The Syreen are a race of bipedal hominids astonishingly similar to the Earthlings. There has been much speculation about the relationship between Humans and Syreen, including possible intervention on the part of the Arilou.
Physiologically and genetically, Syreen are Human: the only visible differences between the races are that Syreen skin tint is somewhat more bluish and their retinas reflect light like an Earth cat's. Additionally, the typical Syreen is more comfortable in a slightly warmer and more humid environment than the typical Human. According to some, Humans and Syreen have nearly identical diurnal cycles, exhibiting even further similarity between the two species. Other sources claim that the Human diurnal cycle differs greatly from that of the Syreen, which consists of twenty hours of wakefulness followed by ten hours of rest. By scanning Syra, the former variant can be confirmed.
Syreen are also more psychically active than humans, to such an extent that the captain of a Penetrator starship can make use of a psychic amplifier to coerce enemy crew. It is not known if Penetrator captains are chosen for exceptional psychic potential, or how common psychic potential is in the general Syreen population, although they do not evince casual telepathic powers that races such as the Pkunk or even the Zoq-Fot-Pik do. On Earth, stereotypes of the Syreen are rampant: "Space Amazons," "Space Gypsies," "warm, breathing pinups," and other sorts abound. Of course, the truth is more complex than such stereotypes would imply.