Piotr Gąsiorek

Determinants and taxonomic consequences of extreme egg shell variability in Ramazzottius subanomalus (Biserov, 1985) (Tardigrada)

Nearly a half of known eutardigrade species lay ornamented eggs. The ornamentation is thought to provide attachment of the egg to the substrate and protection for the developing embryo, but from the taxonomic point of view chorion morphology may also provide key characters for species differentiation and identification, especially between closely related taxa. Nonetheless, despite the evolutionary and taxonomic importance of the egg shell, the determinants of its morphology are very poorly, if at all, understood. Here, we combine morphological, molecular and experimental approaches in an attempt to separate the genetic and environmental factors that shape egg chorion morphology in Ramazzottius subanomalus (Biserov, 1985). Our integrative study, based on a population of R. subanomalus isolated from a single moss sample, revealed (1) remarkable variation in egg shell morphology, but (2) relatively little variation in animal morphometric traits, and (3) genetic differentiation, expressed as two ITS-2 haplotypes, but no parallel polymorphism in COI. Although animals did not differ morphometrically between the haplotypes, eggs laid by haplotype 1 and 2 females exhibited highly statistically significant differences in all measured traits. The study demonstrates, for the first time, a correlation between phenotypic and genetic variability within a tardigrade species. The revealed congruence between genetic and morphological traits might be viewed as an example of incipient speciation that illustrates early evolutionary steps leading to species complexes that differ primarily in terms of egg shell morphology. Moreover, our data confirm the value of the ITS-2 fragment in distinguishing very closely related tardigrade lineages.

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

ABSTRACT Mesocrista 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

Unmasking hidden species diversity within the Ramazzottius oberhaeuseri complex, with an integrative redescription of the nominal species for the family Ramazzottiidae (Tardigrada : Eutardigrada : Parachela)

Outdated and inaccurate original descriptions of species nominal for genera or species complexes give birth to notorious difficulties in species identification and often translate into erroneous classifications of multiple species as one. This, in turn, results in severe overestimations of specific geographic ranges and ultimately in underestimations of the diversity of organisms living on our planet. Tardigrades, ubiquitous microscopic metazoans exhibiting relatively few taxonomically useful traits, bear many such problematic species. In this paper, we investigated, morphologically and molecularly, 10 European populations of Ramazzottius cf. oberhaeuseri (Doyère, 1840), a putatively cosmopolitan nominal species for the family Ramazzottiidae. The analysis of COI sequences revealed eight potential species, including one from Paris, the type locality of R. oberhaeuseri, which we used to integratively redescribe the nominal taxon. The identification of seven further species in a handful of samples collected from a single continent explicitly shows the considerable undescribed species diversity within this group and puts in question the cosmopolitan distribution of R. oberhaeuseri. The integrative redescription of R. oberhaeuseri opens the opportunity for descriptions of other species in the complex. http://zoobank.org/urn:lsid:zoobank.org:pub:50B99B53-C317-4DBD-8CF1-16297B85C4F3

Description of Macrobiotus scoticus sp. nov. (Tardigrada : Macrobiotidae : hufelandi group) from Scotland by means of integrative taxonomy

Abstract. A new species of the Macrobiotus hufelandi group is described from Scotland. Both light and scanning electron microscopy were used for collecting morphological and morphometric data whereas genotyping allowed sequences for three nuclear (18S rRNA, 28S rRNA and ITS-2) and one mitochondrial (COI) DNA fragment to be obtained. By undertaking in vitro culturing, we were able to obtain a number of eggs and provide a detailed description. Macrobiotus scoticus sp. nov. exhibits a reduced oral cavity armature, with only the ridges of the third band of teeth visible under light microscopy, therefore the animals of the new species are most similar to individuals of M. almadai Fontoura et al., 2008; M. diversus Biserov, 1990; M. madegassus Maucci, 1993; M. martini Bartels et al., 2009; M. modestus Pilato and Lisi, 2009; and M. paulinae Stec et al., 2015. However, M. scoticus sp. nov. lays eggs with strongly modified processes, which makes this species unique not only among the species listed above but from all hufelandi group taxa. In contrast to mushroom-shaped egg processes found in the majority of the hufelandi complex species, processes in M. scoticus sp. nov. are in the shape of spatulas, with longitudinally flattened terminal portions. Superficially, the eggs of the new species resemble those of M. kristenseni Guidetti et al., 2013, which exhibits elongated, spike- or filament-like processes. Nonetheless, the eggs of M. kristenseni have a smooth inter-process surface whereas in the new species the surface is covered with a very dense reticulum. Moreover, M. kristenseni has a better developed oral cavity armature, with all three bands of teeth detectable under light microscopy.

