Morphological investigations into Floriceps minacanthus (Trypanorhyncha: Lacistorhynchidae) with analysis of the systematic utility of scolex microtriches

Morphology and molecular phylogeny of trypanorhynchid metacestodes infecting commercial fish of the Mediterranean Sea

ABSTRACT Members of the order Trypanorhyncha are cestode parasites that are frequently found infecting the muscles of several marine fish species, affecting fish health, and resulting in consumers’ rejection of fish. Fifty-two specimens of marine fish were freshly caught throughout the year 2020 from boat landing sites at the Alexandria coast along the Mediterranean Sea in Egypt, including the grey trigger fish Balistes carolinensis (F: Balistidae); the mottled grouper Mycteroperca rubra (F: Serranidae) and the common sole Solea vulgaris (F: Soleidae). Blastocysts were isolated and ruptured; the generated pleurocerci were described morphologically and morphometrically by light and scanning electron microscopy. Also, multiple-sequence alignment was performed, and a phylogenetic tree was constructed following maximum likelihood analysis of the 18s and 28s ribosomal RNA sequences of the recovered worms. Thirty fish were infected; the infection was recorded as blastocysts embedded in fish flesh. Three different parasitic species were recovered and classified morphologically as Gymnorhynchus isuri, Pseudotobothrium dipsacum and Heteronybelinia estigmena. The taxonomic position of these parasites was justified by molecular analysis of their 18s and 28s rRNAs, which revealed high percentages of homology with species recovered from the GenBank. The accession numbers ON157059, ON139663 and ON139662 were respectively assigned to the recovered parasites after their deposition in GenBank. The results obtained from the molecular analyses confirmed the morphological records of the recovered parasites. Since metacestodes are found in the musculature of infected fish specimens, it is necessary to remove these areas in the commercialization of fish.

Larval cestodes infecting commercial fish of Alexandria coast along the Mediterranean Sea: morphology and phylogeny

Members of the order Trypanorhyncha are cestode parasites that are frequently found infecting the muscles of several marine fish species, affecting fish health and resulting in consumers' rejection. Seventy-five specimens of marine fish were freshly caught from boat landing sites at the Alexandria coast along the Mediterranean Sea in Egypt, including two Carangids, the greater amberjack Seriola dumerili and the gulley jack Pseudocarans dentex; two Serranids, the Haifa grouper Epinephelus haifensis and the mottled grouper Mycteroperca rubra. Forty-five fish were infected; the infection was recorded as blastocysts embedded in fish flesh. Blastocysts were isolated and ruptured; the generated plerocerci were described morphologically, where, four different species were recovered; Callitetrarhynchus gracilis, Callitetrarhynchus speciosus, Protogrillotia zerbiae, and Grillotia brayi. The taxonomic position of these parasites was justified by multiple-sequence alignment and a phylogenetic tree was constructed following maximum likelihood analysis of the 18s rRNA sequences of the recovered worms. The accession numbers MN625168, MN625169, MN611431and MN611432 were respectively assigned to the recovered parasites. The results obtained from the molecular analyses confirmed the morphological records of the recovered parasites. Since metacestodes are found in the musculature of infected fish specimens, it is necessary to remove these areas in the commercialization of fish.

Microthrix pattern of Pseudogilquinia thomasi (Palm, 2000) (Cestoda: Trypanorhyncha) and a review of surface ultrastructure within the family Lacistorhynchidae Guiart, 1927

The microthrix pattern of larvae of Pseudogilquinia thomasi (Palm, 2000) is described for the first time using scanning electron microscopy. The surface ultrastructure of this species consists of three main forms of microtriches: papilliform filitriches, acicular filitriches and quadridigitate to octadigitate palmate spinitriches. The bothria are covered with palmate spinitriches interspersed on some parts with papilliform filitriches. Palmate spinitriches with papilliform, acicular and capilliform filitriches adorn the pars vaginalis and at the anterior part of the pars bulbosa, there is a transition zone in which the palmate spinitriches are replaced by papilliform to acicular filitriches towards the end of the scolex. ANOVA tests with Duncan's post hoc analyses revealed that there are significant differences in the length of spinitriches and their prongs, whether on the surfaces of the bothria or on the surfaces of the scolex peduncle. Callitetrarhynchus gracilis Pintner, 1931 is the second lacistorhynchid species for which surfaces of the segments were examined and the occurrence of large structures called scutes are reported for the first time from this species. There were also significant differences in the base length as well as height of the scutes in different parts of the strobila. In addition to describing the surface ultrastructures of the two lacistorhynchid species, all the available information on the microtriches within the family Lacistorhynchidae is reviewed herein and generic diagnoses related to microtriches are amended.

