COSMOCERCOIDEA Raillet, 1916

González, Cynthya Elizabeth & Hamann, Monika Inés, 2013, Schrankiana chacoensis sp. nov. (Nematoda: Atractidae) from Leptodactylus bufonius Boulenger, 1894 (Anura: Leptodactylidae) from Argentina, Journal of Natural History 48 (1 - 2), pp. 35-49 : 36-47

Superfamily COSMOCERCOIDEA Raillet, 1916

Family ATRACTIDAE (Railliet, 1917 subfam.) Travassos, 1919 Genus Schrankiana Strand, 1942 (= Schrankia Travassos, 1925 ; = Schranknema Travassos, 1949 ) Schrankiana chacoensis sp. nov.

( Figures 1 , 2 )

Description

General. Cylindrical nematodes with fine transversally striated cuticle, distance between striations 3–4 µm at level of excretory pore. Males and females of similar length, maximum width occurring at level of oesophageal–intestinal junction in males and at half of total body length in females ( Figure 1A, B ). Lateral alae present in both sexes. Oral opening triangular with three lips; dorsal lip with two large papillae, subventral lips with one large papilla on each one. One forked amphid on each subventral lip. Each lip with cuticular flange overhanging mouth opening ( Figures 1C , 2A ). Pharynx relatively elongate and slender; oesophagus divided into three parts: muscular corpus, short isthmus and well-developed posterior bulb with valves ( Figure 1D ). Anterior extremity of oesophagus with three large and relatively elongate tooth-like projections. Excretory pore anterior to level of bulb; large, slit-like, with small comblike fringe in the posterior and anterior edges ( Figure 2B, C ). Viviparous. Monodelphic and prodelphic; vulva located just anterior to anus. Tail conical and sharply pointed in both sexes ( Figure 2D, F ). Somatic papillae minute, distributed over body surface.

Male. (measurements of holotype and paratypes are given in Table 1). Lateral alae extending from anterior third of oesophagus to the level of first pair of precloacal papillae. Tail short, conical, with caudal appendage. Fourteen pairs of sessile caudal papillae and one unpaired papilla anteriorly to cloaca; these papillae present the following disposition ( Figures 1E , 2D ; Table 2): five pairs of precloacal papillae [distance

Females

Length 1.93 ± 79.12 mm (1.8–2.07) [2.01 mm] 2.51 mm (2.33) 2.9 mm (2.9–3.2) 2.41 mm (2.14–2.41) [a: 2.70–2.81; b: 1.43–1.75]

Width 100.8 ± 11.9 (85–135) [90] − − 170 (130–200)

Pharynx 28 ± 3.29 (20–32) [27] × 19.06 ± 4.65 − 52 (35–48) 42 (25–31 × 13–17) (15–30) [15]

Oesophagus (total length) 423.15 ± 45.88 (310–476) [477] 392 (400) 737 (645–753) 400–480 [a: 483–513;

b: 377–440]

Corpus 287.69 ± 46.53 (190–350) [330] × 34.3 − 570 (510–585) 270–340 × 31–42

± 3.9 (28–40) [34]

Isthmus 52.28 ± 13.16 (38–80) [65] × 19.64 ± − 35 (25–40) 42–80 × 17–25

2.13 (16–25) [20]

Bulb 83.06 ± 8.41 (60–95) [82] × 76.2 ± 5.5 − 80 (72–90) 84 × 84 (76–88 × 76–92) (66–87)[71]

Nerve ring ∗ 157.36 ± 18.48 (130–195) [180] 153 (151) 250 (245–280) 210 (180–220) [a: 186–219; b: 165–180]

Excretory pore ∗ 324.73 ± 48.3 (250–500) [380] 288 (279) 580 (495–615) 370 (330–380) [a: 378–408; b: 269–330]

Tail 125.46 ± 19.10 (110–175) [120] 190 (204) 152 (149–170) 150 (110–160) [a: 164–179; b: 126–134]

Vulva ∗∗ 309.3 ± 55.49 (260–425) [285] 448 (471) 337 (325–367) 350 (320–390) [a: 356–390; b: 251–274]

Vagina 85.16 ± 6.20 (75–93) [85] − 300 140–220 [a: 120–200]

Distance Vulva / Anus 172.45 ± 28.07 (145–225) [165] − − −

Eggs 216.26 ± 26.42 (181–300) [287] × 109.6 − 235–335 × 95–150 217 × 122 (165–235 ×

± 13.53 (94–150) [117] 104–174) (Continued)

