Bucco-pharyngeal Apparatus Research Articles

An integrative description of Mesobiotus mandalori sp. nov. (Eutardigrada, Macrobiotoidea) from Poland

In this paper we provide integrative description (morphological and genetic) of the new eutardigrade species Mesobiotus mandalori sp. nov. from central Poland, found during research on the vertical distribution of Tardigrada in the Czerniejewskie Forests. Mesobiotus mandalori sp. nov. belongs to the harmsworthi group, but it differs from the members of this group in some morphometric characters of the bucco-pharyngeal apparatus, claws and/or eggs. Morphologically, Meb. mandalori sp. nov. is most similar to Meb. pseudocoronatus, but it differs from it by a larger bare egg diameter and smaller number of egg processes on egg circumference. Morphometrical data were supported by results of comparative genetic analysis of four molecular markers: 18S rRNA, 28S rRNA, ITS2 and COI. According to COI the new species is most similar to Meb. skorackii with the genetic distance of 21.1%.https://zoobank.org/urn:lsid:zoobank.org:act:0222E328-CF9E-4D04-8F8C-69C80515FEE2

Composition and structural organization of tardigrades feeding apparatus focusing on chitin and other autofluorescent molecules

Abstract Chitin is a structural sugar broadly distributed among all kingdoms, and it is present in Tardigrada as α-chitin. Its presence in the buccopharyngeal apparatus of tardigrades was confirmed in previous studies and associated with autofluorescence emission, and within this emission three components were identified. This study aimed to localize the chitin in the buccopharyngeal apparatus and to understand the nature of the other autofluorescent components. Calcofluor white staining of three tardigrade species (Echiniscus sp., Milnesium sp., Macrobiotus sp.) allowed the chitin localization in the feeding structures and the separation of its signal from the whole autofluorescence emission via confocal laser scanning microscopy. Comparing different fluorochromes found in tardigrades and in the nematode Panagrellus pycnus, lambda and square lambda analyses showed that part of the autofluorescent signal is imputable to a collagen-like compound. The images acquired were analysed for morphological, functional, and evolutionary purposes. Chitin and the other autofluorescent compound were localized in the structures of the buccopharyngeal apparatus. Their distribution highlighted the presence of different levels of ‘flexibility/strength’ of the structures providing better understanding of their mechanical properties and relating them to the characteristics of the three major limnoterrestrial clades of the phylum Tardigrada.

Considerations on the claws of the Apochela and a novel detail of the bucco-pharyngeal apparatus of the genus Milnesium (Tardigrada: Apochela: Milnesiidae)

This article clarifies two morphological problems, the first regarding all Apochela Schuster, Nelson, Grigarick and Christenberry 1980, and the second the genus Milnesium Doyère, 1840. Among Eutardigrada Richters, 1926, Apochela have four claws per leg, while Parachela Schuster, Nelson, Grigarick and Christenberry 1980 have two double claws per leg. Until now, the four claws per leg of Apochela have been denominated as if they had derived from two parachelan-like double claws undergoing branch separation. However, morphological and molecular data indicate the relative phylogenetic distance of Apochela from Parachela as sister groups; the ancestor of Eutardigrada was probably similar to a primitive heterotardigrade in having four separate claws per leg, which organised and differentiated in couples but without fusion in Apochela, while they fused to form proper double claws only in Parachela. If this hypothesis is correct (Apochela would have retained four separate claws per leg as plesiomorphic character), the denomination of apochelan claws must be adapted to reflect it. The second problem regards the valvular system present between buccal tube and pharyngeal bulb in the genus Milnesium. Until now, only one valvular system type was known, attributed to Milnesium tardigradum (today sensu lato), or to Milnesium cf. tardigradum. We reveal a second type recognisable in many species. The two types are described, discussing their possible correlation with life stage, sex, some morphological and morphometric traits, mounting medium, geographic distribution and currently available phylogenetic trees; the valvular system type is probably species-specific and we attribute to most species of the genus the correct type. Our conclusions are preliminary, but, in any case, the present study indicates that the exact morphology of the discussed portion of the bucco-pharyngeal apparatus in Milnesium is still not well known.

