STUDIES ON THE GENUS LAGENONEMA ANDRASSY , 1987 ( NEMATODA : THORNENEMATIDAE )

The genus Lagenonema was established by Andrassy (1987) belonging to the subfamily Thornenematinae Siddiqi, 1969, family Thornenematidae Siddiqi, 1969 under the order Dorylaimida. He erected the genus by differentiating it from Thornenema Andrassy, 1959 in having abruptly narrowed, bottle-shaped anterior region, well sclerotized spatulate cephalic framework, ventrally concave spear and smaller amphids. Jairajpuri and Ahmad (1992) did not agree with him and noted that Lagenonema was close to Thornenema. Gantait, Bhattacharya and Chatterjee (2010) however agreed with Andrassy's opinion that Lagenonema is a well defined, distinct genus.

thornei from west Bengal, India.We want to add Thornenema spicatum Shaheen and Ahmad, 2005 to this genus.Presently the genus possesses seven species globally.A compendium of these seven species and a revised species key of the genus are being provided hereunder.
Tail 3-15 anal diameters long; tapering gradually to the finely rounded tip, or first hemispheroid then digitate to filiform.Male unknown in all the species of the genus.

Relationship:
The genus Lagenonema is related to the genus Thornenema Andrassy, 1959.But it differs from that in the abruptly narrowed, bottle-shaped anterior region, the well sclerotized spatulate cephalic framework, ventrally concave spear and the smaller amphids.Besides, all the species of the genus Lagenonema are monosexual whilst the Thornenema species are bisexual.
The species is characterized in having almost straight, cylindrical body, tapering over about three body widths anteriorly and from beginning of prerectum posteriorly.Cuticle smooth, thick opposite to spear base.Lip region rounded, amalgamated and distinctly narrower than adjacent body, about one-fifth as wide as body at base of oesophagus.Odontostyle basically cylindroid, its aperture about one-third of its length.Odontophore as long as odontostyle.Guiding ring appeared fine and simple.Slender part of oesophagus slightly constricted posterior to spear extensions and at nerve ring.Basal expanded part of oesophagus occupied 37-44% of total oesophageal length.Oesophago-intestinal vulve globular.Vulval opening transverse, vaginal opening cross-like; no sclerotization in vulval region.Gonad opisthodelphic.Prerectum about two and a half anal body widths long.Rectum about one anal body width long.Tail elongate-conoid with a rounded lip in most specimens.Carbonell and Coomans (1986) redescribed the species from Maraoue, Ivory Coast from grass savanna.Despite some differences in measurements their specimens are considered conspecific with the type populations of Yeates (1970).
T. caudatum and T. longicaudatum were described by Jairajpuri et al. (1979) from Imphal of Manipur state, India.The specimens were collected from soil around roots of unidentified wild flowering plants.T. caudatum has almost straight body, tapering towards both the extremities.Cuticle finely striated.At base of lip region the cuticle suddenly thickens and then becomes thinner at level of base of odontophore.A little above the anus it again gradually starts to become thicker and remains so in the anterior one-third of tail length.Lip region amalgamated, strongly sclerotized, very narrow, about one-fourth of body width as base of oesophagus.Odontostyle cylindroid, about two head-widths long; its aperture about one-fourth of its length.Odontophore equal to spear length.Guiding ring appeared fine and simple.Basal expanded part of oesophagus occupied 35-38% of total oesophageal length.Vulva a transverse slit.Vagina thick walled, about one-half of body-width long.Gonad opisthodelphic, reflexed.Prevulval uterine sac almost absent.Prerectum 1.5-2.3anal body widths long.Rectum about one anal body width long.Tail long, two parts; the first part hemispheroid and covered with very thick cuticle, the second part elongate filiform with a rounded terminus.Sauer (1981) redescribed the species from Gemas, Malaysia, collected from paddy soil.Carbonell and Coomans (1986) also redescribed the species based on two para types, deposited in the nematode collection of the Instituut voor Dierkunde, Gent, Belgium, by Jairajpuri et al. (1979).Carbonell and Coomans (1986) found two principal differences with respect to the original description Gairajpuri T. longicaudatum has ventrally curved body, tapering towards both the extremities.Cuticle finely striated.At base of lip region the cuticle suddenly expands and then becomes thinner at level of base of odontophore.Lip region amalgamated, strongly sclerotized, very narrow, about 1/6 th -l/S th of bodywidth as base of oesophagus.Odontostyle cylindroid, about two head-widths long; its aperture about one-fifth of its length.Odontophore nearly