Females

Length 2.05–3.07 mm [a: 2.61–2.78; 2.08–2.51 mm (2.5) 4.62–6.53 mm [a: 2.68–3.05 [a: 2.5–3.6; b:

b: 2.70–2.80] 5.0–6.2; b: 6.82–7.32] 2.51–3.64; c: 3.5–4.15] Width 130–140 [a: 140–210; b: –] 120–180 (160) 230–350 [a: 300; b: –] 150–190 [a: 190–200;

b: 170–250; c: 200–250] Pharynx 41–49 [a: 38–44 × 21–27; b: –] 34–42 × 21–25 96–113 × 26–29 29–34 × 38–40 [a: 33–40 ×

[a: 100–110; b: –] 33–40; b: 32; c: –] Oesophagus (total length) − [a: 560–710; b: 587–682] 540–680 (550–600) 1.02–1.35 mm 440–460 [a: 450–490;

[a: 1.02–1.2; b: 1.45–1.58] b: –; c: –]

Corpus − [a: 450–560 × 38–50; b: –] 470–580 × 31–46 Corpus divided Corpus divided Isthmus [a: 38–63 × 21–25; b: –] 340–550 × 21–34 29–35 × 25–43 [a: –; b: –] 59–63 × 29–31

[a: –; b: 40–80; c: –]

Bulb 99–107 × 83–107 84–101 × 76–101 71–113 × 84–113 84–92 × 84–97 [a: –;

[a: 67–105 × 76–113; b: –] (100–120 × 70–100) [a: 80–100; b: –] b: 69–110; c: –]

Nerve ring ∗ 200–210 [a: 220–270; b: 204–219] 210–250 330–340 [a: 340–370; 180–190 [a: 150–160;

b: 320–372] b: 120–190; c: –] Excretory pore ∗ [a: 460–610; b: 398–547] 460–580 70–95 [a: 800–900; 350–380 [a: 360–370;

b: 845–980] b: 280–360; c: –]

Tail 132–157 [a: 130–150; b: 168–190] 160–220 (160–200) 280–330 [a: 370; 150–200 [a: 174–249;

b: 335–380] b: 160–240; c: 220] Vulva ∗∗ 260–290 [a: 300–370; b: 290–363] 290–430 (350–370) 480–600 [a: 550–620; 550–800 [a: 590–770;

b: 575–696] b: 72–99; c: 350–400] Vagina − [a: 100–160; b: –] 140–190 − 100–160 [a: –; b: –; c: –] Distance Vulva / Anus − − − −

Eggs 207–282 × 99–124 [a: 200–287 × 270–278 × 113–174 398–548 × 199–300 261–299 × 130–149

130–200; b: –] (250 × 100) [a: 425–475 × 225–300; [a: 373 × 199; b: 240–350 ×

b: –] 110–240; c: 360 × 320] Notes: ∗ From anterior end.

∗∗ From posterior end.

† Measurements based on Freitas (1959) and in brackets based on Baker and Vaucher (1988) from L. fuscus (a) and from L. elenae (b).

‡ Measurements based on Fahel (1952) and in brackets based on (a) Freitas (1959) and (b) based on Baker and Vaucher (1988).

§ Measurements based on Freitas (1959) and in brackets based on Travassos (1925).

¶ Measurements based on Freitas (1959) and in brackets based on (a) Travassos (1927) and (b) based on Baker and Vaucher (1988).

∞ Measurements based on Freitas (1959) and in brackets based on (a) Fahel (1952), (b) based on Guimarães et al. (1976) and (c) based on Vaz (1933).

(1988) papilla. Anterior half of tail: pairs I and II

(subventral), near cloaca.

Posterior half of tail: pair III (lateral),

IV (subventral) and V (subdorsal). Total pairs: 12 S. incospicata † Freitas (1959) Total : 3 sublateral pairs Total: 3 small papillae. Total: 3 pairs Total pairs: 6 pairs + 3 S. schranki † Freitas (1959) Total : 3 sublateral pairs. Total: 3 small papillae. Total: 3 pairs. Total pairs: 6 pairs + 3 S. brasili Baker and Vaucher Total : 4–5 subventral Total: 3 pairs + 1 unpaired Total: 5 pairs.

(1988) pairs papilla. Anterior half of tail: pairs I and II

(subventral), near cloaca. Total pairs: 12–13 Posterior half of tail: pair III (lateral),

IV (subventral) and V (subdorsal). S. brasili Freitas (1959) Total : 3 sublateral pairs. − Total: 2 pairs. Total pairs: 5 S. larvata Fahel (1952) and Total: 3 sublateral pairs − Total: 3 pairs.

Freitas (1959) Total pairs: 6 S. larvata Baker and Vaucher Total : 4–5 subventral Total: 3 pairs + 1 unpaired Total: 5 pairs.

