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PubMed1983

[Biology of cestodes of domestic ducks and wild water birds].

Life cycles of 16 cestode species of the families Hymenolepididae and Diploposthidae were studied in 52 ponds of the State Fishery in Bohemia and Moravia. The parasites were recovered from domestic ducks kept on the ponds and from wild birds, mostly of the genera Anas and Aythya, occurring in these water biotopes. Cestode larvae were found in 9 species of Copepoda (9669 out of 1 600 200 examined specimens, i. e. 0.6%) and 3 species of Ostracoda (500 out of 272 300 examined specimens, i. e. 0.18%). Five species of water snails serving as reservoir hosts harboured cysticercoids of 5 cestode species (680 out of 10 212 examined specimens, i. e. 6%). The studies of cestode life cycle under natural conditions were supplemented with 680 successful experiments with intermediate hosts and 179 successful experiments with definitive hosts. The development of larvae was related to the temperature and lasted approximately 13-20 days at 18-25 degrees C. The highest intensity of infection occurred incrustaceans under experimental conditions, a lower intensity was found in crustaceans from duck farms and the lowest in crustaceans from other parts of ponds (e. g., in the case of Fimbriaria fasciolaris in Copepoda, 37, 22 and 10 cysticercoids). The intermediate hosts infected with cestode larvae can live for 3-6 weeks (Copepoda) and 4-7 weeks (Ostracoda) and after invagination of cysticercoids for 20-25 days, on the average. The cysticercoids survive their hosts for 14-18 h at 4-6 degrees C, for 10-11 h at 12-14 degrees C, for 6-7 h at 18-20 degrees C and for 3-4 h at 24-26 degrees C. If they are swallowed by water snails at that time (dead crustaceans are a component of their food), they survive in their digestive tract even for two years (the longest period demonstrated experimentally) and after this time they are able to develop into an adult cestode in the definitive host. The infectivity of cysticercoids increases with their age. It is the lowest immediately after invagination (10-15%), during the stay of cysticercoids in crustaceans it gradually increases (30-60% on days 10-20 after invagination) and it is the highest in cysticercoids from snails (45-55% after 20-50 days in snails, 60-80% after 50-100 days in snails and 70-90% after more than 100 days in snails).

Animals↗
PubMed2003

The embryonic development of the bodywall and nervous system of the cestode flatworm Hymenolepis diminuta.

Cestodes (tapeworms) are a derived, parasitic clade of the phylum Platyhelminthes (flatworms). The cestode body wall represents an adaptation to its endoparasitic lifestyle. The epidermis forms a non-ciliated syncytium, and both muscular and nervous system are reduced. Morphological differences between cestodes and free-living flatworms become apparent already during early embryogenesis. Cestodes have a complex life cycle that begins with an infectious larva, called the oncosphere. In regard to cell number, cestode oncospheres are among the simplest multicellular organisms, containing in the order of 50-100 cells. As part of our continuing effort to analyze embryonic development in flatworms, we describe here the staining pattern obtained with acTub in embryos and larvae of the cestode Hymenolepis diminuta and, briefly, the monogenean Neoheterocotyle rhinobatidis. In addition, we labeled the embryonic musculature of Hymenolepis with phalloidin. In Hymenolepis embryos, two different cell types that we interpret as neurons and epidermal gland cells express acTub. There exist only two neurons that develop close to the midline at the anterior pole of the embryo. The axons of these two neurons project posteriorly into the center of the oncosphere, where they innervate the complex of muscles that is attached to the hooklets. In addition to neurons, acTub labels a small and invariant set of epidermal gland cells that develop at superficial positions, anteriorly adjacent to the neurons, in the dorsal midline, and around the posteriorly located hooklets. During late stages of embryogenesis they spread and form a complete covering of the embryo. We discuss these data in the broader context of platyhelminth embryology.

Animals↗
PubMed2005

Concentration of some toxic elements in Oryctolagus cuniculus and in its intestinal cestode Mosgovoyia ctenoides, in Dunas de Mira (Portugal).

