Observable effects from spacetime tunneling

Assuming that spacetime tunnels -wormholes and ringholes- naturally exist in the universe, we investigate the conditions making them embeddible in Friedmann space, and the possible observable effects of these tunnels, including: lensing and frequency-shifting of emitting sources, discontinuous change of background temperature, broadening and intensity enhancement of spectral lines, so as a dramatic increase of the luminosity of any object at the tunnel's throat.