Acanthostrongylus secundus, Guerrero, 2019

Guerrero, Ricardo, 2019, On two genera of spiny Pudicinae (Nematoda: Trichostrongylina) parasites of the spiny rat Proechimys simonsi (Mammalia: Echimyidae) from Peru, Zootaxa 4629 (1), pp. 133-140 : 134-135

Acanthostrongylus secundus n. sp.

Diagnosis: Small nematodes, coiled on ventral axis with inflated cuticle; there are two rows, one behind the other, of well-developed spines posterior to the base of the oesophagus. Caudal bursa subsymmetrical, pattern 2-2-1, rays 6 and 8 close and parallel along their entire length. Female monodelphic.

Description. General: Nematodes pink when living, in the anterior third reddish, coiled on ventral axis with inflated cuticle posteriorly to the end of oesophagus. In apical view circular oral opening and small neodont. Six externo-labial papillae of which the latero-externo labial papillae fused with amphids. Four cephalic papillae. Cephalic vesicle usually wider than long. In addition to the synlophe, two rows of longitudinal spines in the anterior third, one followed by the other on the ventral side.

Synlophe: With ten continuous ridges throughout the body in both sexes, but nine in most anterior and posterior part of body. Careen slightly remarkable only in anterior part of body made up of two medium sized ridges, one ventral developed comarete, and five dorsal smaller ridges. At middle body the size of the careen decreased and is the same size as the other ridges. Right side of body free of ridges. Axis of orientation inclined close at 45° to sagittal axis. With two rows of spines in ventral side, posterior to end of oesophagus, and divided in two parts one after the other.

Males: [holotype and 2 (except as indicated) paratypes]: Body length 2341 [2661, 2578], maximum width 91 [100, 107], width at mid-body 71 [67, 64], width at oesophago-intestinal junction 67 [65, 64]. Cephalic vesicle 38 [36, 41] long and 37 [38, 43] wide. Nerve ring, deirids and excretory pore at 176 [171, 170], 226 [216] and 271 [218] (n = 1) from apex, respectively. Oesophagus 457 [476, 432] long, OeL/BL 19.5 [17.9, 16.8] %. First row of spines at 94 [63] (n = 1) from oesophagus base, 161 [168, 193] long with 9 [9, 10] spines. Second row of spines at 271 [257, 314] posterior to first row, 225 [178, 201] long with 13 [13, 13] spines. Spicules 472 [452, 512] long, SpL/BL 20.2 [17.0, 19.9] %.

Caudal bursa subsymmetrical, pattern 2-2-1. Rays 2-3 arising first and together from the trunk of rays 2 to 6; rays 4 and 5 diverging at distal extremities; ray 6 long; dorsal trunk arising on common trunk of rays 2-6. Dorsal trunk deeply divided at proximal third; ray 8 running close and parallel to ray 6; ray 9 diverging distally and slightly longer than ray 10. Gubernaculum absent. Genital cone wider than long with papilla zero small and papillae 7 developed. Tips of spicules slightly different.

Females: [Allotype and 3 (except as indicated) paratypes]: Body 3081, 2877 [2650-3071 ± 212) long; maximum width 121 [100] (n = 1), width 65, 77 [70-83 ± 6.5] at mid-body and 69, 79 [75–84 ± 4.6] at oesophago-intestinal junction. Cephalic vesicle 42, 39 [37–42 ± 2.9] long, 44, 38 [30–44 ± 7.4] wide. Nerve ring, deirids and excretory pore at 198, 175 [156–198 ± 21], 262 [278] (n = 1), and 239, 263 [242–305 ± 36] from apex, respectively; oesophagus 489, 502 [464-547 ± 42] long, OeL/BL 15.9, 17.4 [17.0–17.8 ± 0.43] %. First row of spines at 20, 122 [104–144 ± 20] from oesophagus base, 167, 210 [198–220 ± 11] long with 10, 10 [9–10 ± 1.0] spines. Second row of spines at 288, 209 [136–276 ± 69] posterior to first row, 255, 218 [198–230 ± 17] long with 14, 13 [12-14 ±1.0] spines. Tail 35, 34 [31–37 ± 3.0] long, TaL/BL 1.14, 1.20 [1.01–1.40 ± 0.19] %; 22, 23 [22–24 ± 1.0] wide.