The need for sentinel organisms reflecting small-scale changes in heavy metal pollution of different habitats has been previously stated and the role of terrestrial mammalian parasites has been pointed out as an important field of research aiming at the potential use of parasitic models as bioindicators. The scope of the present study was to assess the concentration of some toxic (Cd, Pb, As and Hg) elements in Dunas de Mira (Natura 2000 PTCON055) while testing the model constituted by the wild rabbit (Oryctolagus cuniculus Linnaeus, 1758) and its intestinal cestode parasite Mosgovoyia ctenoides Railliet, 1890 as potential bioindicators. Wild rabbits were harvested by hunters and analysed for intestinal cestodes. Samples of kidney, liver, intestinal mucosa, muscle of host and also M. ctenoides were taken and deep-frozen for posterior element analysis by ICP-MS. In general, levels of contamination in rabbit tissues were found to be low although some of the elements were detected in higher quantities when compared to other previous reports for wildlife in Europe. The highest quantity of Pb was found in rabbit muscle (3.81 ppm) while highest Cd and Hg values were found in kidney (1.02 and 0.08 ppm). Significant linear relationships were found between Pb concentration in the parasite and Pb concentration in kidney (P=0.0047), muscle (P=0.0002) and intestinal mucosa (P=0.0181) and between As concentration in the parasite and As concentration in liver (P=0.0024), kidney (P=0.0010), muscle (P=0.0003) and intestinal mucosa (P=0.0047). The most significant relationships for Pb and As were detected between element concentration in the cestode and in host muscle. However, maximum Pb and As concentrations in M. ctenoides were only twice as high as those found for rabbit kidney and therefore it is not possible to confirm the role of the model O. cuniculus/M. ctenoides as a promising bioindicator system unlike other mammalian host/cestode models tested in other studies. The contrasting results might be due to differences in the absorption processes in the tegument of different cestode families. Furthermore, the large size of the cestodes used in the present study might also explain the relatively low element concentration values obtained.

Animals↗
PubMedDate not supplied

Vaccination against cestode parasites.

Cestode parasites are important because they cause production losses, particularly in the sheep, beef and pig meat industries, and because some species are zoonotic parasites which cause serious disease in humans. Research on the development of vaccines to prevent infection with cestode parasites has concentrated on the taeniid cestodes. Two strategies can be adopted for vaccine research: vaccines against infection in the definitive hosts and vaccines for use in the intermediate hosts. The number and accessibility of definitive hosts would favour these as potential targets for vaccines over intermediate hosts, however little success has been achieved in demonstrating immune-mediated resistance to infection in definitive hosts. In comparison, immunity in the intermediate hosts is a prominent feature of the host-parasite relationship in taeniid cestodes. This has favoured the development of vaccines against Taenia and Echinococcus species in their intermediate hosts. This paper reviews the progress which has been made in vaccination against cestode parasites and the prospects for practical application of these vaccines.

Animals↗
PubMed1990

On the infracommunity structure of adult cestodes in freshwater fishes.

The distribution-co-occurrence and exchange of adult cestode species in two fish communities (the Bothnian Bay and Lake Yli-Kitka both in Finland) was studied. Coexistence of two or more mature cestode species in the same fish host population was zero for all fish species studied (33) except pike in the Bothnian Bay and whitefish in the lake. It was found that 60% of the fish species studied in the Bothnian Bay and 80% of the fish species studied from Lake Yli-Kitka harboured only 1 mature cestode species. Exchange of adult cestode species between the different fish species in these two fish communities was found to be as rare as coexistence. The infra-community structure of adult cestodes in freshwater fish thus turned out to be markedly different from what is known to be the situation in birds. The evolutionary explanation behind the differences is discussed.

Animals↗
PubMed1991

Cestode vaccines.

Studies over the past 20 years have clearly shown the potential for developing vaccines against larval cestode infections of man and animals. The important larval cestode infections of man (Echinococcus granulosus--hydatidosis: Taenia solium--cysticercosis) involve domesticated animals as intermediate hosts in their natural life-cycles. These animals develop strong immunity against reinfection, and immunity can be artificially induced by vaccination with oncosphere antigens. A major stumbling block in developing commercial vaccines against cestodes has been the difficulty in obtaining adequate supplies of these antigens. Recent studies with Taenia ovis, a larval cestode causing cysticercosis in sheep, have demonstrated the feasibility of developing commercial vaccines against cestodes using recombinant DNA technology. A cDNA library prepared using mRNA obtained from T. ovis oncospheres was used to isolate a clone which expressed T. ovis polypeptide antigen 45W as a fusion protein with Schistosoma japonicum glutathione S-transferase (GST-45W). GST-45W gave up to 94% protection against challenge infection when used to vaccinate sheep with saponin as adjuvant. The vaccine antigen was shown by SDS PAGE to be unstable, a major disadvantage in subsequent attempts to obtain high yields of antigen for commercial production. The fusion protein has now been stabilized by reducing the size of GST-45W cDNA through deleting 19 carboxyl terminal hydropathic acids, and the resultant fusion protein GST-45W (B/X) was highly host-protective. Another experiment showed that the 45W T. ovis polypeptide cleaved enzymatically from GST-45W was still host-protective, suggesting that GST had no influence on the immunogenicity of GST-45W fusion protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Biotechnology research on cestodes in the Philippines, Malaysia, and Indonesia.

