Paudicus sawtus
Paudicus sawtus is descended from the Itericot Paudicus captus, a parasite of the Sea Net. It has adapted several traits to allow it to better reproduce, as its ancestor was admittedly kinda clunky in execution. Its scientific name P. sawtus is based off of its calcerous spicule, which has serrated edges to allow it to more quickly and gracefully cut the cell membrane and nucleus. These serrations originally came from just a duplicated spicule, which allowed for the cell to waste less time poking into the cell. Gradually, new modifications were created, such as it growing smaller, getting onto the spicule, and duplicating until it becomes functionally serrated.
Early on, the what-would-become-P. sawtus had developed a mutation that gave it a protein that it didn't need, but it didn't really hurt it. Thus, the protein was just expelled out of the body and barely affected the survivalhood of the microbe. There was a few times, however, that they expelled this protein onto the nuclear membrane right after it is cut. This protein had a sticky property, allowing for the nucleus to survive without rupturing, and significantly improving its likelihood of survival. This happened enough times that random chance caused them to save it for right at the moment, allowing the nucleus to survive. The protein is rather shoddy, admittedly, and can easily break apart. It still gives enough time for the nucleus to recover and fix the membrane (which pushes the protein away from membrane.) The protein is expelled immediately, barely allowing any time for the nucleus to rupture.
When the cell ends up in the nucleus, it will of course replace its host's DNA with its own. Then, it dies inside of the nucleus, as there's no other way to escape besides risking damaging the nucleus again. The parasitized net cell with then create more individuals of Paudicus sawtus via mitosis of the net cell.