Hedruris anguila, Ailán-Choke & Arredondo & Davies, 2023

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, Zootaxa 5263 (1), pp. 122-134 : 123-127

publication ID	https://doi.org/ 10.11646/zootaxa.5263.1.7
publication LSID	lsid:zoobank.org:pub:D8DC9A40-3CDD-4B82-85B9-620F11B35F0A
DOI	https://doi.org/10.5281/zenodo.7805400
persistent identifier	https://treatment.plazi.org/id/3133879B-7414-EA1F-FF7B-F9EDE7B2FC2B
treatment provided by	Plazi
scientific name	Hedruris anguila
status	sp. nov.

Treatment

Hedruris anguila sp. nov.

Type-host: Synbranchus marmoratus Bloch View in CoL

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) GoogleMaps .

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 View FIGURE 1 View FIGURE 2 View FIGURE 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 View FIGURE 1 ; 3A, B View FIGURE 3 ). Base of each pseudolabium supported by posteriorly directed cuticular ridge ( Fig. 3A View FIGURE 3 ). 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 View FIGURE 3 ). Buccal cavity thin walled. Oesophagus not clearly divided into muscular and glandular portions ( Fig. 1A View FIGURE 1 ). Deirids simple, situated just posterior to nerve ring and above the level of excretory pore ( Fig. 1A View FIGURE 1 ). Females with a sclerotized hook for attachment to host and male generally found encircling female ( Figs. 2A, B View FIGURE 2 ; 3E View FIGURE 3 ).

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 View FIGURE 3 ). 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 View FIGURE 1 ; 3F, G View FIGURE 3 ). 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 View FIGURE 1 ). Spicules 127–177 (160) long, slender fused on its mid-length, curved in distal tip with lateral membranous expansions ( Fig. 1F View FIGURE 1 ). Gubernaculum absent. Tail 228–344 (293) long, with caudal spike ( Figs. 3F, G View FIGURE 3 ).

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 View FIGURE 1 ). Vulva 530–786 (701) from posterior end, 216–383 (322) from anus ( Figs. 2A, B View FIGURE 2 ). Uterus prodelphic, filled with eggs. Tail curved dorsally, 314–452 (377) long ( Figs. 2A View FIGURE 2 ; 3D, E View FIGURE 3 ). Caudal eversible prehensile structure armed with sclerotized hook 98–147 (113) long and two lateral projections 30–69 (46) long ( Figs. 2A View FIGURE 2 , 3D View FIGURE 3 ). 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 View FIGURE 3 ). 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 View FIGURE 2 ).

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 View 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 View 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 View 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 View 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 View TABLE 1 ).