Hydruka were a breed of sea Rahi which the Matoran of Mahri Nui used to harvest air bubbles from the fields of air. Hydruka were able to sense which stalks of airweed contained the most air. They were notoriously stubborn and ill-tempered. They defended themselves by launching solid air spheres at enemies.
Hydruka were scorpion-like sea creatures. They were domesticated beasts used by the Matoran of Mahri Nui to harvest air bubbles from airweed. Their means of defense, launching air bubbles at enemies, inspired the Matoran to build their own launchers for the defense of their city. Hydruka were notoriously sensitive, stubborn, and temperamental. They worked at their own pace, and attempting to rush them only frightened or angered them.
Hydruka were domesticated Rahi and as such were given names by their herders.
The hydruka were domesticated animals.
Hydruka would refuse to move if the Matoran tried to use them as steeds.
Hydruka weren't that fast.
Hydruka tended to be stubborn by nature.
The hydruka were undersea Rahi, so they belonged in the waters around Mahri Nui.
Hydruka weren't amphibious.
The hydruka were never on Voya Nui.
Launchers were natural parts of the hydruka's bodies.
Hydruka could launch multiple air bubbles with only a really short interval between.
The solidified air launchers were natural tools of the Hydruka.
There were probably around 100 or so Hydruka in Mahri Nui.
The ability of hydruka to identify which airweed contained air was just a natural talent.
- Greg Farshtey didn't have room to give the hydruka a lot of screen time, and since they were small sets, there was no real pressure on him to do so.
- Hydruka were listed as Matoran on LEGO's Shop At Home page. This was purely for convenience since it didn't make sense to make a whole new category for them.