Nigel Marley
Plymouth University, Marine Biology and Ecology Research Centre (MBERC), Department Member
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... Subdivisions of the Phylum Tardigrada with habitat classifications: ... Positive identification with keys in the current literature may be difficult because of inadequate and often vague generic descriptions, additions of new genera... more
... Subdivisions of the Phylum Tardigrada with habitat classifications: ... Positive identification with keys in the current literature may be difficult because of inadequate and often vague generic descriptions, additions of new genera ... An updated comprehensive key would be very useful. ...
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Little is known about distribution patterns of micrometazoan organisms at different spatial scales and the mechanisms driving these patterns across different environments. Here we explore the fine-scale structure of tardigrades in a... more
Little is known about distribution patterns of micrometazoan organisms at different spatial scales and the mechanisms driving these patterns across different environments. Here we explore the fine-scale structure of tardigrades in a high-elevation <i>Polylepis</i> forest in northern Ecuador. To investigate spatial patterns of tardigrade abundance, we collected samples from different bryophyte taxa (hosts) on the woodland floor. We identified some tardigrades to species, but most taxa were considered at the level of morphological operational taxonomic units. Tardigrade assemblages differed in composition between host taxa, with some tardigrade taxa associated more with certain hosts, which might relate to host architecture or chemistry. Tardigrade occupancy, richness and abundance varied considerably between samples, and we estimate that more than 50 samples are required to estimate tardigrade taxon richness in this forest habitat. Physical distance between samples was no...
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Key to the species of the genus <i>Platicrista</i> 1. With additional cuticular bar on legs............................................................................. 2 Without additional cuticular bars on... more
Key to the species of the genus <i>Platicrista</i> 1. With additional cuticular bar on legs............................................................................. 2 Without additional cuticular bars on legs..................................................................... 3 2. Legs I–III with an oblique cuticular bar on the internal side of the leg from near the base of the internal claw. All legs with a small transverse cuticular bar, positioned between the base of the internal and external claws, but not touching the bases. Cuticle with polygonal pattern <i>..................................................................... Platicrista cheleusis</i> Legs I–III with oblique cuticular bar on the internal side of the leg from near the base of the internal claw. No small transverse cuticular bar present positioned between bases of the internal and external claws on any of the legs. Cuticle without polygonal pattern <i>.........................
FIGURES 11–12. Holotype of Platicrista ramsayi sp. nov. 11) buccopharyngeal tube, 12) spiral annulations on the pharyngeal tube and the thin sets of placoids. PhC, scale bars = 10µm.
FIGURES 4–7. Paratype 1, Platicrista ramsayi sp. nov., 4–6), claws of leg pairs I–III respectively showing the oblique cuticular bars; 7) buccopharyngeal apparatus. DIC, scale bars 4 –7 = 10µm.
FIGURE 2. Simplified topographical map with the collecting stations (numbered 1–5) for the broader study. Map produced by Dr. Paul Ramsay.
FIGURE 3. Holotype, Platicrista ramsayi sp. nov., (drawn from phase contrast microscope; PhC). Scale bar = 100µm.
FIGURE 1. Map of the location of Volcán Chiles on the international border between Colombia and Ecuador. Map produced by Dr. Paul Ramsay.
FIGURES 8–10. Holotype of Platicrista ramsayi sp. nov. 8–9) claws on leg III with the oblique cuticular bar; 10) claws of leg IV showing the smooth expanded bases without lunules. PhC, scale bars = 10 µm.
FIGURE 4. Stylised diagrams of the apophysis for the insertion of the stylet muscles (AISM) (in lateral view, left —dorsal, right—ventral). Hook shaped AISM of Hypsibioidea, Hypsibiidae, Hypsibiinae: A. Hypsibius, simple hooks; B.... more
FIGURE 4. Stylised diagrams of the apophysis for the insertion of the stylet muscles (AISM) (in lateral view, left —dorsal, right—ventral). Hook shaped AISM of Hypsibioidea, Hypsibiidae, Hypsibiinae: A. Hypsibius, simple hooks; B. Borealibius, modified spherical hooks; C. Acutuncus, accentuated hooks. Modified hook shaped AISM of Hypsibioidea, Microhypsibiidae: D. Microhypsibius, accentuated hook and hook with ridge. Modified hook shaped AISM of Hypsibioidea, Calohypsibiidae: E. Calohypsibius, triangular hook and triangular hook with triangular ridge. Modified hook shaped AISM of Hypsibioidea, Ramazzottidae: F. Hebesuncus, asymmetric triangular and basic hook, G. Ramazzottius, asymmetric hooks. Ventral crest ASIM of the Macrobiotoidea, Macrobiotidae: H. Macrobiotus, asymmetric crest, 10 peribuccal lamellae present. Ventral crest ASIM of the Macrobiotoidea, Murrayidae: I. Dactylobiotus, asymmetric crest with hook, 10 peribuccal lamellae present. Ridge shaped AISM of Eohypsibioidea, E...
