Brenda Lía Doti

Range Extension of Pseudidothea Miersii (Studer, 1884) (Isopoda, Valvifera) and New Evidence of Its Likely Commensal Relationship with a Sea Urchin

BRENDA L. DOTI1,3), DANIEL ROCCATAGLIATA1,4) and FABRIZIO SCARABINO2,5) 1) Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, UBA, Ciudad Universitaria, C1428EHA, Buenos Aires, Argentina 2) Dirección Nacional de Recursos Acuáticos, Constituyente 1497, C.C. 1612, C.P. 11200, Montevideo, Uruguay; and Museo Nacional de Historia Natural y Antropología, C.C. 399, C.P. 11000, Montevideo, Uruguay

On two paramunnid species from the Beagle Channel, Argentina (Crustacea: Isopoda: Asellota)

ABSTRACT Austrosignum fuegiae, a new species, is fully described on the basis of specimens collected in the shallow waters of the Beagle Channel. The genus Austrosignum Hodgson, 1910 is in need of revision, and the inclusion of A. fuegiae in this genus should be considered provisional. Austrosignum fuegiae is most similar to A. dentatum Winkler, 1994, which was previously known from the Magellan Strait and is herein recorded for the Beagle Channel for the first time. These two species have a head with bilobed frontal margin, short eyestalks, and mandibles with palps, a group of characters that is not shared by the type species of the genus, A. grande Hodgson, 1910.

On the South American species of the genus Meridiosignum (Crustacea: Isopoda: Asellota: Paramunnidae)

Meridiosignum undulatum n. sp. and M. disparitergum n. sp. are described from off the Río de la Plata estuary. These two new species are easily distinguished from other members of the genus Meridiosignum in having the lateral margins of pereonites 2 and 3 bilobed (the concavity is much more pronounced in M. disparitergum), and those of pereonite 4 produced into a single process. The terminal male instar of Meridiosignum menziesi (Winkler, 1994) is described, and this species is herein reported from the Beagle Channel and Puerto Deseado. All the species currently placed in Meridiosignum were found in shallow waters in the southern hemisphere, M. undulatum n. sp. and M. disparitergum n. sp. being the species recorded at the greatest depth (129 m).