Ahead of print online version FOLIA PARASITOLOGICA 58[4]: 279–288, 2011 © Institute of Parasitology, Biology Centre ASCR ISSN 0015-5683 (print), ISSN 1803-6465 (online) http://www.paru.cas.cz/folia/ Ritacestus gen. n. (Cestoda: Proteocephalidea) and redescription of R. ritaii comb. n., a parasite of Rita rita (Siluriformes) in India Alain de Chambrier1, Tomáš Scholz2, Anirban Ash2 and Pradip Kumar Kar3 1 Department of Invertebrates, Natural History Museum, P.O. Box 6434, CH-1211 Geneva 6, Switzerland; 2 Institute of Parasitology, Biology Centre of the Academy of Sciences of the Czech Republic & Faculty of Science, University of South Bohemia, Branišovská 31, 370 05 České Budějovice, Czech Republic; 3 Jhargram Raj College, Jhargram, Paschim Medinipur, West Bengal 721507, India Abstract: A new genus, Ritacestus, is proposed to accommodate Ritacestus ritaii (Verma, 1926) comb. n. (syn. Proteocephalus ritaii), a parasite of the catfish Rita rita (Hamilton) in India. The new genus, which is placed in the Gangesiinae, is characterized by (i) a small, subspherical scolex formed by four large lobes separated from one another by longitudinal grooves, with a large, widely oval to pyriform rostellum-like apical organ, larger than suckers and possessing an apical hemispherical depression; (ii) paramus- cular and cortical position of some vitelline follicles (most follicles are situated medullary); (iii) ventral and dorsal bands of vitel- line follicles usually uninterrupted ventral to terminal genitalia and reaching to the posterior margin of proglottides; (iv) the vagina always anterior to the cirrus-sac; (v) a large size of the body (length up to 51 cm); and (vi) development of the uterus of type 2. In its morphology, especially shape of the scolex and apical organ, and paramuscular and cortical position of some vitelline follicles, Ritacestus resembles Postgangesia Akhmerov, 1969, but differs in the presence of a genital atrium (both genital pores of Postgan- gesia are separate), the anterior position of the vagina (almost always posterior in the latter genus), position of vitelline follicles in cross sections (dorsal and ventral bands in Ritacestus versus only a lateral band in the latter genus), and dorsal excretory canals indistinguishable in mature and gravid proglottides of R. ritaii (well developed in Postgangesia spp.). The type and only species of the genus, R. ritaii, is redescribed on the basis of new material from the type host from the Ganges River basin in India and its neotype is designated. Keywords: morphology, taxonomy, neotype, Eucestoda, Gangesiinae, freshwater fish, Ganges River, India A high number of tapeworms (Cestoda) of three orders especially those from other zoogeographical regions such (Caryophyllidea, Bothriocephalidea and Proteocephali- as the Neotropical, Ethiopian and Indomalayan regions, dea) have been described from freshwater fish in the In- actually do not belong to Proteocephalus sensu stricto domalayan Region, with a great majority of them being (= Proteocephalus aggregate of de Chambrier et al., 2004) based on material collected in India (for lists of species, and should be placed in other genera. see Mackiewicz 1981, Schmidt 1986, Hafeezullah 1993, In this paper, one of these species, Proteocephalus rit- Kuchta and Scholz 2007, Ash et al. 2011). Two cestode aii Verma, 1926, a parasite of the catfish Rita rita (Ham- species have been placed in Proteocephalus Weinland, ilton, 1822) (Siluriformes: Bagridae) in India, is rede- 1858, namely P. ritaii Verma, 1926 and P. vitellaris (Ver- scribed on the basis of new material from the type host ma, 1928) (syn. Ichthyotaenia vitellaris Verma, 1928) (type specimens could not be located) and a new genus is (Verma 1926, 1928), but recent studies have provided evi- proposed to accommodate it. dence that this genus represents an artificial assemblage of morphologically dissimilar and phylogenetically unre- MATERIALS AND METHODS lated taxa (de Chambrier et al. 2004a, Hypša et al. 2005). The present study is based on morphological evaluation of Therefore, de Chambrier et al. (2004a) proposed the cestodes collected by the present authors from the intestine of Proteocephalus aggregate to accommodate species para- Rita rita in two localities of West Bengal, India: (i) 12 whole- mounts of three adult specimens (one without scolex) and sitic in the Holarctic freshwater fish that share similar 29 slides with cross sections from the Pagla River at Kaliachak morphology (see Scholz and Hanzelová 1998) and form near Malda (English Bazar – 24°51.65′N; 88°01.08′E), West monophyletic clade (de Chambrier et al. 2004a, Hypša et Bengal, March 2 and 3, 2009, deposited in the Natural History al. 2005, Scholz et al. 2007). The remaining species of the Museum, Collection