The tardigrade fauna of Tunisia, with an integrative description of Bryodelphax maculatus sp. nov. (Heterotardigrada: Echiniscidae)

The current knowledge of the diversity and distribution of tardigrade species in northern Africa is scarce and far from satisfactory. In this paper we review old and provide new faunistic records for various regions of Tunisia. Among the newly recorded taxa, we found a new heterotardigrade Bryodelphax maculatus sp. nov. The new species belongs to the weglarskae group, characterised by the presence of ventral plates, but differs from its congeners by a different arrangement of ventral plates and by conspicuous groups of cuticular tubercles on the ventral cuticle. The analysis of larval, juvenile and mature instars of the new species revealed, for the first time in heterotardigrades, ontogenetic variability in the development of ventral armature.

Untangling the Echiniscus Gordian knot: Stellariscus gen. nov. (Heterotardigrada : Echiniscidae) from Far East Asia

Abstract. Species constituting the family Echiniscidae are highly derived, armoured and inhabit terrestrial habitats, in contrast to other heterotardigrades that are predominantly marine. The genus Echiniscus C.A.S. Schultze, 1840, nominal for the family Echiniscidae, is currently the most speciose tardigrade genus. However, the great morphological variability, in comparison with other heterotardigrade genera, suggests the polyphyletic character of the genus. Here, we analyse new specimens of Echiniscus pseudelegans Séméria, 1994 collected in Japan and conclude that the species as well as two other related taxa, E. elegans Richters, 1907 and E. latifasciatus Dudichev and Biserov, 2000, represent a new genus, Stellariscus, gen. nov. The new genus is characterised by a mixture of peculiar morphological apomorphies: black eyes, star-like dorsal plate sculpturing, no trunk appendages (only cephalic cirri present), two types of ventral plates, and striking sexual dimorphism in both qualitative and quantitative traits. Morphological phylogeny of the family Echiniscidae suggests a close affinity between Stellariscus, Hypechiniscus Thulin, 1928 and Pseudechiniscus Thulin, 1911. The polyphyletic status of both Echiniscus and Testechiniscus Kristensen, 1987 is also inferred. The taxonomic significance of ventral armature in echiniscid phylogeny and taxonomy is discussed.

Three Echiniscidae species (Tardigrada: Heterotardigrada) new to the Polish fauna, with the description of a new gonochoristic Bryodelphax Thulin, 1928

During a faunistic survey in the Pieniny and Tatra Mountains three species of Echiniscidae new to Poland, including one new to science, were found. Bryodelphax instabilis sp. nov. is characterised by an instable number of ventral plates, deep faceting of the scapular plate, having dorsal plates covered either with pseudopores or pores, and striking sexual dimorphism. Two first records, namely Echiniscus militaris and E. spiniger, are rare taxa of upland-mountain character, which have already been reported from a few European countries since the original description at the beginning of the XXth century. The interspecific appendage length variability and development of pedal plates in the spinulosus group, to which E. spiniger belongs, and their taxonomic importance is discussed. Notes relating to sexual dimorphism within the newly recorded Pseudechiniscus facettalis, are also presented. Echiniscus testudo is reported from the Polish part of the Tatra Mountains for the first time. Succeeding findings confirm the high tardigrade α-diversity in the Polish mountain ranges. An amended key for Polish Heterotardigrada is provided.