Surface ultrastructure and the mitochondrial gene rrnl of Parachristianella indonesiensis Palm, 2004 (Trypanorhyncha: Eutetrarhynchidae) with the amended generic diagnosis

The microthrix pattern of adult Parachristianella indonesiensis Palm, 2004 is described for the first time based on the standardized terminology for microtriches, and the generic diagnosis of Parachristianella Dollfus, 1946, regarding microtriches, is also amended. The surface ultrastructure of P. indonesiensis consists of three kinds of microtriches so that the proximal and distal bothrial surfaces are covered respectively with acicular to short capilliform filitriches and aristate gladiate spinitriches interspersed with capilliform filitriches. The remainder of the scolex bears capilliform filitriches. The surface of the proglottid is adorned with acicular filitriches. There was no significant difference in the length of the capilliform filitriches covering the different parts of the scolex peduncle. For the first time, the uniciliated papillae adorned with filitriches as sensory receptors are reported from this parasitic species. The partial rrnl of P. indonesiensis is also presented as the only known sequence of this gene in the superfamily Eutetrarhynchoidea Dollfus, 1969. The pairwise comparisons of rrnl between P. indonesiensis and the trypanorhynch species for which rrnl sequence is available were in accordance with the last phylogeny presented for the order Trypanorhyncha. The infection parameters (prevalence, mean abundance, and mean intensity) of P. indonesiensis parasitizing Pastinachus sephen (Forsskål) from the eastern Persian Gulf were also compared during approximately 5 years, and no significant differences were observed. This may be interpreted as the stability of the factors playing important roles in the life cycle of P. indonesiensis in the eastern Persian Gulf during this period.

Redescriptions and new records of species of Otobothrium Linton, 1890 (Cestoda: Trypanorhyncha)

Redescriptions are provided for five incompletely described species of Otobothrium Linton, 1890: Otobothrium alexanderi Palm, 2004 from two species of carcharhinid sharks, Carcharhinus cautus (Whitley) and C. melanopterus (Quoy & Gaimard) at three localities off northern Australia; O. australe Palm, 2004 based on material collected from the type-host and type-locality and from six additional myliobatid and carcharhinid host species off Western Australia, the Northern Territory and northern Queensland; O. insigne Linton, 1905 from Rhizoprionodon terraenovae (Richardson) and Sphyrna tudes (Valenciennes) in the Atlantic Ocean off Senegal and the Democratic Republic of the Congo; O. mugilis Hiscock, 1954, previously known only from larval stages, based on adults from five sphyrnid and carcharhinid definitive host species off northern Australia and Malaysian Borneo; and O. penetrans Linton, 1907 from material collected from two species of hammerhead sharks (Sphyrnidae) in the Red Sea off Jordan and the Indian Ocean off Western Australia. Additional host and locality records are added for the type-species, O. crenacolle Linton, 1890 and for O. carcharidis (Shipley & Hornell, 1906). Two descriptions are provided for Otobothrium spp. treated here as Otobothrium sp. 1 from C. melanopterus off northern Australia and Otobothrium sp. 2 from Sphyrna zygaena (Linnaeus) in the Gulf of California, Mexico.

Studies on monieziasis of sheep I. Prevalence and antihelminthic effects of some plant extracts, a light and electron microscopic study

