Extreme secondary sexual dimorphism in the genus Florarctus (Heterotardigrada: Halechiniscidae)

Secondary sexual dimorphism in florarctin tardigrades is a well-known phenomenon. Males are usually smaller than females, and primary clavae are relatively longer in the former. A new species Florarctus bellahelenae, collected from subtidal coralline sand just behind the reef fringe of Long Island, Chesterfield Reefs (Pacific Ocean), exhibits extreme secondary dimorphism. Males have developed primary clavae that are much thicker and three times longer than those present in females. Furthermore, the male primary clavae have an accordion-like outer structure, whereas primary clavae are smooth in females. Other species of Florarctus Delamare-Deboutteville & Renaud-Mornant, 1965 inhabiting the Pacific Ocean were investigated. Males are typically smaller than females, but males of Florarctus heimi Delamare-Deboutteville & Renaud-Mornant, 1965 and females of Florarctus cervinus Renaud-Mornant, 1987 have never been recorded. The Renaud-Mornant collection was re-examined, and type series were analysed. Florarctus heimi and F. cervinus were always found together in the coralline sand of Heron Island (Great Barrier Reef). The animals were kept alive and surveyed in the laboratory of the Queensland Museum. All studied individuals of the larger F. heimi (up to ca. 400 μm) were females, and all adults of the smaller F. cervinus (about 170 μm) were males. Males of F. cervinus were observed mating with females of F. heimi. Following those morphological and behavioural lines of evidence, we propose that F. cervinus is a junior synonym of F. heimi. Based on the discovery of dimorphism in F. bellahelenae sp. nov. and the strong sex-related morphological disparities in F. heimi, we suggest that extreme secondary dimorphism may be present in other florarctin arthrotardigrades

An integrative description of Mesobiotus ethiopicus sp. nov. (Tardigrada : Eutardigrada : Parachela : Macrobiotidae : harmsworthi group) from the northern Afrotropic region

A new species of the Mesobiotus harmsworthi group is described from Ethiopia. An integrative taxonomy approach was applied by combining morphological and morphometric analyses-imaging under phase contrast and scanning electron microscopy with molecular analysis (18S rRNA, 28S rRNA and COI markers)-to cross-verify the status of the population as a new species. The specimens of esobiotus ethiopicus sp. nov. are most similar to two taxa of the harmsworthi complex: M. harmsworthi obscurus (Dastych, 1985) and M. peterseni (Maucci, 1991). Nevertheless, the new species can be easily distinguished from the first of these taxa by the absence of additional teeth in the oral cavity and by a different accessory point morphology on the claws, and it can be distinguished from the second species mostly by a completely different egg process anatomy. Mesobiotus ethiopicus sp. nov. is only the second tardigrade species formally described as new for science from Ethiopia so far

A zoogeographic study of the limnoterrestrial fauna on the Faroe islands

The Faroe islands (62°N, 7°W) are an archipelago of 18 small islands situated in the northeast Atlantic ocean between Iceland and the Shetland islands. A zoogeographic investigation (2001-2004) of the limnoterrestrial tardigrade fauna of these islands revealed 48 limnoterrestrial species and subspecies and one marine species, of which 29 were new records for the Faroe islands. Among the findings were three species in the recently described genus belonging to the family Eohypsibiidae. A faunistic comparison was also done with Iceland, Svalbard islands, Disko island (Greenland), Greenland (West and East), Scotland, England and with Newfoundland. On the basis of presence/absence data of the tardigrade species from the different countries a cluster analysis was computed, based on Bray-Curtis similarities, and a dendrogram was constructed. The interesting results show that the Faroese tardigrade fauna is mostly similar with Iceland, which could be expected, but more surprising it is also very similar to the tardigrade fauna on Disko island (West Greenland). Several of the reported species exhibit a boreo-alpine disjunction (i.e. species only found in northern latitudes and in high altitudes farther south). These facts could indicate that the tardigrade fauna on the islands is very ancient and could have survived glaciation periods in refuges such as nunataks which occurred on the Faroes during glaciation periods. This study also includes a closer inspection of the altitudinal distribution of the tardigrade species found compared with similar data from Poland

An integrative description of Minibiotus ioculator sp. nov. from the Republic of South Africa with notes on Minibiotus pentannulatus Londoño et al., 2017 (Tardigrada: Macrobiotidae)

The genusMinibiotusis morphologically diverse, which may suggest its polyphyletic character. However,scarce genetic data and often also the lack of detailed morphological data currently do not allow for theverification of the relationships within this genus. Here, for the veryfirst time, we provide an integrativedescription of a newMinibiotusspecies.Minibiotus ioculatorsp. nov.from the Republic of South Africadiffers from other congeners mainly by egg ornamentation with processes on the egg shell that resemblethe hat of a royal jester. We also provide new taxonomic data onMinibiotus pentannulatusbased on apopulation newly found in Tanzania, which constitutes thefirst African record of this species originallydescribed from South America. Our study involved both classical taxonomic methods, which includemorphological and morphometric analyses conducted with the use of light and scanning electron mi-croscopy, and genetic data in the form of DNA sequences of four markers (three nuclear: 18S rRNA, 28SrRNA, ITS-2, and one mitochondrial: COI). The results of this study allow a discussion of speciescomposition withinMinibiotusand question the validity of the current diagnosis of the genus

