Eisenia Hortensis Wormers

Eisenia hortensis, also known as Dendrobaena veneta (European nightcrawler)

E. hortensis is a large worm species well suited for use as a bait worm. Its ideal temperature range is a bit cooler than is that of E. fetida and it requires higher moisture levels than do the other species tested for use in bin culture and vermicomposting, but the species tolerates handling and disruption to its environment, and environmental fluctuations very well. Because this worm has a very low reproductive and growth rate, relatively speaking, it is considered the least desirable species of those tested for either bin culture or vermicomposting systems. It is used in a few vermiprocessing systems in Europe for the remediation of very wet organic materials.

· Temperature range: Minimum; 45° F, maximum; 85° F, ideal range; 55° F-65° F.
· Reproductive rate: Just under 2 young per worm per week under ideal conditions.
· Average number of young per cocoon: Approximately 1.
· Time to emergence from the cocoon: Approximately 40-125 days under ideal conditions.
· Time to sexual maturity: Approximately 55-85 days under ideal conditions.
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Search the vermicomposting forums on the Internet for the hot topic of the day and you’ll likely find the worm species Dendrobaena veneta generating a lot of discussion. Reclassified by taxonomists to the genus and species Eisenia hortensis, and commonly referred to as the European or Belgian nightcrawler, this species has suddenly emerged as the hot worm to try in today’s vermicomposting and vermiculture systems. Dendrobaena veneta is one of the handful of earthworm species studied in detail for use in vermicomposting. Doctors Adrian Reinecke and Sophie Viljoen conducted detailed studies on the reproduction and maturation rates and environmental requirements of this species in the early 1990s, which confirmed studies conducted on this species by Dr. Clive Edwards in the late 1980s. The researchers found D. veneta to be a large worm with a low reproductive rate and slow maturity rate compared to Eisenia fetida, Perionyx excavatus and Eudrilus eugeniae; findings which suggest this species is the least suitable for vermicomposting of those studied. Even so, D. veneta has demonstrated some value in vermicomposting. Studies demonstrate that this species performs better in excessively wet environments than the other species used for vermicomposting, leading to its use in some large-scale European vermiprocessing systems remediating paper sludges. Observations of small-scale vermicomposting and vermiculture systems using mixed cultures of Eisenia fetida and Dendrobaena veneta show that E. fetida tends to remain in the upper, dryer regions of the bin and D. veneta to populate the lower bedding areas where moisture concentrations are highest.

Some U.S. worm growers have become fans of Dendrobaena veneta and dispute the research data, believing the worm to reproduce and grow as rapidly as Eisenia fetida in their vermiculture and vermicomposting systems. Their observations are compelling and, coupled with the great size of this worm, are likely responsible in part for the sudden popularity of the species. Many home vermicomposters are interested in a larger worm species for use as fish bait which can be raised on household food scraps.

While there are questions surrounding the use of Dendrobaena veneta in general vermicomposting systems, there is no denying that this species is a top notch bait worm. This species is much larger than Eisenia fetida, making it easier to fit on a hook, but not so large as Lumbricus terrestris (common nightcrawler), which is sometimes considered to be too large. Claims of D. veneta secreting enzymes highly attractive to fish are unsubstantiated, but many anglers swear by this large, robust worm.

The current challenge to those interested in this species is finding a supplier with enough worm stock that they are willing to sell. The interest D. veneta is generating has gotten the worm into the U.S., but worm growers need time to build their breeding stock. The slow reproductive and growth rates of this species make this an even more time-consuming process than for some of the other cultured earthworms. As such, many growers who have the worm are not yet ready to sell it. Some of those who are selling the worm are selling mixed cultures of D. veneta and E. fetida in an effort to get the worm into the market without depleting their breeding stock. It is believed these mixed cultures may be partly responsible for the disparity as regards breeding and growth rates between the research data and the observations of some growers.

Each worm species has its niche in nature. Likewise, those studied seem to have found their place in the vermiculture industry. While not the best choice for most vermicomposting systems, if one seeks a large bait worm which can be easily bin-cultured, Dendrobaena veneta fits the bill nicely.

