New species of free-living aquatic nematodes from south-western Australia (Nematoda: Axonolaimidae and Desmodoridae)

Abstract

Descriptions of 10 new species of free-living aquatic nematodes are presented. Four of the new species belong to the Axonolaimidae, i.e. Ascolaimus australis, Parascolaimus brevisetus, Odontophora serrata and Parodontophora aurata. The remaining six species belong to the Desmodoridae, i.e. Bolbonema spiralis, Onyx cephalispiculus, O. potteri, Eubostrichus otti, Catanema australis and Leptonemella peronensis. All 10 species were found in sediments taken from near-shore waters of either the Swan River Estuary or marine waters of the Perth region (Western Australia). Ascolaimus australis differs from its only congener A. elongatus in that its spicules are non-barbed and have rounded proximal cephalations. Parascolaimus brevisetus is different from its four other congeners by its short cephalic setae, which are less than one quarter the length of any other Parascolaimus, and the spicule cephalations are rounded rather than simple or spade-shaped. Parodontophora aurata is distinguished from six morphologically similar species by the unique arrangement ((4D-2V)2) and greater length (6 μm) of the opisthocephalic setation. Odontophora serrata is distinct from other Odontophora species in that each odontiuim bears seven dentate projections, which is more projections than similar species, O. bermudensis (5), O. villoti (3) and O. paravilloti (3). Bolbonema spiralis has spiral amphids with two turns, in contrast to those of B. longisetosum, which are only a single loop. Onyx cephalispiculus is most similar to O. sagittarius but has more robust spicules with large, bilobed cephalations. Onyx potteri is the only Onyx species to exhibit spicules with a distinct constriction and one of only two species with ten tubular precloacal supplements. The other, O. dimorphus, has sexually dimorphic amphids whereas O. potteri does not. Eubostrichus otti is most similar to E. topiarus but is only half the size. Cephalic setation is also divergent, with E. otti having two cephalic crowns, eight setae in the anterior, four in the posterior, whereas this arrangement is reversed for E. topiarus. Catanema australis is most similar to C. exilis but is distinguished from that species by the lack of prominent, tubular, postcloacal supplements and having only four pairs of normal setae on the tail. Leptonemella peronensis is most similar to L. granulosa but differs in its non-granular cephalic capsule, shorter tail and different circumcloacal setation (two precloacal, four postcloacal and one terminal double pair v. L. granulosa’s seven postcloacal pairs).