Neowardula brayi, Al-Jahdali, Mohammed O., 2010

Al-Jahdali, Mohammed O., 2010, Helminth parasites from Red Sea fishes: Neowardula brayi gen. nov., sp. nov. (Trematoda: Mesometridae Poche, 1926) and Sclerocollum saudii sp. nov. (Acanthocephala: Cavisomidae Meyer, 1932), Zootaxa 2681, pp. 57-65 : 59-60

Neowardula brayi sp. nov.

( Fig. 1 A–C)

Description. Based on 20 fully gravid-specimens. Body robust, elongate, somewhat dorso-ventrally flattened, broadest in posterior third, 2,916–5,346 (4,131) in length, 778–1,408 (1,093) in maximum width at its posterior third. Ventral surface anterior to intestinal bifurcation greatly modified, forming a well-developed, relatively deep pouch or an accessory attachment structure encircling the genital pore, 273–481 × 238–408 (377 × 323), representing about 10% of the body length. Tegument armed with fine spines dorsally and ventrally. Eye-spot pigment absent. Ventral sucker absent. Pharynx relatively small, sub-terminal, globular, 178–304 × 142–238 (241 × 190); oral opening antero-ventral. Esophagus relatively long, narrow, without muscular bulb, 395–705 (550) in length. Intestinal bifurcation at the end of anterior fifth of body; caeca simple, wide, extend to near anterior border of anterior testis. Testes 2, relatively large, post-caecal, constantly diagonal, entire, oval, contiguous, near posterior extremity, sub-equal, 481–851 × 361–631 (666 × 496). Seminal vesicle tubular, narrow, sinuous, ends as narrow ejaculatory duct; pars prostatica apparently absent.

Genital atrium present. Genital pore median, at center of accessory attachment structure; nearly midway between pharynx and intestinal bifurcation. Ovary spherical, entire, nearly median, overlapping posterior bοrder οf pοsteriοr testisʼ 2₁9—273 (296) in diameter• Μehlisۥ gland pοsterο̄median tο οVary• Laurerۥs canal opens dorsally. Vitelline follicles irregular, ventral, extending in the lateral fields along the entire length of intestinal ceca. At the level of cecal ends, diagonal vitelline collecting ducts arising from vitelline follicles on each side, and running posteriorly to open into a spherical vitelline reservoir, 91–149 (120) in diameter, situating medially, ventral to the ovary. Uterus long, forms regular transverse loops in intercaecal space, may form 2–3 short loops in post-testicular space. Metraterm absent. Eggs numerous, moderately large, thinshelled, operculate, without polar filament, yellowish, 58–72 × 42–52 (65 × 47). Excretory system reticular, with a tiny postovarian excretory vesicle; excretory pore dorso-subterminal.

Type host. Acanthopagrus bifasciatus Forsskål (Teleostei, Sparidae )

Site. Middle intestine.

Type locality. Red Sea off the coast of Rabigh, Saudi Arabia.

Prevalence. 4/16 fishes examined; 25%.

Type material. Holotype and paratypes are deposited in the Natural History Museum, London, Reg. no. 2010.8.2.1 and 2010.8.2.2–5

Etymology. The generic name Neowardula is from Neo (= similar) and from Wardula and indicates a similarity to this genus. The specific name brayi is for Dr R.A. Bray, Department of Zoology, Natural History Museum, London, in recognition of his great contributions to marine helminthology.

Remarks. As mentioned above, 5 valid genera are presently recognized within the family Mesometridae , i.e. Mesometra Luhe, 1901 , Centroderma Luhe, 1901 , Wardula Poche, 1926 , Elstia Bray, 1884 and Parawardula Jones et Blair, 2005 . In the first, the entire ventral surface is concave, while in the others, a part or most of the ventral surface anterior to the intestinal bifurcation is concave and acts as an accessory attachment structure. Neowardula brayi (described above) agrees typically with the concept of Mesometridae and its ventral surface anterior to the intestinal bifurcation is greatly modified into a well-developed, relatively deep pouch encircling the genital pore, and its testes are constantly diagonal. These characteristics are unique and sufficient to differentiate the current trematode from 5 genera in this family. Each of these genera possesses a set of generic characters lacking in the current species: Mesometra Luhe, 1901 possesses a distinctly rounded body, eye-spot pigments, an oesophageal bulb, intestinal caeca encircling gonads, symmetrical testes and an irregular or lobed ovary; Centroderma Luhe, 1901 possesses eye-spot pigments, an oesophageal bulb, symmetrical testes, a genital pore closely posterior to pharynx and vitelline follicles extending to near the posterior extremity of body; Wardula Poche, 1926 possesses eye-spot pigments, an oesophageal bulb, intestinal caeca bifurcating just pre-equatorial, tandem testes and a genital pore closely or distinctly posterior to pharynx (see Jones et Blair, 2005); Elstia Bray, 1984 possesses eye-spot pigments, an oesophageal bulb, symmetrical testes, a genital pore closely posterior to pharynx and eggs with long polar filaments; Parawardula Jones et Blair, 2005 possesses intestinal caeca terminating close to posterior end of body, tandem testes, terminal genitalia including hermaphroditic duct, vitelline follicles terminating anteriorly far behind intestinal bifurcation, an excretory vesicle with a long arm on each side and a terminal excretory pore.

Generally, the characteristics of the current trematode exclude it from the 5 known genera of the family Mesometridae . Therefore, Neowardula gen. nov., as defined above, is proposed as a new mesometrid genus for this species.

Figures

FIGURE 1. Neowardula brayi gen. nov. sp. nov. (ventral view) from Acanthopagrus bifasciatus, Red Sea. A. Wholemount (holotype). B. Terminal genitalia. C. Excretory system. Scale bars = 1 mm (A, C) and 500 µm (B).