Witold Morek

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.