There are essentially no reports on the use of modern biotechnological methods on the study of cestode parasites in the Philippines, Indonesia or Malaysia. The only recent reports of cestode studies in these countries have been on reports of new species in animals and on prevalence rates of cestode parasites in humans; Taenia solium and cysticercosis, Taenia saginata and Hymenolepis nana, etc. Reports on the use of biotechnology has emanated from outside the area on cestodes of humans and animals, and some of these methods could be used to study cestodes in this part of the world.

Animals↗
PubMed2026

"Not flying solo": phylogenetic identification and life-cycle insights of larval cestodes in the European flying squid Todarodes sagittatus (Cephalopoda: Ommastrephidae).

The European flying squid Todarodes sagittatus Lamarck is a widely distributed ommastrephid cephalopod in the Northeast Atlantic and Mediterranean Sea, yet its parasite fauna remains poorly documented in the Mediterranean Sea. In this study, two cestode larvae species infecting T. sagittatus from the Algerian coast (Western Mediterranean) were investigated using an integrative approach combining morphological observations and molecular analyses. A total of 63 squids were examined for parasitic infection. Cestodes in plerocercoid stage were detected in 31 individuals (prevalence of 46%), primarily located within the gastrointestinal tract, including the stomach, intestine, and caecum. Morphological features of the larvae were consistent with members of the order Phyllobothriidea but did not allow identification to the species level. Molecular analysis of the D1-D3 region of the 28S rDNA revealed two distinct larval lineages belonging to the genus Crossobothrium Linton, 1889. One lineage showed 100% sequence identity with the adult cestode Crossobothrium dohrnii (Oerley, 1885), a parasite of hexanchid sharks, confirming the identity of these larvae as plerocercoids of C. dohrnii. The second lineage clustered within the Crossobothrium clade but could not be assigned to a known species and is therefore referred to as Crossobothrium sp. The occurrence of these larvae in T. sagittatus, together with ecological data on squid diet and predator-prey relationships, suggests that this cephalopod acts as an intermediate or paratenic host in the life cycle of hexanchid cestodes. Infection likely occurs through predation on crustaceans acting as first intermediate hosts, while transmission to definitive hosts occurs when infected squids are consumed by sharks. These findings provide the first molecular identification of cestode larvae from T. sagittatus in the Mediterranean and highlight the important role of ommastrephid squids in the trophic transmission of elasmobranch parasites in pelagic ecosystems.

Crossobothrium↗
PubMed1998

Evidence for strategic egg production in a hermaphroditic cestode.

The cestode Schistocephalus solidus is a simultaneous hermaphrodite that grows in 2 intermediate hosts and reproduces rapidly within a few days in the gut of a bird. Reproduction takes place by self- or cross-fertilization. Here, it was tested whether egg production differs between S. solidus that reproduce alone and those that are allowed to reproduce in pairs. Egg production in an in vitro system was found to depend on the cestodes' social situation. When kept alone, larger cestodes produced larger eggs. This was not so when kept in pairs--the difference between these 2 reproductive modes being highly significant in this respect. Further experiments revealed that, within the first 3 days, these hermaphrodites produced a larger total egg mass when kept alone than when kept in pairs. This was also reflected by the energy contents of the cestodes after this time-span: selfers had used up more energy than paired worms. Furthermore, S. solidus appeared to adjust its investment per egg depending on whether the offspring will be the result of self- or cross-fertilization. Selfers produced larger numbers of eggs, but these eggs were smaller and contained even smaller embryos per given egg size than eggs of potentially outbreeding cestodes. Selfed eggs reached lower hatching rates. Although this is to be expected from inbreeding depression it may also be an effect of the reduced maternal investment per egg. The observed phenotypic plasticity in the reproduction of S. solidus is discussed within 4 evolutionary frameworks: local mate competition adjusted for hermaphrodites, the hermaphrodite's dilemma, bet-hedging, and sib-competition.

