Aplectana nebulosa, Piñeiro Gomez, Mauricio D., González, Cynthya E. & Sanabria, Eduardo A., 2017

Piñeiro Gomez, Mauricio D., González, Cynthya E. & Sanabria, Eduardo A., 2017, A new species of Aplectana (Nematoda: Cosmocercidae) parasite of Pleurodema nebulosum (Anura: Leptodactylidae) from the Monte desert, Argentina, with a key to Neotropical species of the genus Aplectana, Zootaxa 4247 (2), pp. 121-130 : 122-125

Aplectana nebulosa sp. nov.

( Figs. 1–2 )

General morphology. Small, slender nematodes. Cuticle transversely striated. Slight sexual dimorphism, females larger than males ( Fig. 1 A, B). Narrow lateral alae present in both sexes, beginning at region of nerve ring and ending at the middle of tail in females and at level of first pair of precloacal papillae in males ( Figs. 1 E–1K). Numerous small somatic papillae present. Mouth with three lips; dorsal lip with two cephalic papillae and each ventrolateral lip with one cephalic papilla and one large amphid ( Fig. 1 C). Excretory pore anterior of oesophageal bulb ( Fig. 1 D).

Male (based on holotype and 15 paratypes): Total length 2.9 ± 0.41 mm (2.2–3.5mm) [2.9 mm]; maximum width 136.5 ± 25.4 (100–178) [125]. Pharynx length 40.7 ± 4.2 (35–49.5) [46], width 34.3 ± 5.1 (25–41) [37.7]; oesophagus: corpus length 320.2 ± 31.4 (280–392) [310] width 34.8 ± 5.3 (25–40) [25]; isthmus length 43.7 ± 8.4 (30–56.5) [30], isthmus width 23.8 ± 5.1 (18–35.5) [25]; bulb length 54.2 ± 9 (35.5–68) [60], bulb width 53.3 ± 5.8 (39–61) [55]. Nerve ring 223.0 ± 23.4 (175–255) [240] and excretory pore 331.7 ± 72.9 (191–502.5) [345], from anterior extremity, respectively. Tail length 167.9 ± 31.3 (105–220) [202.2]. Cloacal papillae arranged as follows ( Fig. 1 E, F): Two rows of 6–7 pairs of precloacal papillae, the last two paris located laterally to the cloaca ( Fig. 2 A); 2 pairs of adcloacal papillae in anterior margin of cloaca and one middle, large unpaired papilla between the two anterior pairs ( Fig. 2 B); 5 pairs of postcloacal papillae (first and second pairs ventral, third pair lateral, fourth pair ventral, fifth pair lateral) ( Fig. 2 C); papillae pattern: 6–7:2:5+1. Spicules slightly equal, length 104.2 ± 12.4 (85–125.9) [110], pointed at distal end and with variably shaped capitulum ( Fig. 1 G). Gubernaculum length 52.2 ± 9.1 (37.4–62.9) [55], weakly sclerotized, ovate in ventral view ( Fig. 1 H).

Female (based on allotype and 13 paratypes): Total length 4.6 ± 0.28 mm (2.9–5.8 mm) [4.54 mm]; maximum width 200 ± 60.1 (100–298) [235]. Pharynx length 58.2 ± 15 (30–83) [70], pharynx width 49.2 ± 12.5 (28–72) [60]; oesophagus: corpus length 395.4 ± 65.0 (277–485) [425], width 47.6 ± 13.2 (30–79.1) [60]; isthmus length 48.5 ± 5.3 (41–58) [50], isthmus width 29.5 ± 4.7 (21–38) [40], bulb length 68.4 ± 9.8 (52–84) [80], bulb width 62.9 ± 9.4 (48–75) [70]. Nerve ring 249.4 ± 40.3 (200–325) [285] and excretory pore 417.7 ± 70 (234–506) [450] from anterior extremity, respectively. Vulva post-equatorial, transverse slit, slightly salient, situated 1.7 ± 0.43mm (1.0– 2.5) [1.40mm] from posterior extremity; muscular ovejector, directed anteriorly ( Fig. 1 I, J), joining 2 uteri, 1 directed anteriorly, 1 posteriorly. Tail, conical, 261.7 ± 41.1 (200–343) [215] in length ( Fig. 1 K). Eggs, unembryonated, thin shelled oval, length 84.8 ± 15.0 (61.5–105) [90], width 67 ± 14.2 (49–90) [80].

Taxonomy summary

Site of infection: small and large intestine.

Type locality: Matagusanos , Ullúm Department, San Juan Province, Argentina ( Fig. 3 B).

Deposition of types: Holotype (male), allotype (female) and paratypes (2 males, 2 females) in Helminthological Collection of the Museum of La Plata (Holotype: MLP-He 7156; Allotype: MLP-He 7157; Paratypes: MLP-He 7158); Paratypes (5 males, 5 females) in Helminthological Collection of Centro de Ecología Aplicada del Litoral (CECOAL 16062601).

Symbiotype: Pleurodema nebulosum (Burmeister, 1861) ( Anura , Leptodactylidae ) ( Fig. 3A ), Herpetology Collection of Fundación Miguel Lillo (Deposited number FML 29422 to 29433).

Etymology. The new species is named in reference to its host.

