The functional morphology of the scolex of Diphyllobothrium Cobbold (Cestoda, Pseudophyllidea). A scanning electron and light microscopical study on scoleces of adult D. dendriticum (Nitzsch), D. latum (L). and D. ditremum (Creplin).

Scoleces of adult D. dendriticum, D. latum and D. ditremum were studied using scanning electron and light microscopy. In D. dendriticum and D. latum the transverse bar between the bothria at the scolex apex always possessed a frontal pit while in D. ditremum no such invagination was seen. The scoleces attach to the host intestine by taking a firm grip with each bothrium around one or two intestinal villi. In D. ditremum and D. latum a layer of secreted substance is present between the scolex apex and the host intestine and between the inner bothrium surface and the host intestinal villi. In D. dendriticum, however, such a secreted layer was only observed at the scolex apex. A general account of the musculature and nervous and excretory systems of a Diphyllobothrium scolex is given.     

Comparative morphology of surface ultrastructure of diphyllobothriidean tapeworms (Cestoda: Diphyllobothriidea)

Microtriches on the scolices and adjacent strobila of seven species of diphyllobothriidean cestodes (Bothridium pithonis, Cephalochlamys namaquensis, Dibothriocephalus latus, Duthiersia expansa, D. fimbriata, Ligula intestinalis, and Schistocephalus solidus) from different hosts (frogs, snakes, lizards, birds, and mammals) and biogeographic areas were examined using scanning and transmission electron microscopy. The basic structure of the tegument of the seven species studied does not differ markedly from that found in other cestodes. The main characteristic is the presence of electron‐dense bodies and vesicles in the distal cytoplasm. However, this study has shown differences in the morphology of microtriches even among species of the same family. Two different types of microtriches were found, filitriches and spinitriches, with the latter represented by two forms. Our study reveals that capilliform filitriches are most commonly found in Diphyllobothriidea. They were observed mainly on the strobila and the scolices of all but one studied species; individuals of L. intestinalis bore only coniform spinitriches on their surface. The same type of microtriches was found on the cirrus in D. latus. Gladiate spinitriches covered the scolex in both species of Duthiersia, and gladiate spinitriches interspersed with capilliform filitriches were observed on the anterior part of the strobila in D. fimbriata and the posterior part of the scolex in B. pithonis. Individuals of C. namaquensis were covered only by small acicular filitriches. No obvious pattern in the type and distribution of microtriches was observed among species that belong to different families and parasitize distantly related definitive hosts.     

The abundance and distribution of Diphyllobothrium dendriticum (Nitzsch) and D. ditremum (Creplin) in the char Salvelinus alpinus (L.) in Sweden

A total of 654 char, Salvelinus alpinus (L.) and 33 brown trout, Salmo trutta L., were examined for the plerocercoids of Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825). Only char were found to be infected. Both parasitic species were abundant. The incidence and mean intensity of infection for D. dendriticum were 83.2% and 8.8, respectively; for D. ditremum 93.7% and 45.0. There was no variation in the intensity of infection between different parts of the lake. The incidence and intensity of infection increased with the age of the fish to age 8+ for both species. From this age the intensity of infection leveled off or decreased. No differences in intensity of infection between the sexes were found. The frequency distribution of parasite counts were overdispersed and fitted the negative binomial distribution even within single age-groups. The two parasite species showed a high positive correlation in intensity of infection, D. ditremum was concentrated in the stomach and pyloric caeca. D. dendriticum was more widely distributed within the host and was supposed to kill heavily infected fish.     

The dynamics of infection of Diphyllobothrium dendriticum (Nitzsch) and D. ditremum (Creplin) in the char Salvelinus alpinus (L.) in Sweden

A total of 654 char, Salvelinus alpinus (L.), from Lake Bjellojaure, Sweden, were examined for plerocercoids of Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825) from September 1969 to December 1974. Plankton samples showed that the dominating copepod species in the lake were Eudiaptomus graciloides (Lilljeborg), Cyclops scutifer Sars and Heterocope appendiculata Sars. E. graciloides passed the winter as adults and C. scutifer as copepodids while H. appendiculata was restricted to a short period in the summer. Copepods occurred in the stomachs in September-October and to a certain extent in April-May, but only cyclopids and Heterocope sp. were found. C. scutifer is proposed to be the main first intermediate host of both D. dendriticum and D. ditremum . The potential final hosts were thecommon gull, Larus canus L., for D. dendriticum and the black-throated diver, Gavia arctica (L.), for D. ditremum . One common gull was experimentally successfully infected with plerocercoids of D. dendriticum . The parasites showed no seasonal cycle in incidence of infection.     

