E. N. Meshcheryakova

The Schrenck newt ( Salamandrella schrenckii , Amphibia, Caudata, Hynobiidae) is the second amphibian that withstands extremely low temperatures

In this connection, it seems promising to study the cold hardiness of another species of the same genus, the Schrenck newt (Salamandrella schrenckii Strauch 1870), whose geographic range in Russia is small com pared to the vast range of the Siberian newt (Fig. 1). The Schrenck newt mostly inhabits the Sikhote Alin, mountains of southwestern Primorsk territory, and adjacent lowlands [2]. The climate of these regions is characterized by considerably milder winters com pared to any other regions of Asian Russia (except for some islands). In contrast, the Siberian newt’s range encompasses almost the entire Siberia and a part of Europe, including Arctic regions. This species is believed to have colonized almost the entire northern Eurasia owing to its unique adaptation to low temper atures. Considering the comparative sizes of the ranges, one might assume that the Schrenck newt is less tolerant to low temperatures. The purpose of this study was to test this assumption.

Spread of the Earthworm Dendrobaena octaedra(Lumbricidae: Oligochaeta) from Europe to Northern Asia Is Restricted by Its Insufficient Frost Resistance

Although the eastern borders of the ranges of most Palearctic earthworm species that spread as far as 55 ° N [1] are varied, they share a common characteristic pattern: as one moves eastward, the borders of the range shift to the south, with the eastern border typically not reaching 40 ° –50 ° E, except for a few species that spread as far as 60 ° E. The factors that form species ranges are not only interesting from the general biological viewpoint, but may also be of practical importance in the case of key species of the ecosystems of areas with a high anthropogenic impact. The range of the cosmopolite earthworm Dendrobaena octaedra stands out because (1) it covers an almost entire European forest zone and European tundra, including the southern island of the Novaya Zemlya, (2) in western Siberia, it is spread farther than other earthworms, although its findings are few, and (3) it appears again farther east, on the Sea of Okhotsk coast near Magadan. The occurrence of D. octaedra in the tundra indicates that it is highly resistant to low temperatures in winter; however, the frost resistance of its northern populations has not been studied. Even approximate comparison of the northern and eastern borders of the D. octaedra range with winter air isotherms, which are known to be meridionally directed (Fig. 1a), suggests a relationship between the distribution of this species and lower limits of temperature in its habitats. To test this suggestion, we studied the frost resistance of D. octaedra and the temperature conditions of its wintering and constructed small-scale schemes of the minimum soil temperatures. The study was performed in 1997–1999. In the vicinity of Magadan, D. octaedra inhabits a narrow (10–15 m) flood plain of the Dukcha River grown with long-boled dwarf willows along several kilometers near the river mouth. In northeastern Asian continental regions, all attempts to find D. octaedra failed. The temperature regimen of the upper soil layers on the terrace of the Dukcha River was studied with the use of electron thermometers (loggers) and minimal meteorological thermometers for verification. The data obtained were normalized for multiyear average values based on regression equations of the soil and air temperatures. The summer microclimate of the Dukcha flood plain is more similar to that of European tundra, e.g., the Bol’shezemel’skaya Tundra and the tundras of the Chaunskaya Bay coast and the Amguema River valley [4–6], than to the microclimate of the forests and sparse-forest areas surrounding the Dukcha valley. In summer, the maximum temperature is 10.2°C in the upper 1-cm layer of the litter and only 6°C at a depth of 10 cm, with the sum of temperatures above zero (by the Celsius scale) throughout a year being 700 and 500 ° C, respectively. The temperatures are so low because of the almost completely closed upper layer of willow growth, large amounts of undecayed leaf debris, high ice content in the substrate, its periodic damping when the water level rises, etc. The average air temperature in January is –18°C . The absolute minimum temperature of the soil at a depth of 3–5 cm in the D. octaedra habitat in the flood plain varied from –9 to –10°C in our study. This temperature was recorded in the late December 1998, when there was little snow. According to our incomplete data, this temperature in the vicinity of Magadan varied from –27 to –2.0°C in different years.

