Karavolicotyla tuyeti, Nguyen & Nguyen & Tatonova, 2020

Nguyen, Hung Manh, Nguyen, Ha Van & Tatonova, Yulia V., 2020, Two new species of Karavolicotyla (Unnithan, 1957) (Monogenea: Heteraxinidae): parasites of two sciaenid fishes (Perciformes) from Vietnam, Raffles Bulletin of Zoology 68, pp. 434-440 : 435-438

Karavolicotyla tuyeti , new species

( Fig. 1 )

Type-host. Nibea albiflora (Richardson) ( Perciformes : Sciaenidae ), yellow drum ( Fig. 2 ).

Type-locality. Off Nhat Le , Dong Hoi district, Quang Binh province, Vietnam (17°28′59″N, 106°37′28″E) .

Site on host. Gills.

Prevalence and intensity. 8.2% (4 of 49 examined fishes); 1–4 monogeneans/fish.

Type-specimens. Holotype (Heteraxinid–20160427–1), and 4 paratypes (Heteraxinid–20160427–2–5) are deposited in the collections of the Department of Parasitology , Institute of Ecology and Biological Resources, Hanoi, Vietnam, another 4 paratypes (Heteraxinid–20160427–6–9) are deposited in the collections of the Vietnam National Museum of Nature, Hanoi, Vietnam.

Etymology. The species name ‘ tuyeti ’ is from the noun (Tuyet). The species is named after the father of the first author.

Description. [Based on nine specimens, see Fig. 1 ; measurements in Table 1] Body elongate, relatively slender and tapering anteriorly. Cephalic glands opening at anterior extremity. Haptor typically heteraxinid, triangular, asymmetrical with two unequal rows. Clamp of microcotylidtype, dissimilar in size, decreasing in size from the middle region to the posterior part of the haptor. Posterior and newly formed anterior clamps smallest; the largest clamp about twice larger than the smallest; the distal end of clamp’s middle looped sclerite with bifid terminations.

Pair of prohaptoral suckers, elongate-oval, muscular, septate. Pharynx subglobular; prepharynx absent. Oesophagus slender, bifurcating at middle between genital atrium and pharynx. The part of oesophagus joining with pharynx developed, contained ear-shaped scleritisation accessory piece (observed in only one specimen). Intestine with numerous diverticula, not confluent, extending posteriorly into haptor; right caecum longer. The diverticula extend from posterior to genital atrium to the end of caeca, and do not cross the median line until the caeca enter into the opisthaptor region.

Testes 16 in number, post-ovarian, occurring in two longitudinal rows, in posterior half of body proper. Vas deferens conspicuous, runs along body midline to genital atrium, ventral to uterus; pars prostatica not well observed. Cirrus spherical and highly muscular, dorsal to the atrium, armed with single large spine on its distal edge. Genital atrium is a spherical depression with muscular edge, armed with circle of 48–52 (n=9) long, thin, small spines extending out of the central pore.

Ovary pretesticular, inverted ɣ shaped. Proximal ovary a more or less spherical mass; oviduct joined by vitelline reservoir in midline. Vaginal canal extending along body midline, from proximal loop of the ovary to the vaginal pore. Vaginal pore unarmed, posterior to genital atrium. Vitellarium extends into most part of body from genital atrium haptor. Vitelline ducts paired, united posteriorly as Y; at the level of ovary and ventral to it, the common vitelline duct is distended at the anterior part but tapering and bending at the posterior part, opening into oötype. Uterus wide, arising from oötype and extending along body midline. Uterus opening between pharynx and genital atrium. Eggs were not observed.

Cephalic glands opening at anterior extremity. Haptor typically heteraxinid, triangular, asymmetrical with two unequal rows. Clamps of microcotylid-type, dissimilar in size; middle looped sclerite of clamps with distal end bearing bi-dentate prolongation.

Remarks. The specimens described above belong to the genus Karavolicotyla , as shown by key features such as clamps on both sides of haptor that are arranged in two unequal rows; armed cirrus and armed genital atrium; dorsomedian vaginal opening immediately distal to level of genital aperture, and absence of an accessory vaginal opening ( Unnithan, 1957; Price, 1962). Karavolicotyla tuyeti , new species, can be distinguished from the type species K. karavoli ( Unnithan, 1957) by the following characters: (1) clamp number in long row of K. tuyeti is 1.5 times greater than short row, while this proportion is six times in K. karavoli ; (2) number and length of atrial spines of K. tuyeti are greater (2 and 1.5 times respectively), than those in K. karavoli ; (3) the cirrus of K. tuyeti is spherical with a single stout hook-like spine on the top, while in K. karavoli , the cirrus is trilobed and armed with several minute spines, in addition to three long and stout-hook like converging spines; (4) the oral organs of K. tuyeti are septate while they are aseptate in K. karavoli . Moreover, hosts are different ( Nibea albiflora , Sciaenidae vs. Parastromateus niger , Carangidae ) and are from distinct localities (Pacific vs. Indian Oceans). These considerations justify that K. tuyeti is a distinct new species.

Figures

Fig. 1. Karavolicotyla tuyeti, new species, from Nibea albiflora. A, holotype, whole body (ventral view); B, anterior part; C, genital atrium; D, atrial spine; E, clamp (ventral view).

Fig. 2. Nibea albiflora. Scale bar = 2 cm.