(1988) pairs. papilla. Anterior half of tail: pairs I and II

(subventral), near cloaca. Total pairs: 12–13 Posterior half of tail: pair III (lateral),

IV (subventral) and V (subdorsal). Notes: ∗ All adcloacal papillae on anterior margin of cloaca. † Pairs of caudal papillae (precloacal and postcloacal) + papillae on anterior margin of cloaca.

first to second pair: 27.25 ± 4.49 (20–30) [29]; distance second to third pair: 23.41 ± 4.92 (17–30) [28]; distance third to fourth pair: 18.1 ± 3.0 (14–25) [25]; fifth pair at level of cloaca]; three pairs of adcloacal and one large unpaired papilla on anterior margin of cloaca ( Figure 2E ); six pairs of postcloacal papillae (first two ventral pairs immediately behind cloaca; third pair lateral, approximately at middle of tail length; fourth pair ventral in posterior third of tail; fifth and sixth pairs at beginning of caudal appendage, these last two pairs at the same level, one ventral and one subventral). Posterior margin of cloaca with cuticular comb-like fringe. Spicules relatively short, curved ventrally, sharply pointed distally and with variably shaped capitulum; gubernaculum sclerotized, elongated, posterior end pointed ( Figure 1F, G ). Caudal alae absent.

Female. (measurements of allotype and paratypes are given in Table 1). Lateral alae extending from anterior third of oesophagus at level of vulva. Vulva, transverse slit, slightly prominent; vagina well developed, directed anteriorly ( Figure 1H ). Uteri with one to three oval eggs, thin shelled, some of them with larvae.

Site of infection

Large intestine.

Type locality

Taco Pozo , Almirante Brown Department, Chaco Province, Argentina (25 ◦ 36 ′ 54 ′′ S, 63 ◦ 15 ′ 54 ′′ W) .

Deposition of types

Holotype (male), allotype (female) and paratypes (five males, five females) in Helminthological Collection of the Museum of La Plata (Holotype: MLP-He 6650; allotype: MLP-He 6651; paratypes: MLP-He 6652); paratypes (five males, five females) in Helminthological Collection of Centro de Ecología Aplicada del Litoral (CECOAL 11101910).

Host

Leptodactylus bufonius Boulenger, 1894 ( Anura , Leptodactylidae ), the Vizcacheras’ White-lipped frog, Herpetology Collection of the Centro de Ecología Aplicada del Litoral (LHC 5062, LHC 5063).

Etymology

The new species is named in reference to its biogeographical region of collection.

Differential diagnosis

Species of the genus Schrankiana are distinguished by their oesophageal shape, cephalic morphology, extent of the lateral alae, location of the vulva, size of the vagina, and male caudal features (e.g. papillae and spicules) ( Baker and Vaucher 1988).

The new species described here is distinguished from the remaining species of the genus by its cephalic morphology: S. chacoensis sp. nov. possesses four large papillae on the lips (two on the dorsal lip and one on each subventral lip) without any other small papillae (which are present in the remaining Schrankiana species ) and the possession of amphids with forked shape; also by having a shorter vagina; the lateral alae ending well anterior to the anus in both sexes, an additional pair of postcloacal papillae compared with the other species, and a “fringe” in the posterior and anterior margins of the excretory pore.

Schrankiana chacoensis sp. nov. differs from Schrankiana fuscus Baker and Vaucher, 1988 mainly by the following characters: (1) smaller size of males and females; (2) smaller size of spicules and gubernaculum; (3) short posterior uterine pouch (absent in S. chacoensis sp. nov. versus present in S. fuscus ); (4) shorter distance between vulva and posterior extremity; (5) presence of caudal appendage; (6) number and arrangement of precloacal and postcloacal papillae (see Tables 1 and 2).

Schrankiana chacoensis sp. nov. differs from Schrankiana freitasi Baker, 1982 by the following characteristics: (1) smaller size of males and females; (2) shorter total length of oesophagus in males and females; (3) smaller spicules and gubernaculum; (4) smaller vagina; (5) short posterior uterine pouch (absent in S. chacoensis sp. nov. versus present in S. freitasi ); (6) presence of a caudal appendage; (7) number and arrangement of postcloacal papillae (see Tables 1 and 2).

The new species differs from Schrankiana formosula Freitas, 1959 by the following characteristics: (1) smaller spicules and gubernaculum; (2) smaller vagina; (3) absence of short posterior uterine pouch [present in Paraguayan specimens studied by Baker and Vaucher (1988)]; (4) number and arrangement of caudal papillae ( Tables 1 and 2).

