nezlin et al., 1994).
After the glochidium attaches to the fin, perhaps integrins of the epithelial cells in contact with the larva bind proteins associated with the shell of the glochidium and influence cell migration.