Scolex morphology of monozoic cestodes (Caryophyllidea) from the Palaearctic Region: a useful tool for species identification

Abstract

A comparative study of the scoleces of caryophyllidean tapeworms (Cestoda: Caryophyllidea), parasitic in cypriniform fishes in the Palaearctic Region, was carried out using light and scanning electron microscopy. Three-dimensional pictures of the scoleces of 18 species of caryophyllidean cestodes of the Capingentidae (1 species), Caryophyllaeidae (7) and Lytocestidae (10), and outlines of the scoleces and anterior extent of the testes and vitelline follicles of 19 Palaearctic taxa were documented. Both species of Atractolytocestus Anthony, 1957 possess a bulboacuminate scolex, whereas species of Archigetes Leuckart, 1876 have fossate scoleces of the bothrioloculodiscate type, with loculi, bothrium-like depressions and an apical disc. Breviscolex orientalis Kulakovskaya, 1962, the only member of the Capingentidae, has a cuneiform scolex, as do both taxa of the lytocestid genus Caryophyllaeides Nybelin, 1922. The scoleces of two species of Caryophyllaeus gmelin, 1790 are flabellate, whereas that of the congeneric C. fimbriceps Annenkova-Chlopina, 1919 is cuneicrispitate. Khawia Hsü, 1935, the most specious Palaearctic genus, with seven taxa that we consider to be valid, has the highest diversity in scolex morphology: semi-bulbate, flabellate, cuneiform, cuneifimbriate, truncated cuneiform-flabellate and festoon-like. Species of Monobothrium Nybelin, 1922 have either a digitiform scolex with widened posterior part or cuneiform, with lateral auricular extensions. Paracaryophyllaeus gotoi (Motomura, 1927) is characteristic in its possessing a bulbate scolex, whereas Paraglaridacris limnodrili (Yamaguti, 1934) has a fossate scolex of the bulboloculate type with bothrium-like depressions and feebly developed lateral loculi. Anterior extent of the testes and vitelline follicles and their mutual position show a somewhat higher variability than scolex shape, with intraspecific variation in some taxa, such as Atractolytocestus sagittatus (Kulakovskaya et Akhmerov, 1965), B. orientalis, Khawia armeniaca (Cholodkovsky, 1915 and K. sinensis Hsü, 1935. Based on scolex morphology and relative position of the anterior testes and vitelline follicles, a key is provided to facilitate the routine identification of 20 Palaearctic caryophyllidean taxa.

Conflict between morphology and molecular data: a case of the genus Caryophyllaeus (Cestoda: Caryophyllidea), monozoic tapeworms of cyprinid fishes

“…The results obtained here suggest that delimiting species of Caryophyllaeus using solely morphological characteristics may be misleading. Morphology of the scolex plays the key role in identification of caryophyllidean species, being quite diverse (Mackiewicz 1972, Oros et al 2010, Ash et al 2012. However, molecular markers do not provide convincing evidence that the morphotypes of both Caryophyllaeus congeners from different fish hosts and geographical regions with markedly different scolex morphology represent individual species.…”

“…Monozoic fish cestodes of the order Caryophyllidea Carus, 1863 seem to represent the most basal group of 'true' tapeworms (Eucestoda) (Olson et al 2001, Waeschenbach et al 2012, Caira et al 2014). Subtle differences in shape and size of the scolex and the anteriormost extent of vitelline follicles and testes play the central role in species identification of some groups of caryophylideans (Dubinina 1987, Oros et al 2010.…”

“…As part of a large-scale survey of monozoic tapeworms parasitising cyprinids, we collected an extensive material of Caryophyllaeus laticeps (Pallas, 1781) from a wide spectrum of cyprinid fishes throughout Europe and processed it using the standardised methodology (Oros et al , 2010. In addition, samples of a less frequently found congeneric species, Caryophyllaeus brachycollis Janiszewska, 1953, were also included into present study.…”

A new genus and species of proteocephalidean tapeworm (Cestoda), first parasite found in the driftwood catfish Tocantinsia piresi (Siluriformes: Auchenipteridae) from Brazil

“…For scanning electron microscopical (SEM) observations, scoleces of the new species were prepared by the method described by Oros et al (2010) and observed with a Zeiss 940a electron microscope at the Natural History Museum, Geneva and JEOL JSM 6700F scanning electron microscope at the Institute of Parasitology, BC CAS, České Budějovice, Czech Republic. Microthrix terminology follows Chervy (2009).…”

Spermiogenesis and spermatozoon ultrastructure of Hunterella nodulosa (Cestoda: Caryophyllidea), a monozoic parasite of suckers (Catostomidae) in North America

“…our results on H. nodulosa support the previous observations, i.e., the presence of a slight rotation of the flagellar bud as one of the most particular characteristics. It was described for the first time by Bruňanská and Poddubnaya (2006) Miquel et al 2008, Bruňanská 2009, 2010, Yoneva et al 2011, Bruňanská and Kostič 2012 and thus seems to be the most common feature of these monozoic cestodes. one of the more recent ultrastructural investigations, i.e.…”