Analysis of Variance↗
PubMed2002

The terminology of larval cestodes or metacestodes.

The terminology associated with the nomenclature of larval or metacestodes is reviewed as well as the various morphological and developmental characters used to define different types of larval cestodes. Based on a review of the literature, the key characters differentiating the types of larval cestodes are the presence of a primary lacuna and the invagination/retraction of the scolex. The presence of a cercomer and of a bladder-like enlargement of the larval cestode were considered to be useful secondary characteristics. Using these characters, six basic types of larval cestodes were identified: the procercoid, an alacunate form which cannot develop further until ingested by a second intermediate host; the plerocercus, an alacunate form with a retracted scolex; the plerocercoid, an alacunate form with an everted scolex; the merocercoid, an alacunate form with an invaginated scolex; the cysticercoid, a lacunate form with a retracted scolex; and the cysticercus, a lacunate form with an invaginated scolex. The diversity of larval types within the broad classifications of cysticercoid and cysticercus can be differentiated by the use of appropriate prefixes. Deficiencies in knowledge of specific types of larval cestodes are identified and further avenues of research are indicated.

Animals↗
PubMedDate not supplied

Role of the calcareous corpuscles in cestode physiology: a review.

Cysticercosis is a parasitic disease caused by the larval stage or cysticercus of the cestode tapeworm Taenia solium. Cysticerci are able to survive in the host tissues for long periods in the presence of an immune response. Tissues of cestodes contain mineral concretions termed calcareous corpuscles. These corpuscles might serve for the focal deposition of exceeding amounts of calcium protecting the larvae against calcification. Studies on the morphology and composition of calcareous corpuscles in cestodes have resulted in a number of hypotheses on their origin and function. Calcareous corpuscles are believed to form either intracellularly or extracellularly and the cell type involved, the place of formation and the mechanism of mineral deposition seem to be also diverse. This review intends to provide an updated guide to the published literature on calcareous corpuscles in cestodes, giving emphasis on their role in larval physiology. Understanding biomineralization might lead to novel ways for the treatment of diseases caused by cestode larvae.

Animals↗
PubMed1981

[Comparative fine structure of the cestode spermatozoon. Relationship to phylogenesis].

The comparison of the ultrastructure of spermatozoa in Cestodes from seven different orders shows that they have the same general pattern of organization. The main common features are following: (a) a long thread-like body; (b) an elongated nucleus; (c) cortical microtubules underlying plasma membrane; (d) the absence of mitochondria and of a typical acrosome. The mode of spermatozoon differentiation indicates an inversion of the polarity. The number of axonemes of the 9 + "1" pattern, characteristic of the platyhelminthes, allow us to distinguish two types of spermatozoa among cestodes: --The "two-axonemes"-type is considered as primitive as it has also been found in the free-living platyhelminths. This type has been observed in the Pseudophyllidea, Proteocephalidea, Tetrarhynchidea and Tetraphyllidea (Onchobothriidae). --The "one-axoneme"-type has been found in the Cyclophyllidea, Caryophyllaeidea, Diphyllidea and Tetraphyllidea (Phyllobothriidae). It has been proved that the one axoneme type of the spermatozoon, observed in Tetraphyllidea, Phyllobothriidae arises from the two axoneme type by early abortion of the second axoneme. In all the tetraphyllidean species studied so far, we found an helicoidal body forming so-called "crested body" or "spiral crest" at the proximal end of the spermatozoon, which is opposite to the nuclear part. This division of the cestodes into two groups, according to the number of axonemes in the spermatozoon is compared with the phylogenetic diagrammes of Cestoda proposed by Freeman (1973) and Euzet (1974). As result, two hypothesis can be forwarded to explain the relationships between the Tetraphyllidea, Proteocephalidea and Cyclophyllidea. The importance of data on the cestode spermatozoa as a criterion in analysis of cestode phylogenesis is drawn and discussed.

