-
Integrative and Comparative Biology Aug 2015Predatory flatworms belonging to the taxon Kalyptorhynchia are characterized by an anterior muscular proboscis that they use to seize prey. In many cases, the proboscis... (Review)
Review
Predatory flatworms belonging to the taxon Kalyptorhynchia are characterized by an anterior muscular proboscis that they use to seize prey. In many cases, the proboscis is armed with hooks, derived either from the extracellular matrix that surrounds the muscles or from intracellular deposits in the epithelium covering the proboscis. Glands associated with the proboscis reportedly are venomous; however, there are few direct tests of this hypothesis. This article reviews the structure and current knowledge of the function of the proboscis in the Kalyptorhynchia, points to areas in which the current understanding of phylogenetic relationships within this taxon is incongruent with our hypothesis of how the proboscis evolved, and addresses areas in need of further research, especially as regards functional morphology and biomechanics.
Topics: Animals; Biological Evolution; Biomechanical Phenomena; Phylogeny; Platyhelminths; Predatory Behavior
PubMed: 26002347
DOI: 10.1093/icb/icv056 -
International Journal For Parasitology Dec 1990
-
Cell and Tissue Research Mar 2021Fueled by the discovery of head regeneration in triclads (planarians) two and a half centuries ago, flatworms have been the focus of regeneration research. But not all...
Fueled by the discovery of head regeneration in triclads (planarians) two and a half centuries ago, flatworms have been the focus of regeneration research. But not all flatworms can regenerate equally well and to obtain a better picture of the characteristics and evolution of regeneration in flatworms other than planarians, the regeneration capacity and stem cell dynamics during regeneration in the flatworm order Polycladida are studied. Here, we show that as long as the brain remained at least partially intact, the polyclad Prosthiostomum siphunculus was able to regenerate submarginal eyes, cerebral eyes, pharynx, intestine and sucker. In the complete absence of the brain only wound closure was observed but no regeneration of missing organs. Amputated parts of the brain could not be regenerated. The overall regeneration capacity of P. siphunculus is a good fit for category III after a recently established system, in which most polyclads are currently classified. Intact animals showed proliferating cells in front of the brain which is an exception compared with most of the other free-living flatworms that have been observed so far. Proliferating cells could be found within the regeneration blastema, similar to all other flatworm taxa except triclads. No proliferation was observed in epidermis and pharynx. In pulse-chase experiments, the chased cells were found in all regenerated tissues and thereby shown to differentiate and migrate to replace the structures lost upon amputation.
Topics: Animals; Brain; Cell Proliferation; Platyhelminths; Regeneration
PubMed: 33159580
DOI: 10.1007/s00441-020-03302-w -
Advances in Parasitology 1994
Review
Topics: Animals; Larva; Phylogeny; Platyhelminths
PubMed: 8122566
DOI: 10.1016/s0065-308x(08)60413-3 -
International Journal For Parasitology Jun 1997A summary is given of the 4 contributions on the origins of parasitism in the Platyhelminthes. Recent ecological literature is used to interpret some of the findings. In... (Review)
Review
A summary is given of the 4 contributions on the origins of parasitism in the Platyhelminthes. Recent ecological literature is used to interpret some of the findings. In particular, recent findings on rugged fitness landscapes, the increasing difficulty of long-jump adaptations, complexity catastrophes, and empty phenotypic space are discussed in order to find an explanation for the large number of Neodermata and the scarcity of parasitic turbellarians; it is concluded that evolutionary stasis of symbiotic turbellarians that are "trapped" in their particular niches is responsible for the small number of symbiotic species of turbellarians, rather than competitive exclusion by the numerous neodermatans. The earliest neodermatans were probably already dependent on the production of many offspring; hence the protoneodermatan was probably a species preadapted to parasitism by high fecundity. Monogenea produce few offspring in spite of their rich and secure food supply; the protomonogenean was either a species with a complex behaviour pattern for habitat selection or, alternatively, a species with high fecundity subsequently reduced to permit the evolution of more complex behaviour patterns (switch from r- to K-strategy). The finding that embryonic replacement of the epidermis is shared by several turbellarian groups, a developmental pattern possibly used and modified in the formation of the neodermis in the Neodermata, can be interpreted as supporting the views that Neodermata and turbellarians with epidermal replacement are all monophyletic, or alternatively, that a similar developmental pattern has arisen several times due to similar selection pressures. However, the possibility of horizontal character transfer should also be considered for explaining similar characters, including similar developmental patterns, in apparently not closely related groups. Horizontal gene transfer and principles for demonstrating horizontal character transfer are discussed.