Egg size and form as taxonomic criteria in Diphyllobothrium (Cestoda, Pseudophyllidea)

The size and form (length, width, and length: width ratio) of eggs of Diphyllobothrium dendriticum, D. ditremum and D. latum vary considerably among individual worms within each species. The size of eggs varies with host species and a decrease in egg size with increasing intensity of infestation is indicated. The egg size of D. latum increases during the first 10-12 days of egg production. For single worm infections in golden hamsters the mean egg length and width of D. ditremum are significantly smaller than the corresponding means of D. dendriticum and D. latum, while D. latum has significantly wider eggs than D. dendriticum. As taxonomic characteristics, egg size and form may contribute to species delimitation at the population level. For identification at the individual level the best possible accuracy is about 80%. This accuracy is considerably reduced when variation in host species and intensities of infestations are introduced. Scanning electron microscope studies did not reveal any differences among eggs of the three species.     

Taenia taeniaeformis (Cestoda) in the rat: ultrastructure of the host-parasite interface on days 8 to 22 postinfection

The host-parasite interface was examined at the ultrastructural level 8 to 22 days postinfection (DPI) with metacestodes of Taenia taeniaeformis in the rat. Throughout this phase of development the parasite surface was invested with a dense surface coat of complex microtriches. At 8 to 14 DPI the plasma membrane of each microthrix extended beyond the distal end of the electron-dense tip, forming a slender tubular streamer over 10 microns long; by 18 DPI these had shortened and withered. Host cell processes interdigitated with the microtriches without evidence of harm to the parasite surface or the underlying tegument. The cells, on the other hand, became damaged, and their contents were shed into the matrix surrounding the microtriches. Lipid inclusions appeared within the parasites, and in the cytoplasm of surrounding inflammatory cells. By 22 DPI fibroblastic activity had resulted occasionally in the formation of a capsule surrounding a free-floating cysticercus, while in others intense granulocytic infiltration persisted with abutment and intermeshing of host cell and parasite surface processes; however there was still no evidence of any adverse effect on the microtriches, though many granulocytes were clearly pyknotic and degenerating. Evidently, the vigorous cellular response of the host is ineffective in either containing the expansion of the parasite or compromising the integrity of its surface membrane. The changing characteristics of the microtriches may be related to the need for dissolution of both intercellular matrices, and host cells as the vesicular organism rapidly increases in volume.     

Surface ultrastructure of the elasmobranchia parasitizing <Emphasis Type="Italic">Grillotiella exilis</Emphasis> and <Emphasis Type="Italic">Pseudonybelinia odontacantha</Emphasis> (Trypanorhyncha,Cestoda)

The surface ultrastructure of two monotypic trypanorhynch genera is described based on new material of Grillotiella exilis (Linton, 1909) and type material of Pseudonybelinia odontacantha Dollfus 1966. In G. exilis, spiniform microtriches cover the bothrial surfaces and the anterior part of the pars vaginalis posterior to the bothria. Bifurcate microtriches adorn the bothrial margins, filiform microtriches the scolex peduncle, and capilliform microtriches the posterior scolex end. This microthrix pattern resembles that found in, e.g., Grillotia erinaceus (van Beneden, 1858), with the difference that the anterior part of the pars vaginalis is covered with a collar of multidigitate palmate microtriches. The position of Grillotiella within the Grillotiinae, Lacistorhynchidae is supported based on these data. The bothria and scolex peduncle of P. odontacantha are covered with acerosate and unciniform microtriches on the distal bothrial surface and capilliform microtriches on the scolex peduncle. Short filiform microtriches cover the appendix. The microthrix pattern resembles that of the Tentaculariidae but with unciniform and acerosate microtriches densely covering the entire distal bothrial surface. Tegumental grooves are present on the posterior bothrial margin. They can be distinguished from bothrial pits in otobothrioid trypanorhynchs in having similar unciniform microtriches compared to the other parts of the bothrial surface and in lacking any spiniform microtriches. With the absence of bothrial pits as characteristic for the otobothrioids and its characteristic microthrix pattern, P. odontacantha together with Paranybelinia otobothrioides Dollfus 1966, both belonging to the Paranybeliniidae change their position in the most recent system from the Otobothrioidea into the Tentacularioidea.     

