Laimydorus istvani, Sen, Debabrata, Chatterjee, Amalendu & Manna, Buddhadeb, 2012

Sen, Debabrata, Chatterjee, Amalendu & Manna, Buddhadeb, 2012, One new and two known species of Dorylaimoidea (Nematoda) from West Bengal, India, Zootaxa 3258, pp. 46-57 : 47-51

Laimydorus istvani sp. n.

( Figs 1 and 2 )

Measurements. See Table 1 . The measurements given are based on the holotype. Minimum-maximum ranges of measurements of paratypes are given in parentheses.

Females. Body almost straight upon fixation, tapering towards both extremities. Cuticle with fine transverse striations, 2–3.5 Μm thick at anterior end at the level of middle of odontostyle and also at mid body, 6–7 Μm thick at the base of the tail. Body pores indistinct. Lip region slightly offset by a depression, narrower than adjoining body, 6 (5–7) Μm high, 14 Μm or 0.7 (0.7–0.8) adjacent body-widths wide. Amphids stirrup-shaped, their apertures occupying 8 (6.5–8) Μm or about 44% (40–44%) of the corresponding body width and at 7 (6.5–8.5) Μm from anterior end. Odontostyle about 2.2 (2–2.3) lip region-widths long, 5 (3.5–5) Μm thick near middle, distinctly thicker than the cuticle at the same level, aperture occupying 10 (10–12) Μm or 31.2 (31.2–37.5)% of odontostyle length. The anterior border of the double guiding ring inconspicuous with a faint impression in the holotype female but prominent in paratypes (both in males and females), 21 (17–21) Μm or 1.5 (1.2–1.5) lip region-widths from anterior end. Odontophore 1 (1–1.2) times the odontostyle length. Nerve ring at 157 (147–173) Μm, or at 28% (25– 29%) of the pharyngeal region, from the anterior end. Expanded portion of pharynx 4.5 (3.8–4.6) times the neck base-width or 53% (49–53%) of the pharyngeal length. Basal expanded portion of pharynx heavily muscular. Glandularium 83% (84–87%) of the cylindrus. Locations of pharyngeal gland nuclei are: D = 55 (51–57)%; AS 1 = 37 (30–38)%; AS 2 = 38 (32–40)%; PS1 = 59 (51–62)%; PS2 = 61 (54–64)%. Cardia rounded-conoid, sometimes wide at pharyngo-intestinal junction, enveloped by intestinal tissue which forms a conical projection extending into the lumen of intestine. A delicate ring-like structure surrounds the junction between the pharyngeal base and the cardia proper, 22 (17–22) Μm long. Vulva transverse, slightly pre-equatorial. Vagina 26.5 (22–29) Μm in length or 41 (32–44) % of corresponding body width, sclerotisation absent. Length of pars proximalis vaginae 17 (14.5– 19.5) Μm, pars refringens vaginae 7 (3.5–7) Μm, combined width of pars refringens vaginae 9.5 (9.5–12) Μm and length of pars distalis vaginae 2.5 Μm. Reproductive system didelphic-amphidelphic, with both genital branches well developed, posterior branch longer than the anterior; anterior branch 600 (431–705) Μm and posterior branch 752 (468–794) Μm long. Uterus short, simple, muscular, tubular but dilated in few specimens because of the presence of intra-uterine eggs, filled with spindle-shaped sperms in some specimens; in the holotype containing two anterior and two posterior intrauterine eggs. One paratype containing five intrauterine eggs – two eggs in the anterior branch measuring (86 × 37) Μm and (88 × 34) Μm, respectively; three eggs in the posterior branch of gonad measuring (86 × 34) Μm, (88 × 34) Μm and (83 × 37) Μm respectively; the size of eggs in holotype within the same range as those in the paratype. Sphincter separating oviduct from uterus, but not very marked. Oviduct narrow, tubular and convoluted joining the ovary subterminally. Ovaries large, reflexed, occasionally surpassing the sphincter level, anterior ovary 233 (120–269.5) Μm and posterior ovary 282 (135–321) Μm long. Oocytes numerous, arranged in a single row except at the terminal growth region. Pre-rectum 3.9 (3.9–4.8) and rectum 1.0 (1.0–1.3) anal body-widths long. Tail elongate filiform, slightly dorsally curved towards terminus, 9.0 (6.2–9.5) anal body-widths long.