Out of 2,343 examined sheep throughout the whole year, 271 were found to be infected with tapeworms (11.5%). The highest infection rate (22.1%) was recorded in autumn, while the lowest (6%) occurred in summer. Six species of cestodes were identified according to their prevalence: Moniezia expansa (74%), Moniezia denticulata (8.5%), Moniezia benedeni (4.8%), Moniezia trigonophora (2.7%), and Thysaniezia giardi (2.7%), T. giardi was recorded in Egypt for the first time. M. expansa was found throughout the year with two peaks in January (92.3%) and June (88.5%). SEM examination revealed that M. expansa scolex has four triangular suckers guarded by an X-shaped fibrous band that makes them open permanently. Also, there is a Y-shaped apical part at the scolex center which may be an embryonically non-developed rostellum. The whole worm body surface is covered with unidirectional microtriches. TEM showed that the tegument is underlaid by a thick fibrous interstitial layer below which an outer circular and an inner longitudinal muscular layer are arranged. Beneath these structures the subtegumental cells are found which have spherical electron-dense inclusions and various other cell organelles. Moreover, M. expansa has interproglottidal glands which contain secretory vesicles and secretions. For biological control of this parasite, different concentrations of crude plant extract of Artemisia cina were used in vitro and in vivo. In vitro, the results indicated that the plant extract is efficacious at all concentrations tested. Electron microscopic examination showed that many structures of the treated worms were affected. The most affected sites were the scolex and the microtriches of the outer tegumental surface. In vivo, treatment of heavily infected animals showed an antihelminthic effect, since the complete absence of eggs was recorded 9 days after treatment when fecal investigations were done.

Nataliella marcelli n. g., n. sp. (Cestoda: Trypanorhyncha: Rhinoptericolidae) from Hawaiian fishes

A new trypanorhynch cestode from Hawaiian waters is described based on specimens in the collection of the Meguro Parasitological Museum, Tokyo, and newly collected specimens. Nataliella marcelli n. g., n. sp. is characterised by its elongate, craspedote scolex with four small, ear-shaped bothria, an elongate pars vaginalis and long bulbs. The homeoacanthous homeomorphous metabasal armature is comprised of five or six slender, solid hooks per half spiral row. A distinctive basal armature is present, including a combination of six characteristically shaped macrohooks not previously described for trypanorhynchs. The surface ultrastructure consists of gladiate spiniform microtriches that cover the distal and proximal bothrial surface and filiform microtriches on the scolex peduncle. The adults are not known. Nataliella is assigned to the family Rhinoptericolidae Carvajal & Campbell, 1975 based on its possession of four bothria, prebulbar organs and no chainette or intercalary hooks. The family diagnosis is amended to accommodate the new genus. Rhinoptericola megacantha Carvajal & Campbell, 1975 is considered the most closely related species, a position that has been confirmed by molecular analyses of the SSU and LSU rDNA. Nataliella n. g. is intermediate in morphology between the homeoacanth family Tentaculariidae Poche, 1926 (superfamily Tentacularioidea) and the Rhinoptericolidae and other eutetrarhynchid genera (superfamily Eutetrarhynchoidea), sharing characters of both superfamilies.

Redescription of Gymnorhynchus isuri (Cestoda: Trypanorhyncha) from Isurus oxyrinchus (Elasmobranchii: Lamnidae)

Specimens of the elasmobranch, Isurus oxyrinchus Rafinesque, captured in 1999 in the state of Santa Catarina, Brazil, were parasitized with the poecilacanthoid trypanorhynch cestode Gymnorhynchus isuri Robinson, 1959, that is redescribed here. New details of scolex and proglottid morphology are given. These details are mainly related to tentacle armature, terminal genitalia and observations of external morphology of proglottids.

Ailinella mirabilis gen. n., sp. n. (eucestoda: pseudophyllidea) from Galaxias maculatus (Pisces: Galaxiidae) in the Andean-Patagonian region of Argentina

Ailinella gen. n. (Pseudophyllidea: Triaenophoridae) is proposed to accommodate Ailinella mirabilis sp. n. from Galaxias maculatus (Jenyns, 1842), a freshwater fish inhabiting the Andean lakes in Argentinean Patagonia. Ailinella belongs to the Triaenophoridae because it has a marginal genital pore, a follicular vitelline gland, and a ventral uterine pore. The new genus can be distinguished from other triaenophorids by the following combination of characters: a small body size, a low number of proglottides, which are longer than wide, a truncated pyramidal to globular scolex, a rectangular apical disc, presence of the neck, lack of internal longitudinal musculature separating the cortex from the medulla, testes distributed in one central field surrounding the ovary laterally and posteriorly, the vagina predominantly anterior to the cirrus sac, vitelline follicles circum-medullary, the genital pores post-equatorial, a saccate uterus, and operculate eggs. Blade-like spiniform microtriches were present on all tegument surfaces, and tumuli on all surfaces of the scolex and the anterior surface of the neck. Microtriches were characterized according to their size and density, and tumuli according to their size, inter-tumulus distance and density. Ailinella mirabilis is the first cestode described from G. maculatus and the second triaenophorid species recorded from a South American freshwater fish.

