Megumu Tsujimoto

Continent-wide risk assessment for the establishment of nonindigenous species in Antarctica

Invasive alien species are among the primary causes of biodiversity change globally, with the risks thereof broadly understood for most regions of the world. They are similarly thought to be among the most significant conservation threats to Antarctica, especially as climate change proceeds in the region. However, no comprehensive, continent-wide evaluation of the risks to Antarctica posed by such species has been undertaken. Here we do so by sampling, identifying, and mapping the vascular plant propagules carried by all categories of visitors to Antarctica during the International Polar Years first season (2007–2008) and assessing propagule establishment likelihood based on their identity and origins and on spatial variation in Antarcticas climate. For an evaluation of the situation in 2100, we use modeled climates based on the Intergovernmental Panel on Climate Changes Special Report on Emissions Scenarios Scenario A1B [Nakićenović N, Swart R, eds (2000) Special Report on Emissions Scenarios: A Special Report of Working Group III of the Intergovernmental Panel on Climate Change (Cambridge University Press, Cambridge, UK)]. Visitors carrying seeds average 9.5 seeds per person, although as vectors, scientists carry greater propagule loads than tourists. Annual tourist numbers (∼33,054) are higher than those of scientists (∼7,085), thus tempering these differences in propagule load. Alien species establishment is currently most likely for the Western Antarctic Peninsula. Recent founder populations of several alien species in this area corroborate these findings. With climate change, risks will grow in the Antarctic Peninsula, Ross Sea, and East Antarctic coastal regions. Our evidence-based assessment demonstrates which parts of Antarctica are at growing risk from alien species that may become invasive and provides the means to mitigate this threat now and into the future as the continents climate changes.

Preliminary description of tardigrade species diversity and distribution pattern around coastal Syowa Station and inland Sør Rondane Mountains, Dronning Maud Land, East Antarctica

Tardigrades are important members of the simple terrestrial ecosystems in the extreme environments in Antarctica. This study provides a baseline description of tardigrade species diversity and distribution pattern within the terrestrial and lake environments of the coastal regions around Syowa Station and the neighbouring inland Sør Rondane Mountains, Dronning Maud Land. We combined data obtained from new and previously described collections and updated data available in the existing literature. We recorded five tardigrade species, three of which (Echiniscus pseudowendti Dastych 1984, Hebesuncus ryani Dastych and Harris 1994, Pseudechiniscus sp.) have not previously been reported from the area, increasing the total recorded tardigrade diversity for this region of continental Antarctica to ten species. The results of our study indicate that tardigrades have been and are major components of the lake environment community in continental Antarctica, with Acutuncus antarcticus (Richters 1904) the most common and dominant species. Our data confirm that the tardigrade species diversity in the vicinity of Syowa Station is very low and suggest potential relationships between individual tardigrade species and terrestrial moss species and depth in freshwater ecosystems.

Does a new transportation system increase the risk of importing non-native species to Antarctica?

Abstract Antarctic terrestrial ecosystems are not immune to the threat of biological invasions, and the urgent need for implementation of effective mitigation measures to minimize the risk has been highlighted. Recently, the transportation and logistic support system of the Japanese Antarctic Research Expedition has undergone substantial changes after the relocation of the cargo handling facility and the commissioning of a new icebreaker in 2009. The potential risk of introducing non-native species into Antarctica through the newly adopted cargo transportation system in comparison with the previously existing system was determined by quantifying both changes in the form of cargo transported and the frequency of propagule attachment on different types of cargo item. We obtained 1022 propagules of at least 26 species, including species known to have resistance to the stresses of cold environments. Larger numbers of propagules, and a greater proportion of affected cargo items, were encountered in the newly adopted transportation system than in its predecessor. The increased risks in the new system were identified as being associated with the major cargo packing type and the cargo storage location. Based upon those findings, we propose appropriate preventative measures in order to minimize the risk of transfer of non-native species into Antarctica.

Effect of lifespan and age on reproductive performance of the tardigrade Acutuncus antarcticus: minimal reproductive senescence

AbstractReproductive output is one of the central attributes of life history, and knowledge of age-specific reproduction can enhance the understanding of population performance and dynamics. Tardigrades are microscopic invertebrates that live in marine, freshwater and terrestrial ecosystems. While changes in fertility in relation to age are known to occur in other invertebrate groups, the subject has not been specifically addressed in tardigrades. The current study demonstrates for the first time the effect of lifespan and age on reproductive characteristics of the tardigrade species, Acutuncus antarcticus (Richters 1904), based on the observation of individuals over their entire lifespan under constant environment conditions in the laboratory. Clutch size of A. antarcticus fluctuated conspicuously throughout individual lifespans. Weak effects of age were observed on oviposition interval and hatching success, with the former increasing slightly and the latter decreasing slightly with age. Numbers of oviposition events and eggs produced per individual varied greatly and were correlated with lifespan. No significant relationships between clutch size, hatching time or hatching success with lifespan were detected. The majority of the individuals continued oviposition until shortly before death, with no suggestion of a post-reproductive lifespan. Our observations suggest that any decline in fertility with age in this species of tardigrade is minimal. The study provides new insight into the reproductive biology and ageing of invertebrate species.

Meiofaunal Richness in Highly Acidic Hot Springs in Unzen-Amakusa National Park, Japan, Including the First Rediscovery Attempt for Mesotardigrada.

Extreme environments sometimes support surprisingly high meiofaunal diversity. We sampled runoff from the acidic hot springs of Unzen, Japan. This is the type locality of Thermozodium esakii Rahm, 1937, the only tardigrade in the class Mesotardigrada, which remains contentious in the absence of corroboration or supporting specimens. Our sampling revealed at least three species of arthropods, four rotifers, and five nematodes living in the hot (ca. 40°C) and acidic (ca. pH 2.5) water, but no tardigrades.

Gilbert Rahm and the status of Mesotardigrada Rahm, 1937

The tardigrade class Mesotardigrada was erected on the basis of the description of Thermozodium esakii by Gilbert Rahm in 1937. In some characteristics, T. esakii is intermediate between members of the classes Eutardigrada and Heterotardigrada. The class Mesotardigrada is known only from Rahms published drawings of T. esakii; no voucher specimens are known, and subsequent attempts to collect it at the locus typicus have been unsuccessful. Among the possible explanations for this situation are that Rahm may have collected specimens of a more typical tardigrade, but misinterpreted what he saw. Alternatively, changes in habitat in the area may have led to the tardigrades extirpation. Perhaps T. esakii is a rare species, such that recent sampling efforts have been insufficient to rediscover it. Finally, Rahms 1937 description may be an attempt at deception. Until physical evidence of T. esakii is found, the species, and by extension the class Mesotardigrada, should be considered nomen dubium.

A new species and the shallowest record of Flabegraviera Salazar-Vallejo, 2012 (Annelida: Flabelligeridae) from Antarctica

A new species of polychaete, Flabegraviera fujiae sp. nov., is described and the first report of F. mundata (Gravier, 1906) from the shallow water around Syowa Station, Antarctica, is presented. Flabegraviera fujiae sp. nov. resembles F. profunda Salazar-Vallejo, 2012 but is discriminated from the latter by having eyes and an exposed cephalic cage. The specimen of F. mundata was collected from a depth of 8 m, providing the shallowest record of this species to date.