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Summary The fine morphology of the buccal capsule and intestine (midgut) of the marine free-living nematode Odontophora deconincki was investigated. The cheilostome is armed with six equal claw-like odontia that can evert radially by opening the mouth. Light-refracting accessory buccal structures within the cheilostomatal cuticle alternate with odontia and consist of two elements: anterior armilloids and posterior granular armilliths. The buccal cavity (pharyngostome) is surrounded by a complex of longitudinal and oblique muscles partially attached to the cheilostome cuticle at the sites of the accessory buccal structures and enabling a wide opening of the mouth. With the described stoma condition, the nematode probably scrapes food particles from the substrate surface. In cross-section, the midgut consists of 5-7 cells that appear uniform throughout its length. An extracellular matrix (glycocalyx) over the microvillar brush varies in thickness and stratification depending on presence or absence of food content in the lumen. Abundant spherocrystals (globular inclusions with concentric striations) were present in all gut cells. No indication of endocytosis or digestive vacuoles was observed in the gut cells and extracellular digestion predominates. Most specimens had a gut content formed from a long cylinder of compressed flocculent material with some barely identifiable components and few spherocrystals expelled from the enterocytes. We assume that the nematode diet comprises a wide range of objects, mainly eukariotic epigrowth organisms, which are shorn off and scraped from the surface of sand grains and then ingested.

Two new plectid species from India are described and illustrated. Plectus glandulatus sp. n. has 917-1307μm long body; strongly annulated cuticle; conspicuously large hypodermal glands; ovoid amphidial apertures; offset lip region; separate, globular, lips; thickly cuticularised, arcuate, cheilostomal walls; basal bulb with four to five paired denticulate ridges; a pair of pseudocoelomocytes located posterior to the cardia and tail with a subterminal spur and three pairs of caudal setae. Chiloplectus indicus sp. n. has 695-1041μm long body; thick, transversely annulated, cuticle; three lateral incisures; markedly offset, narrow, lip region; lips with conical apices and slightly raised papillae; inner margin of lips forming well cuticularised oral framework; prorhabdion as long as wide and comprising 20% of the stoma length; basal bulb with six pairs of denticulate ridges; paired pseudocoelomocytes located posterior to the cardia, genital tract weakly developed and tail with one median spur and two pairs of caudal setae.

Abstract Two known and one new species of Paraphanolaimus are described, viz. P. behningi from Germany, P. anisitsi from Paraguay and Germany and P. paraguayensis sp. n. from Paraguay. Paraphanolaimus paraguayensis sp. n. is characterised by 0.84-0.94 mm long body, presence of 37-44 lateral epidermal glands, strongly sclerotised and broad cylindrical stoma, swollen tail tip; female reproductive system with developed spermathecae, straight vagina; male without neck setae, 16-19 tubular supplements, two precloacal and nine to ten caudal setae, spicules 32-33 μm long, arcuate, with oval manubrium and fusiform shaft, platelike gubernaculum. Paraphanolaimus indicus and P.micoletzkyi are considered as species inquirendae. An emended diagnosis and a revised classification of Paraphanolaimus are proposed and a key to the species of the genus is provided. Aphanonchus bayensis (Keppner, 1988) comb. n. is proposed for Paraphanolaimus bayensis Keppner, 1988.

The genus Anonchus is revised. The genera Assia and Haconnus are considered to be synonymous with Anonchus on the basis of the morphological analysis. Additional descriptions of six species, viz. A. maculatus , A. mirabilis , A. millelacunatus , A. palaeotropicus , A. coomansi and A. pulcher are provided on the basis of type material or recently collected populations. The lectotype of A. monohystera is designated and described and the synonymy of this species with A. maculatus is confirmed. Two new species are described; A. winiszewskae sp. n. from Paraguay and A. venezolanus sp. n. from Venezuela. Several aspects of the morphology are described and the variability and diagnostic significance of the main morphological characters discussed. A study of intrageneric and suprageneric taxonomy of the genus Anonchus is presented. The subfamily Aphanolaiminae is reinstated for the genera Aphanolaimus, Aphanonchus and Paraphanolaimus and raised to family rank. The family Aphanolaimidae includes two subfamilies: Aphanolaiminae and Anonchinae. An emended diagnosis and a revised classification of Anonchus are proposed and a key to the species of the genus is provided.