proloculus
/prəʊˈlɒkjʊləs/(also proloculum) Zoology
noun
The first chamber formed by the zygote of a foraminiferan.
Origin
Early 20th century. From pro- + classical Latin loculus compartment; originally in form proloculum, with alteration of the ending after Latin (neuter) nouns in -um, and with corresponding plural form prolocula.