Sea monkeys (brine shrimp) travel through time in the normal way, but they get both the benefits and hazards of having sex with others of their species from different time-periods. This is because these other brine shrimp are in differing places in evolution.
Brine shrimp lay eggs that only become viable when the environment is correct for them to hatch. There is no consistent time for this to happen. The wait for viability can be of decades duration – or less. From an evolutionary point of view it is rather like a given shrimp is mating with a time-traveler.
Nicolas Rode, of the Center for Functional and Evolutionary Ecology, was inspired by this concept to mate sea monkeys of different time periods, and thus elucidate the no-doubt controversial subject of brine shrimp evolution and sex. As the creatures evolve, the males get better claspers for holding females, while the females get better at wrestling. The claspers hold the female tight for the mating, while the wrestling skills are used for evading the effort.
So, for his tests, the Montpellier-based Rode utilized dormant brine shrimp eggs from 1985, 1996 and 2007 — which he obtained from Utah's Great Salt Lake area (quite a distance from his French workplace). He then chose who was going to mate, and whether they would be matched with shrimp of their own time or another one. The 1985 female brine shrimp were at a great disadvantage when paired with males from later periods, fatally so. A 1985 female mating with a 2007 male would, on average, suffer a life loss of 12 percent. In brine shrimp terms, it was like mating with someone from 160 generations in the future.
— Douglas Chapman
"Sea monkeys from the future make deadly lovers," MNN (Mother Nature Network), http://www.mnn.com/earth-matters/animals/stories/sea-monkeys-from-the-future-make-deadly-lovers, 6/19/11
"Time-Traveling Male Sea Monkeys Make Bad Mates," Wired Science, http://www.wired.com/wiredscience/2011/06/time-travel-mating/, 6/18/11