Hedruris anguila Ailán-Choke & Arredondo & Davies 2023, sp. nov.
Creators: name: Ailán-Choke, Lorena G.
name: Arredondo, Nathalia J.
name: Davies, Dora
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Nematoda
Secernentea
Spirurida
Habronematidae
Hedruris
Hedruris anguila

description: Hedruris anguila sp. nov.
Type-host: Synbranchus marmoratus Bloch
Site of infection: Stomach and intestine.
Type-locality: River Paraná-Guazú (tributary of the River Paraná; Lower Paraná), Entre Ríos Province, Argentina (33°54′S; 58°52′W).
Prevalence: 18.8% (6 of 32 fishes examined).
Mean intensity: 28.7 (2–124 nematodes per fish).
Mean abundance: 6.6 nematodes per examined fish.
Type-material: Holotype: male (MACN-Pa 746); allotype: female (MACN-Pa 747); paratypes: 8 males, 10 females (MACN-Pa 748).
Etymology: The specific name refers to common name of the fish host.
Description (Figs. 1–3)
General. Medium-sized nematodes. Cuticle thick with fine transverse striations. Anterior end rounded, with two large pseudolabia, each bearing a pair of digitiform papillae, a pair of sessile papillae and an amphid (Figs. 1B, C; 3A, B). Base of each pseudolabium supported by posteriorly directed cuticular ridge (Fig. 3A). Dorsal and ventral interlabium between pseudolabia, each with two bifurcated lateral cuticular projections extending posteriorly, with cuticular ridge posteriorly directed between bifurcations (Figs. 3A, B). Buccal cavity thin walled. Oesophagus not clearly divided into muscular and glandular portions (Fig. 1A). Deirids simple, situated just posterior to nerve ring and above the level of excretory pore (Fig. 1A). Females with a sclerotized hook for attachment to host and male generally found encircling female (Figs. 2A, B; 3E).
Males (based on nine specimens). Body length 7.1–11.1 (8.7) mm, maximum body width 202–317 (274.4). Pseudolabia 81–110 (96) long. Oesophagus 1.2–1.6 (1.4) mm long. Nerve ring 260–324 (291), deirids 217–295 (250) and excretory pore 363–485 (427) from anterior extremity. Posterior end of body spirally coiled. Caudal alae present, narrow, supported by caudal papillae (Figs. 3F, G). Precloacal papillae absent, eight pairs of postcloacal subventral papillae; in one male, arrangement of subventral papillae asymmetrical, 7 papillae on one side and 8 on opposite site (Figs. 1E; 3F, G). A single pair of phasmids present. Area rugosa with six ventral longitudinal ridges with scale-like knobs, extending 1.6–1.7 (1.7) mm from cloaca (Fig. 1D). Spicules 127–177 (160) long, slender fused on its mid-length, curved in distal tip with lateral membranous expansions (Fig. 1F). Gubernaculum absent. Tail 228–344 (293) long, with caudal spike (Figs. 3F, G).
Females (based on 11 gravid specimens). Body length 10.6 –14.8 (12.7) mm, maximum body width 432–634 (525.1). Pseudolabia 83–130 (106) long. Oesophagus 1.5–2.2 (1.9) mm long. Nerve ring 295–383 (329), deirids 221–363 (295) and excretory pore 432–579 (509) from anterior extremity (Fig. 1A). Vulva 530–786 (701) from posterior end, 216–383 (322) from anus (Figs. 2A, B). Uterus prodelphic, filled with eggs. Tail curved dorsally, 314–452 (377) long (Figs. 2A; 3D, E). Caudal eversible prehensile structure armed with sclerotized hook 98–147 (113) long and two lateral projections 30–69 (46) long (Figs. 2A, 3D). Accessory elongate sclerotized structure formed by two arms, 187–314 (230) long; both arms extending lateroventrally from hook base to anterior part of body, not reaching the anus. Cuticular spines in posterior part of body, distributed in two areas: perianal and dorsal on tail tip. Dorsal area densely covered by large, sharply pointed spines, distributed in transverse lines and decreasing in size anteriorly (Fig. 3D). Perianal spiny area with irregular rows of small spines extending anteriorly to vulval area. Non-mammillated larvated eggs, 37–44 (40) long, 12 wide, operculated at each end (Fig. 2C).
Remarks. To date, Hedruris comprises 25 valid species described from amphibians, reptiles and fishes distributed worldwide (Bursey & Goldberg 2000; Brugni & Viozzi 2010; Rossin & Timi 2016; Palumbo et al. 2020). The specimens examined in the present study were assigned to Hedruris based on the presence of a retractable sclerotized hook on the female tail (Baker 1986; Anderson et al. 2009). Species of Hedruris are distinguished on the basis of the morphology of cephalic structures, the number and arrangement of caudal papillae in males, the shape of eggs in females, the size of spicules, and the female caudal hook (Baker 1986; Bursey & Goldberg 2000; 2007). The new species herein described can be differentiated from all other congeners by the morphology and size of spicules, the number and arrangement of caudal papillae and the presence of a caudal spike on the male tail, and the shape and size of eggs.
