Care & Feeding
General Care, feeding, and breeding of Hirudo verbana
Water:
This is a critical environmental factor. Tap water is typically treated with chlorine and/or chloramine. Chlorine will dissipate after a few days and the water will be just fine. However, given that chlorine will dissipate many municipalities are now also treating water with chloramine, which will be a constant, unless treated. Check your local aquarium store for water treatment solutions which will remove both additives. Make sure you follow the treatment to water volume recommended. If you are not sure if your water has the chloramine additive you can usually find this information on your community’s local web site. Well water is ideal as is rain water. You might want to test these for acidity. A neutral pH is the best. Spring water is also excellent. You can often find this in your supermarket. If your water is mineral poor one might also add aquarium salts, again at the manufactures suggested amount. Distilled water may also be used but this must receive aquarium salts as these minerals are vital to leech health. Well water is also a good alternative however, both well and spring water may be high in calcium and must be tested. The ideal pH is < 7.
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The number of leeches per water volume will depend a great deal on the size of your leeches. Young leeches may be kept in a liter/quart jar and will comfortably hold 20 – 30 leeches or more. However, as they are fed and grow you should keep no more than five or so per liter/quart, less once they get very large.
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Water changes will be necessary, especially after feeding. Water changes can be stressful so try not and do this too often. This will often be a judgement call based upon the discoloration of the water. There is a lot of digesting going on right after feeding and the leeches will excrete ammonia and defecate a great deal leaving the water quite foul. Immediately after feeding one might change the water every few days for a couple of weeks and then reduce the water changes to weekly or bi-weekly. The number of leeches in your container will also drive the need for water changes. If one of your leeches dies the water will discolor quickly and will take on a reddish color, especially if fed recently. Dispose immediately of the dead leech and change the water. Some leech enthusiasts change only a partial amount of the water while others do a 100% change. I change the water entirely, but this is up to you. One will continue to see an accumulation of brown material collecting on the side of your container. This is probably Aeromonas hydrofila, a symbiotic bacteria necessary for the leech to digest the blood. This can be both good and bad. A greater bacterial load is good for the leech but potentially hazardous for the patient. Prior to use it is advisable to reduce the bacterial load as much as possible by increasing the water changes and just prior to application to gently hose down the leech with water to remove bacteria on the leech surface.
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Feeding:
Without trying to overstate the obvious, medicinal leeches will feed on blood. If one is working with Buffalo leeches, these may feed for over 3 hours, they even tend to fall asleep during feeding. Buffalo leeches are known for being slow eaters. They easily are released from the food source by spraying some water on them. Never pull a feeding leech since they can regurgitate their last meal including their gut content which contains bacteria like Aeromonas hydrofila that helps the leech to digest its meal. Finding blood can be a tricky search, unless one feeds them on yourself. Search for local slaughter houses and they may be quite happy to give the blood to you. I find the smaller ones are more open to these requests. Larger industrial slaughter operations may find this request too onerous to meet. The blood from slaughter operations will clot quickly. The blood not clotted may be stored and frozen for future use. Leeches will feed on clotted blood although this can be a messy operation, especially if one is feeding large quantities of leeches. Leeches will feed on cool blood such as that found in amphibians however, getting the blood to about 37 °C / 97 °F is helpful. Young leeches often feed on amphibians exclusively before including warm blooded animals in their diet.
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If feeding on clotted blood, a simple container (i.e. plastic food container) with the clotted blood will suffice, make sure it is well sealed. After feeding the leeches will become very sluggish and escape is less likely. The most common feeding method is to fill a sausage skin with the blood and warmed in a container of warm water. Simply tie off one end of the sausage skin and fill with the blood. The open end (filling end) will need to be inserted into a small kitchen type funnel and then tied off once the amount of blood you need is in the sausage skin. Sausage skins can be found at hunting supply stores such as Bass Pro or Cabelas in the food preparation area. Sometimes these skins will be preserved in salt. If so, the skins must be soaked in water, rinsed, and soaked again numerous times to remove the salt. The unused skins can be frozen for future use. Immediately after feeding, one will find the water to be very red from blood seeping from the leech bite area on the sausage skin. Change the water right away and keep an eye on this for several days. Never keep unfed leeches in the same container as fed leeches as the unfed leeches will attack those recently fed. The leeches will typically feed for 20 – 30 minutes.
