Observations on the moving colonies of the genus Tethya (Demospongia, Porifera)

Abstract

Observations on two species of sponges, Tethya seychellensis from the Red Sea, and T. aurantium from the Mediterranean Sea revealed that young colonies are able to detach from their sites of settlement and by means of filamentous podia, to move to other sites in the vicinity. These podia are 10–16 mm long extensions of the sponge body wall that bear an adhesive knob on their distal ends. After being attached, the contracting ‘podia’ pull the spherical colonies of 2.0–3.0 cm in diameter, transporting them to a new site. EM observations showed that in the podia the matrix is rich in contractile myocytes, primary archaeocytes, nucleated archaeocytes and scleroblastic cells, each of which takes part in the moving ability of the podium. It was also shown that some of the archaeocytes go over a process of ripening within the podium and produce collagenic filaments deposited in the internal matrix.