The Neotropical species of Hedruris are characterized by possessing only postcloacal papillae, except H. heyeri Bursey & Goldberg, 2007 and H. siredonis Baird, 1858 (also recorded in Nearctic Region) that exhibit a different arrangement of caudal papillae (Baker 1986; Bursey & Goldberg 2000, 2007) (see Table 1). Based on the presence of eight pairs of postcloacal papillae, Hedruris anguila sp. nov. resembles H. juninensis Bendezú, 1974 and H. mucronifer Schuurmans Stekhoven, 1952, but differs in having smaller eggs (37–44 vs. 43–53) and smaller spicules (127–177 vs 200–430). The new species shares the shape of eggs with H. bifida; H. basilichtensis; H. moniezi Ibañez & Córdova, 1976; H. orestiae and H. suttonae, but differs in having a distinctly smaller female hook (98–147 vs. 137–292 µm), smaller spicules (127–177 vs. 175–326) and a different number of caudal papillae (16 vs. 18) (Bursey & Goldberg 2000; Brugni & Viozzi 2010; Rossin & Timi 2016; Palumbo et al. 2020) (see Table 1). Moreover, Hedruris anguila sp. nov. can be distinguished from H. dratini Palumbo, Servián, Sánchez & Diaz, 2020 by having non-mammilated eggs and also the number of pairs of postcloacal papillae (16 vs. 18) (Palumbo et al. 2020). Of the Hedruris species previously mentioned, H. bifida, H. suttonae, H. basilichtensis and H. orestiae were found infecting only fish hosts, of which the first two were found in characid and galaxiids from Argentina, respectively. The remaining species, except H. dratini, were found in frog hosts (Bursey & Goldberg 2000; Palumbo et al. 2020). Hedruris dratini was recorded in freshwater turtles from Argentina, e.g. Hydromedusa tectifera and Phrynops hilarii (Palumbo et al. 2020).
It should be noted that the non-mammilated eggs are also characteristics of H. longispicula Thomas, 1959, H. minuta Andrews 1974, H. spinigera Baylis, 1931, H. hanleyae Bursey & Goldberg, 2000, H. saltuarii Jones, 2013, H. wogwogensis Jones & Resasco, 2016 (Australian species); H. transvaalensis Baker, 1982, (Etiophian species); H. pendula (Leidy) Chandler, 1919 (species recorded in Nearctic and Palearctic Regions); H. miyakoensis Hasegawa, 1989 and H. neobythitis Yamaguti, 1941 (Oriental species). In addition, H. anguila sp. nov. shares the presence of only eight pairs of postcloacal papille with H. transvaalensis, but differs in the length of spicules (127–177 vs. 456) and female hook (98–147 vs. 170). Moreover, the new species also differs from H.longispicula, H. spinigera, H. hanleyae, H. pendula and H. saltuarii in showing smaller spicules (127–177 vs. 190–360). Hedruris minuta, H. miyakoensis and H. neobythitis present spicule length somewhat similar to H. anguila sp. nov., but have different number and arrangement of caudal papillae than the new species (all with more than ten pairs of caudal papillae) (Table 1).
In respect to H. androphora Nitzsch, 1821 (Palearctic species) and H. ijimai Morishita, 1926 (Oriental species); both parasites of amphibians resemble the new species in the length of spicules and hook in the female tail, but differ by having mammillated eggs (Table 1) (Bursey & Goldberg 2000; Rossin & Timi 2016). In addition, Hedruris hipsirhinae Chatin, 1876, H. bryttosi Yamag uti, 1935 (Oriental species) and H. lutjanenses Ramadan, Awad & Taha, 2014 (Palearctic species), the last two species of which parasitize fish, can be distinguished from the new species in number and arrangement of caudal papillae (with ten or more pairs of caudal papillae) (see Table 1).
description: Published as part of Ailán-Choke, Lorena G., Arredondo, Nathalia J. & Davies, Dora, 2023, A new species of Hedruris Nitzsch, 1821 (Nematoda: Hedruridae) parasitic in eel Synbranchus marmoratus Bloch (Synbranchiformes: Synbranchidae) from Argentina, Neotropical Region, pp. 122-134 in Zootaxa 5263 (1) on pages 123-127, DOI: 10.11646/zootaxa.5263.1.7, http://zenodo.org/record/7797908