Comparative karyological studies on the species of Eubothrium Nybelin, 1922 (Cestoda: Pseudophyllidea)

Karyotypes of Eubothrium salvelini, E. crassum and Eubothrium sp. were studied using conventional Giemsa staining and comparative karyometric analysis. The karyotypes, reported here for the first time, consist of eight chromosome pairs. The two first pairs of homologues are metacentric and markedly larger than the remaining elements. The obvious similarity in karyotype structure does not exclude the possibility of discriminating E. salvelini and E. crassum using karyotypic characters. The best cytogenetic marker is the last pair of chromosomes, which is acrocentric in the karyotype of E. salvelini and metacentric in that ofE. crassum. Karyological observations provide strong evidence for assigning Eubothrium sp. from Clupea harengus membras to E. crassum. Comments are made on the karyotypes of these and related species with respect to their phylogenetic links.     

The karyotype of Eubothrium rugosum (Cestoda: Pseudophyllidea)

The diploid chromosome set of Eubothrium rugosum contains 16 elements. The karyotype consists of three pairs of metacentric, three pairs of acrocentric and two pairs of submeta-metacentric chromosomes. Their mean absolute length ranges from 2.20 to 8.80 microns. The first two pairs of large metacentric chromosomes comprise over 45% of the total complement length.     

Re-description of Eubothrium vittevitellatus Mamaev, 1968 (Cestoda: Pseudophyllidea) from sand fish (Trichodon trichodon Tilesius) in Kamchatka Bay with an assessment of its distribution

Eubothrium vittevitellatus is re-described with particular attention being paid to scolex characters seen by scanning electron microscopy in material obtained from the intestines of the sand fish (Trichodon trichodon) from Kamchatka Bay. It is confirmed as a valid species distinguishable from others in the genus by the combined characters of scolex shape, muscle arrangement and position of vitelline follicles. Peculiarities in the distribution and specificity of the species of Eubothrium highlighted by E. vittevitellatus are discussed.     

A comparison of the internal transcribed spacer of the ribosomal DNA for Eubothrium crassum and Eubothrium salvelini (Cestoda: Pseudophyllidea), parasites of salmonid fish

The internal transcribed spacers (ITS-1 and ITS-2) and 5.8S subunit of the ribosomal RNA gene of Eubothrium crassum and Eubothrium salvelini, cestode parasites of salmonid fish, were sequenced and compared. The lengths and GC contents of the regions sequenced were 1119 bp and 50.1% for E. crassum, and 1117 bp and 50.5% for E. salvelini, respectively. Sequence alignment and comparison of both taxa showed 97.9% similarity. Within the ITS-1 and ITS-2 of both species, the restriction enzymes MspI and Bsh1236I possessed different cleavage sites and could be employed for rapid differentiation of both species of Eubothrium by PCR-RFLP.     

Final stages of carbohydrate metabolism in a cestode Eubothrium rugosum (Cestoda: Pseudophyllidea)

Characteristics of final stages of carbohydrate metabolism in a cestode Eubothrium rugosum from the burbot intestine have been studied. It is found out that in the course of in vitro incubation the worms produce lactic acid to the environment with a concomitant acidification of the medium. The rate of pH changes and lactate production eventually fell during the incubation. The medium pH being the result of helminth's metabolism varies within the normal physiological limits of the host intestine pH and pH optima for its basic digestive enzymes.     

The biology, specificity and habitat of the species of Eubothrium (Cestoda: Pseudophyllidea), with reference to their use as biological tags: a review

The literature pertaining to the distribution, habitat, specificity, life cycles and population biology of all the species of Eubothrium is reviewed. Records in which scolex morphology is used to identify species cannot be used as this character is too variable to be of value in specific recognition. Study of the valid records suggests that E. crassum comprises three races. There is a freshwater race, whose preferred host is non-migratory Salmo trutta fario, but which also infects parr, smolts and landlocked adult S. salar and parr of migratory S. trutta trutta. Its distribution is confined to Europe and Eurasia and is co-extensive with that of S. trutta: it does not occur in N. America or E. Asia. It may be carried to sea in migratory salmonids, where it dies out in S. salar but may survive in S. trutta. Its life cycle only takes place in fresh water, and requires a copepod as the only intermediate host. Other fish species may serve as paratenic or accidental hosts. The preferred host of the marine Atlantic race of E. crassum is S. salar, but S. trutta is also infected. Its distribution is co-extensive with that of S. salar on both sides of the Atlantic Ocean. It may be carried into fresh water by both hosts, when its numbers decline in S. salar but not in S. trutta. The life cycle is unknown, but infection probably takes place in marine coastal waters. The preferred hosts of the marine Pacific race are all species of Oncorhynchus, with which its distribttion is co-extensive on both sides of the Pacific Ocean. It may also be carried into fresh water, and its life cycle is also unknown. E. salvelini comprises two races. The European freshwater race is specific to Salvelinus alpinus, and does not infect Salmo spp. Its life cycle takes place in fresh water and involves only one intermediate host, a copepod. It may be carried to sea in migratory fish, and survive to return to fresh water. The American race, found throughout North America and East Asia, infects species of Salmo, Salvelinus, Oncorhynchus, Cristivomer and other genera. Its biology is otherwise similar to that of the European race, although its return from the sea has not yet been confirmed in America. The other species of Eubothrium are more local in their distribution, some being endemic; do not comprise different races, and infect marine and anadromous fish. Nothing is known of their biology or life cycle. Eubothrium is recognised as being a marine genus that has invaded fresh water with anadromous fish. The inability to distinguish the races of E. crassum and E. salvelini on morphological characters, their low rate of survival in the other medium and their wide distribution renders them unsuitable as biological tags.     