COMPARISON OF MICROTHRIX ULTRASTRUCTURE AND MORPHOLOGY ON THE PLEROCERCOID AND ADULT SCOLEX OF CALLIOBOTHRIUM CF. VERTICILLATUM (TETRAPHYLLIDEA: ONCHOBOTHRIIDAE)

The distal bothridial surfaces of adult triloculate onchobothriids are covered with short structures that have been tentatively classified as very short filitriches, but this hypothesis has never been tested. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to investigate microthrix morphology in the plerocercoid and adult forms of Calliobothrium cf. verticillatum, a triloculate onchobothriid tapeworm from Long Island Sound (Connecticut). Plerocercoids of C. cf. verticillatum were collected from the anterior midgut ceaca of Pagurus pollicaris Say, 1817 (flat-clawed hermit crab), and adults were collected from the spiral intestine of the dusky smooth hound Mustelis canis (Mitchell, 1815). Two plerocercoids and 2 adults were examined using SEM; 2 plerocercoids and 2 adults were examined using TEM. Microthrix distribution and morphology (including measurements of total length, base length, shaft length, and base width) were investigated on all surfaces of the plerocercoid and adult scolex. Slender filitriches and large bladelike spinitriches were observed extending from the tegument of plerocercoid and adult forms. The filitriches were found to have significantly narrower bases than the spinitriches (65-167 nm vs. 466-1,936 nm, respectively). The scolex proper of the plerocercoid and adult forms were found to have filitriches of medium-length and bladelike spinitriches. The distal bothridial surfaces differed dramatically in microthrix morphology between plerocercoid and adult forms; on the distal surfaces of the plerocercoids were long filitriches and bladelike spinitriches. However, the distal surfaces of the adults had short structures (previously hypothesized to be short filitriches) and a few bladelike spinitriches. Serial transverse sections revealed that the short structures on the distal bothridial surfaces of the adults were homologous with filitriches. They included all of the structural components of a filithrix as well as a base width that conformed to the filitriches found on other surfaces. The bothridial margins of the plerocercoid and adult forms had a microthrix pattern similar to that seen on the proximal bothridial surfaces except that the filitriches on the margins were significantly longer than those found anywhere else on the bothridia. The most dramatic difference between the plerocercoid and adult forms occurred on the distal bothridial surfaces, where the filitriches of the adult cestodes were significantly shorter and narrower, and the spinitriches were almost entirely lacking.

FIRST EVIDENCE OF THE PRESENCE OF MICROTRICHES IN THE GYROCOTYLIDEA

The Gyrocotylidea, a small and enigmatic group of intestinal parasites of chimaeras, has been considered to be related either to the Monogenea, or, more frequently, to the most primitive monozoic tapeworms (Cestoda), i.e., the Amphilinidea and Caryophyllidea. The present study, based on transmission electron microscopical observations of a species of Gyrocotyle from the rabbit fish, Chimaera monstrosa, in the North Atlantic, demonstrates for the first time the presence of microtriches as surface structures of gyrocotylideans. Because microtriches are considered to be an autapomorphy of tapeworms (Cestoda), in which they differ from other Neodermata (Monogenea and Trematoda), the present data represent another source of evidence in support of a close relationship between the gyrocotylideans and the tapeworms sensu stricto (Eucestoda). Simple morphology, small size, and shape uniformity of the microtriches of Gyrocotyle sp. may indicate they represent an original (plesiomorphic) form that then evolved in more derived cestode groups into a variety of types present mainly on the scolex. The microtriches of Gyrocotyle sp. resemble those found in caryophyllidean, spathebothriidean, pseudophyllidean, and trypanorhynch cestodes, which are considered to represent the most basal groups of the Eucestoda.