FIGURE 3. Diagrammatic representation of Parachela claw structure and nomenclature. A. Exploded diagram of a parachelan claw to explain component parts. a—accessory spines; b—basal tract; l—lunule (edge may be smooth or dentate);... more
FIGURE 3. Diagrammatic representation of Parachela claw structure and nomenclature. A. Exploded diagram of a parachelan claw to explain component parts. a—accessory spines; b—basal tract; l—lunule (edge may be smooth or dentate); p—primary branch; s—secondary branch. B. Stylised diagram of macrobitid claw (2112). Secondary branch—2; primary branch—1; primary branch—1; secondary branch—2. C. Stylised diagram of a hypsibid claw (2121). Secondary branch—2; primary branch—1; secondary branch—2; primary branch—1. D. Stylised diagram of: i—isohypsibid (basal section and secondary branch at right angles) and h—hypsibid (basal section and secondary branch forming continuous arc) claws. E. Stylised diagram of Eohypsibiidae-type claw—claws are clearly delineated by septa into basal section, secondary branch and primary branch.
Intra- and interspecific variability, being at the very core of alpha taxonomy, has been a long-standing topic of debate among tardigrade taxonomists. Early studies tended to assume that tardigrades exhibit wide intraspecific variation.... more
Intra- and interspecific variability, being at the very core of alpha taxonomy, has been a long-standing topic of debate among tardigrade taxonomists. Early studies tended to assume that tardigrades exhibit wide intraspecific variation. However, with more careful morphological studies, especially those incorporating molecular tools that allow for an independent verification of species identifications based on phenotypic traits, we now recognise that ranges of tardigrade intraspecific variability are narrower, and that differences between species may be more subtle than previously assumed. The taxonomic history of the genus Milnesium, and more specifically that of the nominal species, M. tardigradum described by Doyère in 1840, is a good illustration of the evolution of views on intraspecific variability in tardigrades. The assumption of wide intraspecific variability in claw morphology led Marcus (1928) to synonymise two species with different claw configurations, M. alpigenum and M...
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FIGURE 1. Phylogenetic topology of the Tardigrada. A. Phylogenetic topology of the Tardigrada based on the current systematic knowledge. B. Proposed phylogenetic topology of the Parachela with the new super families.
The preservation of tardigrade eggs and exuviae in Antarctic lake sediments provided an opportunity to assess post-glacial colonisation and Holocene tardigrade dynamics on the southern continent. Tardigrade eggs were recovered from five... more
The preservation of tardigrade eggs and exuviae in Antarctic lake sediments provided an opportunity to assess post-glacial colonisation and Holocene tardigrade dynamics on the southern continent. Tardigrade eggs were recovered from five lakes, two from the maritime Antarctic and three from continental Antarctica. Eggs were identified from the following species: Dactylobiotus cf. ambiguus, Macrobiotus furciger, Macrobiotus blocki, Minibiotus weinerorum and Acutuncus antarcticus. Other, unornamented eggs were also observed. The preservation of some of these eggs in exuviae allowed identification to at least genus. Significant variations were observed in egg abundance within the sediment of each lake, and in one lake a species (Dactylobiotus cf. ambiguus) became locally extinct, probably as the result of penguin-associated eutrophication. Tardigrades generally did not become abundant for a considerable period after the lakes ’ formation. The presence of an in-part endemic fauna is cons...
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FIGURE 4. The positions of M. alpigenum Ehrenberg, 1853 and M. inceptum sp. nov. on the Milnesium phylogenetic tree based on the concatenated data set of ITS-2 and COI sequences. Branch support values are BI posterior probabilities.... more
FIGURE 4. The positions of M. alpigenum Ehrenberg, 1853 and M. inceptum sp. nov. on the Milnesium phylogenetic tree based on the concatenated data set of ITS-2 and COI sequences. Branch support values are BI posterior probabilities. Species names in square brackets and in grey font are GenBank labels that are incorrect species identifications, uncertain identifications, or invalid names (correct identifications are provided in black font, before the incorrect labels). Filled circles represent both ITS-2 and COI sequences, empty circles indicate COI sequences only. Scale bar shows the number of substitutions per site.
FIGURE 3. Graphs illustrating the relationships between the first three principal components revealed by the PCA for the single population of M. alpigenum Ehrenberg, 1853 and the three pooled populations of M. inceptum sp. nov.
