Small bathyal sponge species from east mediterranean revealed by a non-regular soft bottom sampling technique

This first study of soft bottom sponges from the Levantine bathyal employed a device comprising a plankton net secured atop a Marinovich type semi-balloon trawl. All of the nearly 500 specimens collected were identified to four sponge species. All four species are of a very small body size. Sponges were not retained by the larger mesh Marinovich trawl net. The study describes a new polymastiid species Tentorium levantinumn. sp., and a new Rhizaxinella shikmonaen. sp. in addition to two Calcareans: Sycnn faulknerin. sp. and a Plectroniniasp. that appears to be a new species. These sponges, which inhabit soft bottom environments, have evolved morphological features such as unattached ground-based cones with a broad base (Tentorium levantinum), or a basal anchoring tuft (Rhizaxinella shikmonae). The absence of these species from previous records of the Mediterranean bathyal may have resulted either from overlooking the small sized species in soft bottom environments for lack of adequate collecting technique or scarcity of studies. It was thus impossible to confirm or reject the pattern of wide geographical distribution of deep-water sponges seen elsewhere, including the western Mediterranean. The new calcareous species was found at greater depths than most other calcareous sponges published so far, while Plectroniniasp. was found at greater depth than all but one record for this genus. It is expected that other small, benthic species may be discovered using the appropriate equipment.