The genus Mastogloia possesses a distinct valvocopula (first girdle band). The valvocopula is marked by one to several internal chambers, called partecta, and tubes that open from the partecta to the outside of the diatom valve. The partecta function to secrete strands of mucilage from the cell.
A partectum is also described as being a chamber.
An alternate term for partectum is locule, used in some of the older literature (Stoermer et al., 1964).
Round, F.E., Crawford, R.M. and Mann, D.G. (1990). The Diatoms. Biology and Morphology of the Genera. Cambridge University Press, Cambridge, 747 pp.
Stoermer, E.F., Pankratz, H.S. and Drum, R.W. (1964). The fine structure of Mastogloia grevillei Wm. Smith. Protoplasma 59: 1-13.
Image Credit: Pat Kociolek
Light micrograph images of Mastogloia smitii showing a high level of focus to show the valve face, and deeper level of focus to reveal the valvocopula. The valvocopula is a complex structure in Mastogloia, with many chambers, or partecta.
Image Credit: Loren Bahls
LM images of the valvocopula of M. pumila. The image on the left shows the entire valvocopula. The image on the right shows several partecta, with one partectum marked by an arrow.