From Life-cycle of the European compost Worm Dendrobaena veneta (Oligochaeta), published in the South African Journal of Zoology, 1991, 26(1) by Sophie A. Viljoen, A.J. Reinecke and L. Hartman:

“The life-cycle of Dendrobaena veneta was studied to assess the potential of this species in vermiculture. The development, growth and reproduction were investigated by rearing worms at 25°C on urine-free cattle manure with a moisture content of 80% over a period of 200 days. It was found that cocoons are produced at a mean rate of 0.28 cocoons per worm per day and production can be sustained for at least 200 days. The mean incubation period of the cocoons is 42.1 days with a very low hatching success. The mean number of hatchlings per cocoon that hatched was 1.1. Sexual maturity may be attained within 20 - 35 days but some worms take up to 130 days. Dendrobaena veneta grew well on cattle manure. This species seems to be less suitable than some other epigeic species for vermiculture, at least in terms of its reproductive capacity in the experimental climatic conditions.”

From Moisture Requirements of Dendrobaena veneta (Oligochaeta), a Candidate for Vermicomposting, published in Soil Biology and Biochemistry, Vol. 26, No. 8, pp. 973-976, 1994 by N.Y.O Muyima, A.J. Reinecke and S. A. Viljoen-Reinecke:

“...Juvenile worms were exposed to different moisture contents in glass flasks filled with cattle manure medium and kept at 15°C (59°F). The highest frequency for clitellate worms was between 77.9 and 78.7% while their moisture preferences ranged between 67.4 and 84.3%. For cocoon production the highest frequency was between 73.1 and 79.9%. The optimum moisture content for growth and maturation of juvenile worms was 75%. From the results it appears that this earthworm species could be utilized in organic waste with a relatively high moisture content. However, comparing the reproductive capacity and maturation time with that of other vermicomposting species, D. veneta seems to be a less successful earthworms species for vermicomposting.”

From The Influence of Temperature on the Life-Cycle of Dendrobaena veneta (Oligochaeta), published in Soil Biology and Biochemistry, Vol. 24, No. 12, pp. 1341-1344, 1992 by S. A. Viljoen, A. J. Reinecke and L. Hartman:

“The life-cycle of Dendrobaena veneta was studied at 15°C (characteristic of the animal’s natural habitat) and at 25°C (77° F — at which the life-cycles of other vermicomposting species have been studied in Southern Africa).

At 15°C the life-cycle was completed in 100 days and it took 150 to complete the cycle at 25°C. At 25°C maturation was quicker, worms started to produce cocoons at a younger age and more cocoons were produced (per worm, per day) than at 15°C. The incubation period and the number of hatchlings per cocoon were more at the lower temperature.”

Photo caption:
Dendrobaena veneta appears violet, purple or olive brown, sometimes with pale striping in segment furrows. Its clitellum is on segments 26-32, its first dorsal pores between segments 4/5, tuberculata pubertatis on segments 30 and 31, its prostomium is epilobic and its setae are widely paired.

Sidebar:
Classification:
Phylum: Annelida (segmented worms)
Class: Megadrilidae (large worms)
Order: Oligochaeta (few setae)
Family: Lumbricideae
Genus: Eisenia
Species: hortensis

The European nightcrawler (Eisenia hortensis) can be cultured in stacking units like the Can O Worms. While this worm species tends to grow a bit larger than does Eisenia fetida, it can still fit through window screen. The holes in the stacking unit trays will be no barrier to them.

Keep in mind that the term "nightcrawler" is essentially meaningless. It is a common name applied indescriminately to many different worm species, and does not represent similarities in environmental preference or behaviors. In fact, the bait worm most commonly sold in the US under the names 'Canadian nightcrawler' and 'common nightcrawler' is a deep-burrowing anecic species, Lumbricus terrestris (most of which are shipped to bait sellers from Canada, though this worm is common to US soils) while the European nightcrawler (Eisenia hortensis) is a surface-dwelling epigeic species with a poor burrowing capacity.

E. hortensis is a species that prefers cooler temperatures than does E. fetida, with the ideal being roughly 60°F, and requires as much moisture in the system as possible without inhibiting airflow in order to maximize activity. As such, these worms will often be found low in the system where moisture collects and where density of material helps insulate the area at cooler, more consistent temperatures. If you manage the entire system with E. hortensis preferences in mind, however, they can be effectively cultured in any commercial worm unit.

Know, too, that E. hortensis has an optimal breeding and growth rate considerably slower than that of E. fetida, so don't be surprised if it takes several months for your worm population to fill the available space. It will generally take at least 18 months under optimal conditions for this species to establish a stable, maximized population, with some growers reporting longer times.