Ahead of print online version FOLIA PARASITOLOGICA 60 [2]: 141–148 2013 © Institute of Parasitology, Biology Centre ASCR ISSN 0015-5683 (print), ISSN 1803-6465 (online) http://folia.paru.cas.cz/ Khawia abbottinae sp. n. (Cestoda: Caryophyllidea) from the Chinese false gudgeon Abbottina rivularis (Cyprinidae: Gobioninae) in China: morphological and molecular data Bing Wen Xi1*, Mikuláš Oros2*, Gui Tang Wang3, Tomáš Scholz4 and Jun Xie1 1 Key Laboratory of Freshwater Fisheries and Germplasm Resources Utilization, Ministry of Agriculture, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, Wuxi, China; 2 Institute of Parasitology, Slovak Academy of Sciences, Košice, Slovakia; 3 Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, China; 4 Institute of Parasitology, Biology Centre of the Academy of Sciences of the Czech Republic, České Budějovice, Czech Republic; *These authors contributed equally to this work Abstract: Khawia abbottinae sp. n. is described from the Chinese false gudgeon, Abbottina rivularis (Basilewsky) (Cyprinidae: Gobioninae), from the Yangtze River basin in China. The new species can be distinguished from the congeneric species mainly by the arrangements of the testes, which form two longitudinal bands (other congeneric species have the testes irregularly scattered throughout the testicular region) and their number (at maximum 85 testes versus at least 160 in the other Khawia spp.), and the mor- phology of the scolex, which varies from cuneiform to widely bulbate scolex, being separated from the remaining body by a short neck and possessing a smooth, blunt or rounded anterior margin. Other typical features of K. abbottinae are its small size (total length less than 1.5 cm) and body shape, with the maximum width at its first third. The distinct status of the new species was confirmed by molecular data (ssrDNA and ITS1 sequences). Phylogenetic analyses revealed a close relationship of the new species with K. rossit- tensis (Szidat, 1937) and K. parva (Zmeev, 1936), parasites of crucian carp and goldfish (Carassius spp.), but both species markedly differ from K. abbottinae in their morphology. Until now, five valid species ofKhawia (K. abbottinae, K. japonensis, K. rossittensis, K. saurogobii and K. sinensis) have been reported from China. Keywords: Cestoda, Khawia, Abbottina, Cyprinidae, Yangtze River, 18S rDNA, ITS1 Caryophyllideans represent a unique group among Khawia Hsü, 1935 is a species-rich genus in the or- ‘true’ cestodes (Eucestoda) because they possess a non- der Caryophyllidea, including 17 nominal species para- strobilate and monozoic body, i.e. containing only a single sitizing cyprinid fishes in Europe, Asia, Africa and North set of male and female reproductive organs (Mackiewicz America. Scholz et al. (2011) have recently revised the 1994, Oros et al. 2008). They are supposed to represent genus, and revealed that only seven species are valid: the most basal order of the Eucestoda, which would imply Khawia sinensis Hsü, 1935 (type species); K. armeniaca tapeworm evolution from simple monozoic to polyzoic, (Cholodkovsky, 1915); K. baltica Szidat, 1941; K. japon- externally segmented (strobilate) forms (Olson et al. 2001, ensis (Yamaguti, 1934); K. parva (Zmeev, 1936); K. ros- Waeschenbach et al. 2012). Molecular analyses carried sittensis (Szidat, 1937); and K. saurogobii Xi, Oros, Wang, out on caryophyllideans have detected some interesting Wu, Gao et Nie, 2009. phenomena, such as paralogous structure of nuclear ribos- Species of Khawia exhibit strict (oioxenous or stenox- omal spacers and nuclear copies of mitochondrial genes enous) host specificity, infecting only one or few close- (Brabec et al. 2012), triploid character of some species ly related fish hosts, except K. armeniaca that exhibits (Špakulová et al. 2011), divergent intragenomic ribos- a wider spectrum of fish definitive hosts (several genera omal internal transcribed spacers (ITS1 and ITS2 rDNA) of barbels – Barbinae) and is widely distributed in Africa, along with multiple rDNA loci and dispersed nucleolar Asia and Europe (Scholz et al. 2011). organizer regions (NORs) (Kráľová-Hromadová et al. During the ichthyoparasitological survey in China, 2012). These findings make caryophyllideans an interest- caryophyllidean tapeworms were found in the Chinese ing model for studies of unusual molecular phenomena in false gudgeon, Abbottina rivularis (Basilewsky) (Cyprini- parasitic flatworms (Neodermata). dae, Gobioninae). Morphological characteristics comple- Address for correspondence: J. Xie, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences, 214081 Wuxi, China. Phone: +086 0510 85559939; Fax: +086 0510 85559939; E-mail: [email protected] 141 Ahead of print online version mented by molecular