Integrative redescription of Hypsibius pallidoides Pilato et al., 2011 (Eutardigrada: Hypsibioidea) with the erection of a new genus and discussion on the phylogeny of Hypsibiidae

An integrative redescription of Hypsibius pallidoides Pilato, Kiosya, Lisi, Inshina & Biserov, 2011 was undertaken following a reexamination of the type material and new material using high-quality light microscopy, scanning electron microscopy and methods of molecular taxonomy. Detailed morphological investigations revealed a unique complex of characters that precluded the attribution of this species to the genus Hypsibius Ehrenberg, 1848. Furthermore, phylogenetic analyses indicated the affinity of this species within the subfamily Pilatobiinae (Hypsibiidae). Notahypsibius gen. nov. is erected for H. pallidoides and two putatively related species: H. scaber Maucci, 1987 and Ramazzottius arcticus (Murray, 1907). An emended diagnosis for the genus Pilatobius is given, while the subfamily Pilatobiinae lacks a cohesive morphological diagnosis despite representing, at the same time, a well-supported molecular clade. Obvious controversy between the results of the morphological and molecular analyses of the phylogeny of Hypsibioidea is discussed. The distribution of morphological characters such as the claw type, organization of the bucco-pharyngeal apparatus, and egg shell sculpture type within Eutardigrada is analyzed and their phylogenetic significance discussed.

Two new genera of long clawed Isohypsibioidea Guil, Jørgensen amp; Kristensen, 2019.

Two new eutardigrade genera Vladimirobius gen. nov. and Weglarskobius gen. nov. are erected for the species Grevenius irregibilis (Biserov, 1992) and Isohypsibius altai Kaczmarek Michalczyk, 2006a, respectively. They are characterized by strongly modified claws, bucco-pharyngeal apparatus of the Isohypsibius variant, pharyngeal apophyses, and placoids present. The primary branches of internal claws of Vladimirobius gen. nov. are wide in lateral view and have very prominent gibbosity-like projections, whereas primary branches of external claws are thin and extremely long. In Weglarskobius gen. nov. claws IV are similar in shape and size, but the primary branches are extremely long, and thin. Moreover, claws on legs I-III vary greatly in size and shape in Weglarskobius gen. nov. Such supposed autapomorphies fully justify erection of the two new genera, even if the genetic data are presently unavailable.

New records of tardigrade species of the Macrobiotus hufelandi group (Tardigrada: Eutardigrada: Macrobiotidae) from Ukraine

Species of the Macrobiotus hufelandi group are among the most well known and commonly found tardigrades. They are reported in almost every study of Tardigrada diversity in terrestrial habitats. In spite of this, zoogeographical data on this group remain ambiguous and insufficient. Since most species of the M. hufelandi group have been described in the last three decades, many older records need to be confirmed or revised. In this study we aimed to investigate, which species may be present in Ukraine, since most Ukrainian records of this group are outdated. We studied samples of mosses and lichens collected from different regions of Ukraine (mainly in the East and South of the country) in 2007–2019. Tardigrades were extracted from samples and mounted on permanent slides in Faure's medium. After primary identification of genera and species groups we focused on 13 samples containing local populations of the M. hufelandi group. Details of animal and egg morphology were studied under high magnifications of phase contrast light microscopy. Species were identified based on morphology of the oral cavity armature, egg shell morphology, animal cuticle granulation, as well as some morphometric characters of claws and bucco-pharyngeal apparatus. This research revealed the presence of at least six different species in Ukraine: M. glebkai Biserov, 1990; M. hufelandi C.A.S. Schultze, 1834; M. macrocalix Bertolani & Rebecchi, 1993; M. polonicus Pilato, Kaczmarek, Michalczyk & Lisi, 2003; M. sottilei Pilato, Kiosya, Lisi & Sabella, 2012; M. vladimiri Bertolani, Biserov, Rebecchi & Cesari, 2011. Three of them: M. macrocalix, M. sottilei, and M. vladimiri are reported in this study from Ukraine for the first time. Adding three more species recorded in earlier studies: M. diversus Biserov, 1990; M. persimilis Binda & Pilato, 1972, and M. sapiens Binda & Pilato, 1984 – gives the total count of at least 9 species of the group in Ukraine. However, according to the recent studies on species complexes the real species diversity is very likely to be higher. Nevertheless, more sampling and obtaining molecular data from different Ukrainian populations of the M. hufelandi group from Ukraine are required.

