Prodorylaimus filamentus, Gagarin, Vladimir G. & Naumova, Tatyana V., 2011

Gagarin, Vladimir G. & Naumova, Tatyana V., 2011, Prodorylaimus filamentus sp. n. and Eutobrilus longicaudatoides sp. n. (Nematoda) from Lake Baikal, Russia, Zootaxa 3103, pp. 57-68 : 58-60

Prodorylaimus filamentus sp. n. ( Dorylaimida : Dorylaimidae )

( Figs 1 , 2 ; Table 1 )

Type material. Holotype male, slide reference number 100/35, deposited in the collection of the Institute of Ecology and Evolution, Center for Parasitology, Russian Academy of Sciences (Moscow, Russia).

Paratypes. One male and one female deposited in the collection of the Institute of Ecology and Evolution, Center for Parasitology, Russian Academy of Sciences (Moscow, Russia); one male and five females deposited in the collection of the Limnological Institute, Siberian Branch of the Russian Academy of Sciences (Irkutsk, Russia).

Measurements. Table 1 .

Type locality. Academical Ridge, Lake Baikal, Siberia, Russia, depth 389 m, silt. Collected on 3 October 2009.

Additional locality. Mud volcano “Malen’kiy” (near settlement Bolshoe Goloustnoe (South Baikal)) from 1368 m depth, silt.

Etymology. The specific epithet means “thread-like”, referring to its long slender body.

Description. Male. Body long and thin, tapering toward both extremities. Cuticle finely transversely striated, 6.0–6.5 µm thick at mid-body. Lateral pores not visible. Lips amalgamated, labial and cephalic papillae indistinct. Labial region weakly off set. Amphidial fovea cup-like, wide, occupying 42–46 % of the corresponding body diameter and situated at the base of lips. Odontostyle straight and slender, 2.3–2.6 times the labial region diameter. Its aperture constituting 30–32% its length. Odontophore rod-like, 0.4–0.5 times as long as odontostyle. Guiding ring double, thick. Pharynx muscular, expanding gradually along its whole length. Pharyngeal gland nuclei indistinct. Cardia conoid, muscular, surrounded with intestinal tissue. Testes paired, opposed. Spicules dorylaimoid, 1.6–1.8 cloacal body diameter long, with two spindle-shaped lateral guiding pieces. In addition to adanal pair, a series of 29–31 contiguous ventromedian supplements are present. Prerectum long, well developed, 5.2–6.4 cloacal body diameters long, intestine-prerectum junction is located anterior to anteriormost supplement. Tail long, with proximal conical and distal thin, whip-like portions, gradually merging into one another. Distal portion of the tail is 15.0–16.2 times as long as its proximal portion.

Female. General morphology is similar to that of males in structure of cuticle and anterior body end. Cuticle finely transversely striated. Lips amalgamated. Labial region weakly off set. Amphidial fovea cup-like, wide, situated at the base of lips. Odontostyle straight and slender, 2.1–2.5 times the labial region diameter. Odontophore rod-like, 0.4–0.5 times as long as odontostyle. Guiding ring double, thick. Pharynx muscular, expanding gradually along its length. Pharyngeal gland nuclei indistinct. Prerectum 2.1–3.0 anal body diameter long. Rectum 1.0 to 1.2 times as long as anal body diameter. Reproductive system didelphic, amphidelphic. Vulva lips sclerotized, not protruding outside the body contour. Ovaries relatively short. Oocytes numerous, first in two rows, then in a single row. Uterus spacious, 2.0–2.5 times as long as the corresponding body diameter, with spindle-shaped spermatozoa. Uterus containing one or two eggs, measuring 162–195 x 55 –80 µm. Vagina extending inwards to half of the corresponding body diameter. Pars proximalis vaginae with straight walls, 53–60 µm long; pars refringens vaginae consisting of two drop-like sclerotizations; pars distalis vaginae short, with rounded walls. Vulva a longitudinal slit. Distance from vulva to anus 1.6–2.2 times as long as tail length. Tail long, with proximal conical and distal thin, whip-like portions, gradually merging into one another. Distal portion 14.5–18.3 times as long as its proximal portion.

Diagnosis. Body long and thin (L = 4.93–5.62 µm, a = 48–55 in males, L = 4.89–60.6 µm, a = 47–58 in females). Cuticle finely transversely striated. Labial region weakly off set. Odontostyle straight and slender, 60–65 µm long; its aperture constituting 30–35 % its length. Odontophore 25–29 µm long. Guiding ring double and thick. Pharynx muscular, expanding gradually along its whole length. Vulva a longitudinal slit. Distance from vulva to anus 1.6–2.2 times as long as tail length. Uterus spacious, with numerous spermatozoa and 1– 2 eggs, measuring 162–195 x 55 –80 µm. Spicules 89–90 µm long; 30–32 contiguous ventromedian supplements. Prerectum in males long, well developed, 5.2–6.4 cloacal body diameters long, intestine-prerectum junction always anterior to anteriormost supplement. Tail long, with proximal conical and distal thin, whip-like portions, gradually merging into one another. Distal portion 14.5–18.3 times as long as its proximal portion.

