Except for a few of the most assimilated, Argonians worship neither Aedra nor Daedra. They do not have "religion" as it is known elsewhere in Tamriel. They are known to venerate the Hist Trees of Black Marsh, but they do not appear to have prayers, priests, or temples.
Argonians also venerate Sithis, the primordial Shadow/Chaos that existed before the gods were born. Unlike most citizens of Tamriel, they do not regard Sithis as "evil." In fact, Argonians born under the sign of the Shadow are taken at birth and presented to the Dark Brotherhood, which in Black Marsh is considered an integral part of society.