It appears Puerto Rico has its own Anthony Weiner.
Arango, a Republican who represents the capital of San Juan, presented his letter of resignation after a weekend meeting, Senate President Thomas Rivera Schatz said.
Schatz did not release the lawmaker's letter, but said the circumstances that led to the resignation "are very lamentable."
Local news media published photos from the application showing a man's nude upper body with a cell phone obscuring his face. Another photo showed a rear view of a nude man on his hands and knees. Another showed a fuzzy image of a face that seemed to match Arango's.
Arango has neither confirmed nor denied suggestions by local media that the photos might be of him and apparently was not asked if he had posted them. During a recent interview with WAPA TV in Puerto Rico, the senator said he has taken pictures of himself with a cellphone to document his recent weight loss.
"I really don't remember having taken those pictures of myself, but it doesn't mean I didn't take them," he told the station. "I really don't remember."
Arango did not return calls Sunday.
A graduate of Louisiana State University and a food importer before turning to politics, he was chairman of a business council for the national Republican Party and municipal director of the Republican Party in Puerto Rico, according to his Web page for Puerto Rico's Senate.
Pedro Julio Serrano, founder of the gay rights group Puerto Rico for Everyone, said Arango failed to support a recent effort to legalize gay marriage on the island.
Local news media said that the pictures first appeared on an iPhone application for gays and bisexuals and that they themselves later received copies from unidentified sources.
In recent days, Puerto Rican Gov. Luis Fortuño had said that if the man was indeed a legislator, he should resign. That echoed the sentiments of other lawmakers, including local House Speaker Jenniffer González.
Based on reporting by the Associated Press.