Activity of digestive enzymes in burbots Lota lota (Linnaeus) depending on their infestation with Eubothrium rugosum (Batch) (Cestoda, Pseudophyllidea)

Nonuniform distribution has been revealed in the activity of the principal digestive hydrolases from the anterior to the posterior portion of the digestive tract in the burbot Lota lota (Linnaeus). It has been found that infestation with the cestode Eubothrium rugosum (Batch) leads to a decrease in the activity of proteinases and glycosidases in the mucosa of the burbot intestine. This infestation particularly strongly impacts the activity of proteolytic enzymes. The activity of the digestive enzymes of the host decreases even if the infestation rate is low.     

Morphometric analysis of four species of Eubothrium (Cestoda: Pseudophyllidea) parasites of salmonid fish: an interspecific and intraspecific comparison

Four species of the genus Eubothrium (E. crassum, E. fragile, E. rugosum and E. salvelini) were subjected to morphometric comparison. Discriminant analysis was conducted utilising 17 characters measured on the scolex and strobila of 101 specimens. Univariate statistics were first used to detect features that were useful for separating individual Eubothrium species and two different host populations of E. salvelini. Subsequent multivariate discriminant analysis, combining all the measured variables, made it possible to separate all four species. A comparison of the four taxa revealed that (1) E. fragile is the most distinct species, possessing a much smaller scolex than the other congeners, and its similarity with the other marine species E. crassum is not proven; (2) the two freshwater taxa, E. rugosum and E. salvelini are the most similar; (3) the characters most suitable for species differentiation are the length of the scolex, the width of the apical disc, the width of the neck and its area, the width of eggs and the number of testes; (4) the width of the apical disc was confirmed to be the most stable character at the intraspecific level (within E. salvelini host populations) and is therefore considered to be a trait of the highest discriminative power in the subset of four Eubothrium species.     

On the Procercoid Protonephridial Systems of Three Diphyllobothrium Species (Cestoda, Pseudophyllidea) and Janicki's Cercomer Theory

Because the types of hooks are so similar in the oncosphacra/procercoid ef cestodes and in several groups of monogenclic trcmatodes and because the exterior of a procercoid with the hooks in a cercomer is so suggestive of a monogenetic nematode, the development of the procercoids of three Diphyllobothrium species was studied. The intention was to determine whether or not the procercoid protonephridial system would have a developmental stage when its type is similar to, or identical with that type which characterizes the monogeneans. Such a conformity would greatly support the theory of a common origin of monogeneans and ceslodes. However, it has emerged that no similar developmental stage exists. The ontogeny revealed a thorough metamorphosis from a very simple primary protonephridial system (identical with that of the miracidium larva in digeneans) to a secondary system, which develops into the system of the adult tapeworm. This fact may be interpreted as an argument against the supposed inter-relalionships between monogeneans and cestodes. However, the type of hooks and the procercoid cercomer still indicate common ancestors. An analysis of the miracidium, the oncosphaera and the oncomiracidium (the monogenean larva) with reference to their different developmental stages when hatching, gave rise to my interpretation of the fundamental structure of both the miracidium and the oncosphaera as primitively simple and not reduced, Especially the identical type of protonephridial system indicates. in my view, that digeneans and ceslodes originally had a common larva type. If the ceslodes and the monogeneans have common ancestors, then the procercoid may be interpreted as the ontogenetic recapitulation of a common hook-armed ancestor, here named hexucanthoid. This rhabdocoelan creature with six hooks in the cercomer and adapted to an ectocommensalic/ectoparasitic mode of life, is thought to have given rise to the monogeneans, the gyrocotylideans, the amphilinideans and the cestodes. The monogeneans were found to have two fundamentally different types of marginal hooks, and on this basis ihe existence of two different lines of evolution in Monogenea is indicated.     