Topics: Animals; Biological Evolution; Female; Fertility; Host-Parasite Interactions; Male; Platyhelminths; Reproduction; Turbellaria
PubMed: 9229255
DOI: 10.1016/s0020-7519(97)00014-3 -
Zoological Science Jun 2020Acotylea is a suborder of Polycladida (Rhabditophora, Platyhelminthes) characterized by lack of a cotyl (sucker-like structure) on the ventral surface of the body. We...
Acotylea is a suborder of Polycladida (Rhabditophora, Platyhelminthes) characterized by lack of a cotyl (sucker-like structure) on the ventral surface of the body. We newly determined partial sequences of two mitochondrial (16S ribosomal RNA and cytochrome oxidase subunit I) and two nuclear (18S and 28S ribosomal RNA) genes from 24 acotylean species (12 families and 14 genera). Based on these sequences in addition to those available in public databases, we inferred the phylogeny of 16 families and 27 genera of Acotylea from molecular phylogenetic analyses (maximum likelihood and Bayesian inference) based on concatenated gene sequences. Our analyses supported three clades corresponding to Discoceloidea, Leptoplanoidea, and Stylochoidea. The phylogenetic position of Callioplanidae remains unclear. Among family- or genus-level taxa, Gnesiocerotidae, Stylochoplanidae, and were not monophyletic. We discuss the validities of Notocomplanidae and , and the family-level assignment of .
Topics: Animals; Genes, Helminth; Genes, Mitochondrial; Helminth Proteins; Phylogeny; Platyhelminths; RNA, Helminth
PubMed: 32549541
DOI: 10.2108/zs190136 -
International Journal For Parasitology Jun 1997This review examines briefly the reproductive capacity of representatives of the 4 principal groups of platyhelminths, the "Turbellaria", Monogenea, Digenea and Cestoda.... (Review)
Review
This review examines briefly the reproductive capacity of representatives of the 4 principal groups of platyhelminths, the "Turbellaria", Monogenea, Digenea and Cestoda. Of the flatworms, 3 main groups are wholly parasitic (monogeneans; digeneans; cestodes). Among the largely free-living "Turbellaria", there are several parasitic representatives in some families (Umagillidae; Graffillidae; Pterastericolidae; Fecampiidae; Acholadidae). Endoparasitic platyhelminths with complex life-cycles produce large numbers of eggs and numbers of offspring are increased further in the digeneans and a few cestodes by asexual multiplication. Like their free-living relatives, most ectosymbiotic and ento- and ectoparasitic flatworms ("turbellarians" and monogeneans) produce, on the whole, far fewer eggs and progeny but are still successful organisms in terms of their numbers of species and diversity. Estimates of parasite fecundity from in vivo experiments are needed for representatives from all flatworm groups. For those parasites that are host-specific, the particular species of host provides a predictable target to be located. Adaptations displayed by the eggs and infective stages of some flatworms increase their chances of finding and recognising their specific host and these are reviewed: attachment of eggs to their "host"; egg hatching in response to host chemicals; rhythmical emergence; special behaviours of infective stages; host recognition.
Topics: Animals; Cestoda; Host-Parasite Interactions; Platyhelminths; Reproduction; Reproduction, Asexual; Symbiosis; Turbellaria
PubMed: 9229253
DOI: 10.1016/s0020-7519(97)00012-x -
Parasite (Paris, France) 2023Five new species of Cosmetocleithrum were described parasitizing the gill filaments of neotropical doradid fishes. Cosmetocleithrum undulatum n. sp., Cosmetocleithrum...
Dactylogyrids (Platyhelminthes, Monogenea) from the gill lamellae of doradids (Siluriformes) with description of five new species of Cosmetocleithrum and new geographical distribution for known species from the Neotropical Region, Brazil.
Five new species of Cosmetocleithrum were described parasitizing the gill filaments of neotropical doradid fishes. Cosmetocleithrum undulatum n. sp., Cosmetocleithrum brachylecis n. sp. and Cosmetocleithrum ludovicense n. sp. are described from Platydoras brachylecis from a market-place of São Luís, State of Maranhão, Brazil. Cosmetocleithrum sacciforme n. sp. and Cosmetocleithrum basicomplexum n. sp. are described from Oxydoras niger from Juruá River, State of Acre, Brazil. Cosmetocleithrum undulatum and Cosmetocleithrum brachylecis resemble Cosmetocleithrum falsunilatum Feronato, Razzolini, Morey & Boeger, 2022 mainly by the unique male copulatory organ (MCO) morphology but differ from these and all congeneric species mainly by the morphology of the MCO, accessory piece and hooks pairs. Cosmetocleithrum ludovicense is closer to Cosmetocleithrum confusus Kritsky, Thatcher & Boeger, 1986 and to Cosmetocleithrum akuanduba Soares, Santos Neto & Domingues, 2018 but differs from those mainly by the morphology of the accessory piece. Cosmetocleithrum sacciforme differs from all congeneric species mainly by the morphology of the accessory piece formed by a single plate of saccular appearance. Cosmetocleithrum basicomplexum also shares morphological characters with Cosmetocleithrum gigas Morey, Cachique & Babilonia, 2019 considering the size of the body and shape of the anchors, but differs mainly in the morphology of the bars and hooks. Besides the new species, new data are presented for Cosmetocleithrum leandroi Soares, Neto & Domingues, 2018, C. akuanduba and C. confusus regarding morphological characteristics and biogeography.