Redescription of Cetorhinicola acanthocapax Beveridge & Campbell, 1988 (Cestoda: Trypanorhyncha) from the basking shark Cetorhinus maximus (Gunnerus)

Cetorhinicola acanthocapax Beveridge & Campbell, 1988 is redescribed based on adult specimens collected from a basking shark Cetorhinus maximus (Gunnerus) off the east coast of New Zealand. Both the mature and gravid segments are described for the first time, and the first scanning electron micrographs of the armature and scolex microtriches are provided. Novel features include the opening of the vagina anterior to the cirrus-sac and the extension of the vagina anterior to the cirrus-sac. Pectinate microtriches are present on the anterior quarter of the pars pedunculus scolecis scattered between filiform microtriches; the bothrial margins are covered with tridigitate microtriches, while the adherent surface of the bothria have pectinate microtriches. The additional morphological features described are consistent with a close association between Cetorhinicola Beveridge & Campbell, 1988 and the Eutetrarhynchoidea Guiart, 1927.

GALAXITAENIA TOLOI N. GEN., N. SP. (EUCESTODA: PSEUDOPHYLLIDEA) FROM GALAXIAS PLATEI (PISCES: OSMERIFORMES, GALAXIIDAE), IN THE PATAGONIAN REGION OF ARGENTINA

Galaxitaenia n. gen. (Eucestoda: Pseudophyllidea) is proposed to accommodate Galaxitaenia toloi n. gen., n. sp. from Galaxias platei, a freshwater fish inhabiting Andean lakes in Argentine Patagonia. Galaxitaenia belongs to the Triaenophoridae because it possesses a marginal genital pore, a ventral uterine pore, and a follicular vitelline gland. The new genus can be distinguished from other triaenophorids by the following combination of characters: a scolex with a prominent rectangular apical disc without hooks, grooves, or indentations; neck present; segments wider than long to quadrangular; testes in 2 lateral fields, often connected anteriorly; cirrus unarmed; an ovary situated posteriorly; a vagina posterior to the cirrus sac; vitelline follicles medullary, in 2 ventral fields forming 2 wings interrupted medially; a uterus saccate to branched; and eggs without operculum. The types, distribution, and density of microtriches were analyzed on the surface of the tegument of scolex, neck, and immature segments. The presence of tumuli were observed on the apical disc of the scolex. Galaxitaenia toloi n. sp. is the first triaenophorid species recorded in a South American freshwater fish and the fourth helminth parasitizing the intestine of G. platei.

Transmission electron microscopy of the scolex and neck microtriches of Silurotaenia siluri (Batsch, 1786) (Cestoda: Proteocephalidea)

Microtriches on different parts of the scolex and neck of the gangesiine cestode Silurotaenia siluri (Batsch 1786) were studied. The neodermis of the central frontal scolex part (around the rostellar furrow) bears filamentous microtriches only. The lateral frontal part and the parts between and posterior to the suckers cover filamentous and spine-like microtriches. Within the suckers there are short spine-like microtriches with bases enforced by electron-dense ribs. The proximal neck part bears filamentous and spine-like microtriches, the middle part solitary distributed blade-like and spine-like microtriches among filamentous ones, and the distal part blade-like microtriches. The functions of different types of microtriches are discussed.

First record of Progrillotia dasyatidis Beveridge Neifar and Euzet, 2004 (Cestoda: Trypanorhyncha) plerocerci from Teleost fishes off the Portuguese coast, with a description of the surface morphology

Plerocerci of Progrillotia dasyatidis Beveridge et al. (2004), family Progrillotiidae Palm (2004), are reported from several teleost fishes off the Portuguese coast, giving a first insight into the life cycle biology of these unique trypanorhynchs. The first description and assignment of the plerocercus to P. dasyatidis is based on morphological features, such as scolex and bothria morphology and tentacular hook arrangement, and is expanded to incorporate the surface morphology, examined by scanning electron microscopy, constituting the first ultrastructural study for a species within this family. Comparisons with other species of the genus Progrillotia are made, based on the scolex and bothria morphology and tentacular hook arrangement, in order to give an overview into the variability within this genus, whereas comparisons with adults from the same species evidence the variability within the same species. The systematic approaches of Campbell and Beveridge (1994) and Palm (1997, 2004) are discussed and emphasis is placed on the utility of microtriches and the characteristic life cycle within the genus as systematic characters.

