This page contains information regarding Star Trek: Short Treks, and thus may contain spoilers.
Tribleustes ventricosus, unlike polygeminus grex; was a type of tribble that bred slowly. However, after Edward Larkin used his own DNA to genetically alter these tribbles, they were capable of breeding even faster than the polygeminus grex species. (ST: "The Trouble with Edward")
Doctor Leonard McCoy described tribbles as being "bisexual" (dual sexed) and were capable of reproducing at will. Born pregnant, and with sufficient food, a single tribble could breed in number exponentially, producing a litter of ten in twelve hours time. (TOS: "The Trouble with Tribbles")