Topics: Male; Animals; Catfishes; Gills; Brazil; Trematode Infections; Fish Diseases; Trematoda; Platyhelminths
PubMed: 38064202
DOI: 10.1051/parasite/2023054 -
Advances in Experimental Medicine and... 2018Lophotrochozoa is a sister taxon of Ecdysozoa in the Protostomia that includes mollusks, annelids, brachiopods, and platyhelminths. Recent studies have clarified the... (Review)
Review
Lophotrochozoa is a sister taxon of Ecdysozoa in the Protostomia that includes mollusks, annelids, brachiopods, and platyhelminths. Recent studies have clarified the structure, expression, and roles of lophotrochozoan Zic family genes. Zic genes in oligochaete annelid Tubifex tubifex (freshwater sludge worm) and polychaete annelid Capitella teleta (bristle worm) are commonly expressed in a subset of developing brain and mesoderm derivatives. The latter includes the naïve mesoderm and the associated chaetal sacs in each body segment, although the segmentation processes differ between the two species. Furthermore, in brachiopod Terebratalia transversa (lamp shell), Zic is expressed in the anterior ectodermal domains and mesodermal derivatives, including those associated with the chaetal sacs. This result suggests the common involvement of Zic genes in the development of chaetae, a lophotrochozoan novelty acquired in the course of evolution. In addition, the highly simplified lophotrochozoan Dicyema acuticephalum (dicyemid mesozoan, a cephalopod endoparasite), which lost its gut, nervous system, and muscles during evolution, expresses its Zic genes in hermaphroditic gonads, highlighting the role of Zic genes in germ cell development. The role of Zic in head regeneration was revealed in studies on platyhelminth Schmidtea mediterranea (freshwater planarian). Planarian Zic expression was induced in a subpopulation of neoblasts that includes adult pluripotent stem cells. It is needed for head regeneration and production of an anterior signaling center. Suppression of Wnt-β-catenin signaling underlies Zic-mediated head regeneration, reminiscent of Wnt-β-catenin suppression by vertebrate Zic genes. Taken together, studies on the lophotrochozoan Zic genes are essential to understanding not only the roles of these genes in body plan evolution but also the molecular mechanism underlying adult stem cell regulation.
Topics: Animals; Helminth Proteins; Oligochaeta; Planarians; Polychaeta; Transcription Factors; Zinc Fingers
PubMed: 29442318
DOI: 10.1007/978-981-10-7311-3_5 -
Zootaxa Jul 2020Catenulida are mostly inhabitants of freshwater ecosystems, like ponds, streams, though the marine species are few (Larsson and Willems, 2010). About 110 species of...
Catenulida are mostly inhabitants of freshwater ecosystems, like ponds, streams, though the marine species are few (Larsson and Willems, 2010). About 110 species of catenulids are known worldwide, with most of the studies conducted in South America (Marcus, 1945a, 1945b; Noreña et al., 2005), North America (Kepner and Carter 1931; Nuttycombe and Waters, 1938) and Scandinavian Peninsula (Luther, 1960, Larsson and Willems, 2010; Larsson et al., 2008). The diversity of catenulids from India has not been studied intensively; however some reports on other turbellaria exists for the country (Annandale, 1912; Whitehouse, 1913; Kapadia, 1947; Basil and Fernando, 1975; Apte and Pitale, 2011; Kalita and Goswami, 2012; Venkataraman et al., 2015). The genus Stenostomum, however, has been studied extensively around the world with identification of over 60 species (Tyler et al., 2006-2016). This is first report of the genus from India. The present study was part of the project to catalogue the diversity of free living protozoan ciliates from the Hooghly stretch of the Ganga River during which the flatworms were found. The worms were studied based on the live observations, with recognition of characters which led to its identification. This study serves to fill knowledge gap in the freshwater flatworms from India.
Topics: Animals; Ecosystem; India; Platyhelminths
PubMed: 33055699
DOI: 10.11646/zootaxa.4816.3.11