I'm reminded that 'Coconut Crabs', those tree-climbing scaries distantly related to the more familiar 'hermits'...
en.wikipedia.org
... are progressively evolving bigger, better book-lungs to augment their juveniles' gills. FWIW, the youngsters 'go hermit' until too big and tough for most predators.
To put it politely, their species seems to have 'growth potential'.
Else-where, there's that wry quip about Earth's hypothetical 'In Their Own Image' Creator or Designer having an inordinate fondness for beetles.
Plus an interesting observation that multiplying segments to extend body-plan lends itself to limb specialisation, then progressive reduction of load-bearers to hexapod...
We already know of copper-based oxygen carrying 'blood',. Though not as efficient in current ~20% O2 atmosphere as our iron-based, it seems to work well in near-anoxic conditions. Equivalent is our 'foetal' heme variant, usually lost within first year.
FWIW, in 'City of Fresno', my current 'WIP', a problem they will face is a planet whose inhabitants have fled massive mainland to defensible off-shore islands. One of their 'forest floor' fauna, an omnivorous 'sorta-protist', went polyploid, grew and multiplied, grew and multiplied, grew and grew to what the astonished humans describe as 'Shoggoids'.
Too many are the size of ground-cars, while each territory's 'Boss Beast' is big as a bus. Seriously difficult to kill: Like sponges, even fragments reform to mini-Shoggoids, continue eating, growing. Fire ? Beam weapons ? Char sloughed, remnant resumes insatiable nomming. Toxins ? Poisoned part gets sloughed. They eat anything in their slow path, including each other. Hermaphrodites, the adults bud clones, but also ovipositor eggs to metres underground.
Locals, happy to trade for minor stuff, demand the humans tackle these 'NSFW Purple Perils' to win permission to refuel 'Fresno' by gas-mining the system's sub-Saturnian for Deuterium and Helium_3. After considering 'Shoggoids' near-immunity to combat weapons, and the locals' triple-helix, wrong-handed biochemistry, the humans devise a cunning plan...