The new species differs from Schrankiana incospicata Frietas, 1959 by the following characters: (1) smaller size of males and females; (2) shorter total length of oesophagus in males and females; (3) smaller vagina compared with Brazilian specimens studied by Freitas (1959); in Paraguayan specimens the vagina is divided into vagina uterina and vagina vera ( Baker and Vaucher 1988); (4) modification of anterior end of oesophageal corpus that includes cuticular rod-shaped structures in S. incospicata ( Baker and Vaucher, 1988) ; (5) number and arrangement of caudal papillae ( Tables 1 and 2).

Schrankiana chacoensis sp. nov. differs from S. schranki ( Travassos, 1925) Strand, 1942 mainly by the following characters: (1) shorter total length of oesophagus in males and females; (2) smaller spicules; (3) smaller vagina; (4) number and arrangement of caudal papillae ( Tables 1 and 2).

Schrankiana chacoensis sp. nov. differs from S. brasili ( Travassos, 1927) Fahel, 1952 by the following characters: (1) shorter total length of males and females; (2) shorter total length of oesophagus in males and females; (3) morphology of the corpus [divided into procorpus and metacorpus in S. brasili ( Freitas, 1959) ]; (4) smaller spicules and gubernaculum; (5) morphology of the vagina [divided into vagina uterina and vagina vera in S. brasili ( Baker and Vaucher, 1988) ]; (6) shorter distance between vulva and posterior extremity; (7) number and arrangement of caudal papillae compared with Paraguayan and Brazilian specimens ( Freitas 1959; Baker & Vaucher 1988) ( Tables 1 and 2).

The new species described here differs from S. larvata ( Vaz, 1933) Fahel, 1952 by the following characteristics: (1) shorter total length of males and females; (2) morphology of the corpus [divided into procorpus and metacorpus in S. larvata ( Freitas, 1959) ]; (3) smaller vagina; (4) shorter spicules and gubernaculum; (5) smaller distance between vulva and posterior end compared with specimens studied by Freitas (1959) and Fahel (1952); (6) number and arrangement of caudal papillae ( Tables 1 and 2).

Below we provide a key for the species of Schrankiana .

1. Lateral alae ending at end of oesophagus in both sexes; 17–19 pairs of subventral precloacal muscle cells; total length of oesophagus 800 µm or longer.................................................................... S. brasili Lateral alae extending beyond end of oesophagus in both sexes; four to six pairs of subventral precloacal muscle cells; total length of oesophagus less than 800 µm........................................................... 2

2. Four large labial papillae; six pairs of postcloacal papillae; forked amphids............................................................... S. chacoensis Ten labial papillae; fewer than six pairs of postcloacal papillae; flat amphids........................................................................ 3

3. Eleven or more pairs of precloacal muscle cells; lateral alae not reaching level of anus................................................................ 4 Fewer than 11 pairs of precloacal muscle cells; lateral alae reaching level of anus................................................................... 5

4. Pharynx elongate and slender; corpus not divided into procorpus and metacorpus; vagina divided into vagina vera and vagina uterina .............................................................................. S. incospicata Pharynx as wide as it is long; corpus divided into procorpus and metacorpus; vagina not divided into vagina vera and vagina uterina ............ S. larvata

5. Pharynx as wide as it is long; total length of oesophagus more than 500 µm 6 Pharynx as wide as it is long or elongate and slender; total length of oesophagus less than 500 µm........................................... 7

6. Posterior uterine pouch present; vagina 300 µm long; spicules 75 µm long.................................................................. S. freitasi Posterior uterine pouch absent; vagina less than 200 µm long; spicules longer than 84 µm................................................... S. schranki

7. Pharynx as wide as it is long; spicules longer than 100 µm; gubernaculum longer than 55 µm.............................................. S. fuscus Pharynx elongate and slender; spicules less than 100 µm long; gubernaculum less than 55 µm long......................................... S. formosula

Figures

Figure 1. Schrankiana chacoensis sp. nov. (A) Male, ventral view; (B) female, lateral view; (C) cephalic end of female, lateral view; (D) anterior end of female, lateral view; (E) posterior end of male, lateral view; (F) spicules and gubernaculum, lateral view; (G) spicules and gubernaculum, ventral view; (H) posterior end of female, lateral view.

Figure 2. Schrankiana chacoensis sp. nov. (A) Cephalic end, apical view; (B) anterior end, ventral view; (C) detail of excretory pore; (D) posterior end of male, ventral view; (E) detail of cloaca and adcloacal papillae; (F) posterior end of female, ventral view. Abbreviations: am: amphid; asterisk: cephalic papillae; ep: excretory pore; arrows: precloacal papillae; up: unpaired papillae; ap: adcloacal papillae; pp: postcloacal papillae; cf: cuticular fringe.