Hydrobiologia 310: 79-86, 1995. 79 ( 1995 Kluwer Academic Publishers. Printed in Belgium. Leptepsilonema santii sp.n. from Spain and data on the variability of L. filiforme (Nemata, Epsilonematidae) N. Gourbault 1 & W. Decraemer 2 1 Museum national d'Histoire naturelle, D.0699 CNRS, Biologie des Invertbres marins, 57 rue Cuvier, F-75231 Paris Cedex 05, France 2 Koninklijk Belgisch Instituut voor Natuurwetenschappen, Departement of Invertebrates, Vautierstraat 29, B-1040 Brussels, Belgium Received 23 March 1994; in revised form 10 August 1994; accepted 7 September 1994 Key words: marine nematodes, Epsilonematidae, Leptepsilonema, taxonomy, new species Abstract The genus Leptepsilonema is recorded for the first time from the Mediterranean: L. santii sp.n. is characterised by a slender body with a large number of annules (122-128). Cuticular ornamentation with clear ridges and a lateral field of small thorns on both sides of the anteriormost annules are also typical as well as the number and arrangement of copulatory thorns (2-3 pairs, 2 fields), the shape and length (49-58 tm) of spicules in males. L. filiforme is recorded from New Caledonia; specimens largely resemble the original types but are larger. The variability of some morphological structures is discussed. Introduction Material and methods Because of the singular epsilon shape of the body of the Epsilonematidae, the family is very easily differen- tiated in all meiobenthic samples. Although this group is rarely recorded, it seems to be common in coarse sediment, mostly in sandy beaches. Some genera are known from tropical or subtropical regions only. This is the case for five of the six species of the genus Lep- tepsilonema described from the Caribbean Sea (San Andres Island, Colombia) including the type species, L. procerum Clasing, 1983 which occurs in Guade- loupe (Gourbault & Decraemer, 1987). L. exile and L. macrum Clasing, 1983 are known from North and South Chile respectively. L. parafiliforme Gourbault & Decraemer, 1987 occurs in Guadeloupe and L. richardi Verschelde & Vincx, 1992 in Kenya. L. filiforme Clas- ing, 1984 was described from the Galapagos, and it is found in large numbers in New Caledonia samples. This allows us to study the variability of morphometric features. The genus Leptepsilonema is recorded for the first time from the Mediterranean by a new species L. santii n.sp., here described. Spanish benthic samples were taken using a manual box corer by Dr Santiago Villora Moreno by SCUBA diving in the Bay of Valencia. New Caledonian spec- imens were collected by Dr Guy Boucher from sandy beaches of two small islands (I11t Lar6gnere and I16t Signal) located in the southwestern part of the lagoon, by the Karaman/Chappuis technique of digging a hole and filtering the seepage water from the bottom (Gour- bault & Warwick, 1994). Samples were fixed with 7% neutralised formalin, sorted by the elutriation-washing technique and mounted in anhydrous glycerine. Draw- ings were made by using a camera lucida on a Reichert Polyvar microscope with interference contrast equip- ment. The type material has been deposited in the type collections of the Mus6um National d'Histoire Naturelle (MNHN) Paris, France and the Koninklijk Belgisch Instituut voor Natuurwetenschappen (KBIN) Brussels, Belgium. Abbreviations used in text and tables: abd, body diam- eter at level of anus (cloacal opening); amph (%),