of Invertebrates, Geneva, Switzerland (ac- Proteocephalus complex (= Proteocephalus sensu lato), ronym INVE), field numbers IND 66 (INVE 63249), 67 (INVE Address for correspondence: T. Scholz, Institute of Parasitology, Biology Centre of the Academy of Sciences of the Czech Republic, Branišovská 31, 370 05 České Budějovice, Czech Republic. Phone: +420 38 53 10 351; Fax: +420 38 5310388; E-mail: [email protected] 279 Ahead of print online version 63242) and 132 (INVE 78786 and The Natural History Muse- testes in anterior third of proglottides. Genital pores irreg- um, London, UK; acronym BMNH – 2011.5.16.5); (ii) whole- ularly alternating, slightly pre-equatorial. Genital atrium mounts of three adult specimens (one used for scanning electron present. Ovary follicular, bilobed, with wide lateral lobes. microscopy – SEM) and two slides with longitudinal sections Vagina anterior to cirrus-sac, with weakly developed of the scolex from the Pagla River at Kaliachak, West Bengal, circular vaginal sphincter. Vitelline follicles arranged in March 11, 13 and 27, 2011, field numbers IND 580 (INVE paired (ventral and dorsal) lateral bands from anterior to 78788), 684 (INVE 78789) and 909 (used for SEM); (iii) four whole-mounts of an adult specimen (without scolex) from the posterior margin of proglottides, usually uninterrupted at Ganges River at Farakka dam lake near Malda (24°49.32′N; level of terminal genitalia. Uterine development of type 87°56.49′E), March 4, 2009, field number 145 (Institute of Para- 2 according to de Chambrier et al. (2004a), with well- sitology, BC AS CR, České Budějovice, Czech Republic – acro- developed uterine glands (chromophilic cells) alongside nym IPCAS C-603 and INVE 63240). uterine stem and diverticula. Type and only species: Rita- Cestodes collected by the present authors from fresh hosts cestus ritaii (Verma, 1926) comb. n. were ���������������������������������������������������������isolated from the intestine, rinsed in saline and immedi- E t y m o l o g y : The generic names is composed of the host ately fixed with hot (almost boiling) 4% formaldehyde solution name (“Rita”) and suffix “-cestus”, which means a tape- (formalin), with pieces of several worms placed before in 99% worm; generic name should be treated as masculine. molecular grade ethanol for DNA analysis. The specimens used for morphological observations were then stained with Mayer’s Differential diagnosis: The new genus is placed in the hydrochloric carmine solution, dehydrated in a graded ethanol Gangesiinae because of the presence of a large, rostellum- series, cleared with eugenol (clove oil), and mounted in Canada like apical organ connected with the neck region by re- balsam. Pieces of strobila and one scolex were embedded in par- tractor muscles, presence of vitelline follicles up to the affin wax, sectioned at 12–15 µm (cross sections of the strobila posterior margin of proglottides, and medullary position and longitudinal sections of the scolex), stained with Weigert’s of genital organs (testes, ovary, uterus and most vitelline haematoxylin and counterstained with 1% eosin B with 1 drop follicles), with some vitelline follicles paramuscular and of acetic acid/100 ml of solution (de Chambrier 2001). Tech- cortical (see de Chambrier et al. 2003). nique of preparation of samples for SEM follows that described The genus is characterized by combination of the by Oros et al. (2010), whereas microthrix terminology follows that proposed by Chervy (2009). Eggs fixed with hot formalin following morphological characteristics (Figs. 1–23): together with worms for morphological study (see above) were (i) a subspherical scolex with a large, widely oval to py- studied in distilled water. riform rostellum-like apical organ with glandular content and with an apical hemispherical depression; apical or- RESULTS gan larger than spherical suckers situated on large lobes separated from one another by four longitudinal grooves; Examination of newly collected material of Proteo- (ii) position of vitelline follicles, most of which are situat- cephalus ritaii from the type host has revealed several ed in the medulla, but some are paramuscular and cortical; morphological characteristics, in which this species (iii) presence of paired (ventral and dorsal) bands of vitel- differs from all remaining congeneric taxa (species of line follicles, usually uninterrupted ventral to the terminal Proteocephalus sensu stricto), but also from other pro- genitalia, reaching to the posterior margin of proglottides; teocephalideans. To reflect a unique morphology of Pro- (iv) anterior position of the terminal part of the vaginal teocephalus ritaii, a new genus, Ritacestus, is proposed canal in relation to the cirrus-sac; and (v) uterine develop- to