The occurrence of Eubothrium crassum (Cestoda: Pseudophyllidea) in salmon Salmo salar and trout S. trutta of the River Exe

The occurrence, size and maturity changes of Eubothrium crassum (Bloch) have been studied in smolts and adult Salmo salar L. and S. trutta L. of the River Exe and other Devon rivers. Adult parasites are found only in salmon and sea trout migrating up river to spawn, and range in size from small and immature to large and mature, though rarely gravid, worms. It is concluded that they are acquired and only become fully mature in the sea and gravid worms are lost on or before arrival in the rivers. During the upstream migration of salmon there is a selective loss of larger and more mature parasites and the survivors do not increase in length or mature, due to the intestine becoming a progressively more unfavourable habitat as the period of fasting continues. As few salmon return to the sea, most parasites in fresh-water die before breeding. In sea trout, which feed in fresh-water, parasites continue to grow and probably mature on return to the sea. It is suggested that parasites found in adult Atlantic and Pacific salmon in rivers are rarely, if ever, the same worms that are carried to sea by smolts but are of marine origin and are residues of a marine life cycle, and that two biological races of E. crassum exist, a marine and a fresh-water one.     

Structure of Reproductive System of the Amphicotyllide Cestode Eubothrium rugosum (Cestoda, Pseudophyllidae)

A tendency for increase both of numerical and of ecological factors of infestation in pseudophyllid cestodes is realized due to morphological peculiarities of the structure of their reproductive system. In the species E. rugosum with the closed bursiform uterus and intrauterine development of eggs, there are revealed the same degree of maturity of oocytes in ovary, the lack of sphincter or filtering cell at the base of the ovicapt infundibulum, and the presence of a large vitelline reservoir. By analogy with trematodes, an interconnection is traced between the degree of egg maturation in the uterus and morphology of uterus and vittelicles. The thickening of the egg membrane has been shown to occur not only by deposits of individual vitelline globules at the internal superficial egg layer, but also by binding of lipid droplets excreted from the surrounding parenchyma to the uterine tube along its entire length to the external egg surface. The male reproductive system of Eubothrium rugosum is characterized by the presence of a small cirrus pouch, by the cirrus supplied with microtrichia, which corresponds to the similar vagina structure, and by localization of prostate glands outside the cirrus pouch. Comparison is presented with other ultrastructural peculiarities of organization of the reproductive system in the earlier studied species of pseudophyllid cestodes, Diphyllobothrium latum.     

A Comparative Study of Eubothrium Salvelini and E. crassum (Cestoda: Pseudophyllidea) Parasites of Arctic Charr and Brown Trout in Alpine Lakes

We compared the morphology, morphometry, and some aspects of the biology and ecology of Eubothrium crassum and E. salvelini, two pseudophyllidean tapeworms in brown trout, Salmo trutta m. lacustris, and Arctic charr, Salvelinus alpinus, in lakes of the western part of the Alps. The taxonomic importance of the apical disc for the discrimination of both taxa was confirmed. The apical disc of E. crassum is rectangular, possessing two deep grooves above the bothriae and 2–16 additional indentations. In E. salvelini, the apical disc is bilobed and bilaterally symmetric. We found new and significant interspecific differences in the length and width of the scolex, the diameter of the apical disc, and the width of the neck, with all measurements being larger in E. crassum. The two species differ in the number and size of the testes (fewer and larger in E. salvelini), the length of the cirrus sac (longer in E. crassum), and the size of vitelline follicles (larger in E. salvelini). Vitelline follicles of E. crassum are always cortical and sometimes enter into the outermost muscle fibres, whereas follicles of E. salvelini are situated largely medullary with few follicles entering between the innermost bundles of muscles. The eggs and the oncospheres of E. salvelini are larger. The embryonic hooks of E. crassum measure 14–18 m whilst those of E. salvelini are 18–26 m. For both taxa, the intraspecific variability in morphometric characters was fairly low. The prevalence and intensity of infection of E. crassum and E. salvelini in their respective fish hosts were very high (prevalence 90–94% mean intensity 36.3 and 6.6, maximums of 172 and 63 tapeworms per fish, respectively). E. salvelini eggs were spontaneously released throughout the year except for winter months; E. crassum laid eggs only in summer (June–August). Natural infection of copepods with Eubothrium procercoids was very low (prevalence 0.002%). The morphogenesis of Eubothrium procercoids was studied in an intermediate host, the copepod Cyclops prealpinus, that had been simultaneously infected with both species.     