Vulva at 78, 82 [72–95 ± 12], from caudal extremity. Dvu/BL 2.53, 2.86 [2.61–3.26 ± 0.35] %. Vagina vera 25, 25 [23–26 ± 1.7] long. Vestibule 67, 66 [63–71 ± 4.4] long. Sphincter 26, 29 [28–31 ± 1.5] long. Infundibulum 104, 119 [106–139 ± 17] long. Uterus 573 long, UtL/BL 18.6 %. Eggs in utero 10, 11 [10–11 ± 0.6], measuring 90, 81 [78-82 ± 2.3] long and 47, 42 [39–44 ± 2.5] wide.

Type material: Holotype male CP-MBUCV N° 6137 , allotype female CP-MBUCV N° 6138 , 2 males and 3 females paratypes CP-MBUCV N° 6139 , host N° 044- 010597 .

Type host: Proechimys simonsi Thomas, 1900 (Mammalia: Hystricomorpha: Echimyidae ).

Type locality: San Martin 3, North of the river Camisea, Cusco, Peru (11° 47’ 9.8’’ S– 72° 42’ 5.3’’ W, 474 m.a.s.l.

Site: Small intestine.

Other studied material: Males [10 exemplars (except as indicated)]: Body 2817 [2700–2889 ± 78] (n = 6) long; 103.7 [87–114 ± 10.6] maximum width, 79.5 [62–91 ± 12.9] (n = 4) width at mid-body and 66.5 [58–73 ± 6.3] (n = 4) wide at oesophago-intestinal junction. Cephalic vesicle 37.0 [32–44 ± 5.2] (n = 8) long and 43.5 [39–47 ± 3.8] (n = 8) wide. Nerve ring, deirids and excretory pore at 146.5 [131–172 ± 18.8], 257 (n = 1), and 206.5 [179–250 ± 33] (n = 8) from apex, respectively. Oesophagus 374.4 [294–417 ± 52] (n = 8) long, OeL/BL 14.3 [13.4–15.6 ± 0.8] (n = 8) %. First row of spines at 81.0 [42–136 ± 49] (n = 3) from oesophagus base, 160.3 [123–189 ± 34] (n = 3) long with 9.3 [9–10 ± 0.6] (n = 3) spines. Second row of spines at 187 (n = 1) posteriorly to first row and 209 (n = 1) long with 13.5 [12-14 ± 1.0] (n = 2) spines. Spicules 465.6 [394–525 ± 43] (n = 10) long, SpL/BL 16.2 [14.6–17.8 ± 1.0] (n = 6) %.

Caudal bursa subsymmetrical, pattern 2-2-1. Rays 2-3 arising first and together from the trunk of rays 2 to 6; rays 4 and 5 diverging at distal extremities; ray 6 long; dorsal trunk arising on common trunk of rays 2-6. Dorsal trunk deeply divided at proximal third; ray 8 running close and parallel to ray 6; ray 9 diverging distally and slightly longer than ray 10. Gubernaculum absent. Genital cone wider than long with papilla zero small and papillae 7 developed. Tips of spicules slightly different ( Figure 1G ).

Females [16 exemplars (except indication)]: Body 3085 [2850–3257 ± 144] (n = 14) long; 148.4 [95–200 ± 46.7] (n = 8) maximum width, 86.1 [65–73 ± 11.5] (n = 10) width at mid-body and 74.6 [59–91 ± 11.6] (n = 9) wide at oesophago-intestinal junction. Cephalic vesicle 40.1 [36–47 ± 4.2] (n = 13) long; 44.8 [40–50 ± 3.4] (n = 13) wide. Nerve ring, deirids and excretory pore at 158.6 [111–190 ± 25.3) (n = 11), 258 [249–263 ± 7.8] (n = 3) and 248.3 [222–279 ± 20.1] (n = 11) from apex, respectively: Oesophagus 448.8 (350–491 ± 40.6] (n = 13) long, OeL/ BL 14.6 [11.3–17.1 ± 1.51] (n = 13) %. First row of spines at 77.3 [51–137 ± 40.8) (n = 4) from oesophagus base, 166.5 [110–226 ± 40.1] (n = 6) long with 9.5 [9–11 ± 0.8] (n = 6) spines. Second row of spines at 234.5 [171–272 ± 16.1] (n = 4) posteriorly to first row, 221 [179–336 ± 65.2] (n = 5) long with 13.6 [11-17 ± 2.7] (n = 5) spines. Tail 33.5 [17–42 ± 6.3] (n = 15) long, 1.10 [0.81–1.32 ± 0.1] (n = 15) % of body length; 25.8 [17–36 ± 5.6) (n = 15) wide.

