Pseudoterranova decipiens species A and B (Nematoda, Ascaridoidea): nomenclatural designation, morphological diagnostic characters and genetic markers

Five genetically distinct and reproductively isolated species have been det ected previously within the morphospecies Pseudoterranova decipiens from th e Arctic-Boreal, Boreal and Antarctic. Morphological analysis was carried o ut on male specimens identified by genetic (allozyme) markers, allowing the detection of significant differences at a number of characters between two members of the P. decipiens complex, namely P. decipiens A and B. On the b asis of such differences, the nomenclatural designation for the two species is discussed. The names Pseudoterranova krabbei n. sp. and P. decipiens (s ensu stricto) are proposed for species A and B, respectively. Morphological and genetic differentiation between the two species is shown using multiva riate analysis. Allozyme diagnostic keys for routine identification of the four members of the P. decipiens complex, namely P. decipiens (s.s.), P. kr abbei, P. bulbosa and P. azarasi, irrespective of sex and life-history stag e, are provided.