A review of the family Ceramonematidae (marine free-living nematodes), with descriptions of nine species from the White Sea

Abstract

Morphology, biology and taxonomy of the nematode family Ceramonematidae Cobb, 1933 are summarised and reviewed. Plesiomorph-apomorph polarities of cuticle sculpture, cephalic sensilla pattern, amphid shape are revealed with use of the out-group comparison and ontogenetic observations. The genera Ceramonema and Pselionema are distinguished by the most apomorph character states; both genera combined comprise the greatest number of species, of the widest overall ecological range. The other ceramonematid genera display more plesiomorph character states and contain much less speces; these are strictly confined to coars sand. Ceramonematidae are related to the families Diplopeltoididae sensu Tchesunov (1990) and Tarvaiidae. The family Ceramonematidae consists of two subfamilies: Ceramonematidae with the genera Ceramonema (= Ceramonemoides, = Cyttaronema), Dasynemella (=Leptodasynemella), Dasynemoides (=Dasynemelloides), Metadasynemella (=Dictyonemella), and Metadasynemoides, and Pselionematinae with the genera Pterygonema and Pselionema (= Pselionemoides). Modified diagnoses of the family, subfamilies and genera are given. Separation of higher ceramonematid taxa is based largely on features of body cuticle annulation as well as on anterior sensilla pattern, while cephalic ratio and finer details of body annulation are important for species discriminaton. Annotated lists of species are given for each genus. The genus Ceramonema is subdivided into two subgenera, Ceramonema s. str. (body cuticular annules with zygapophyses) and Proceramonema subg. n. (body annules devoid of zygapophyses). New species from the With Sea (Ceramonema fluctuosum sp. n., C. marisalbi sp. n., C. mokievskii sp. n., Dasynemoides crassus sp. n., Metadasynemoides labiatus sp. n., Pselionema concinnum sp. n., P. mirabile sp. n.) are described. Dasynemella riemanni Haspeslagh is recorded for the first time the With Sea. The description of Pselionema simplex De Coninck from the White Sea is supplemented with notes on juveniles.