Animals↗
PubMed1992

Segregation and co-occurrence of larval cestodes in freshwater fishes in the Bothnian Bay, Finland.

Two autogenic (Triaenophorus crassus and T. nodulosus) and four allogenic (Diphyllobothrium latum, D. dendriticum, D. ditremum and Schistocephalus solidus) larval cestode species were found in 13 out of 31 fish species studied from the Bothnian Bay, NE Baltic. Gasterosteus aculeatus was the most heavily infected fish with 4 larval cestode species; for two of them (D. ditremum and S. solidus) the three-spined stickleback was found to be the required fish intermediate host. Among allogenic cestode species, those restricted to different definitive host species segregated their larval population in relation to the fish host, while, for example, D. ditremum and S. solidus, both maturing in fish-eating birds, had the highest percentage of co-occurrences. D. dendriticum, which had the widest range of definitive hosts, was found in the greatest number (8) of fish species and co-occurred with all other species found except T. crassus. The two autogenic species totally segregated their larval population from each other although they both require pike as definitive host. The ecological and evolutionary relationships behind the patterns found for larval cestodes are discussed.

Animals↗
PubMed1987

The prevalence and epidemiology of cestodes in dogs in Clwyd, Wales. II. Hunting dogs.

Studies of a foxhound pack and gundog kennel in Clwyd, Wales showed 47 of 162 foxhounds (29%) and six of 25 gundogs (24%) to be infested with cestodes. Taeniia species were found in both groups, T. hydatigena being most common. Echinococcus granulosus and Dipylidium caninum were found in hounds only. The husbandry of the dogs was investigated and close relationships were found between diet, worming procedures and cestode infestation. These dogs play an important role in disseminating cestode eggs in the environment. Recommendations for control of the problem are made. Foxhounds and other hunting dogs play a particularly important role in the life-cycle of cestodes because their diet frequently includes uncooked carcasses and because they hunt over large areas of countryside, facilitating the widespread dissemination of infective eggs.

Animal Husbandry↗
PubMed1990

Cestode infections in animals: immunological diagnosis and vaccination.

Cestode infections in animals are important because several species are zoonotic, causing cysticercosis and hydatidosis in man, and because of the economic losses incurred due to infections in livestock. Information on immunological diagnosis of and vaccination against cestode infection is restricted almost exclusively to the taeniid cestodes in which two groups of mammalian hosts are concerned: the intermediate host infected with the larval parasite and the definitive host infected with the adult tapeworm parasite. Research towards developing serological tests for the diagnosis of larval cestode infection in animals has been largely unsuccessful. Substantial problems remain, due to the frequent existence of multiple infections with different taeniid species and antigenic crossreactivity between these related parasites, and the low level of specific antibody response to infection. Problems with poor specificity and sensitivity of traditional serological tests for cysticercosis and hydatidosis have prevented the development of any practical test for ante-mortem diagnosis of infection. A recent new approach to the diagnosis of Taenia saginata infection by detecting circulating parasite antigen offers some prospect for the development of a practical diagnostic test for cysticercosis in cattle. The effectiveness of the arecoline purge for detection of Echinococcus granulosus in dogs has been reduced by the widespread availability of praziquantel. A serological method for diagnosis of E. granulosus in dogs has been developed which offers equivalent or superior diagnostic sensitivity compared with arecoline purge. This test should provide a valuable tool in hydatid control campaigns for the diagnosis of existing or recent past infections in dogs. Substantial progress has been made towards developing a practical vaccine for the prevention of T. ovis infection in sheep. An antigen derived from the parasite egg has been identified and produced in Escherichia coli using recombinant DNA techniques. The vaccine, which protects sheep against challenge infection with T. ovis, is the first highly effective defined antigen vaccine against any parasite infection of man or animals. Commercial development of this vaccine is in progress. The success achieved with the T. ovis vaccine augurs well for the rapid development of other recombinant vaccines against cysticercosis caused by other taeniid species and against hydatidosis in animals.

Animals↗
PubMed1988

Cestode transmission patterns.