Male: B. Entire body, D. Pharyngo-intestinal junction and cardia, G. Posterior end showing ventromedian supplements, spicule and tail, J. Anterior end of male showing double guiding ring, L. Spermatozoa.

Males. Similar to females in general body shape and morphology, except in details of the reproductive system. Testes outstretched. Spermatozoa fusiform or spindle-shaped measuring 8–12Μm. Ventromedian supplements arranged in a contiguous series of 22–27, with an adanal pair. One pair of post anal papillae present. Spicules 49– 54 Μm long along the median axis or 1.3–1.4 anal body-widths long. Lateral guiding piece about 1/4–1/3 of the spicule length. Pre-rectum longer than female, 6.2–8.1 and rectum 1.1–1.5 anal body-widths long. Tail short, ventrally curved, rounded, 0.5–0.7 anal body-width long.

Type habitat and locality. Collected on 23.09.2005 from the soil around the roots of guava at Kalibari, Palpara and Sikharbali of Baruipur block (latiude 22.36° east and longitude 88.43° north) and from Bishnupur block ((latiude 22.38° east and longitude 88.27° north), South, 24-Parganas district, West Bengal, India.

Type specimens. Holotype registration number WN 1016 along with three female and two male paratypes on the same slide. Paratype registration numbers WN 1017 (four females, three males) and WN 1018 (four females, four males), deposited in the National Zoological Collection, Zoological Survey of India, Kolkata, India.

Etymology. The new species has been named after the eminent nematologist Dr. István Andrássy.

Diagnosis and relationships. Laimydorus istvani sp. n. is characterized by its medium body length (L = 2.5– 2.9 mm), slender body evident from a value (a = 39–46), shorter tail (213–323 µ m) in relation to body length evident from c -value (c = 9.0–13.4), odontostyle being distinctly thicker than the cuticle at the same level and by the shape of cardia (cardia rounded-conoid, sometimes wide at pharyngo-intestinal junction, enveloped by intestinal tissue which forms a conical projection extending into the lumen of intestine; a delicate ring-like structure surrounding the junction between the pharyngeal base and the proper cardia).

Laimydorus istvani sp. n. comes close to L. multialaeus ( Khera, 1970) Baqri, 1985 , L. siddiqii Baqri & Jana, 1982 and L. baldus Baqri & Jana, 1982 . The proposed new species comes close to L. multialaeus due to its odontostyle being distinctly thicker than cuticle at the same level as indicated by Andrássy (1988). Other similarities include overlapping body length in female and number of ventromedian supplements in male, but it differs from L. multialaeus in having longer body in males (L = 2.5–2.7 vs. 2.0– 2.2 mm); higher a value (a = 39–46 vs. 35–38), lower b value (b = 4.7–5.0 vs. 5.3–5.9) and longer odontostyle (30–34 vs. 25–28 Μm) in females. Males differ from those of L. multialaeus in having longer lateral guiding pieces (12–20 vs. 9–11 Μm) and tail (22–27 vs. 20–21 Μm).

From L. siddiqii , females of the new species differ in having a shorter tail in relation to body length (213–323 vs. 322–363 Μm), evident from higher c -value (c = 9.0–13.4 vs. 7.8–8.2), shorter cardia with different shape, shorter pre-rectum (135–164 vs. 177–208 Μm) and longer rectum (37–47 vs. 33–35 Μm). Males differ from those of L. siddiqii in number of ventromedian supplements (22–27 vs. 21-26 supplements) and shorter spicules (49–54 vs. 53–57 Μm).

From L. baldus it differs in having a longer body (L = 2.5–2.9 vs. 1.9–2.4 mm), higher a -value (a = 39–45.5 vs. 31-36), longer odontostyle (30-34 vs. 24–26.5 Μm) and odontophore (32–36 vs. 29–41 Μm), and longer tail (213– 323 vs. 167-224 Μm) in females. Laimydorus istvani sp. n. differs from the males of L. baldus in having a longer body (L = 2.5–2.7 vs. 1.8–2.1 mm), much greater c value (c = 94.3–112 vs. 77–79.8) and somewhat lesser number of ventromedian supplements (22–27 vs. 24–28).