Young and baby leeches will feed quite frequently and will accept food weekly. As they grow older they will accept frequent food offerings with less enthusiasm. Adult leeches can go for up to a year or more without food. If the leeches are to be used medicinally it is best to allow them to fast for about three months or more. This will almost always ensure enthusiastic feeding. After feeding all they will want to do is retire to a nice dark area and digest for some time. You will see a considerable increase in size after feeding and no more until the next feeding. This type of growth is referred to as saltatory growth, not continuous.
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Containers:
Your choice of container for your leeches may vary considerably depending upon what your personal choice might be. One might want to keep them as display, such as an aquarium, or as strictly functional. In either case, escape is something to pay close attention to. A completely sealed container, although escape proof, will not provide air circulation therefore a compromise must be used. For more functional uses, simple glass quart containers (i.e. Ball Jars) will suffice and work very well. The picture below shows Ball glass jars with the top removed and using just the screw lid over a piece of cloth or paper towel. Alternatively, a cloth over the top secured with a rubber band also works well. The container should never be filled up completely as leeches are not strictly aquatic and do need above water space to hang out in.
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Should you like to display your leeches, aquariums fitted to prevent escape are just fine. However, with aquariums, finding the proper escape proof seal and sufficient ventilation can be a challenge. One may find a fine wire mesh reptile aquarium lid that can be weighed down to provide ventilation and prevent escape. One might also attach two sided Velcro to the top and bottoms of the lid edge for additional security although in my experience the Velcro does not stay put. Note – small leeches will happily get through fine mesh so perhaps keep them in a more secure location until they are large. Plants, rocks etc. are all nice additions for display purposes. Do not use any sort of limestone rocks as these will be toxic.
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All enclosures will benefit from some rocky material such as gravel or pebbles so that the leeches can use this to scrape away old skin. Do not use dyed or colored pebbles as these may dissolve unwanted chemicals into the water. Colored gravel from aquarium stores are probably fine but why risk it. It is best not to keep your containers exposed to direct sunlight but if this is the case, make sure there are areas for refugia available, such as a small inverted clay pot or other hiding spot.
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Breeding:
The overall process to produce cocoons is rather straight forward however, there are some complications that will occur.
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Tank setup: There are numerous tank setups that will work, all will need a container that provides temperature and cocoon deposition areas. A tank with some water and an area with sphagnum moss for cocoon laying are required. The following describes my setup but there are numerous variations to this.
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Although cocoons will be produced without temperature regulation, the scientific literature shows that a water temperature of between 75 and 80 °F (24 to 27 °C) will increase fecundity considerably. A proper temperature range will ensure more numerous cocoons and more offspring per cocoon. I use a plastic container where I have drilled a small hole in one side above the water line to insert the electric cable for an aquarium heater. One will have to cut the cable, insert through the hole and re-splice on the outside of the tank. Get some help if fussing with electric connections a challenge for you. A hanging basket with the base touching the water level and with sphagnum moss in the basket. This container may be screwed to the side. Sphagnum moss may be purchased at your local garden supply store. Make sure the moss has not been chemically treated. Although not necessary, I have included a small tap at the bottom of the tank to make water changes a lot easier. The lid must be as escape proof as possible. I have cut a hole in the top of the lid and placed a fine screen mesh over the hole secured with silicone glue for ventilation. If your leeches are large enough to breed the clipping lid should be enough to keep them from escaping. Some however, will persist and get out. As stated before, a bed of gravel is also helpful. A dark environment is best suited for breeding and if possible some sort of light – dark diurnal change.
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Depending upon the age and size of your leeches, cocoons may be expected within one to two months. Leeches are hermaphrodites (actually protandrous but this is a nuance) and two or more will produce cocoons. It is best to have several in a tank.
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Cocoon management:
This can be a tricky problem. One may leave the cocoons in the hanging basket and simply allow the young leeches to hatch and drop into the container below. When they are seen swimming about remove them to a separate container and feed them. Alternatively, they may be removed and maintained separately in a container (glass jar) with damp moss and allow them to mature. Young will leave the cocoon anytime between 4 and 6 weeks. There exists a continuing conundrum with the maturing cocoons as there is typically a high failure rate. Cocoons, quite frequently, will fail. What one will see is a black mass within the cocoon instead of maturing young. The cause of this in not entirely clear, however the consensus is that there is a problem with moisture and ventilation.
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Sick Leeches:
On occasion, your leeches will get sick and it will become immediately obvious. Their normal elongated body will develop lumps and hard parts. Treatment for these include isolation and the addition of Catappa leaves and/or alder cones. You may be able to find Catappa leaves in your more professional aquarium supplier. Both may be purchased on eBay. In time they should heal however, this may not always be the case. An excellent youtube video on treating sick leeches may be found here.
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