Nomimoscolex semenasae n sp (proteocephalidea: Monticelliidae), a cestode parasite of Diplomystes viedmensis (Pisces: Siluriformes) from the Patagonian region of Argentina

Nomimoscolex semenasae n. sp. is described from the primitive fish Diplomystes viedmensis (Siluriformes) from the Patagonian region of Argentina. The new species is placed in Nomimoscolex because of the cortical position of the vitelline follicles, medullary position of the testes, ovary and uterus, and having a scolex with four uniloculate suckers. N. semenasae differs from all other species in the genus by the following combination of characters: (1.apical organ absent; (2). strobila acraspedote; (3). vagina anterior or posterior to cirrus-sac and lacking a sphincter; (4). testes in one irregular layer and in two fields connected anteriorly; (5). uterine stem cortical in immature proglottides, growing from cortical stem into medullary region in mature proglottides; (6). long uteroduct; and (7). presence of spiniform microtriches on all regions of the scolex, proliferation zone and immature proglottis. This is the first record of a proteocephalidean tapeworm in D. viedmensis and in the family Diplomystidae.

Ultrastructure of the scolex, rhyncheal system and bothridial pits of Otobothrium mugilis (Cestoda: Trypanorhyncha)

The ultrastructure of the scolex tegument, bothridial pits (=ciliated pits) and rhyncheal system of Otobothrium mugilis Hiscock, 1954 is described from plerocerci collected from the teleosts Arius graeffei Kner et Steindachner and Mugil cephalus Linnaeus. Scanning electron microscopy revealed that filamentous microtriches with shortened caps are abundant across the entire surface of the tegument. Palmate microtriches are dominant on the bothridia and their margins. The surfaces of bothridial pits were covered with large bifid microtriches. The bothridial pits are strongly muscularised invaginations of the tegument. Nervous tissues were not observed within the pits and it is probable that these structures function as accessory attachment structures. The wall of each tentacle sheath consists of one to three bands of fibrils, lined internally by a thin cytoplasmic layer. The tentacular walls are cellular, containing myofilaments. The fibrils of the tentacular walls are arranged into discrete blocks of parallel fibrils and appear to be intracellular. Tentacular walls are lined externally by a modified membrane with an external glycocalyx. Tentacular hooks are solid, bound externally by a membrane. The body of the hook contains numerous longitudinal canaliculi and an electron-opaque medulla lies at the centre of the hook.

Prochristianella spinulifera n. sp. (Cestoda: Trypanorhyncha) from Australian dasyatid and rhinobatid rays

Prochristianella spinulifera n. sp. (Cestoda: Trypanorhyncha: Eutetrarhynchidae) is described from the spiral valves of the rays Rhinobatos typus (Rhinobatidae) and Himantura fai (Dasyatidae) from Heron Island, Queensland, Australia. The new species is distinguished from all congeners by the deltoid microtriches covering the anterior 80% of the scolex and the presence of a dorsoventrally elongate genital atrium. The species occurred in the anteriormost section of the spiral valve of R. typus. The orientation of the armature of this and other congeners is such that principal rows of hooks begin on the bothridial surface of the tentacle and end on the antibothridial surface.

On the phylogenetic relationships among tetraphyllidean, lecanicephalidean and diphyllidean tapeworm genera

