Novel mode of postembryonic development in Ammothea genus (Pycnogonida: Ammotheidae) from Antarctic waters

In this paper the postembryonic development of Ammothea glacialis (family Ammotheidae) is described. The studied material was collected during the Italica XIX cruise to Victoria Land, Ross Sea, Antarctica. The external morphology of three larval instars is described and illustrated. The development of A. glacialis has the following characteristics: (1) protonymphon hatch from the eggs; (2) the larvae have yolk reserves and relatively large size (0.7 mm in length); (3) the larvae remain on the ovigerous legs of males during several moults; (4) the larvae have reduced larval II-III appendages and the spinning apparatus is absent; (5) the development of walking legs is sequential. This development is compared with those previously known, especially with Propallene longiceps and Nymphon grossipes .