equal to spear length.Basal expanded part of oesophagus occupied 40-45% of total oesophageal length.Vulva a transverse slit.Vagina thick walled, about one-half of body-width long.Gonad opisthodelphic, reflexed.Prevulval uterine sac almost absent.Prerectum 1.5-2.5 anal body widths long.Rectum 1.2-1.6 anal body widths long.Tail long filiform with rounded terminus.Sauer (1981) redescribed the species from Bachok, Malaysia, collected from tobacco field.Carbonell and Coomans (1986) also redescribed the species based on one paratype, deposited in the nematode collection of the Instituut voor Dierkunde, Gent, Belgium, by Jairajpuri et al. (1979).Carbonell and Coomans (1986) observed the specimen differs from the original description Gairajpuri et al., 1979) in amphidal shape, position of pharyngeal gland nuclei and a distinct sphincter between uterus and oviduct.Jairajpuri et al. (1980) opined that the description of T. thienemanni by Jairajpuri (1966) is no longer conspecific with Dorylaimus (= Thornenema now Dorylaimoides) thienemanni Schneider, 1937.Accordingly, a new name has to be proposed by them for T. thienemanni apud Jairajpuri, 1966. Jairajpuri et al. (1980) designated it as T. 100ft and described as new species.The species is characterized in having ventrally curved body, tapering towards both the extremities.Cuticle finely striated.Lip region amalgamated, strongly sclerotized, very narrow, about l/sth of bodywidth as base of oesophagus.Odontostyle cylindroid, about two head-widths long; its aperture about one-fourth of its length.Odontophore about 1.5 times the odontostylet length.Basal expanded part of oesophagus occupied 45% of total oesophageal length.Cardia tongue shaped.Vulva a transverse slit.Vagina thick walled, about one-half of body-width long.Gonad opisthodelphic.Prerectum 1.5-2.0anal body widths long.Rectum 1.2-1.5 anal body widths long.Tail long, gradually tapering with rounded terminus.Carbonell and Coomans (1986) also redescribed the species based on a population, collected from Maraoue, Ivory Coast from grass savanna.They observed that the specimens differed in body length and vulval position from the type population described by Jairajpuri (1966).Since then they also studied three females, collected from soil, near the bank of the Mayel Sao river, Ouro Haousas, Cameroon and found that the measurements of the specimens are closer to those of the type population Gairajpuri, 1966).Both Ivory Coast and Cameroon populations studied, differ in amphid shape from that description by Jairajpuri (1966).Andrassy (1987) described L. tropicum (holotype female; two female and a juvenile paratypes) from Gogol River, Papua New Guinea, humus from a primary rain forest.The species is characterized in having ventrally curved body, tapering towards both the extremities.Cuticle smooth.Head very narrow, 4.5-5.0im, about half as wide as adjacent body.Lips amalgamated.Labial frame work and collare sclerotized.Spear almost twice the head diameters; its aperture about one-fourth of its length.Guiding ring very thin.Basal expanded part of oesophagus occupied 64-65% of total oesophageal length.Cardia short, tongue shaped.Vulva a transverse slit, not sclerotized.Vagina piriform, slightly directed backward.Gonad monoopisthodelphic.Anterior uterine sac practically absent.Rectum as long as prerectum, 1.0-1.6 times longer than anal body diameter.Tail 4 anal body diameters long, first rounded then elongatedigitiform with finely rounded terminus.Andrassy (1987) opined that the species of Coomans and Carbonell (1981) described as Thornenema 100ft from the Ivory Coast agrees very well with L. tropicum.Shaheen and Ahmad (2005) described Tlwrnenema spicatum from soil around roots of forest trees from Haflong, North Cachar Hill, Assam State, India.The species is characterized by having small sized body (L=0.6 mm); abruptly narrowed, bottle-shaped anterior region; amalgamated lips; genital system mono-opisthodelphic with anterior uterine sac less than one anal body width long and spicate tail.In the characteristic shape of lip region the species closely resembles to the species of the genus Lagenonema.Thus we shifted the species from the genus Thornenema to Lagenonema, and described as L. spicatum.Besides the above characteristics, the other important characters of the species are slightly curved ventrad body upon fixation; cuticle with fine transverse striations; amphids with cup-shaped fovea and slit-like aperture; spear 1.8-2.0times the lip region width long with its aperture about one-third of its length; guiding ring single; odontophore 1.2-1.5 times the spear length; cardia dome-shaped; vulva a transverse slit, not sclerotized; prerectum and rectum 2.4-2.9 and 1.2 anal body widths long respectively; tail hemispheroid then spicate, terminus rounded.