Are kaitas and fusions new species?

When borahk and rahkshi fuse, the gain a new name and form (same counts for toa and matoran but they mainly get bigger) but are these fusions new species? If not, how do they do this? I imagine the turn into liquid protodermis, mush together, and form into a fusion. It’s like taking two clay figures, smashing them together, and making a bigger figure.