Description of Aegialoalaimus bratteni sp. n. from Skagerrak and a review of the genus (Aegialoalaimidae, Nematoda incertae sedis)

BACKGROUND The genus Aegialoalaimus de Man, 1907 includes 12 nominal species, of which three species are considered valid, two species were transferred to other genera and seven species have uncertain taxonomic status. NEW INFORMATION New species, Aegialoalaimus bratteni sp. n. was found in Skagerrak off the west coast of Sweden. It is particularly characterized by the 1.5-1.8 mm long body, short papilliform cephalic sensilla, excretory pore opening just posterior to nerve ring level, spicules that are straight in shape, supplements and gubernaculum absent, separating it from other valid species of the genus. It can be further differentiated from Aegialoalaimus elegans in having longer body (1.5-1.8 mm in A. bratteni sp. n. vs 0.8-1.3 mm in A. elegans), shape and size of spicules (straight and 22-29 µm long in A. bratteni sp. n. vs arcuate and 34 µm long in A. elegans), absence of precloacal supplements (vs seven-eight in A. elegans), absence of gubernaculum (vs present in A. elegans); from A. setosa in having shorter tail (c´=2.6-3.1 in A. bratteni sp. n. vs c´=4.2 in A. setosa), shorter cephalic sensilla (0.5-1.0 µm in A. bratteni sp. n. vs 9 µm in A. setosa), shape and size of spicules (straight and 22-29 µm long in A. bratteni sp. n. vs arcuate and 40-45 µm long in A. setosa), absence of precloacal supplements (vs eight in A. setosa), absence of gubernaculum (vs present in A. setosa); from A. leptosoma in having longer body (1.5-1.8 mm in A. bratteni sp. n. vs 0.5-0.7 mm in A. leptosoma) and other measurements, shape of spicules (straight in A. bratteni sp. n. vs arcuate in A. leptosoma), absence of precloacal supplements (vs three-five in A. leptosoma), absence of gubernaculum (vs present in A. leptosoma). Type specimens of Aegialoalaimus cylindricauda Allgén, 1933 and A. paratenuicaudatus Allgén, 1959 are redescribed and taxonomic status of these two species is re-evaluated. A taxonomic review, tabular compendium and identification key for species of the genus Aegialoalaimus are also given.