New and known species of the genus Campylaimus Cobb, 1920 (Nematoda: Araeolaimida: Diplopeltidae) from North European marine habitats

The genus Campylaimus is a broadly distributed but relatively uncommon genus of marine and brackish nematodes with 20 nominal species and one nomen nudum. Many species descriptions and redescriptions are based on very few (single) individuals, which limits our understanding of inter- and intra-specific variability and morphology-based species boundaries. Two new species were found in the Skagerrak off the west coast of Sweden. Campylaimus triclados sp. n. is characterised by body 0.59–0.69 mm long; cuticle without longitudinal striation; anteriormost edge of the amphid anterior to the oral opening; dorsal limb of the amphid equal to 1.6–2.5 labial region diameters in male, 1.9 labial region diameters in female; ventral limb of the amphid extends towards anterior part of the intestine in male and midpharynx in female, 4.3–5.5 times the length of the dorsal limb in male and 2.2–2.8 times the length of the dorsal limb in female; ventral limb of the amphid is as wide as the dorsal limb; interamphideal space extends further than the posterior end of the dorsal limb but not reaching the posterior end of the ventral limb; secretory-excretory pore opens posterior to the cardia; spicules 19–24 µm long; two precloacal supplements; tail equal to 4.3–5.6 anal body diameters in length, with conoid terminal part. Campylaimus longispiculus sp. n. is characterised by body 0.56–0.65 mm long; cuticle without longitudinal striation; anteriormost edge of the amphid anterior to the oral opening; dorsal limb of the amphid equal to 1.8–2.1 labial region diameters in male; ventral limb of the amphid extends towards anterior part of the intestine in male, 2.8–3.5 times the length of the dorsal limb in male; ventral limb of the amphid is as wide as the dorsal limb; interamphideal space absent; secretory-excretory pore opens posterior to the cardia; spicules 28–35 µm long; two precloacal supplements; tail equal to 4.9–5.3 anal body diameters in length, with clavate terminal part. In addition, following nine species are new records for the fauna of Sweden: Campylaimus amphidialis, C. inaequalis, C. lefeverei, C. minutus, C. orientalis, C. rimatus, C. siwaschensis, C. striatus and C. tkatchevi.