Limno-terrestrial Species Research Articles

Macrobiotus rebecchii sp. nov.: A New Limno-Terrestrial and Hermaphroditic Tardigrade from Kyrgyzstan.

A new tardigrade species of the genus Macrobiotus C.A.S. Schultze, 1834 from Kyrgyzstan, is described and illustrated in this paper. Macrobiotus rebecchii sp. nov. is a hermaphroditic and limnoterrestrial species found in a moss growing on a rock in Toluk village. Specimens of the new species were examined for its morphological details using contrast phase light microscope (PCM) and scanning electron microscope (SEM). Genetic data in the form of DNA sequences of commonly used molecular markers were also obtained (18S rRNA, COI). Phenotypically the new species is most similar to Macrobiotus joannae Pilato & Binda, 1983, Macrobiotus punctillus Pilato, Binda & Azzaro, 1990, and Macrobiotus hannae Nowak & Stec, 2018, but can be easily differentiated from all of them by its body granulation pattern.

Establishment of an isogenic strain of the desiccation-sensitive tardigradeIsohypsibius myrops(Parachela, Eutardigrada) and its life history traits

Tardigrades are aquatic micrometazoans found in various habitats. Many limno-terrestrial species can tolerate desiccation by entering a metabolically inactive dehydrated state called anhydrobiosis, whereas most species in constantly hydrated habitats, such as freshwater or marine species, cannot undergo anhydrobiosis and are susceptible to desiccation. Although comparative analyses between anhydrobiotic species and desiccation-sensitive species will lead to a better understanding of anhydrobiosis, almost all studies on anhydrobiosis have been performed only in anhydrobiotic species. In the present study, we established a rearing system and an isogenic strain of Isohypsibius myrops collected from activated sludge. This strain is highly sensitive to desiccation and cannot tolerate exposure to relative humidity (RH) of 97–98% for 2 days or 94–95% for 1 day. Life history traits revealed that this strain has a short hatching time (3.6 days) and a short lifespan (18.8 days). The strain frequently lays eggs, on average 19 eggs per oviposition at mean interval of 2.5 days, enabling their rapid proliferation. The high fecundity of desiccation-sensitive species implies a possible trade-off between anhydrobiotic ability and fecundity. The established strain provides a good experimental model of desiccation-sensitive tardigrades, especially for comparative molecular analyses of anhydrobiosis mechanisms.

First observation of the marine tardigrades Batillipes mirus and Batillipes noerrevangi (Arthrotardigrada, Batillipedidae) from a strongly brackish part of the Polish Baltic Sea coast

The tardigrade fauna of Poland is one of the better known in Europe. However, almost all studies have been carried out on the limno-terrestrial species, while marine Tardigrada have been neglected. To the best of our knowledge only one report on marine Tardigrada for Polish waters has been published up to now. In the present study the first records of two marine arthrotardigrade species, Batillipes mirus and Batillipes noerrevangi, from Puck Bay (Baltic Sea) are reported. The lowest salinity value in the study area was 3–4 PSU, and B. noerrevangi should be considered the most brackish water-tolerant arthrotardigrade. Samples were collected from the vegetated seabed (seagrass and macrophytes) and the bare sandy bottom in different seasons. A single specimen of B. mirus was found only during the autumn campaign. Specimens (adults and larval stages) of B. noerrevangi were found in all samples during spring, summer and autumn campaigns. Additionally, morphometric data with detailed microphotographs of B. noerrevangi (PCM, DIC) and B. mirus (PCM) as well as a discussion of the new records are presented. The validity of the occurrence of B. dicrocercus in Poland, which was determined based on a single larva from the Międzyzdroje area by Hummon, is also discussed. The larva from Międzyzdroje should be regarded as an undetermined species; thus, the marine tardigrade fauna from Poland consists of only the two newly recorded species.

A zoogeographic study of the limnoterrestrial tardigrade 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.

Current knowledge of the Tardigrada of Svalbard with the first records of water bears from Nordaustlandet (High Arctic)

The first investigations of the tardigrades of Svalbard took place in the early 20th century and 30 papers on the subject have been published to date. In this article, we summarize available information on the distribution of tardigrades in this Arctic archipelago with remarks on the dubious species and records. Additionally, we examined 28 new moss, lichen and soil samples collected from the islands of Nordaustlandet, Edgeøya and Prins Karls Forland. These samples yielded 324 specimens, 15 exuvia and 132 free-laid eggs belonging to 16 limnoterrestrial species (Heterotardigrada and Eutardigrada). These include five first records of water bears from Nordaustlandet, eight new records for Edgeøya and four for Prince Karls Forland. The most dense population of tardigrades was found in a sample with 253 specimens/10 g of dry material and the least dense population in a sample with three specimens/10 g of dry material. The most frequently recorded species in samples collected in this study were Testechiniscus spitsbergensis Scourfield, 1897, Macrobiotus harmsworthi harmsworthi Murray, 1907, and M. islandicus islandicus Richters, 1904. This article also provides the first ever scanning electron microscope photomicrographs of Tenuibiotus voronkovi Tumanov, 2007.Keywords: Checklist; Edgeøya; new species; Prins Karls Forland; soil fauna; Svalbard biodiversity(Published: 20 November 2013)To access the supplementary material for this article, please see Supplementary files in the column to the right (under Article Tools).Citation: Polar Research 2013, 32, 20886, http://dx.doi.org/10.3402/polar.v32i0.20886