Host-parasite data. Prevalence 58.5%, twenty-four of the frogs were found to harbour 397 nematodes.

Remarks. The genus Aplectana is characterized by possessing lateral alae and somatic papillae, males without rosettes or plectanes on the posterior end, and females with numerous thin-shelled eggs in the uteri, and 2 ovaries anterior to the vulva ( Gibbons, 2010). Nematodes of this genus parasitize mainly amphibians and some species of reptiles worldwide ( Baker, 1987).

The species of genus Aplectana are grouped mainly according to the presence and absence of gubernaculum; other features that distinguish these helminths are the number and arrangement of caudal papillae, and the size of the gubernaculum and spicules.

According to Bursey et al. (2011), there are 26 species reported for the Neotropical Realm, 19 of them with gubernaculum: A. adaechevarriae Ramallo, Bursey and Goldberg, 2008 , A. albae Adamson and Baccam, 1988 , A. elenae Baker and Vaucher, 1986 , A. hamatospicula Walton, 1940 , A. herediaensis Bursey, Goldberg and Telford, 2006 , A. hylambatis (Baylis, 1927) Travassos, 1931 , A. incerta Caballero, 1949 , A. itzocanensis Bravo Hollis, 1943 , A. lopesi Silva, 1955 , A. membranosa (Schneider, 1866) Miranda, 1924 , A. mexicana (Caballero, 1933) Ballesteros –Marquez, 1945, A. micropenis Travassos, 1925 , A. paraelenae Baker and Vaucher, 1986 , A. pusilla Miranda 1924 , A. raillieti Travassos, 1925 , A. ryšavýi Barus and Coy Otero, 1969 , A. travassosi (Gomes and Motta, 1967) Baker, 1980 , A. tucumanensis Ramallo, Bursey and Goldberg, 2008 , and A. vellardi Travassos, 1926 .

Apart from this, two groups can be identified, following the characteristics of caudal papillae: those with a large unpaired papilla anterior to the cloaca, and those without this character. Of the above mentioned species with gubernaculum, eleven have an unpaired papilla: A. albae , A. elenae , A. hamatospicula , A. hylambatis , A. itzocanensis , A. membranosa , A. paraelenae , A. raillieti , A. ryšavýi , A. travassosi , and A. vellardi .

The new species described here belongs to the group of species that possess both a gubernaculum and an unpaired papilla anterior to the cloaca, being more related to A. membranosa , A. paraelaenae and A. travassosi for possessing four adcloacal papillae, pre-oesophageal excretory pore, males with tail tapering gradually to spike-like distal portion, and gubernaculum elongated, with posterior end pointed and thickened borders.

However, the new species differs from A. membranosa by the following characters: 1) number of precloacal papillae (6–7 pairs vs. 3 pairs); 2) number and arrangement of postcloacal papillae (1° and 2° ventral, 3° lateral, 4° ventral, 5° lateral vs. 1° and 2° ventral, 3° lateral, 4° ventral); 3) shape and size of spicules (no forked spicules, 85– 125.9µm vs. forked spicules, 227–234.3µm).

Aplectana nebulosa sp. nov. can also be distinguished from A. paraelenae by the following characters: 1) number of precloacal papillae (6–7 pairs vs. 3 pairs, respectively); 2) number and arrangement of postcloacal papillae (1° and 2° ventral, 3° lateral, 4° ventral, 5° lateral vs. 1°, 2°, 3° subventral, 4° and 5° subdorsal, 6° lateral); 3) size of spicules (85–125.9 µm vs. 227µm); 4) position of end of lateral alae in males (precloacal, at the level of 3° pair of precloacal papillae vs. postcloacal, at middle of tail).

Finally, Aplectana nebulosa sp. nov. differs from A. travassosi by the following characters: 1) number of precloacal papillae (6–7 pairs vs. 3 pairs); 2) number and arrangement of postcloacal papillae (1° and 2° ventral, 3° lateral, 4° ventral, 5° lateral vs. 1° pair ventral, 2°, 3° and 4° subventral); 3) size of spicules (85–125.9µm vs. 230– 245µm); 4) size of gubernaculum (37.4–62.9µm vs. 80–95µm).

We provide a key for the species of Aplectana from amphibians and reptiles from Neotropical Realm.

Figures

FIGURE 1. Aplectana nebulosa sp. nov. from P. nebulosum. A. Female, general view. B. Male, General view. C. Male, anterior extremity, apical view. D. Male, anterior extremity, lateral view. E. Male, posterior extremity, ventral view. F. Male, posterior extremity, lateral view. G. Spicule, ventral view. H. Gubernaculum, ventral view. I. Female, vulva and ovejector, ventral view. J. Female, vulva and ovejector, lateral view. K. Female, posterior extremity, lateral view.

FIGURE 2. Aplectana nebulosa sp. nov. from P. nebulosum. A. Posterior end of male, detail of precloacal papillae. B. Posterior end of male, detail of adcloacal papillae and spicules. C. Posterior end of male, detail of postcloacal papillae. Abbreviations: ap: adcloacal papillae; up: unpaired papilla. In figure A, closed arrows indicate precloacal papillae; open arrows indicate lateral alae; in figure C, closed arrows indicate postcloacal papillae.

FIGURE 3. A. Adult male of Pleurodema nebulosum from Matagusanos. B. Panoramic view of type locality.