Two new species of Karavolicotyla (Unnithan, 1957) (Monogenea: Heteraxinidae): parasites of two sciaenid fishes (Perciformes) from Vietnam Author Nguyen, Hung Manh Author Nguyen, Ha Van Author Tatonova, Yulia V. text Raffles Bulletin of Zoology 2020 2020-06-03 68 434 440 journal article 10.26107/RBZ-2020-0059 2345-7600 4577343 740F69A9-B092-48CA-BA48-4A7BC8637467 Karavolicotyla ruber , new species ( Fig. 3 ) Type-host. Otolithes ruber (Bloch & Schneider) ( Perciformes : Sciaenidae ), tigertooth croaker ( Fig. 4 ). 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. 11.8% (2 of 17 examined fishes); 1 monogenean/fish. Type-specimens. Holotype is deposited in the collections of the Department of Parasitology , Institute of Ecology and Biological Resources, Hanoi , Vietnam (Heteraxinid–20140625–1) and the paratype is deposited in the collections of the Vietnam National Museum of Nature , Hanoi , Vietnam . Etymology. The species name refers to specific name of the type-host, Otolithes ruber . Description. [Based on two specimens, see Fig. 2 ; measurements in Table 1 ] Body elongate, tapering anteriorly. Pair of prohaptoral suckers oval, muscular, aseptate. Prepharynx absent; pharynx subglobular. Oesophagus slender, bifurcating at middle level between genital atrium and pharynx. Intestine with numerous diverticula, not confluent, extending posteriorly into haptor; right caecum longer. Testes 8 or 9 in number, post-ovarian, occurring in two longitudinal rows, intercaecal, in posterior half of body proper. Vas deferens conspicuous, runs along body midline to genital atrium, ventral to uterus. Cirrus pine nut-shaped and highly muscular, dorsal to the atrium, armed with a circle of 14 small spines on its distal edge. Genital atrium is a spherical depression, with a muscular edge armed with circle of 33 or 34 long, thin spines. Ovary pretesticular, U-shaped, intercaecal. Proximal ovary a spherical mass; oviduct joined by vitelline reservoir in midline. Vaginal canal difficult to observe, the part connecting with vaginal pore extending along body midline. Vaginal pore unarmed, posterior to genital atrium. Vitellarium extends in most part of body from genital atrium to haptor zone but not entering it. Vitelline ducts pair, united as Y, at level of ovary. Uterus wide, arising from oötype and extending along body midline. Uterus opening at level of intestine bifurcating. Eggs were not observed. Remarks. Karavolicotyla ruber , new species , differs from its congeners K. karavoli and K. tuyeti , new species , by the greater number of clamps present. The cirrus shape and armature also differ among Karavolicotyla spp. (i.e., pine nut-shaped and armed with a circle of 14 short strong curve spines in K. ruber ; spherical and armed with a single spine in K. tuyeti ; trilobed and armed with several minute spines and three long and stout hook-like converging spines in K. karavoli ). Both K. ruber and K. karavoli have oral organs with aseptate lumina while K. tuyeti has septate oral organs. Moreover, the three species differ widely in the number of atrial spines: 25 in K. karavoli ; 52 in K. tuyeti ; and 33–34 in K. ruber . In addition, the fish hosts are different.