An upgraded comprehensive multilocus phylogeny of the Tardigrada tree of life

AbstractProviding accurate animals’ phylogenies rely on increasing knowledge of neglected phyla. Tardigrada diversity evaluated in broad phylogenies (among phyla) is biased towards eutardigrades. A comprehensive phylogeny is demanded to establish the representative diversity and propose a more natural classification of the phylum. So, we have performed multilocus (18S rRNA and 28S rRNA) phylogenies with Bayesian inference and maximum likelihood. We propose the creation of a new class within Tardigrada, erecting the order Apochela (Eutardigrada) as a new Tardigrada class, named Apotardigrada comb. n. Two groups of evidence support its creation: (a) morphological, presence of cephalic appendages, unique morphology for claws (separated branches) and wide‐elongated buccopharyngeal apparatus without placoids, and (b) phylogenetic support based on molecular data. Consequently, order Parachela is suppressed and its superfamilies erected as orders within Eutardigrada, maintaining their current names. We propose a new classification within the family Echiniscidae (Echiniscoidea, Heterotardigrada) with morphological and phylogenetic support: (a) subfamily Echiniscinae subfam. n., with two tribes Echiniscini tribe n. and Bryodelphaxini tribe n.; (b) subfamily Pseudechiniscinae subfam. n., with three tribes Cornechiniscini tribe n., Pseudechiniscini tribe n. and Anthechiniscini tribe n.; and (c) subfamily Parechiniscinae subfam. n., with two tribes Parechiniscini tribe n. and Novechiniscini tribe n. Reliable biodiversity selection for tardigrades in broad phylogenies is proposed due to biased analyses performed up to now. We use our comprehensive molecular phylogeny to evaluate the evolution of claws in the clawless genusApodibiusand claw reduction across the Tardigrada tree of life. Evolutionary consequences are discussed.

Hypsibius vaskelae, a new species of Tardigrada (Eutardigrada, Hypsibiidae) from Russia.

Hypsibius vaskelae sp. nov. (Tardigrada, Eutardigrada, Hypsibiidae) is described from a freshwater sample collected in the vicinity of Saint-Petersburg. The new species has wrinkled cuticle, bucco-pharyngeal apparatus with two elongate macroplacoids and septulum, and cuticular bars between the bases of inner and outer claw and near the base of the inner claw on legs I-IV. Hypsibius vaskelae sp. nov. is most similar to Hypsibius marcelli Pilato, 1990 and H. septulatus Pilato, Binda, Napolitano Moncada, 2004, but differs from both in having wrinkled dorsal cuticle, thinner claws, and presence of lunules on the claws of all legs.

Two new species of Eutardigrada from Victoria Land, Antarctica

Two new species are recorded from Victoria Land (Antarctica): Mixibius felix sp. nov. and Milnesium validum sp. nov. A third species, Diphascon sanae Dastych, Ryan & Watkins, 1990, is a new report for this region of the Antarctic continent. Mixibius felix sp. nov. has a smooth cuticle, eyes present, bucco-pharyngeal apparatus of the Mixibius type (rigid buccal tube without ventral lamina and with hook-shaped asymmetrical apophyses for the insertion of the stylet muscles); stylet supports inserted on the buccal tube at 65.7–68.0% of its length; pharyngeal bulb with apophyses and two macroplacoids; microplacoid and septulum absent; as is characteristic of the genus, the external claws are of Isohypsibius type and the internal are a modified Isohypsibius type. Milnesium validum sp. nov. has smooth cuticle; eye spots present; six triangular peribuccal lamellae with basal stripes; stylet supports inserted on the cylindrical buccal tube at 61.1–64.8% of its length; claw configuration [3-3]-[3-3] (i.e. all secondary claws with three points); secondary claws stout, with distal portion clearly wider than the basal portion and each with a rounded basal thickening (lunule); primary claws with accessory points; a long cuticular bar present under claws I–III. Adding the three above mentioned species, the list of species present in Victoria Land rises from 12 to 15; 11 of these are recorded exclusively to this region of the Antarctic continent.