FIGURE 2. Milnesium inceptum sp. nov. A—habitus, ventral view (holotype, PCM). B—dorsal cuticle (holotype, German population, PCM). C—dorsal cuticle with faint pseudopores (specimen from Bulgaria, the white arrowhead indicates the area... more
FIGURE 2. Milnesium inceptum sp. nov. A—habitus, ventral view (holotype, PCM). B—dorsal cuticle (holotype, German population, PCM). C—dorsal cuticle with faint pseudopores (specimen from Bulgaria, the white arrowhead indicates the area where the pseudopores are more densely arranged, PCM). D—dorsal cuticle with the barely visible outline of a pseudoplate (paratype, SEM). E—pseudoplate surface (paratype, SEM). F—buccal apparatus (holotype, PCM). G—six peribuccal lamellae with the 4+2 configuration. H—claws I with the cuticular bar below (paratype, PCM). I—claws IV (paratype, PCM). All scale bars in µm.
FIGURE 1. Milnesium alpigenum Ehrenberg, 1853. A—habitus, ventral view (neotype, PCM). B—habitus, dorsal view (SEM). C—dorsal cuticle, the arrow indicates area with visible pseudopores (neotype, PCM). D—dorsal cuticle with the barely... more
FIGURE 1. Milnesium alpigenum Ehrenberg, 1853. A—habitus, ventral view (neotype, PCM). B—habitus, dorsal view (SEM). C—dorsal cuticle, the arrow indicates area with visible pseudopores (neotype, PCM). D—dorsal cuticle with the barely visible outline of a pseudoplate (neoparatype, SEM). E—buccal apparatus (neotype, PCM). F—six peribuccal lamellae with the 4+2 configuration (neoparatype, SEM). G—claws III with the cuticular bar below (neoparatype, PCM). H—claws IV (neotype, PCM). All scale bars in µm.
We assessed the available morphological evidence to see if this corroborates the paraphyly in the Parachela (Tardigrada) as suggested by recent molecular data. We reconcile molecular phylogenetics with alpha morphology, focusing on claw... more
We assessed the available morphological evidence to see if this corroborates the paraphyly in the Parachela (Tardigrada) as suggested by recent molecular data. We reconcile molecular phylogenetics with alpha morphology, focusing on claw and apophysis for the insertion of the stylet muscles (AISM). We combine molecular and morphological evidence to define six new taxa within the Parachela Schuster et al 1980. These include two new families of Isohypsibiidae fam. nov. and Ramazzottidae fam. nov. along with four new superfamilies of Eohypsibioidea superfam. nov., Hypsibioidea superfam. nov., Isohypsibioidea superfam. nov., and Macrobiotoidea superfam. nov.
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Introduction THE Tardigrada are microscopic animals which can be found around the world in a very wide variety of habitats including marine, brackish, freshwater and terrestrial interstitial systems. As a phylum they show great diversity... more
Introduction THE Tardigrada are microscopic animals which can be found around the world in a very wide variety of habitats including marine, brackish, freshwater and terrestrial interstitial systems. As a phylum they show great diversity in their feeding, reproductive and survival strategies. Feeding preferences range from bacteria and plant cells for some species, to Rotifer a, Nematoda and other Tardigrada for carnivorous species. There are even a few parasitic species, including Tetrakentron synaptae Cuenot which lives on the tentacles of the sea cucumber, Leptosynapta galienei Herapath, in the English Channel, (Ramazzotti & Maucci 1983). During unfavourable microclimate conditions many of the freshwater species encyst until optimal conditions return. However, terrestrial species have been shown to have remarkable survival abilities. Many of the terrestrial species can retract their legs and shrink their bodies into a barrel-shaped tun. Inside this structure they lose almost all ...
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This thesis is based on published papers, however there have been issues encountered with copyright permissions, therefore a fuller version may be submitted in the future.
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The recent re-description of Paramacrobiotus Guidetti, Schill, Bertolani, Dandekar and Wolf, 2009 has inadvertently led to the description of an objective synonym within its subgenera nominal taxa. To resolve this issue, we have... more
The recent re-description of Paramacrobiotus Guidetti, Schill, Bertolani, Dandekar and Wolf, 2009 has inadvertently led to the description of an objective synonym within its subgenera nominal taxa. To resolve this issue, we have re-described both subgenera, and proposed a new substitute name for one subgenus, in line with the International Code of Zoological Nomenclature. Additionally we have confirmed the placement of two recently published Paramacrobiotus species, not included in the last revision, within the respective subgenera established herein.
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... Subdivisions of the Phylum Tardigrada with habitat classifications: ... Positive identification with keys in the current literature may be difficult because of inadequate and often vague generic descriptions, additions of new genera... more
... Subdivisions of the Phylum Tardigrada with habitat classifications: ... Positive identification with keys in the current literature may be difficult because of inadequate and often vague generic descriptions, additions of new genera ... An updated comprehensive key would be very useful. ...