[en] We have measured EUV spectra from tungsten, gadolinium and neodymium ions in optically thin plasmas produced in the Large Helical Device (LHD) at the National Institute for Fusion Science. Following the injections of solid pellets into hydrogen plasmas, EUV spectra were recorded by a grazing incidence spectrometer under the conditions with various electron temperatures. It has clearly been observed that the spectra feature changes from discrete to quasicontinuum as the electron temperature decreases. Several spectral lines from charge states in the neighborhood of Cu-like ions were identified in the discrete features. The atomic structure calculations suggest that the quasicontinuum emissions largely arise from Δn=0 transitions of open 4f subshell ions. (author)