Survival in extreme environments – on the current knowledge of adaptations in tardigrades

Tardigrades are microscopic animals found worldwide in aquatic as well as terrestrial ecosystems. They belong to the invertebrate superclade Ecdysozoa, as do the two major invertebrate model organisms: Caenorhabditis elegans and Drosophila melanogaster. We present a brief description of the tardigrades and highlight species that are currently used as models for physiological and molecular investigations. Tardigrades are uniquely adapted to a range of environmental extremes. Cryptobiosis, currently referred to as a reversible ametabolic state induced by e.g. desiccation, is common especially among limno-terrestrial species. It has been shown that the entry and exit of cryptobiosis may involve synthesis of bioprotectants in the form of selective carbohydrates and proteins as well as high levels of antioxidant enzymes and other free radical scavengers. However, at present a general scheme of mechanisms explaining this phenomenon is lacking. Importantly, recent research has shown that tardigrades even in their active states may be extremely tolerant to environmental stress, handling extreme levels of ionizing radiation, large fluctuation in external salinity and avoiding freezing by supercooling to below -20 °C, presumably relying on efficient DNA repair mechanisms and osmoregulation. This review summarizes the current knowledge on adaptations found among tardigrades, and presents new data on tardigrade cell numbers and osmoregulation.

Global diversity of tardigrades (Tardigrada) in freshwater

Tardigrada is a phylum closely allied with the arthropods. They are usually less than 0.5 mm in length, have four pairs of lobe-like legs and are either carnivorous or feed on plant material. Most of the 900+ described tardigrade species are limnoterrestrial and live in the thin film of water on the surface of moss, lichens, algae, and other plants and depend on water to remain active and complete their life cycle. In this review of 910 tardigrade species, only 62 species representing13 genera are truly aquatic and not found in limnoterrestrial habitats although many other genera contain limnoterrestrial species occasionally found in freshwater.

“Smoky Bears”—Tardigrades of Great Smoky Mountains National Park

Abstract As part of the All Taxa Biodiversity Inventory (ATBI) in Great Smoky Mountains National Park (GSMNP), we have collected nearly 600 samples from soil/decomposed leaf litter, lichens and mosses on trees, and stream sediment and periphyton within all 19 permanent ATBI plots, with additional samples from caves, rock lichens, seeps, and bird nests. Tardigrades have been extracted from samples using centrifugation with Ludox AMTM and mounted on individual microscope slides in Hoyer's medium for identification under phase and DIC microscopy. Prior to our study, only three species of tardigrades had been reported from a few samples in the park. We have now examined over 9000 slides from 401 samples and recorded 73 species, 14 of which we believe may be new to science. Using EstimateS 7.5 software for each of the major tardigrade habitats, we estimate a total species richness of ≈96 limnoterrestrial species in the park. In this paper, we discuss challenges inherent in tardigrade taxonomy and the need for ...

Evolution of the Reproductive Mechanisms in Tardigrades — A Review

Although tardigrades can reproduce only through gametes they have exploited several modes of reproduction, which may be determined by their environment. Marine species (mainly heterotardigrades) are gonochoristic; hermaphroditism is only cited once, and parthenogenesis is unknown. In many cases females mature one egg at a time throughout adult life, whereas males are semelparous. Gonochorism is still present in limno-terrestrial species, while sporadic hermaphroditism occurs in several eutardigrade families. Thelytoky is the most common mode of reproduction in non-marine Tardigrada. Females are iteroparous, laying groups of eggs (free or in the exuvium), while males are semelparous (in a limnic species) or iteroparous with a continuous or cyclical maturation of the spermatozoa (in species from moss and leaf litter). Self-fertilisation appears to characterise hermaphroditic species, found in freshwater, mosses, leaf litter and soil. Egg maturation in these species is similar to that of the gonochoristic species, while spermatozoa mature in appreciable numbers before the oocytes, subsequently maturing continuously but in small numbers over the life of the animal. Parthenogenesis in limno-terrestrial tardigrades always appears continuous. In many species only females occur, but morpho-species populations may be found with both bisexual amphimictic (diploid) and unisexual thelytokous (often but not always polyploid) cytotypes. We can hypothesise that with the evolution of cryptobiosis and passive dispersal unstable and isolated habitats may favour parthenogenesis and self-fertilisation, as both reproductive modes allow colonisation of a new territory by a single individual. Parthenogenesis and hermaphroditism do not occur in the same species, and we can surmise that self-fertilisation will only evolve where parthenogenesis has never occurred.