Integrative taxonomy identifies two new tardigrade species (Eutardigrada: Macrobiotidae) from Greenland

In this paper we describe Macrobiotus engbergi sp. nov. and Tenuibiotus zandrae sp. nov. from Greenland. Our study has involved both classical taxonomic methods, which include morphological and morphometric analyses conducted with the use of light and scanning electron microscopy, and genetic analysis based on four molecular markers (three nuclear: 18S rRNA, 28S rRNA, ITS-2, and one mitochondrial: COI). Moreover, we re-examined the type series of Tenuibiotus voronkovi (Tumanov, 2007) as well as the original sample where the species was found and we provide new morphological data from light and scanning electron microscopy which enabled us to amend its description. Finally, we also analysed slides with animals and egg of two populations from Nordaustlandet and Edgeøya (archipelago of Svalbard, Norway) designated as T. voronkovi within its recent redescription. The results and comparisons presented in our study question the validity of this designation.

Genetic diversity in the parthenogenetic reproducing tardigrade <i>Echiniscus testudo</i> (Heterotardigrada: Echiniscoidea)

Little is known about the genetic structure of microscopic animals from mosses and lichens. A few studies have investigated the geographic variation in tardigrades from mosses, but so far no study has investigated the intra-population or local clonal lineage variation. Echiniscus testudo (Echiniscoidea: Echiniscidae) belongs to a large cosmopolitan genus of terrestrial tardigrades comprising more than 150 species. It is a common tardigrade in mosses in the temperate part of the Northern hemisphere, and is highly tolerant of desiccation and freezing. In a previous study, we reported a maximum of 1.28% sequence variation (uncorrected p-distance) in cytochrome c oxidase subunit I (COI) haplotypes between clonal lineages covering a large geographical area. However, in this previous study we used pooled specimens to constitute a sample, and the genetic diversity from single specimens within a locality therefore remains unknown. Accordingly, the present study investigates the COI sequence variation and haplotype diversity between single specimens of E. testudo collected at three Danish localities, separated by 80 m and 186 km. A total of 10 COI haplotypes were found in the present study (Et2, Et3, Et9, Et12-Et18); only three of these were previously reported (Et2, Et3 and Et9). The uncorrected COI sequence diversity ranged between 0-2.07%, with haplotype Et18 having the highest genetic difference. The second most variable haplotypes (Et14, Et15, and Et17) all showed a maximum diversity of 1.19% compared to the other haplotypes. No general pattern of haplotype distribution was evident. Our data suggest that E. testudo has dispersed across the Baltic sea as haplotypes Et3, Et13 and Et14 are present at all three localities. The most likely dispersal mode is passive wind dispersal in the cryptobiotic tun stage. The current study emphasises that numerous sequences from single specimens are needed to describe the genetic diversity within single moss cushions

Comparative myoanatomy of Tardigrada:new insights from the heterotardigrades <i>Actinarctus doryphorus</i> (Tanarctidae) and <i>Echiniscoides sigismundi</i> (Echiniscoididae)

Abstract Background Tardigrada is a group of microscopic invertebrates distributed worldwide in permanent and temporal aquatic habitats. Famous for their extreme stress tolerance, tardigrades are also of interest due to their close relationship with Arthropoda and Cycloneuralia. Despite recent efforts in analyzing the musculature of a number of tardigrade species, data on the class Heterotardigrada remain scarce. Aiming to expand the current morphological framework, and to promote the use of muscular body plans in elucidating tardigrade phylogeny, the myoanatomy of two heterotardigrades, Actinarctus doryphorus and Echiniscoides sigismundi, was analyzed by cytochemistry, scanning electron and confocal laser scanning microscopy and 3D imaging. We discuss our findings with reference to other tardigrades and internal phylogenetic relationships of the phylum. Results We focus our analyses on the somatic musculature, which in tardigrades includes muscle groups spanning dorsal, ventral, and lateral body regions, with the legs being musculated by fibers belonging to all three groups. A pronounced reduction of the trunk musculature is seen in the dorsoventrally compressed A. doryphorus, a species that generally has fewer cuticle attachment sites as compared to E. sigismundi and members of the class Eutardigrada. Interestingly, F-actin positive signals were found in the head appendages of A. doryphorus. Our analyses further indicate that cross-striation is a feature common to the somatic muscles of heterotardigrades and that E. sigismundi—as previously proposed for other echiniscoidean heterotardigrades—has relatively thick somatic muscle fibers. Conclusions We provide new insights into the myoanatomical differences that characterize distinct evolutionary lineages within Tardigrada, highlighting characters that potentially can be informative in future phylogenetic analyses. We focus our current analyses on the ventral trunk musculature. Our observations suggest that seven paired ventromedian attachment sites anchoring a large number of muscles can be regarded as part of the ground pattern of Tardigrada and that fusion and reduction of cuticular attachment sites is a derived condition. Specifically, the pattern of these sites differs in particular details between tardigrade taxa. In the future, a deeper understanding of the tardigrade myoanatomical ground pattern will require more investigations in order to include all major tardigrade lineages