Most of the earthworms can survive during the freezing weather. The temperature below the soil surface is always several degrees warmer than the air temperature or ambient temperature. The large size (21 – 30 cm) deep-burrowing earthworm species (anecic earthworms) and medium size (11 – 20 cm) upper-soil earthworm species (endogeic earthworms), burrow deeper during the winter because they cannot survive at the temperature below -1 °C. Amazingly, their compound eggs or cocoons are able to survive at -5 °C.
During Winter most anecic and endogeic earthworms stay in their burrows. They are coiled into a slime-coated ball and go into a sleep state or hibernation (like in large mammals) called estivation. The mucus or slime on the surface of the earthworm body in coil position, keeps the earthworms from drying up. The adult earthworms will survive in frozen and dry soils by estivation until conditions improve. Some species of earthworms lay their cocoons before the peak of the winter as their cocoons are more resistant to freezing temperatures than the adult earthworms
The small size (8 – 10 cm) epigeic earthworms or compost worms have different mechanisms against the freezing winter. They are called surface-soil litter or near the compost heap of green and brown wastes compost worm species, which cannot penetrate the soil. So, they have a special mechanism to pass the cold hardiness in freezing temperatures below -5 °C. It was reported by the scientific research that compost worms or red wigglers, mostly Eisenia fetida and Eisenia andrei, produce antifreeze agent during the peak of the Winter.
The studies of the cold hardiness in relation to the supercooling point (SCP) of the compost worms have been reported recently. The average of the SCP of the adult compost worms was -2.8 °C, while the SCP of the worm cocoons was -6.1 °C. The resistance to cold in red wiggler cocoons was not revealed under the preserved attributes of the mechanism of protective dehydration. The water content decreased in cocoons under cooling and was accompanied by the formation of the ice cover on the thick cell walls of the cocoons.
It is found that the antifreeze agent produced by juvenile and adult red wigglers, can stay longer in their bedding until the end of Spring or early Summer. It means the temperature of the bedding of the red wigglers population from Winter has a lower temperature of about 5 up to 8 °C compared to the bedding of the red wigglers from the warmer temperature in late spring or early summer. This phenomenon of the cooler temperature of the bedding with the high density of the red wigglers in the worm containers or wormeries in warmer weather, will also help the reproduction of the red wigglers in warmer climates.
It is reported that red wigglers produce lumbrokinase as an anti-blood clot enzyme to prevent their blood from being frozen. Moreover, the high density of red wigglers in the herds will keep them warmer rather than as an individual. Antifreeze agent outside the body of the compost worms, anti-blood clot lumbrokinase inside their body, heat created by the herd touching and some carbon-rich organic waste can make the compost worms population safe and thrive during the freezing winter at an ambient temperature of -15 °C or bedding temperature of above -5 °C.
Perhaps we can learn from the red wigglers to stay warm by huddling together in this Winter season in Northern Hemisphere with our loved ones. Happy Prosperous New Year 2022!
The photo of the red wigglers above was taken during the peak of winter.
PS. The cloud-like background of the image of a handful of the red wigglers in my hand is actually snow.