Arctic woolly bear moth
Gynaephora groenlandica, the Arctic woolly bear moth, is an erebid moth native to the High Arctic in the Canadian archipelago, Greenland and Wrangel Island in Russia. It is known for its slow rate of development, as its full caterpillar life cycle may extend up to 7 years, with moulting occurring each spring. This species remains in a larval state for the vast majority of its life. Rare among Lepidoptera, it undergoes an annual period of diapause that lasts for much of the calendar year, as G. groenlandica is subject to some of the longest, most extreme winters on Earth. In this dormant state, it can withstand temperatures as low as −70 °C. The Arctic woolly bear moth also exhibits basking behavior, which aids in temperature regulation and digestion and affects both metabolism and oxygen consumption. Females generally do not fly, while males usually do.
This species has an alpine subspecies which is notable for its geographic distribution south of the High Arctic.
This species was highlighted in BBC's sequel to Planet Earth, called Frozen Planet.
In general, G. groenlandica larvae are large (~300 mg) and densely coated in soft hair. While they are usually a distinctive tan-brown cast, their color may vary. They are characterized by a distinct hair tuft on their eighth abdominal segment, which has been described as a "rudimentary hair pencil". Later larval instars are notable for the color pattern of this dorsal hair tuft. They can also be identified by the spinulose form of their hairs, which are spineless, in contrast to the finer, feather-like (plumose) hairs of their close relative, G. rossii. They may also be distinguished from G. rossii in terms of wing pattern: G. groenlandica lack the broad, dark band along the edge of their hind wings that is characteristic of G. rossii. In general, G. rossii also have more wing patterning than G. groenlandica.
The eggs are around 1.6mm.
The cocoons of this species are double-layered, with a distinct pocket of air between the two layers, as opposed to the single-layered cocoons of G. rossii.
The nominate subspecies of Arctic woolly bear moth is native to the High Arctic of Greenland and the Canadian Arctic Archipelago including Ellesmere Island, or above approximately 70°N latitude. It is one of the most northern members of the Lepidopteran order in the Northern hemisphere. It occurs as far north as Ward Hunt Island in Canada and northernmost Greenland. A new subspecies G. groenlandica beringiana was described in 2013 south of the Arctic Circle in the alpine environment of the Ruby Range in southwest Yukon, 900 km south of the previously known range. A further subspecies G. groenlandica kusnezovi has as of 2015 only been found on Wrangel Island, Russia.
G. groenlandica is well-adapted to living in conditions of extreme cold in the High Arctic.
At two distinct field sites on Ellesmere Island, it was discovered that G. groenlandica, when in a diapausal state, tend to exist in specific microhabitats rather than in a random geographic distribution. Hibernacula are frequently found secured to the base of rocks, as opposed to being attached to vegetation. At one investigation site, hibernacula were observed primarily on the leeward (on the side sheltered from the wind) side of rocks, suggesting that wind direction plays a role in the selection of hibernation sites.
In captivity, G. groenlandica have also been observed anchoring themselves to leaf litter of Salix arctica during the diapausal period.
The G. groenlandica caterpillar moves up to several meters per day, primarily in order to acquire the necessary resources. In comparing a group of caterpillars physically transferred between different Salix arctica (Arctic willow) plants and a second group in which each individual was restricted to a single willow for the duration of the larval active period, it was observed that transferred larvae demonstrated higher herbivory and growth rates compared to the stationary group. This implies that the acquisition of high quality resources is a primary reason for the movement of G. groenlandica larvae between host plants.
The life history traits of G. groenlandica are dictated by the short, cold nature of summers in the High Arctic. Due to its restricted seasonal growth period, G. groenlandica has a life cycle of approximately 7 years. In contrast, its lifespan is much shorter (2–3 years) in warmer, alpine environments. Arctic woolly bear moths remain larvae for the vast majority of their lives, with the exception of up to 3–4 weeks of a single summer. This extended developmental period is not only attributed to low environmental temperatures, but also to the nutrition provided by its host plants. While they remain in their extended larval stage, G. groenlandica experience annual winter diapauses that commence in late June or early July. Larval mortality in an experimental caged environment on the tundra was found to be 10%.