An integrative revision of Mesocrista Pilato, 1987 (Tardigrada: Eutardigrada: Hypsibiidae)

ABSTRACTMesocrista is a Holarctic tardigrade genus currently classified within the subfamily Itaquasconinae (Eutardigrada: Parachela: Hypsibiidae). The position of the genus has been so far inferred solely on the basis of light microscopy observations. Here, we present the first-ever scanning electron microscopy images of a dissected bucco-pharyngeal apparatus and DNA sequences for Mesocrista from Spitsbergen, mainland Norway and Poland. The new data allowed an integrative redescription of the nominal M. spitzbergensis from the locus typicus and uncovered a new species, M. revelata, from the European localities. The two species differ phenotypically by the oral cavity armature and claw morphology as well as by a number of morphometric traits, and they are also distinct genetically in all sequenced DNA markers, three nuclear (18S rRNA, 28S rRNA, ITS-2) and one mitochondrial (COI). Both molecular and morphometric data presented in this paper suggest that previous records of M. spitzbergensis should be treated with caution, since most probably some of them signify different Mesocrista species. Our phylogenetic analysis confirmed that Mesocrista is indeed a member of the Itaquasconinae. We also found that the most closely related, among genera for which there are molecular data available, is Adropion, from which Mesocrista differs by the shape of the apophyses for insertion of stylet muscles and the width of the bucco-pharyngeal tube. Finally, we advocate that Diphascon marcusi, a rare species hypothesised to represent either Mesocrista or Adropion, should be transferred to the latter genus and that the species should be redescribed to confirm its validity and systematic position.http://zoobank.org/urn:lsid:zoobank.org:pub:6515D58D-8469-4854-8687-177232112BDA

Two new freshwater eutardigrade species from Sicily.

Two new species of freshwater Eutardigrada are described from Sicily: Isohypsibius rusticus sp. nov. and Isohypsibius zappalai sp. nov. The former species has eye spots, ornamented body surface with many, variously sized tubercles; bucco-pharyngeal apparatus of the Isohypsibius type; pharyngeal bulb with apophyses and two rod-shaped macroplacoids; microplacoid absent; claws, of the Isohypsibius type, well developed, with long and thin common basal portion; main branches of all claws without free accessory points; very thin lunules present; cuticular bars on the legs absent. Isohypsibius zappalai sp. nov. has eye spots; entire body surface with small tubercles rounded in shape, fairly uniformly sized and tending to form transverse lines; bucco-pharyngeal apparatus of the Isohypsibius type, pharyngeal bulb with apophyses and two macroplacoids; microplacoid absent; claws of the Isohypsibius type, well developed, with long common basal portion and both main and secondary branches with a wide proximal portion. Main branches of all claws with accessory points; small, flexible lunules present; cuticular bars on the legs absent.

Soil tardigrade biodiversity with the description of a new eutardigrade genus and its phylogenetic position

Sixteen tardigrade species have been identified from a total of 943 specimens isolated from 69 positive soil samples collected in southern Spain (Andalusia, Huelva). Three genera (Hexapodibius, Xerobiotus and the new genus Sarascon) and eight species are new records for the Iberian Peninsula, increasing Iberian tardigrade biodiversity by 6%, and 10 species are new records for soil habitats, increasing soil tardigrade biodiversity by 9% (from 96 to 108 species). A newly discovered species and genus are described, followed by an analysis and discussion of the species' phylogenetic position and synapomorphies, based on morphological and total evidence (morphology and molecular – 18S and 28S rRNA – data combined) phylogenetic analyses. The new genus is distinguished from other Itaquasconinae genera, to which it is phylogenetically related, by having a Parascon buccopharyngeal apparatus and Ramajendas claws. In contrast to general eutardigrade evolution, which is primarily determined by claw morphology, itaquasconid evolution is more related to buccopharyngeal apparatus morphology, which shows homoplastic evolution at superfamily, family and subfamily levels, and also defines functional trophic groups in soil-related environments.http://zoobank.org/urn:lsid:zoobank.org:pub:068B9D87-27E2-4B26-8920-FF03CEF9869A

Looking at tardigrades in a new light: using epifluorescence to interpret structure.