Discussion. Khera (1970) described the new species Dorylaimus multialaeus from Lucknow, India. Baqri (1985) re-studied the specimens and re-designated the specimens as Laimydorus multialaeus , a new combination, due to the absence of cuticular longitudinal ridges (the presence of longitudinal ridges on the cuticle is characteristic of the genus Dorylaimus and some other members of the subfamily Dorylaiminae). Jairajpuri and Ahmad (1992) included the species under the genus Dorylaimus but Andrássy (1988) again placed it under Laimydorus supporting the view of Baqri (1985). The present new species of Laimydorus has been compared with L. multialaeus because of their morphological similarities.

Figures

FIGURE 1. Laimydorus istvani sp. n. Female: A. Entire body, C. Anterior end, E. Pharyngo-intestinal junction and cardia, F. Tail, H. Posterior branch of gonad showing intra-uterine eggs, I. Anterior end showing amphid, K. Anterior end of a female paratype showing double guiding ring.

FIGURE 2. Photomicrographs of Laimydorus istvani sp. n. Female: A. Entire body, C. Anterior end, D. Vulva and intrauterine eggs, E. Rectum and prerectum, F. Tail end, G. Pharyngo-intestinal junction and cardia. Male: B. Entire body, H. Spicules, I. Posterior end, J. Pharyngo-intestinal junction and cardia, K. Ventromedian supplements.

Tables

TABLE 1. Morphometrics of Laimydorus istvani sp. n. (All measurements are in Μm except L and body ratios, L in mm).

Characters	Holotype female	Paratype females	Paratype males
n		11	9
L	2.8	2.7±0.19 (2.5–2.9)	2.5±0.09 (2.5–2.7)
a	41.8	42.0±2.69 (39–45.5)	36.5±1.90 (34–38.6)
b	5	4.8±0.08 (4.7–4.9)	4.6±0.18 (4.4–4.8)
c	9	10.2±1.83 (9–13.4)	101.2±7.02 (94.3–112)
c’	9	8.5±1.29 (6.2–9.5)	0.6±0.08 (0.5–0.7)
V %/ T%	42.5	44.8±1.46 (42.7–46.6)	56.5±1.77 (54.8–59.2)
G1%	21.4	21.1±2.82 (17.5–24.3)	––
G2 %	26.8	22.1±3.71 (18.7–27.2)	––
Odontostyle length	32	32.4±1.67 (30–34)	32.4±0.89 (32–34)
Odontophore length	32	35.2±1.09 (34–36)	34.4±1.67 (32–36)
Odontostyle aperture	10	10.8±0.83 (10–12)	10.8±1.09 (10–12)
Odontostyle width	5	4.4±0.67 (3.5–5)	4.6±0.55 (3.5–5)
Maximum body width	67	66.6±7.58 (54.0–73.5)	70.3±5.80 (66.0–80.0)
Body width below lip region	18	18.6±0.89 (17–19)	18.6±0.89 (17–19)
Body width at neck base	66	66.1±7.50 (54–74)	67.6±5.09 (63.5–76)
Body width at vulva	66	66.1±8.62 (51–73)	––
Pharynx length	556	570±38.06 (510–605)	555.6±38.49 (519–610)
Expanded part of pharynx	297	285.6±25.64 (252–319)	279.8±23.27 (257–311)
Glandularium	247.5	248.5±12.02 (240–257)	243.8±39.88 (215.6–272)
Length of cardia	15	18.0±2.8 (14.5–22)	15.8±3.14 (12.0–19.5)
Length of anterior gonad	600	591.8±111.21 (431–705)	––
Length of posterior gonad	752	617.6±130.03 (468–794)	––
Anterior end to vulva	1191	1250.6±90.18 (1122–1340)	––
Tail length	309	276.8±41.95 (213–323)	25.5±2.23 (22–27)
Anal body width	34	32.6±2.19 (29–34)	37.2±2.05 (34–39)
Length of prerectum	135	146.0±14.28 (135–164)	272.5±33.37 (245–319)
Length of rectum	37	41.9±4.88 (37–47)	44.7±2.05 (42–47)
Testis length	––	––	1451.8±67.15 (1397–1531)
Length of spicules	––	––	52±2.74 (49–54)
Lateral guiding piece	––	––	15.9±2.95 (12–19.5)
Ventromedian supplements	––	––	24±1.87 (22–27)