data (partial sequences of ssrDNA the above procedure, except for the annealing temperature hav- and ITS1) indicate that these tapeworms represent a new ing been reduced to 52 °C, and three clones of each species of species of Khawia. Therefore, this new species is de- Khawia available having been selected for sequencing. scribed in the present paper and its phylogenetic relation- The ssrDNA and ITS1 sequences were assembled and in- TM ships to other congeneric species are discussed. spected using SeqMan (DNASTAR, Inc.) and aligned with available sequences of caryophyllideans in GenBank using the program MEGA5.1 with default setting (Tamura et al. 2011). MATERIALS AND METHODS The ambiguously aligned positions were excluded from subse- Between April 2007 and April 2011 several tens of tape- quent phylogenetic analyses based on minimum evolution (ME), worms were found in the intestine of the Chinese false gudgeon maximum likelihood (ML) and Bayesian inference (BI) criteria. Abbottina rivularis from water bodies of the middle and lower The appropriate nucleotide substitution model was estimated reaches of the Yangtze River basin (Niushan Lake in Wuhan, in MEGA 5.0. The phylogenetic trees based on 18S rDNA were Yangtze River in Wuhan, Hubei Province, and Taihu Lake in analyzed by ME with Tamura-Nei + G model and ML with Wuxi, Jiangsu Province) in China (Table 1). Tapeworms found TN93+G+I model methods in MEGA 5.0. BI analyses were were rinsed in saline solution prior to fixation. Specimens used conducted in MrBayes ver. 3.1.2 (Ronquist and Huelsenbeck for morphological studies, including observations with scan- 2003), employing TN93+G+I model, running two independ- ning electron microscopy (SEM) and histology, were fixed with ent MCMCMC runs of four chains for one million generations hot (almost boiling) 4% formaldehyde solution (see Oros et al. and sampling tree topologies every 100 generations. Posterior 2010). After two weeks, formalin was replaced by 70–75% etha- probability values were used as support for the Bayesian topol- nol for storage before further processing. Specimens used for ogy. In the case of ITS1 of Khawia, the phylogenetic trees were molecular studies were fixed and stored in 100% ethanol. analyzed by ME using Tamura-Nei model, ML and BI using For light microscopical observations, specimens were HKY+I model. stained with iron hydrochloric carmine, destained in 70% acid ethanol, dehydrated in an alcohol series, cleared in clove oil RESULTS and mounted in Canada balsam as permanent preparations. Il- lustrations were made using a drawing attachment of a Leica Khawia abbottinae sp. n. Figs. 1, 2 DM 5000 B microscope with the use of Nomarski differential Description (based on 15 whole-mounted specimens, interference contrast. Measurements were taken using the Ts- five slides of cross-sections and five slides of sagit- view 7.1 program (Tucsen, China) and LAS V3.8Ink program tal and longitudinal sections, from Abbottina rivularis (Leica, Switzerland). Histological sections (cross, longitudinal from Taihu Lake in Wuxi and from the Yangtze River and sagittal sections) were made from hot formalin-fixed speci- in Wuhan): Caryophyllidea, Lytocestidae. Testes and mens using standard protocols (thickness of sections 10–12 μm), ovary medullary, vitelline follicles cortical. Body elon- stained with hematoxylin and eosin, and mounted in Canada balsam. Four specimens used for SEM observations were proc- gate to almost spindle-shaped, with relatively narrow essed as described by Oros et al. (2010). Measurements are in scolex and neck, maximum width at anterior third, then micrometres (μm) unless otherwise indicated. slightly narrowing continuously towards rounded poste- Genomic DNA of specimens from Taihu Lake (collec- rior end. Total length of body 6.8–13.0 mm, maximum tion numbers TaiL201104, TaiL200401) was extracted using width 0.8–2.0 mm (n = 9). Surface uniformly covered QIAamp DNA kit (QIAGEN). The small nuclear ribosomal with acicular filitriches. Inner longitudinal musculature RNA subunit (ssrDNA or 18S rDNA) was amplified by PCR well developed, formed by small bundles of muscle fibers. using primer pairs WormA and WormB (Littlewood and Olson Osmoregulatory canals about 6–8 pairs, external to vitel- 2001). Each PCR reaction consisted of 20 pmol of each primer, line follicles. 5 μl 10× Ex Taq buffer, 250 μM of each dNTP, 1 U of Takara Ex Scolex afossate, widely bulbate to almost cuneiform, TaqTM, 2 μl DNA template and nuclease-free water to 25 μl vol- 0.4–0.6 mm long and 0.7–1.5 mm wide, wider than neck, ume. Amplifications were performed on Eppendorf Mastercy- cler with an initial denaturation step of 95 °C for 3 min followed with smooth, blunt or rounded anterior margin. Neck dis- by