Tapeworms of Gangesia Woodland, 1924 (Cestoda: Proteocephalidea) parasitic in freshwater fishes in the Indomalayan Region were critically reviewed. Evaluation of type specimens and newly collected materials from Bangladesh, Cambodia and India, as well as critical examination of extensive literature have shown that only the following four species, instead of 48 nominal species of Gangesia and Silurotaenia Nybelin, 1942 reported from this region (36 new synonymies proposed), are valid: Gangesia bengalensis (Southwell, 1913), type-species of the genus and most common parasite of Wallago attu (Siluridae), G. macrones Woodland, 1924 typical of Sperata seenghala (Bagridae), both species characterized by the possession of two circles of hooks on the rostellum-like organ and several rows of hooklets on the anterior margins of suckers; G. agraensis Verma, 1928 from W. attu (typical host), which has the scolex with only one circle of hooks and 1–3 incomplete rows of tiny hooklets on the suckers; and G. vachai (Gupta and Parmar, 1988) n. comb. from several catfishes, which possesses 4–6 circles of hooks and 5–11 rows of hooklets on the anterior half of suckers. Scolex morphology, including surface ultrastructure (microtriches), of all but one species (G. vachai) is described for the first time using scanning electron microscopy. A phylogenetic analysis based on the partial sequences encoding the large nuclear ribosomal subunit RNA gene has shown that three Indomalayan species, namely G. bengalensis, G. macrones and G. vachai, form a monophyletic group within Gangesia, whereas G. agraensis tends to form a clade with the Palaearctic species of the genus. A table with differential characters of all species from the Indomalayan Region is also provided together with a key to identification of genera of the subfamily Gangesiinae. The present study demonstrates that species of Silurotaenia do not occur in the Indomalayan region.

Revision of monozoic cestodes (Caryophyllidea) parasitic in commercially important walking catfish Clarias batrachus (L.) in tropical Asia (Indomalayan zoogeographical region) was carried out, based on the evaluation of newly collected material from India, Indonesia, and Thailand, as well as a study of type specimens. Instead of the 59 nominal taxa of 15 genera from 3 caryophyllidean families previously described, only 8 species of the Lytocestidae are considered to be valid: Bovienia indica (Niyogi, Gupta and Agarwal, 1982) n. comb.; Bovienia raipurensis (Satpute and Agarwal, 1980) Mackiewicz, 1994; Bovienia serialis (Bovien, 1926) Fuhrmann, 1931; Djombangia penetrans Bovien, 1926; Lucknowia microcephala (Bovien, 1926) n. comb.; Lytocestus indicus (Moghe, 1925) Woodland 1926; Pseudocaryophyllaeus ritai Gupta and Singh, 1983; and Pseudocaryophyllaeus tenuicollis (Bovien, 1926) n. comb. All valid species are redescribed and SEM photomicrographs of their scolices and photomicrographs of their eggs are provided for the first time. Crescentovitus Murhar, 1963, Heeradevina Srivastav and Khare, 2005, Pseudobatrachus Pathak and Srivastav, 2005, Pseudobilobulata Srivastav and Lohia, 2002, Pseudoclariasis Pathak, 2002, and Pseudoinverta Pathak, 2002 are invalidated and 50 nominal species are newly synonymized, including 4 species described from other fish hosts. Taxonomic status of the remaining caryophyllidean taxa reported from C. batrachus (at least 6 taxa) could not be clarified because of the unavailability of their original descriptions. A key to identification of caryophyllidean tapeworms parasitic in C. batrachus is provided. To avoid current inflation of descriptions of invalid taxa, researchers are strongly encouraged to work only with well-fixed material; damaged, decomposed, or strongly flattened specimens should not be used for taxonomic studies, and type specimens must always be deposited in internationally recognized collections.

The stinging catfish Heteropneustes fossilis (Bloch) (Siluriformes: Heteropneustidae) has been reported to harbor as many as 19 species of caryophyllidean tapeworms (Cestoda) of 11 genera in tropical Asia (Indomalayan zoogeographical region). However, a critical review of the species composition has shown that only 1 species, Lucknowia fossilisi Gupta, 1961 (Lytocestidae), is a specific parasite of H. fossilis. Three other species, Djombangia penetrans Bovien, 1926 (syn., Djombangia caballeroi Sahay and Sahay, 1977 ), Pseudocaryophyllaeus ritai Gupta and Singh, 1983 (syn. Pseudocaryophyllaeus lucknowensis Gupta and Sinha, 1984 ), and Pseudocaryophyllaeus tenuicollis (Bovien, 1926) Ash, Scholz, Oros and Kar, 2011 (syn. P. mackiewiczi Gupta and Parmar, 1982 ), were found only once. Lucknowia fossilisi is redescribed on the basis of new material collected in West Bengal and voucher specimens from Maharashtra, India. A total of 9 species of Capingentoides, Lucknowia, Lytocestus, Pseudoadenoscolex, Pseudocaryophyllaeus, Pseudoheteroinverta, and Sukhapatae are newly synonymized with L. fossilisi and previous synonymies of 9 other species, proposed by Hafeezulah (1993), are confirmed. Generic diagnosis of Lucknowia Gupta, 1961 is amended. In addition, 1 species of Pseudobatrachus and 2 species of the monotypic genera Pseudoneckinverta and Sudhaena are invalidated as nomina nuda.