The adult female's remains - including a head and hands found in a bag - were discovered in eight locations, Irish police have confirmed.
They are investigating whether the death is linked to a personal dispute.
More than 200 gardaÃ­ (police), Irish soldiers and civil defence personnel are continuing to search the area.
The man arrested remains in police custody in Bray, 20km (12 miles) south of Dublin, where he can be questioned for up to 24 hours.
He presented himself to GardaÃ­ in County Wexford on Tuesday night and was subsequently arrested, Irish broadcaster RTE reported.
The focus of the murder investigation changed following a series of developments on Tuesday evening.
The results of DNA tests from the partial torso discovered by two walkers in the undergrowth, close to Military Road, on Saturday night showed the body was that of a woman.
More human remains, including a head and hands, were discovered over a 30km-area on Tuesday.
Police said they had now recovered most of the remains, and that there is only one victim.
Supt Pat Ward, described the unprecedented case as "troubling".
"We are conscious of the fact that the body found is that of a loved one," he said.
"What we have found are limbs, we've also found some significant parts of the torso and we've also found in one of the locations, in a bag, the head and the hands of the deceased," he added.
A 32-year-old man is being questioned in connection with the murder of a woman whose body was cut up and dispersed in the Wicklow Mountains.