Free-living nematodes from a colonisation experiment in the upwelling area of Arraial do Cabo, Rio de Janeiro, Brazil: Lavareda decraemerae gen. n., sp n. and emended diagnosis of Cricolaimus Southern, 1914 (Plectida: Rhadinematidae)

Lavareda decraemerae gen. n., sp. n. is characterised by a cheilostom with a sclerotised ring bearing six anterior projections, a funnel-shaped to tubular stegostom, a large unispiral amphid with wide groove and males with a single precloacal setiform sensillum and 19 tubular supplements in a continuous series. The new species is similar to Cricolaimus coronatus in having the cheilostom consisting of a cuticularised ring with anterior projections. Re-examination of C. elongatus revealed clear differences to the new species, the former showing a bilateral symmetry anteriorly with a lateral axis: the lips are merged into one large dorsal and one large ventral lip with elongated inner and outer labial sensilla and the cheilostom has a cuticularised oblique ring, higher dorsally and ventrally than laterally, with two anteriorly directed claw-like projections, one mid-dorsal and one mid-ventral, whereas the new species has a radial symmetry with low lips with inner and outer labial papillae indistinct and a cheilostom with a cuticularised ring with six anteriorly directed projections, thereby justifying the proposal of Lavareda gen. n. to accommodate the new species from Brazil and L. coronatus comb. n. (= C. coronatus). An emended diagnosis of Cricolaimus is given. This is the first record of a species belonging to the Rhadinematidae colonising an artificial substrate.