The use of epifluorescence microscopy coupled with ultraviolet (UV) autofluorescence is suggested as a means to view and interpret tardigrade structures. Endogenous fluorochromes are a known component of tardigrade cuticle, claws and bucco-pharyngeal apparatus. By imaging the autofluorescence from tardigrades, it is possible to document these structures in detail, including the subdivisions and boundaries of echiniscid (heterotardigrade) plates and the nature and spatial relationships of the texture (pores, granules, papillae and tubercles) on the various plates. This allows the determination of taxonomic features not easily seen with other microscopic techniques.

High level of phenotypic homoplasy amongst eutardigrades (Tardigrada) based on morphological and total evidence phylogenetic analyses

Much of what is known about the phylogenetic relationships of the neglected phylum Tardigrada comes from molecular data, rather than from morphology-based phylogenetic studies. Several molecular phylogenies have been proposed, but morphological and total evidence phylogenetic approaches are scarce. We performed the first morphological phylogeny (based on maximum parsimony and Bayesian inference) including all genera from the class Eutardigrada. Furthermore, we carried out a total evidence approach adding molecular information available in public databases. We compared the morphological and total evidence phylogenies with current molecular hypotheses and Eutardigrada classifications, which our results partially support. These classifications were supported only when homoplastic characters (related to the buccopharyngeal apparatus) were excluded. The importance of morphological phylogenies is discussed as well as their utility for questioning current phylogenetic hypotheses and classifications based solely on molecular information. Lastly, we propose evolutionary hypotheses about eutardigrade phylogenetic relationships that should be tested based on our morphological results. © 2013 The Linnean Society of London

Definition of families, subfamilies, genera and subgenera of the Eutardigrada, and keys to their identification

The systematic arrangement of the Eutardigrada has radically changed since 1969 due to the new evaluation of characteristics of the claws and of the bucco-pharyngeal apparatus and the use of some characters overlooked before. After that date, as a consequence, four new families and 40 genera have been instituted. Given the changes and number of novelties, the authors have updated the definitions of all familial and generic taxa and have provided keys to aid identification.

Minibiotus xavieri, a new species of tardigrade from the Parque Biologico de Gaia, Portugal (Eutardigrada: Macrobiotidae)

A new tardigrade, Minibiotus xavieri sp. nov., is described from lichen and moss samples collected in Parque Biologico de Gaia, Avintes, Portugal. The new species has variously shaped pores forming transverse bands around the cuticle; granulation on legs absent. Peribuccal lamellae absent, peribuccal papulae present as in all species of Minibiotus. Buccal tube narrow with an anterior bend; pharyngeal bulb with apophyses, three small macroplacoids and microplacoid. Minibiotus xavieri sp. nov. differs from the species of the genus with a similar cuticular ornamentation (with pores of variable shape forming transverse bands) (M. eichorni Michalczyk & Kaczmarek, 2004, M. orthofasciatus Fontoura, Pilato, Lisi & Morais, 2009, M. vinciguerrae Binda & Pilato, 1992, M. furcatus (Ehrenberg, 1859)) in some qualitative or quantitative characters of the bucco-pharyngeal apparatus, and/or claws and of the eggs. The new species is also similar to two species today ascribed to the genus Macrobiotus but whose systematic position needs to be better analyzed, Macrobiotus lazzaroi Maucci 1986 and Macrobiotus pseudofurcatus Pilato, 1972. Minibiotus xavieri sp. nov. differs from them in some characters of the animal (narrower buccal tube, some characters of the claws) and of the eggs.

Tardigrades of the Seychelles Islands, with the description of three new species

In the context of the project “The Nature Protection Trust of Seychelles”, three species new to science are described (Macrobiotus creber sp. n., Macrobiotus perfidus sp. n. and Macrobiotus diguensis sp. n.) and two species (Macrobiotus madegassus and Minibiotus continuus) are recorded for the Seychelles for the first time. Macrobiotus creber sp. n. belongs to the furciger group but it differs from the members of this group in some metric characters of the buccopharyngeal apparatus, or of the claws, and in some characters of the eggs. Macrobiotus perfidus sp. n. is similar to M. pseudocoronatus but it differs from it in having small cuticular tubercles, in lacking an anterior band of teeth and a less developed posterior ring of triangular teeth in the buccal cavity, in having slightly shorter macroplacoids, slightly longer and slender claws and in characters of the eggs. Macrobiotus diguensis sp. n. is similar to M. snaresensis and M. erminiae but it differs from them in metric characters of the bucco-pharyngeal apparatus, in having more slender claws and in some characters of the eggs.