While females of this species have fully developed wings and may take flight for a short time, they usually do not fly. Although Arctic-inhabiting females generally remain flightless, females of southerly alpine subspecies are often more mobile.
In contrast, males tend to fly high, fast, and erratically during the day.
G. groenlandica spends much of its life in a larval state, and food resources are necessary for development of the larvae. Salix arctica, the Arctic willow, is the primary host plant and food source for this species. The larvae may also feed on plants of other families, such as the flowers of Saxifraga oppositifolia and the senescent leaves of Dryas integrifolia. In the nominate High Arctic subspecies, less than 3% of larvae, however, were found to choose these alternatives. The lower latitude Canadian populations of G. g. beringiana of the alpine environments of southwest Yukon have larvae eating a broader spectrum of plants and proportionately less S. arctica.
While larvae rarely eat the catkins (petal-less flower clusters) of S. arctica, they readily consume the plant's leaves. 97% of larvae which actively eat at the onset of their feeding season are consuming the new leaf buds of this plant. Comparing the nutrient concentrations of plant leaves to those of larval frass, has shown that larvae remove nitrogen and potassium from the plant. Larvae appear to only feed in June, which is when the leaves of S. arctica reach their peak concentrations of nutrients and carbohydrates such as starches and sugars. The caterpillars decrease their food intake towards the end of the month and into the summer. At this time, the levels of carbohydrates and nutrients in S. arctica leaves tend to decrease, and the leaves become less palatable as concentrations of phenols and tannins increase. The decrease in nutrients and carbohydrates, combined with an increase in secondary metabolites, may account for this decline in consumption.
It appears to be adapted to a narrow thermal range. It is able to eat the most at temperatures intermediate to its range.
On Ellesmere Island the females typically lay their eggs in a mass on or in their cocoon, although they sometimes lay their eggs on the ground or on vegetation around the cocoon.
This species spends the vast majority of its life as a late larval instar; its early larval and adult stages represent only 6% of its full life cycle. It is the later instars which experience multiple annual periods of diapause. During this dominant stage of their lives (from the third to sixth instar phases), G. greenlandica moult annually.
Larval activity is confined to a short period following snowmelt. The High Arctic presents a short growing season of 45–70 days, and the G. groenlandica cease foraging at the end of June, prior to mid-summer. Larvae tend to spend 95% of their time either basking in the sun, feeding, or moving, and only 5% of their time fully immobile. More specifically, about 60% of their time as larvae is spent basking, 20% is spent feeding, and 15% is spent moving.
In late June or early July, the larvae prepare to overwinter by weaving silken hibernacula and entering diapause until the subsequent snowmelt. This typically occurs when daytime temperatures are at a maximum of 5-10 °C. In their diapausal state, G. groenlandica can withstand temperatures as low as -70 °C, and winter mortality is limited to, on average, a maximum of 13% of the population.
The developmental stages of pupation, emergence, mating, egg laying, eclosion, and molting to the second instar stage are all confined to a period of 3–4 weeks during a single summer. Emergence and reproduction may occur within a single 24-hour period.
Due to the brief lifespan of fully mature adult individuals, adult moths of this species are difficult to find in the wild.
At warmer temperatures, arctic moth larvae generally tend to have higher respiration rates and lower growth rates. They also tend to shift their diets to more nutrient-rich foods in this type of environment. For instance, the herbivory rate of the main food source for G. groenlandica, S. arctica, is altered at elevated temperatures. This implies environmentally dependent host plant plasticity in G. groenlandica. It also suggests that an increase in temperature due to global warming may have significant effects on the behavior of northern herbivore invertebrates such as G. groenlandica, as well as effects on the herbivory rates of their food sources. Thus, G. groenlandica may represent a potential indicator species for future studies on climate change.
