Publication

Taxonomy, diversity, and habitat ecology of Irish tardigrades

DeMilio, Erica
Citation
Abstract
Tardigrades (phylum Tardigrada Doyère, 1840) are obligate aquatic, microscopic animals that inhabit marine and freshwater habitats, as well as the terrestrial environment. They occur in limnoterrestrial settings including soil and in association with mosses, lichens, and leaf litter. Tardigrades are best known for their ability to survive challenging environmental conditions, as demonstrated in the terrestrial environment by their presence on all continents and in all biomes. Despite this ubiquity, tardigrades have been poorly known in Ireland. The sparse information relating to Irish tardigrades was scattered and to a great extent, taxonomically outdated. The status of the phylum in Ireland required a thorough evaluation. All previous records of Tardigrada from the Republic of Ireland and Northern Ireland were compiled and reviewed. A new record for Echiniscus quadrispinosus quadrispinosus Richters, 1902 was also added from County Clare. Resultingly, a Checklist of Irish Tardigrade Species that included 16 heterotardigrades and 35 eutardigrades was established. Most pre-existing records for Irish tardigrades originated from the work of James Murray as part of the original Clare Island Survey (1909–1911). The tardigrades of Clare Island were reinvestigated through participation in the New Survey of Clare Island. In the time between surveys the presence of many morphologically similar species complexes within Tardigrada had been reported. The importance of recognising such complexes was apparent as the original survey recorded the single taxon Macrobiotus hufelandi C.A.S. Schultze, 1834 as the most frequently occurring in samples, while the new survey found that nine morphotypes of the M. hufelandi species complex were present among its Clare Island samples. Ten other tardigrade species, including two not previously known from Ireland, Dianea sattleri (Richters, 1902) and Notahypsibius pallidoides (Pilato, Kiosya, Lisi, Inshina and Biserov, 2011), were also recorded by the New Clare Island Survey. Following these foundational studies, a new islandwide survey of Tardigrada, The All-Ireland Tardigrade Survey (AITS) was designed and launched with the objectives to characterise the Irish tardigrade fauna, evaluate its diversity, and collect habitat data using newly established standardised protocols for sample collection and processing. Five broad- scale Irish habitat types of the terrestrial environment were included: bog, built land, exposed rock, semi-natural grassland, and semi-natural woodland. A subset of AITS samples was used to demonstrate analyses for evaluating and comparing diversity between tardigrade communities including estimations of species richness, sample completeness, sample coverage, and evenness. Taxa representing multiple new records for Ireland were present within the samples comprising the selected subset. Two AITS samples from limestone pavement in Ireland’s Burren region contained specimens that were targeted for detailed taxonomic analyses involving intensive light (LM) and scanning electron microscopy (SEM) with the addition of morphometric and limited phylogenetic results. This work facilitated the description of two new species, Bryodelphax pucapetricolus DeMilio, Tumanov, Lawton, Kristensen & Hansen, 2022 and B. wallacearthuri DeMilio, Tumanov, Lawton, Kristensen & Hansen, 2022 and a revision of morphological characters important in that genus and with relevance to other heterotardigrade genera. The diagnoses of Bryodelphax Thulin, 1928 and Bryochoerus Marcus, 1936 were thereupon emended. Further recommendations, including for the revision of some related species and increased inclusion of the morphometric values of gonopore diameter and gonopore to anus distance and details of the anus morphology in the descriptions of limnoterrestrial heterotardigrade genera were made. The genus Parechiniscus Cuénot, 1926 was recorded from Ireland for the first time, as were two other heterotardigrades, Echiniscus spiniger Richters, 1904 and Testechiniscus spitsbergensis spitsbergensis (Scourfield, 1897). Detailed LM and SEM analyses of Irish Parechiniscus specimens led to a new interpretation of the configuration of the dorsal cuticular plates and the first accounts of tertiary clavae in that genus and new information on the Parechiniscus sexual system. These observations warranted a new emendation to the genus diagnosis. Leaf litter as a habitat for tardigrades was explored in Ireland and Scotland for the first time with 25 taxa encountered, including multiple new records for each country. The Irish Checklist of Species was further updated to include all newly obtained data for a total of 25 heterotardigrades and 52 eutardigrades, a 54% increase of known Irish species. The presented body of research thereby progressed the characterisation of the Irish tardigrade fauna, made contributions to the field of tardigrade taxonomy, and offered an approach to the study of tardigrade habitat ecology.
Funder
Publisher
NUI Galway
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Rights
Attribution-NonCommercial-NoDerivs 3.0 Ireland
Attribution-NonCommercial-NoDerivs 3.0 Ireland