These photos are of desert goby eggs, laid on the inside of a bit of 3/4″ PVC pipe. They’re a week old, and must be just about to hatch since each clearly holds a tiny fish ready to scoot out.
The guy who mailed me the parents included the PVC tube and a little bag of salt and said “If you add the salt and the cave you should have eggs in a week or two.” That was less than three weeks ago. It felt a lot like getting sea monkeys from a comic book.
Desert gobies are about as extremophilic as a vertebrate can get. According to the wiki page linked above, if their water gets too hot they’ll climb out and cool off in the breeze.