Orygmatobothrium spp. (Cestoda: Tetraphyllidea) from triakid sharks in Argentina: redescription of Orygmatobothrium schmitti and description of a new species

Two species of Orygmatobothrium were found inhabiting triakid sharks collected from the coast of Buenos Aires Province, Argentina. Orygmatobothrium schmittii from Mustelus schmitti is redescribed, including new information on the microtrich pattern. Orygmatobothrium juani n. sp. from Mustelus fasciatus can be distinguished from all other species in the genus using the following combination of characters: worm length, number of proglottids, number of testes, testes distribution, size of eggs, ornamented egg shell, shape of bothridial cleft at level of the marginal accessory sucker, and the extension of vitelline follicles. Species in Orygmatobothrium share a common microtrich pattern with the distal bothridial surface covered with maisiform microtriches interspersed with filiform microtriches, a proximal bothridial surface covered with trifid microtriches, with a medial projection conspicuously larger than the lateral basal projections interspersed with filiform microtriches, an inner and outer surface of the accessory sucker and glandulomuscular organ covered with short filiform microtriches, the scolex proper and cephalic peduncle surface covered with bladelike microtriches, and the germinative zone and entire strobila covered with scutes formed by densely packed filiform microtriches. This general configuration is basically similar to the microtrich pattern described in species of Orectolobicestus and Paraorygmatobothrium.     

An electron microscope study of the tegument of Hunterella nodulosa Mackiewicz and McCrae, 1962 (cestoidea: Caryophyllidea)

Ultrastructural observations using transmission and scanning electron microscopy reveal the tegument to be basically similar to that of other cestodes. The syncytial distal cytoplasm is devoid of organelles except for rod-shaped bodies, believed to be secretory vesicles, and lamellated bodies which probably contribute the raw material for new microtriches. There is evidence that these vesicles originate from the Golgi found in the sub-cuticular cells.Three types of microtriches are described: typical ones with well-developed spines, ones with short filaments instead of spines, and ones with no spines. Microtriches with spines are found only on the anterior part of the worm and may serve to anchor the worm. Microtriches on the posterior have no spines and are believed to be primarily involved in the absorption of nutrients. Between these two regions there is a transitional zone where all three types of microtriches can be found. In general the microtriches are quite uniformly distributed throughout the surface of the worm. The presence of cestodarian-like microtriches raises interesting evolutionary questions.Histochemical tests localized acid and alkaline phosphatase activity on various parts of the tegument, as well as on host intestine, while acian blue tests showed that acid mucopolysaccharide levels correspond with the concentration of the tegument vesicles.     

The fine structure of the cysticercoid of Hymenolepis diminuta. III. The scolex.

Transmission electron microscopy of the scolex of the 8-day-old Hymenolepis diminuta cysticercoid demonstrates its resemblance to the scolex of the adult. A syncytial tegument composed of external and internal layers is connected by cytoplasmic extensions. Fully developed microtriches are present. Furthermore, a basement membrane, muscle layers, and medullary region containing flame cells, nerve tissue, and other cell bodies are observed. Of particular interest is the presence of discrete sensory endings whose function is discussed.     

Redescription of <Emphasis Type="Italic">Cetorhinicola acanthocapax</Emphasis> Beveridge &; Campbell, 1988 (Cestoda: Trypanorhyncha) from the Basking Shark <Emphasis Type="Italic">Cetorhinus maximus</Emphasis> (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.     

