Two new species of Geodiidae (Porifera, Demospongiae, Astrophorina) from the Emperor Seamounts, North Pacific Ocean

摘要

Two new species of Geodiidae from the Emperor Seamounts, North Pacific Ocean are described and compared to congeners. Erylus imperator n. sp. differs from all other species of Erylus from the region in having large oxyasters, present in only one other species from which it differs in several other characters. Furthermore these oxyasters most often display the tendency to reduce the number of rays to a degree that they appear as triods, microxeas or even microtylostyles, depending on the number of retained rays. The second new species, Geodia arma n. sp. is a Geodia without triaenes, a group formerly described under the genus Geodinella. We compared G. arma n. sp. with all congeners lacking triaenes and determined that it is the only known species with a cortex of up to 6 mm in thickness and also the only species with oxeas up to 6 mm in length Which range from thin and sinuous to thick and straight. To our knowledge these are the first descriptions of sponge species from the Emperor Seamount region.