The paradox of high prevalence but low probability of having an egg develop to an adult has been resolved by the evolution of 3 major and basic strategies involving transmission: evolution of life cycles interpolated into host biology; presentation of infective stages that increase probability of contact between host and parasite; and increase in reproductive potential. The rarity of direct cycles confirms that cycles in themselves, with at least 2 hosts, are a key element of cestode success because they provide a vehicle for dispersal and transmission of infective stages. Transmission is primarily by passive stages that become incorporated through intermediate hosts or accidentally in the food chain. High host specificity results from efficient transmission pathways but may represent a fragile system for the evolution of the species. Probability of transmission is increased through diversity of intermediate hosts, making eggs more susceptible to ingestion and by behavioral manipulation of hosts by parasite stages. Spatial and temporal aspects of transmission may be increased through paratenesis. Asexual proliferation of immature stages is uncommon and is favored where there is selective predation; such proliferation may be part of a transmission strategy of colonial cestodes that require high infrapopulations in order to survive. Hyperapolysis may be part of a transmission strategy used by the Tetraphyllidea, Trypanorhyncha, and Lecanicephalidea to increase proglottid production. The dynamics of transmission for cestodes of humans and domestic animals require a different perspective than those of wild hosts. All strategies are reviewed within the framework of certain cestode morphological and ecological constraints. A total of 11 figures and 48 references complements the text.

Animals↗
PubMed2003

Pyruvate: an in vivo marker of cestodal infestation of the human brain on proton MR spectroscopy.

PURPOSE: To study intracranial cestodal cysts using in vivo proton magnetic resonance spectroscopy ((1)H MRS) in an effort to identify metabolite(s) that may help in recognizing the parasitic etiology and, perhaps, viability of such tapeworm cysts. Cestodal infestations of the human central nervous system (CNS)-cysticercosis and hydatidosis-are not rare. Identification of a scolex is considered diagnostic of cysticercosis on imaging. In its absence, however, the features are non-specific. MATERIALS AND METHODS: Three patients with intracranial hydatid cysts and 13 patients with intracranial cysticercal cysts (four intraventricular, seven parenchymal, and two subarachnoid racemose cysts) were studied on a 1.5-T MR system. In vivo (1)H MRS was performed by multivoxel two-dimensional hybrid chemical shift imaging technique (TE = 135 msec). In vitro (1)H NMR and mass spectroscopy (matrix assisted laser desorption/ionization [MALDI]) were performed on excised cysticercal and hydatid cyst fluid. MALDI spectra for pyruvate and succinate were also obtained. RESULTS: Alanine, pyruvate, and acetate were seen in all the three hydatid cysts. Lactate was seen in racemose cysticercal cysts. A large resonance at 2.4 ppm, confirmed as pyruvate at mass spectroscopy, was seen in 13 cestodal cysts. Pyruvate was not seen in one each of racemose, intraventricular, and parenchymal cysticercal cysts. CONCLUSION: Pyruvate is the predominant metabolite in cestodal cysts infesting the human CNS. It may be a marker of parasitic etiology and perhaps that of viability of such intracranial cysts.

Biomarkers↗
PubMed1997

Isolation and characterization of five actin cDNAs from the cestode Diphyllobothrium dendriticum: a phylogenetic study of the multigene family.

Five cDNAs (pDidact2-pDidact6), representing different actin genes, were isolated from a Diphyllobothrium dendriticum cDNA library, and the DNA as well as the putative amino acid sequences were determined. The corresponding Didact2 and Didact4 genes code for peptides 376 amino acids long, with molecular weights 41,772 and 41,744 Da, respectively, while the deduced Didact3 protein is 377 amino acids long and weighs 41,912 Da. The pDidact5 and -6 cDNAs lack nucleotides corresponding to three to six amino acids at the amino-terminus. Two of the five cDNAs contain the conventional AATAAA as the putative polyadenylation signal, one has the common variant ATTAAA, whereas the hexanucleotide AATAGA is found 15 and 18 nucleotides, respectively, upstream of the poly(A) site in two of the cDNAs. Phylogenetic studies including 102 actin protein sequences revealed that there are at least four different types of cestode actins. In this study three of these types were found to be expressed in the adult D. dendriticum tapeworm. Structurally the cestode actin groupings differ from each other to an extent seen only among the metazoan actins between the vertebrate muscle and cytoplasmic isoforms. In the phylogenetic trees constructed, cestode actins were seen to map to two different regions, one on the border of the metazoan actins and the other within this group. It is, however, difficult to say whether the cestode actins branched off early in the metazoan evolution or if this position in the phylogenetic tree only reflects upon differences in evolutionary rate.

Actins↗