Bindius triquetrus gen. nov. sp. nov. (Eutardigrada, Hypsibiidae) from Sicily (Italy)

A new species is described for which a new genus, Bindius gen. nov., is also instituted. This new genus belongs to the family Hypsibiidae. The claws are of the Hypsibius type; the bucco-pharyngeal apparatus is of the Diphascon model (i.e., with an anterior rigid buccal tube and a posterior, flexible pharyngeal tube), and it is a variant of the Diphascon type; it is characterized by large apophyses for the insertion of the stylet muscles, asymmetrical with respect to the frontal plane for shape and dimensions; the dorsal apophysis is triangular in shape with rectilinear dorsal margin and posterior apex very distant from the buccal tube wall; the ventral apophysis is similar to the one of Diphascon, i.e., in the shape of a semilunar hook, but larger. The new species, Bindius triquetrus sp. nov., has smooth cuticle; eye spots absent; elongated pharyngeal bulb with small apophyses and three long, rod-shaped macroplacoids; a small, very faint, microplacoid may be present; septulum absent; claws slender; lunules and other cuticular thickenings on the legs absent.

Tardigrades from Portugal: four new records and description of two new species

Six species of Eutardigrada are recorded from Portugal; four of them, Macrobiotus crenulatus Richters, 1904, Hypsibius seychellensis Pilato, Binda & Lisi, 2006, Diphascon (Diphascon) pingue (Marcus, 1936) and D. (Diphascon) patanei Binda & Pilato, 1971 are recorded for the first time in Portugal. Two species, Minibiotus orthofasciatus sp. nov. and Bertolanius (new name of Amphibolus) portucalensis sp. nov. are new to science. Minibiotus orthofasciatus sp. nov. is one of the species of the genus with three macroplacoids, microplacoid and cuticular pores forming transverse bands. The new species differs from all existing species by one or more of the following characters: distribution of the pores, shape of the pores, absence of dots on the legs, level of insertion of the stylet supports on the buccal tube. To the new species is attributed an unembryonated egg similar to those of Minibiotus intermedius (Plate, 1888), M. poricinctus Claxton, 1998, M. floriparus Claxton, 1998, and M. weglarskae Michalczyk, Kaczmarek & Claxton, 2005 but different from them in some details. Bertolanius portucalensis sp. nov. is very similar to the other species of the genus, but it differs from them in having very small cuticular tubercles. From some of them it differs by characters of the buccopharyngeal apparatus and/or of the eggs. This is the first record of the genus and of the Eohypsibiidae family in the Iberian Peninsula.

Description of three new species of Tardigrada from the Seychelles

In the context of the project “The Nature Protection Trust of Seychelles”, three species new to science are described: Calcarobiotus (Calcarobiotus) parvicalcar sp. n., Macrobiotus modestus sp. n., and Itaquascon pisoniae sp. n. Calcarobiotus (Calcarobiotus) parvicalcar sp. n. differs from the other species of the genus in having very small basal spurs of the claws; from some of them also in lacking eyes or in metric characters of placoids or claws. Macrobiotus modestus sp. n. has a very simple buccal armature (only three thin transverse ventral ridges are present and the three dorsal ridges are joined together forming a single transverse dorsal arc), and a long and narrow buccal tube with stylet supports inserted at 67–70 % of its length. It differs from the most similar species, Macrobiotus humilis and Macrobiotus madegassus, in some characteristics of bucco-pharyngeal apparatus and eggs. Itaquascon pisoniae sp. n. has the buccal tube slightly longer than the pharyngeal tube (pbf index = 54–55), pharyngeal apophyses and placoids are absent, a very faint cuticular bar near the internal claws of the first three pairs of claws, and no cuticular thickenings on the hind legs. It differs from the most similar species of the genus, Itaquascon placophorum, in having a smooth cuticle, shorter claws, in lacking placoid and the cuticular bar between the claws of the hind legs. Including this study, 30 species are recorded in the Seychelles, 15 of which are currently considered endemic for that archipelago.