Differential diagnosis. Prodorylaimus filamentus sp. n. is similar to P. longicaudatoides Altherr, 1968 and P. kralli Tsalolikhin, 1975 . From the former species it differs in the longer body (L = 4.89–6.06 mm versus L = 2.0– 3.5 mm in P. longicaudatoides ), relatively longer tail (c’ = 18.4–25.0 versus c ʹ = 14–18 in P. longicaudatoides ), longer odontostyle (60–65 µm long versus 32–37 µm long), presence of a wide, double guiding ring (guiding ring is single in P. longicaudatoides ), longer spicules (89–90 µm long versus 70–78 µm long P. longicaudatoides ) ( Altherr 1968; Andrássy, 2009). From P. k r a ll i it differs in the longer tail (c = 4.3–6.0, c ʹ = 18.4–25.0 versus c = 7.0–8.0, c’ = 11–16 in P. k r a l l i), “vulva-anus to tail length” ratio (1.6–2.2 versus 2.5–3.0 in P. k r a l l i), shorter odontostyle (60–65 µm long versus 75–80 µm long in P. k r a l l i) ( Tsalolikhin, 1975).

Discussion. The genus Prodorylaimus includes 22 valid species ( Alekseev & Dolgova, 1993; Loof, 1996; Vinciguerra & Orselli, 2011; present article). Four of them are found in Lake Baikal and are endemic to this lake: P. kralli , P. eliavai , P. kukuy , and P. filamentus sp. n. ( Table 2). P. kralli was synonymized with P. longicaudatoides Altherr, 1968 by Andrássy (1988). However, it differs from P. longicaudatoides in the longer body (L = 3.28–5.60 mm versus L = 2.0– 3.5 mm in P. longicaudatoides ), longer odontostyle (75–80 µm long versus 32–37 µm long in P. longicaudatoides ), presence of double and wide guiding ring (single, thin guiding ring in P. longicaudatoides ), “vulva-anus to tail length” ratio (2.5–3.0 versus 1.5 in P. longicaudatoides ), longer spicules (91 µm long versus 70–78 µm long in P. longicaudatoides ) ( Altherr, 1968; Tsalolikhin, 1975) ( Table 2). Therefore we consider P. k r a l l i to be a valid species of the genus Prodorylaimus .

eliavai kukuy kralli filamentus

males females males females males females males females L 4880–4950 2900–4200 2200–2500 2100–2800 4650 3280–5500 4933–5624 4890–6063 a 31–35 22–28 17–23 17–25 60 37–44 48–55 47–58 b 4.4–4.8 3.5–4.2 3.7–4.1 3.4–4.0 5.1 4.7–5.5 5.7–5.8 5.2–6.6 c 15.7–35.3 5.0–16.8 15.3–19.4 15.0–18.0 7.7 7.0–8.0 4.3–5.5 4.7–6.0 cˏ 3.5 6.5 3.0 3.5 11–16 18.6–23.2 18.4–25.0 V, % – 48–55 – 49–53 47–50 – 40.0–48.1 ods. 45–70 45–49 75–80 63–65 60– 63 v. a. t. – 5.0–6.0 – 6.0–7.0 2.5–3.0 – 1.6–2.2 spic. 90–93 – 70–75 – 91 – 89–90 –

n. sup. 29–31 – 26–29 – 28 – 30–32 –

Figures

FIGURE 1. Prodorylaimus filamentus sp. n., holotype male and paratype female. A: male, entire body; B: female, entire body; C: male head; D: vulval region; E: male, posterior body end. Scale bars: A, B = 500 µm; D = 100 µm; E = 70 µm; C = 40 µm.

FIGURE 2. Prodorylaimus filamentus sp. n., paratype male and female. A: male, entire body; B: female, entire body; C: vulval region and egg; D: anterior ovary; E: male head; F: spicules; G: supplements. Scale bars: A, B, D = 200 µm; C = 100 µm; E, F, G = 20 µm.

Tables

TABLE 1. Morphometrics of Prodorylaimus filamentus sp. n. (all measurements are given in µm unless otherwise stated, except for the ratios a, b, c, c ʹ, V, n. sup., ods. l. g., pr. an. n., spic. cl. and v. a. t.)

Character	Holotype male	Paratype males (n=2)	Paratype females (n = 6) range mean
L a b	5610 48 5.8	4933, 5624 49, 55 5.8, 5.7	4890–6063 5516 47–58 50 5.2–6.6 5.7
c cˏ V, %	5.3 18.6 –	4.3, 5.5 23.2, 22.1 –	4.7–6.0 5.5 18.4–25.0 20.9 40.0–48.1 45.6
diam. l. r. diam. midb. a. d.	26 117 57	25, 28 100, 101 50, 52	25–28 27 102–123 109 45–52 49
ods. ods. l. r. odph.	63 2.5 27	64, 65 2.6, 2.3 27, 29	60–63 62 2.1–2.5 2.3 25–28 27
am. w. ph. l. dis. ph. cl.	18 960 3588	18, 20 850, 962 2925, 3512	18–21 19 925–1077 972 – –
dis. ph. v. dis . v. a. t. l.	– – 1062	– – 1158, 1150	1375–1700 1533 1582–2525 1964 863–1200 1047
v. a. t. pr. l. pr. an.	– 296 5.2	– 278, 333 5.6, 6.4	1.6–2.2 1.9 100–155 125 2.1–3.0 2.5
spic. spic. cl. gub. l.	89 1.6 –	90, 89 1.8, 1.7 –	– – – – – –
l. g. p.	15	16, 15	– –
n. sup. l. sup. r.	32 370	32, 30 328, 362	– – – –