Phosphofructokinase in the plerocercoids of Schistocephalus solidus (Cestoda:Pseudophyllidea)

Beis I. and Theophilidis G. 1982. Phosphofructokinase in the plerocercoids of Schistocephatus solidus (Cestoda: Pseudophyllidea). International Journal for Parasitology12: 389–393. The Phosphofructokinase from the plerocercoids of Schistocephalus solidus was found to be inhibited by ATP. AMP relieves the ATP inhibition and activates the enzyme. In contrast to mammalian phosphofructokinase, the plerocercoid enzyme does not appear to be sensitive to inhibition by citrate at physiological ATP concentrations. Except for AMP and 3'–5' cyclic AMP no other monophosphate nucleotides were found to activate the enzyme. Succinate, α-ketoglutarate, malate, isocitrate, β-hydroxybutyrate, butyrate, acetoacetate and CoA all inhibit the plerocercoid enzyme at the concentrations tested. The significance of these results in the regulation of glycolysis and the tricarboxylic acid cycle in this parasite is discussed.     

The Comparative Systematics of Species Comprising the Hymenostome Ciliate Genus Tetrahymena*

SYNOPSIS. It has been 10 years since the taxonomic composition of the important hymenostome genus Tetrahymena has been given overall consideration, and even then the treatment was not extensive. New data of significance have been accumulated and a fresh analysis is clearly in order. Also today we recognize that entire assemblages or combinations of characteristics must be considered in understanding the species-composition of a protozoan genus, and such an approach has never been uniformly applied in a comparative systematic study of all ciliates belonging to the Tetrahymena group. Three complexes within the genus may now be identified. In the 1st, the pyriformis complex, are placed T. pyriformis (the type-species), T. setifera, and T. chironomi. In the 2nd, the rostrata group, are assigned T. rostrata, T. limacis, T. corlissi, and T. stegomyiae. In the 3rd, the patula complex, are found T. patula, T. vorax, and T. paravorax. Three additional, formerly independent species are here recognized as doubtful forms: T. faurei, T. glaucomaeformis, and T. parasitica. In spite of some overlapping in certain characters, such as total number of kineties or ciliary meridians, the 3 complexes may be considered distinctive on the basis of constellations of features of taxonomic value, including physiologic and morphogenetic as well as structural characteristics. Yet within each complex it is possible to differentiate clearly a number of separate species. The present analysis in no way closes the door to discovery of still additional, new species of Tetrahymena in the future, but it attempts to lay the groundwork for a uniform usage of combinatiomnas of criteria in comparative taxonomic studies of these and other relatively undifferentiated hymenostome species which possibly will be of some value in the whole area of ciliate systematics.     

On the Early Development of the Protonephridial Systems in Some Species Belonging to the Genera Diphyllobothrium, Triaenophorus and Schistocephalus (Cestoda, Pseudophyllidea)

Malmberg, G. {Department of Zoology, University of Stockholm, Stockholm, Sweden.) On the early development of the protonephridial systems in some species belonging to the genera Diphyllobothrium, Triaenophorus and Schistocephalus {Cestoda, Pseudophyllidea). Zool. Scripta 1 (5): 227–228, 1972.–The protonephridial systems of coracidia (oncospheres) and procercoids of four Diphyllobothrium species, of Triaenophorus nodulosus (Pallas) and of Schistocephalus solidus (Muller) were studied. In the oncospheres of Diphyllobothrium and Schistocephalus the two flame bulbs of the primary protonephridial system were present, but not in the oncospheres of Triaenophorus. In Schistocephalus the two flame bulbs were found to be inactive in the oncosphere (studied inside the coracidium), but very active in the youngest procercoids, which may imply that the primary protonephridial system does not start its function until the oncosphere has entered the copepod body cavity. The primary protonephridial system of the Triaenophorus procercoids was totally (most specimens) or partly reduced. The secondary protonephridial system, however, began developing more or less simultaneously with the integumental hooklets, the cercomer and the first calcareous bodies, which is in accordance with what is described concerning Diphyllobothrium. The ciliated, excretory bladder described by Rosen in 1919 was found to be a posteriorly open invagination, surrounding the “cercomer shaft”. Reverse bends of the posterior main canals of the secondary system are located closely around the wall of, though very likely not emptying into this invagination.     

Cestode egg production dynamics and fertility in Diphyllobothrium dendriticum (Cestoda, Pseudophyllidea)

Dynamics of egg production of the tapeworm Diphyllobothrium dendriticum has been estimated experimentally in nestlings of the herring gull Larus argentatus per day and per reproductive period. The number of eggs in strobiles has been estimated for the maturation period. Mean egg production of the tapeworm per day (10.43 +/- 2.72 mln) is two orders of magnitude as high as the maximum number of eggs in a mature strobile (0.206 +/- 0.007). It is proposed to estimate coefficient of reproduction intensity as the ratio of egg output per unit of time and maximum egg number in a mature strobile.     

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.