Is the western boundary of the Siberian salamander (Salamandrella keyserlingii, Amphibia, Caudata, Hynobiidae) range determined by the specific features of its wintering?

97 It is considered that the Siberian salamander Sala mandrella keyserlingii Dybowski 1870 has colonized almost the entire Northern Asia, first and foremost, owing to its cold hardiness unique for a vertebrate animal: it is tolerant in a frozen state to a cooling to –35°C [1]. However, paradoxical as it may seem, this species is absent in milder climates in the major part of European Russia and Western Europe (Fig. 1). The western boundary of this species does not coincide with any geographic landmark.

Ranges and cold hardiness of two earthworm subspecies (Eisenia nordenskioldi, Lumbricidae, Oligochaeta)

The ranges of two earthworm subspecies, Eisenia nordenskioldi nordenskioldi (Eisen 1879) and E. n. pallida Malevi 1956, differ in area and partially overlap. E. n. nordenskioldi populates the entire Asian Russia and eastern regions of the Russian Plain, from the lower reaches of the Volga and Don rivers to the Arctic Ocean coasts, while E. n. pallida has not expanded to the Asian permafrost zone and does not occur in European Russia and in the Urals. These subspecies “hold the record” in cold hardiness: the worms and cocoons of the nominotypical subspecies withstand temperatures down to −34 and −40°C, and those of E. n. pallida, to −28 and −23°C, respectively. Hence, their distribution is independent of subzero temperatures, and their ability to overwinter at any phase of the life cycle makes them also independent of heat supply during the summer period. Differences in geographic range may also be due to biological features of the subspecies. The nominotypical subspecies feeds belongs to the epiendogeic morphoecological type (feeding on the ground surface), whereas E. n. pallida is a true endogeic earthworm. Both subspecies have similar requirements for soil acidity; however, conditions in coarse-humus organomineral horizons of frozen soils appear to be unfavorable for E. n. pallida, which accounts for the absence of this subspecies in the permafrost zone.

The Mechanism of Cold Hardiness of Egg Cocoons of the Earthworm Dendrobaena octaedra (Sav.) (Lumbricidae: Oligochaeta)

In the past decade, the third (along with freeze tolerance and supercooling) state, in which organisms can survive low temperatures, has been discovered and partly described [1]. This state is apparently analogous to the state of cells of freeze-tolerant organisms during freezing; however, in this case, water is removed beyond the limits of the organism rather than into the intercellular and intertissue space [2]. This phenomenon, termed “protective dehydration”, has been observed during cooling egg cocoons of D. octaedra (Sav.) in open plastic dishes placed on the surface of chopped ice, which, in turn, was placed into a closed vessel [1]. This model simulated the conditions in freezing soil. The difference in water vapor pressure above the surface of ice and supercooled cocoon led to its dehydration. In this state cocoons survived when kept for 15 days at –20°C [3]. Water losses were so significant (up to 85% from the initial value) that, eventually, there was nothing to be frozen in the dried cocoon [4].

Extreme negative temperatures and body mass loss in the Siberian salamander (Salamandrella keyserlingii, amphibia, hynobiidae)

Frozen Siberian salamander safely tolerates long (45 days) stay at–35°C. Short-term (3 days) cooling down to–50°C was tolerable for 40% of adult individuals; down to–55°C, for 80% of the underyearlings. Generally, the salamanders lose about 28% of the body mass during the pre-hibernating period (before winter, at temperatures as low as 0°C) and during the process of freezing (as low as–5°C). The body weight remained constant upon further cooling (to–35°C). The frozen salamanders have no physiological mechanisms protecting from sublimation.