Vulva at 77.9 [52–92 ± 10.8] (n = 15) from caudal extremity. Vagina vera 31.6 [26–37 ± 3.1] (n = 15) long. Vestibule 68.6 [53–104 ± 13.5] (n = 15) long. Sphincter 31.5 [21–43 ± 5.3] (n = 15) long. Infundibulum 148.1 [107–196 ± 25.2] (n = 14) long. Uterus 555.3 [420–701 ± 108.8] (n = 8) long, UtL/BL 18.3 [13.6–23.7 ± 3.79] (n = 8). Eggs in utero 12.1 [7–19 ± 2.9] (n = 14), measuring 78.9 [71–88 ± 6.0] (n = 15) long and 40.8 [33–48 ± 4.5] (n = 15) wide.

Material deposited: 1 male and 3 females CP-MBUCV N° 6140 host N° 091- 010597; 6 males and 4 females CP-MBUCV N° 6141 host N° 059- 010597; 3 males and 4 females CP-MBUCV N° 6142 host N° 320- 010597 and 5 females CP-MBUCV N° 6143 host N° 223- 010597.

Localities: Hosts Nº 059- 010597, and 091- 010597 are from: San Martin 3, North of the river Camisea, Cusco, Peru (11° 47’ 9.8’’ S– 72° 42’ 5.3’’ W, 474 m. a.s.l.. Hosts N° 223- 010597, and 320- 010597 are from: Cashiriari, South of the river Camisea, Cusco, Peru (11° 51’ 51.3’’ S– 72° 46’ 45.6’’ W, 579 m. a.s.l..

Etymology: The species is the second species in the genus.

Prevalence: 50 %, 5 hosts infected of 10.

Intensity: In hosts infected with less than 100 heligmonellids, A. secundus was absent. In other hosts as follow: 044- 010597, 7 exemplars of 1752 Heligmonellids; 059- 010597, 7 exemplars of 510; 091- 010597, 3 exemplars of 1014; 233- 010597, 5 exemplars of 377, 320- 010597, 7 exemplars of 211.Then the range was 3- 7 specimens and the Mean Intensity = 5.8.

Remarks: The genus Acanthostrongylus was created by Travassos (1937) for parasites of Proechimys oris from Brazil, containing only one species: A. acanthostrongylus and characterized by the presence of ten continuous ridges: two of them small, forming a careen, and three ventral ridges, median being comarete; and two longitudinal rows of right-ventral spines arranged one behind the other, and separated by a space. The same characters are observed in the exemplars studied here. Durette-Desset & Tchéprakoff (1983) and Durette-Desset et al. (2017) briefly redescribed the species, described the synlophe and detailed the male bursa. The specimens described here clearly differ in morphology of the caudal bursa: in A. acanthostrongylus the bursal pattern is 1-4, the dorsal trunk is divided in the distal third and rays 6 are far apart from rays 8 and diverge at the same level as ray 3 and distal to the origin of pair 4-5. In A. secundus n. sp. the bursal pattern is 2-2-1, dorsal trunk is divided in the proximal third and rays 6 and 8 are close together and parallel. Ray 6 diverges before ray 3 and proximal to the origin of 4-5; in A. acanthostrongylus the careen and comarete are throughout the body length but in A. secundus the careen is only in the anterior part of body and after the midbody all ridges have the same size. The differences in synlophe and the bursal pattern between A. acanthostrongylus and A. secundus n. sp. are remarkable but the presence of two ventral rows of strong spines separated by a space, a unique character in Heligmonellidae , make both species congeneric.

Figures

FIGURE 1. Acanthostrongylus secundus n. sp. A male apical view. B female head lateral view. C female anterior extremity. D female posterior extremity. E male caudal bursa. F male genital cone. G male tips of spicules. H female anterior extremity showing spines. Synlophe: Female: I Cross-section in anterior 1/4. J in anterior 1/3. K in mid-body. Male: L in mid-body. M in 3/4 posterior. N Photograph of female spines. O Both rows of spines. (Figures A, F, G, bar = 10 µm; B, D, H, K, L, M, bar = 25 µm; C, E, I, J, O, bar = 50µm, N, bar = 100µm).