Echiniscidae (Heterotardigrada) of Tanzania and Uganda

Faunistic survey of Tanzania and Uganda resulted in the finding of eight species belonging to the genus Echiniscus C.A.S. Schultze, 1840, three of which are new to science. Echiniscus belloporus n. sp. has no trunk cirri and dorsal plates densely covered with pores (sculpture of the spinulosus type); it lacks a spine I and the dentate collar IV, a combination of traits so far unseen in Echiniscus. Echiniscus ornamentatus n. sp. possesses regularly distributed pores on its dorsal plates, scapular and caudal plates with contrasting faceting, and anterior portions of the paired plates distinctly darker than their posterior parts. Echiniscus tristis n. sp. is also a new member of the spinulosus group, but differs from all other species of this complex by having small pores, a trunk appendage combination C-Dd-E, and large spurs on its internal claws. Three other species: Echiniscus baius, Echiniscus dariae and Echiniscus manuelae, are recorded as new additions to the African fauna. Two last species: Echiniscus africanus and Echiniscus cirinoi, are scarcely reported elements of the Afrotropical fauna. Scanning electron microscopy microphotographs supplementing the description of E. dariae, and amendments to the outdated description of E. manuelae are also provided. http://zoobank.org/urn:lsid:zoobank.org:act:B8494205-58D5-4E54-B54E-2C40976892E1http://zoobank.org/urn:lsid:zoobank.org:act:F439D375-F44F-4C3A-997F-EDC0D0A45F88http://zoobank.org/urn:lsid:zoobank.org:act:B602FA08-3E17-4149-A1FE-22829E13DFFD

Temperature (latitude) and nutrient (seabird guano) effects on limno-terrestrial Tardigrada (Testechiniscus spitsbergensis and Pilatobius recamieri) body size

ABSTRACT Surveys of terrestrial microinvertebrate morphometry, especially spatial patterns of body size at wider geographical scales, including the polar regions, are very scarce. In this study, we focused on Tardigrada, common limno-terrestrial microinvertebrates. Considering Bergmann’s rule, originally formulated for endothermic animals, we tested the hypothesis that body length of limno-terrestrial tardigrades augments with increasing latitude and decreasing temperature. Since some of our sampling areas adjoined seabird colonies, we also explored the effects of nutrients from seabird guano deposits. Individual body length of Testechiniscus spitsbergensis was measured in populations obtained from seven localities distributed along a latitudinal gradient extending from 45°N (northern Italy) to 80°N (northern Svalbard), and for Pilatobius recamieri from three localities in Svalbard (77°N-80°N). Considering both latitude and proximity to a seabird colony there were significant effects of locality on the body length of T. spitsbergensis; however, no clear pattern of increasing individual body size with increasing latitude could be detected. Immense differences in body size may be a signal for cryptic species diversity within this genus. No effect of latitude, or proximity to a seabird colony, on the body length of Arctic populations of P. recamieri was documented. Evidently, there is no tendency towards body size increase along the latitudinal gradient in either T. spitsbergensis or P. recamieri. Our study, and recent literature, indicates that larger body size in polar regions reported for several groups of micro-fauna may be a taxon-dependent response, and cannot be taken as a universally applicable rule for limno-terrestrial animals.

Echiniscus testudo (Doyère, 1840) in New Zealand: anthropogenic dispersal or evidence for the ‘Everything is Everywhere’ hypothesis?

ABSTRACT Many species of microscopic invertebrates, such as tardigrades or rotifers, have been traditionally regarded as cosmopolitan. This conviction was based on classical taxonomic observations of very similar phenotypes across the globe and hypothetical abilities of micrometazoans for large-scale dispersal with air and water currents. However, several recent studies showed that micrometazoan species may have restricted geographic ranges, suggesting that microscopic size is not the only determinant of dispersal. Here, we describe the first Australasian record of Echiniscus testudo, a heterotardigrade originally described from the Holarctic. Morphological and genetic analyses gave congruent conclusions and confirmed that European and New Zealand populations represent a single species. Importantly, however, without broader sampling in primeval localities, it is not possible to test whether the New Zealand record of E. testudo is a result of natural dispersal or whether the species was brought to Australasia by humans.