Male mosquitofish lifespans are considerably shorter than females. Hummingbirds have long lifespans for organisms with such rapid metabolisms. Most hydromedusae have shorter lifespans than the larger scyphozoan jellyfish. They also tend to live shorter lifespans. Generations hatched early in the year have shorter lifespans than generations hatched after September. Conversely, the Mechonis is home to the mechanical humanoid Machina, whose lifespans span several millennia. Current generations of nuclear submarines never need to be refueled throughout their 25-year lifespans. Parasites are artificially-created and have short lifespans. This leads to low fertility, short lifespans, and high puppy mortality. Some estimations of lifespans of wild birds has exceeded 50 years. The lifespans of wild females average 50 years. Estimates of lifespans for wild orcas vary. This led to the observed longer lifespans and higher egg-laying rates in the experimental field. That comets have finite lifespans has been known for some time. Eldar have very long lifespans and all of them are psykers.