Three new species of free-living marine nematodes of the Microlaimus genus (Nematoda: Microlaimidae) from the continental shelf off northeastern Brazil (Atlantic Ocean).

Three new species of the Microlaimus genus (Nematoda: Microlaimidae) are described from sample sediments collected in the South Atlantic, along the Continental Shelf break of Northeastern Brazil. Microlaimus paraundulatus sp. n. possesses four setiform cephalic sensillae, a buccal cavity with three small teeth, arched and slender spicules and a wave-shaped gubernaculum. Microlaimus modestus sp. n. is characterized by four small cephalic sensillae, a buccal cavity with three teeth (one large dorsal tooth), cephalated spicules and a strongly arched gubernaculum in the distal region. Microlaimus nordestinus sp. n. is characterized by the following set of features: relatively long body, eight rows of hypodermal glands that extend longitudinally along the body and a funnel-shaped gubernaculum surrounding the spicules at the distal end. An amendment of the diagnosis is proposed for the genus.

Two new species of Acantholaimus (Nematoda, Chromadoridae) from the deep southeastern Atlantic (Santos Basin).

Two new species of the genus Acantholaimus (Nematoda, Chromadoridae) are described from the South Atlantic, in the Santos Basin off the slope of southeastern Brazil. Acantholaimus pugious sp. n. is characterized by a narrow and elongated anterior end; teeth that are thin and long stylet-like (two in number), amphidial fovea located far from the anterior end and occupying most of the corresponding body diameter. Acantholaimus bidentatus sp. n. is characterized by a narrow anterior end, cuticle with more evident dots on both body extremities (up to amphidial fovea and tail); two long, protractible thin teeth (similar to stylet), with curved proximal part. The two species are similar in the shape of the teeth. The teeth morphology may be correlated to the process of adaptive convergence of these species. An emended diagnosis of the genus is provided.

A new species of Cephalanticoma (Enoplida: Anticomidae) from Brazilian coast (Atlantic Ocean), with emended diagnosis and dichotomous key to the genus.

A new species of the genus Cephalanticoma is described for the Atlantic Ocean in the Potiguar Basin off the continental shelf of northeast Brazil. Cephalanticoma rugatusa sp. n. is characterized by bearing head capsule ending on the level of amphideal fovea, a tubular precloacal supplement and two rows of thin precloacal setae. Cephalanticoma rugatusa sp. n. differs from all other species of the genus by having a precloacal cuticular papilla in front of the cloaca and a cuticular transversal wrinkle which extends from the papilla elevation to the conical-cylindrical portion of the tail occupying both subventral regions. An emended diagnosis and a dichotomous key to species based on both genders are provided.

First record of spiral fovea amphidialis in Acantholaimus (Chromadoridae: Nematoda), with a description of a new species from shallow sediments of the South Atlantic and an emended diagnosis of the genus.

A new species of the genus Acantholaimus is described from the South Atlantic, in the Potiguar Basin off the continental shelf of northeast Brazil. Acantholaimus marliae sp. n. is characterized by the long body; numerous somatic setae arranged in four sublateral longitudinal rows; buccal cavity with five solid teeth (four subventral and one dorsal), with the largest tooth dorsally located and the most protuberant between the subventral teeth shaped similarly to a "bottle opener"; and spiral fovea amphidialis. Acantholaimus marliae sp. n. is the only species described for the genus that has a spiral fovea amphidialis. This is the fifth species of Acantholaimus described from shallow water. An emended diagnosis of the genus is provided.