Ultrastructure of the tegument of the cestode Paraechinophallus japonicus (Bothriocephalidea: Echinophallidae), a parasite of the bathypelagic fish Psenopsis anomala

Abstract. The ultrastructure of the tegument in Paraechinophallus japonicus (Bothriocephalidea: Echinophallidae), a cestode parasite of the bathypelagic fish Psenopsis anomala , was studied using scanning and transmission electron microscopy. Paraechinophallus japonicus lacks a true scolex. Four different types of microtriches have been observed on the tegumental surface of P. japonicus. Capilliform (∼2.3-μm long) and blade-like spiniform (∼1.4-μm long) microtriches are intermingled on the surface of the pseudoscolex. Capilliform microtriches are distinct in possessing a short base and a long electron-lucent cap. The strobila is covered with two types of microtriches, namely filiform (∼2.1-μm long) and tusk-shaped microtriches (≤4.5-μm long). Tusk-shaped microtriches are limited to the posterior border of each proglottid and are characterized by a short and narrow base, and a large and wide, sharply pointed, electron-dense cap. Similar tusk-shaped microtriches were previously found in members of the family Echinophallidae and may represent an autapomorphy of echinophallid cestodes, all of them being parasitic in centrolophid fish. A unified terminology of microthrix parts is proposed.     

Microtriches of tetraphyllidean metacestodes from Western Mediterranean striped dolphins (Stenella coeruleoalba)

The tegumental structures of two types of tetraphyllidean plerocercoids and two types of merocercoids (Phyllobothrium delphini and Monorygma grimaldii) from Mediterranean striped dolphins, Stenella coeruleoalba, are described for the first time using scanning electron microscopy. The tegument of all of the specimens was fully covered with microtriches. Four basic types were found: filitriches, blade-like spinitriches of different sizes and shapes, cone-shaped spinitriches (with two parallel small projections of equal length at the apex), and crowned cylindrical spinitriches (with 6-7 small papillae forming a crown at the apex); the two latter types are newly described. The two types of plerocercoids had a similar morphology and distribution of microtriches; in addition, cilium-like projections appeared interspersed among the microtriches on the apical sucker, accessory suckers, and distal bothridial loculus. Merocercoids exhibited a greater variety of tegumental structures, especially on the distal bothridial loculus. Both merocercoid types had regularly spaced papillae or "buttons" on the accessory suckers and the distal bothridial loculus that were composed of a central cilium-like projection surrounded by numerous filitriches. However, crowned cylindrical spinitriches were specific to P. delphini and cone-shaped spinitriches were specific to M. grimaldii. Differences in the morphology and distribution of scolex microtriches of adult cestodes have been considered useful for species identification. A previous molecular study has suggested that P. delphini and M. grimaldii are actually different congeneric species. Our study has shown that significant differences in the morphology and distribution of microtriches occur between these species at the merocercoid stage.     

Two new species of Echinobothrium (Cestoidea: Diphyllidea) from myliobatiform elasmobranchs in the Gulf of California, México

Two new species of diphyllidean cestodes, Echinobothrium mexicanum n. sp., and Echinobothrium fautleyae n. sp., are described, the former from the spiral intestines of the bat rays Myliobatis californicus and Myliobatis longirostris and the latter from the spiral intestine of the cownose ray Rhinoptera steindachneri, all caught in the Gulf of California, México. Echinobothrium mexicanum is most easily distinguished from the majority of the species of the genus by the number of large apical hooks in each dorsoventral group (23) and from the remainder in the number of lateral hooklets in each group on the scolex. Echinobothrium fautleyae differs conspicuously from all other members of the genus in that the first and last lateral hooklets in each group are distinctly larger than the other hooklets in each group. Serial sections of the scoleces of these 2 new species confirm that the attachment structures on the scolex are bothria, rather than bothridia, as has been described in other species in the genus, suggesting that the attachment structures of the scolex should be examined in more detail in the genus in general. Palmate microtriches of various forms cover the proximal bothrial surfaces of both new species and are also found on the dorsal bothrial surfaces of E. fautleyae. The distal bothrial surfaces of E. mexicanum are covered with slender spiniform and short filiform microtriches. The cephalic peduncles of both species possess short filiform microtriches only. Comparison of these 2 new species with the other 3 species in this genus that have been examined with SEM suggests that the various forms and distributions of these microtriches is unique in each of these 2 species. We believe these features will prove to be taxonomically useful.     

