Miodorylaimus istvani, Sen, 2019

Sen, Debabrata, 2019, A new species and a new record of Nematoda (Dorylaimida) with further observation on Neoctinolaimus chitwoodi (Moorthy, 1937) Thorne, 1967 from Uttar Pradesh, India, Records of the Zoological Survey of India 119 (4) : -

1. Miodorylaimus istvani sp. n.

Measurements: See Table 1. The minimum-maximum ranges of measurements given hereafter are based on holotype and one female paratype.

Description of female: Body moderately slender,slightly ventrally curved on fixation, gradually tapering towards both extremities. Cuticle thin, 1-1.5μm thick at the level of odontostyle, 1.5-2μm at mid body, 2-2.5μm on tail. Body pores indistinct. Lip region rounded, confluent with the body contour or very minutely set off by depression, with same diameter or narrower than adjoining body, 4μm high, 10μm wide or 1/2.5 to one third of body width at neck base. Amphids cup-shaped, 6-6.5μm wide or about more than half (1/1.5-1/1.6) of the corresponding body width. Odontostyle slender, 12-13µm or about

1.2-1.3 lip region-widths long, its aperture about one-third of stylet length or occupying 33.3 - 38.4% of stylet. Odontophore weak, straight, 1.6-1.8 lip region-widths long. Guiding ring thin, not prominent, 7-8μmfrom anterior end. Nerve ring at 86-92μm from anterior end. Expanded portion of pharynx starts little posterior to the middle of the pharynx occupying 45.2-48.7% of the total pharyngeal length. Cardia 20μm long in holotype, conoid, terminally pointed. Vulva transverse, not cuticularised, slightly pre-equatorial. Vagina extending inward half of the corresponding body width. Reproductive system amphidelphic, posterior gonad slightly longer than anterior gonad in Holotype but both the gonads are almost same in length in Paratype. Both ovaries reflexed, posterior ovary longer than anterior ovary. Oocytes arranged in a single row except at tip. Prerectum 2.2-2.6, rectum 1.1-1.2 anal-body-width long. Tail 7.8 anal-body-widths long, attenuated, aneriorly convex and posteriorly A new species and a new record of Nematoda ( Dorylaimida ) with further observation on Neoctinolaimus chitwoodi ... narrow, gradually tapering, ending in a pointed terminus.

Description of male: Similar to females in general morphology with the following exceptions. Posterior half of body more ventrally curved. Testes outstretched. Spicules well developed, cuticularised, 1.7-1.9 anal-body-widths long when measured through its median axis, dorylaimoid. Supplements conspicuous, distinct on the outer cuticular body wall, consists of 8 almost regularly spaced ventromedians and an adanal pair, the space between supplements ranges between 7-11mm, the space being less towards the posterior-most supplement. Prerectum 2.7-3.0, rectum 1.6-1.8 anal-body-widths long. Tail short, little ventrally curved, terminally round, one anal-body-width long (1.0-1.05).

Diagnosis and characteristics: Body medium and moderately slender. Cuticle thin. Lip region continuous with body contour or minutely separate by little depression. Odontostyle slender with weak and straight odontophore.

A B

D

F

C

E

G

H

J

I

Expanded portion of pharynx starts posterior to the middle of pharynx. Vulva not cuticularised. Tail dissimilar in sexes as usual in the family Dorylaimidae . Female tail long with anterior convex portion and gradually narrow and attenuated posterior portion. Male tail short and rounded. Spicules well developed, dorylaimoid. Supplements well marked and consists of 8 spaced ventromedians.

Differential diagnosis and relationship: Miodorylaimus istvani sp. n. comes close to M. decens Andrásssy, 1986 and M. iucundus Andrásssy, 1986 in general morphology and in some morphometrics with some well marked differences leading towards its separate identity. The females of proposed new species differs from M. decens in having a comparatively less slender and wide body evident from ‘ a ’ value and maximum body width, anteriorly located vulva, shorter rectum and prerectum and longer tail (in female of M. decens a = 50; maximum body width = 22-25μm; V = 52%; prerectum = 3.3 and rectum = 1.4 anal-body widths long; tail length = 123μm). The males of the new species differ by the possession of wider body as in females, shorter tail, well developed longer spicules and well marked 8 ventromedian supplements (in males of M. decens a = 46-49; tail length = 22-25μm; length of spicules = 24- 25μm and number of ventromedian supplements = 4. Miodorylaimus istvani sp. n. differs from M. iucundus in having males, longer and comparatively more slender body evident from ‘ a ’ value, longer pharynx, shorter tail and longer prerectum in females (in females of M. iucundus total body length (L) = 0.88 -0.90mm; a = 32- 33; length of pharynx = 192-195μm; tail length = 222- 225μm; c / = 14-15 and prerectum = 1.8 anal-body width long; males unknown in M. iucundus )

Morphometrics of M. decens and M. iucundus after Andrásssy (1986a)