The Japanese tree frog ( Hyla japonica ), one of the most cold-resistant species of amphibians

The Japanese tree frog, a representative of the Manchurian fauna, is characterized by an outstanding cold resistance among the anuran amphibian species studied so far. Almost 70% of the specimens from the population inhabiting the middle Amur River withstand the cooling down to–30°C; some animals, down to–35°C. This exceeds more than twofold the cold hardiness of the wood frog (Lithobates sylvaticus LeConte, 1825), which has been considered earlier to be the most cold-resistant species. The ability of H. japonica to survive for four months in the frozen state at low temperatures makes this species independent of the temperature overwintering conditions.

Cold hardiness, adaptive strategies and invasion of slugs of the genus Deroceras (Gastropoda, Pulmonata) in Northeastern Asia.

Abstract-Four species of slugs have been identified in the vicinity of Magadan: Deroceras laeve, D. altaicum, D. reticulatum, and D. agreste. They exemplify three different life cycle schemes, with D. reticulatum and D. altaicum wintering at the egg phase; D. laeve, at the slug phase; and D. agreste, at either phase. The D. altaicum and D. reticulatum slugs and D. laeve eggs are intolerant of subzero temperatures. D. laeve’s tolerate freezing and survive at temperatures below −28°C. The eggs of other species, which lose up to 35% of water upon cooling, can withstand temperatures as low as −15 to −17°C (D. altaicum), −25°C (D. agreste), and −35°C (D. reticulatum). According to preliminary data, D. agreste slugs survive at temperatures down to −10°C. The almost ubiquitous distribution of D. laeve in regions with cool summers (including zonal tundras) is accounted for not so much by the high rate of ontogeny as by its significant cold hardiness and ability to winter at different phases of the life cycle (except for the egg phase), which allows the period of development to be prolonged for the next seasons. The last is confirmed by the fact that the slugs collected before and after hibernation proved to have identical patterns of distribution by body weight. Three species of slugs introduced in the vicinity of Magadan fail to spread inland. In the case of D. reticulatum, this is explained primarily by the fact that the frost-free season in inland areas is too short to allow these slugs to complete ontogeny and lay eggs. The barriers to their expansion appear to be insuperable, since this process remains unsuccessful over no less than 75–80 years.

The Siberian wood frog survives for months underwater without oxygen

Few of the amphibian species that occur in the Subarctic and in mountains are adapted to low sub-zero temperatures; most of these species overwinter underwater. It is believed that the distribution of the species that overwinter underwater can be limited by the low oxygen levels in waterbodies covered with ice. We show that the colonisation of the coldest areas of Northern Asia (to 71°N) by the Siberian wood frog (Rana amurensis) was facilitated by a unique adaptation, the ability to survive extreme hypoxia — and probably anoxia — in waterbodies during overwintering. The oxygen content in the overwintering waterbodies that we have studied in different parts of the range of this species fell to 0.2–0.7 mg/L without causing any large-scale mortality among the frogs. In laboratory experiments the R. amurensis survived for up to 97 days in hermetically sealed containers with water that contained less than 0.2 mg/L oxygen at temperatures of 2–3 °C, retaining the ability to respond to external stimuli. An earlier study of a broad range of frog species has shown that very few of them can survive even brief (up to 5–7 days) exposure to oxygen-free water. The revealed adaptation to prolonged extreme hypoxia is the first known case of this kind among amphibians overwintering in water.

Cold hardiness and range of the earthworm Eisenia sibirica (Oligochaeta, Lumbricidae)

A hypothesis of range formation of the earthworm Eisenia sibirica Perel et Graphodatsky 1984, which is an endemic species of the Altai–Sayan mountain system and is also found on the adjacent plains of Siberia across the valleys of the rivers, is suggested. The limited distribution of the species can be connected with the insufficient cold hardiness of the worm stage (–10 to–12°C). The plains of Western Siberia lie in an area of minimum soil temperature isotherms at a depth of 3 cm:–12 to–14°C, i.e., on average 2–4°C below the tolerable limits for this species. Foothill and mountain soils are warmer, since they obtain much more solid precipitation. Low soil temperatures of the plains apparently “lock up” this species within the Altai–Sayan system. At the same time, there are reasons to consider the northernmost locations of E. sibirica to be relict.