The ultrastructural localization of acetylcholinesterase activity in the scolex of the cysticercus of Hydatigera taeniaeformis

Acetylcholinesterase activity in the scolex of the cysticercus of Hydatigera taeniaeformis was studied by means of electron microscopy. Acetylthiocholine iodide was used as the substrate and 10(-4) M of eserine used to inhibit acetylcholinesterase activity. The sites of activity were visualized within the microtriches of the distal cytoplasm, muscle bundles, cytoplasm, vesiculated bodies, flame cells and hooks of the rostellar region. Enzyme activity was also localized within the nuclear membrane, neuroplasm, and membranes of nerve cells.     

<Emphasis Type="Italic">Nataliella marcelli</Emphasis> 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.     

An unusual blood sequestering tapeworm (Sanguilevator yearsleyi n. gen., n. sp.) from Borneo with description of Cathetocephalus resendezi n. sp. from Mexico and molecular support for the recognition of the order Cathetocephalidea (Platyhelminthes: Eucestoda)

Sanguilevator yearsleyi n. gen., n. sp. and Cathetocephalus resendezi n. sp. are described from the Broadfin shark, Lamiopsis temmincki, in Malaysian Borneo and Carcharhinus leucas in Mexico, respectively. The new genus is unusual in its possession of internal chambers and channels in its scolex that appear to house extensive quantities of host white and red blood cells, respectively. Histology reveals an extremely intimate association between host tissue and the surface of the apical pad of the scolex. Positive staining with periodic acid-Schiff of the surface of the pad of the scolex and the linings of the chambers and channels suggests that an adhesive substance may be produced in these regions. However, explanations for how and why host blood cells come to reside within the scolex remain elusive. Cathetocephalus resendezi n. sp. is distinctive in the form of the papillae in the papillate band of the scolex and also in the inconspicuous nature of the rugose base of the scolex. Scanning electron microscopy of both new taxa as well as Cathetocephalus thatcheri, Cathetocephalus australis and an undescribed species of Cathetocephalus collected from Carcharhinus amboinensis in Australia, suggests that the papillae surrounding the pad of the scolex are of significant taxonomic utility in distinguishing among species in these groups. Parsimony and Bayesian analyses of sequence data (766 bases of 18S rDNA and 405 bases of 28S rDNA) generated from ethanol preserved specimens of C. thatcheri and S. yearsleyi, when compared with equivalent data available for 40 cestode species in GenBank, resulted in trees that support previous propositions that Cathetocephalus should be placed in the order Cathetocephalidea. The results suggest that Sanguilevator should also be considered to belong to this order.     

Antigenic affinity of species of the genus Diphyllobothrium (Cestoidea, Diphyllobothriidae) distributed in the territory of Karelia

Experiments on ringprecipitation reactions with homologous and heterologous antigenes of four species of diphyllobothriids have shown that D. dendriticum and D. ditremum are in a more close antigenic affinity. In relation to the above two species D. vogeli is approximately at the same level. D. latum displayed no antigenic affinity with the above species that, apparently, is connected with its parasitism only in mammals. Schemes of immunization of rabbits for obtaining antisera are given.     

Comparative study of the microtriches of adult Cestodes (Proteocephalidea: Monticelliidae), and some comments on their systematic value

The surface of the tegument of the scolex and the immature proglottides of Monticellia belavistensis, M. ventrei, Nomimoscolex chubbi, and N. lopesi is described using scanning electron microscopy. Only blade-like spiniform microtriches and filiform microtriches were observed in the species studied. The types, size and density of microtriches on the apical region surface of the scolex, central cavity surface of suckers, marginal ring surface of suckers, non-adherent surface of suckers, proliferation zone surface, and immature proglottis surface were compared among these species. The distribution pattern of the microtriches was not a reliable feature to discriminate among the genera considered in this study. It varied in each of the species of Monticellia examined, and did not permit to split the heterogeneous genus Nomimoscolex. However, the microthrix pattern can be regarded as an additional diagnostic feature to distinguish among species of proteocephalideans. Further comparative research involving other species of proteocephalid taxa is needed to elucidate the systematic value of the tegumental morphology.