This study had two main objectives: (1) to construct an extensive, explicit list of characters and character states that might serve as a starting point, and perhaps even a model, for the compilation of a more complete list of characters for all cestode taxa; and (2) to use this character list to generate a hypothesis of the phylogenetic relationships among species representing most of the tetraphyllidean, lecanicephalidean and diphyllidean genera. Specimens of one species in each of 48 genera of tetraphyllideans, eight genera of lecanicephalideans, the three genera of diphyllideans, two genera of proteocephalideans and two genera of trypanorhynchs, were examined as whole-mounts and sections, with light and scanning electron microscopy. A list of 120 morphological characters was compiled. Four phylogenetic analyses were conducted using PAUP* and/or NONA. The first was a comprehensive analysis with the 56 tetraphyllidean and lecanicephalidean species as ingroups and the remaining seven species as outgroups. The second was an analysis of the three diphyllidean species as ingroups and the two proteocephalidean and the two trypanorhynch species as outgroups. The third was an analysis of the eight lecanicephalidean species and the "tetraphyllideans" Echeneibothrium sp. and Pseudanthobothrium n. sp. as ingroups and an outgroup consisting of the seven species used as outgroups in the first analysis. In the fourth analysis, the ingroup consisted of the 14 hooked tetraphyllideans (onchobothriids), and the outgroup consisted of the seven species used as outgroups in the first analysis. The results of these analyses support the following phylogenetic hypotheses: The diphyllideans are monophyletic and Echinobothrium n. sp. and Macrobothridium sp. are more closely related to one another than either is to Ditrachybothridium macrocephalum. The tetraphyllideans, lecanicephalideans and proteocephalideans are more closely related to each other than they are to the diphyllideans or the trypanorhynchs. The ordinal status of the lecanicephalideans is dubious. The lecanicephalidean species are more closely related to some of the tetraphyllidean taxa than these tetraphyllidean taxa are to the remainder of the tetraphyllidean taxa. The proteocephalideans appear to belong within the tetraphyllidean clade. The "tetraphyllidean" species Echeneibothrium sp. and Pseudanthobothrium n. sp. are members of the lecanicephalidean clade. The position of "Discobothrium" n. sp. within the lecanicephalideans is dubious. Within the tetraphyllideans, the non-acetabulate species Litobothrium daileyi, Disculiceps galapagoensis and Cathetocephalus sp. are the most basal members of the group. The family Onchobothriidae is monophyletic, as it is currently defined. Within the onchobothriids, the uniloculate species are basal to the multiloculate species; the species with unipronged hooks are basal to the species with multipronged hooks. Although relationships among the phyllobothriids, as they are currently defined, remain poorly resolved, the family Phyllobothriidae is not monophyletic. These results suggest that some aspects of the classification of the lecanicephalidean and tetraphyllidean taxa require revision. However, such revision should be based on further analyses including a broader representation of the genera and species in these groups.

Structure and diversity of cestode epithelia

Eucestodes have a simple aceolomate body structure and are conservative in terms of the numbers and nature of their cell types. Nevertheless, the cestodes form a diverse group with many strikingly different forms distinguished by the structure of their holdfasts, sexual tissues and embryos. These morphological adaptations have their origins in subtle variations in the structure of their cells and extracellular matrices. This review is concerned with the biology of eucestode epithelia and examines their structure and functions, interrelationships with other tissues, and gives insight into how their components are modified among the many taxa. Three features of cestode epithelia, namely, the occurrence of regional specialisation, microtriches and secretory components, are described. In addition, evidence is presented to suggest that some cestode epithelia are involved in developmental processes such as the nurture of embryos and maintenance of surrounding tissues.

Cestode systematics: any progress?

In this short review, I summarize the recent advances, the present state and future for research in the field of cestode systematics. First, within an historical context, I briefly outline why our understanding of relationships within the Eucestoda has been problematic and contentious. On this foundation, I then summarize and discuss recent progress at various supraspecific levels, and at the specific level. Of particular interest in this respect is the discrepancy between the methods applied to understand the evolution of a few well-studied taxa, for instance the complex of Echinococcus species, contrasted with our relative ignorance about the systematic status of the vast majority of species. This leads to a review of the diversity of classical and new methodologies currently applied in the field of cestode systematics. Applications of morphoanatomical investigations as well as more recent molecular tools are examined, and some less common approaches are also reviewed. Finally, several practical and theoretical difficulties that are specific to the domain are discussed. These include problems in accessibility of material and adequate consideration of host-specificity. Our current state of knowledge represents an apparent paradox in that significant progress has indeed been achieved during the last 15 years, but appears limited to very specific cases, principally among medically important taxa. Conversely, more general works whose utility has been long recognized have not been addressed despite their conceptual simplicity. Consequently the development of new techniques, especially molecular ones, to allow access to new classes of characters is encouraged. However the need for continuous effort using more traditional approaches, including continued field collection, excellent and detailed descriptions and redescriptions, as well as critical revisions of classical monographs is also emphasized. A synergism linking morphological and molecular characters and phylogenetic approaches to analysis provides a firm foundation for rapid and seminal advances in the elucidation of relationships among the Eucestoda.