Hirudo medicinalis, keeping the medicinal leech at home.

As with most animals I've always thought of the medicinal leech Hirudo medicinalis as pretty cool and after working a bit with them at ZSL I wanted to try them at home, here's how I got on. 

Housing is easy as long as its escape proof, sounds obvious but they really can get out of a tiny gap. I've used a plastic tank with a muslin mesh top under the lid until I found they could bite through the muslin when excited. Now if using a plastic tank (R.U.B, Ferplast, Hagen etc) I'd use a stronger mesh such as a pillow case and then put the lid on over the top to hold it. I'd then place the whole set up in the bath (with the plug in) for a while so you can see if any can get out and catch them if they do.
I now keep them in a custom made aquarium approximately 60 x 60 x 15cm (L x H x W) with plastic mesh (from a pound shop colander) glued over the vents. Water level varies between 15 and 50 cm.

Leeches in temporary tub for feeding, placed in the bath so if they escape I can see them. If left unattended for anytime I would add damp towels for hiding places to lessen the chance of them climbing out. 

(Note the plug is always put in).

Heating; Kept in the coolest room in my flat which is the toilet, winter night time temps can go down to around 10oC but often a few degrees higher. Although never really cold it will lessen the times I need to feed in the winter. If kept cool they need to warm up a bit to feed which they can do quickly but then if too cold there's a chance they will regurgitate their meal over the following days (but if cold there is less likelihood of them biting each other after feeding.)

Water changes,
I keep them in "matured" London tap water, normally by dripping in water from a nearby fishtank. Although the water isn't clean it is mature and near the same temperature as in the same room. I often fill it higher then drain down later that day or the next to help dilute any remaining waste. There is a small internal filter to help with water quality, at first they showed a lot of interest in this but within a day or so seem to ignore it unless other disturbances are happening. On may sites it mentions they can live in dirty water a while, I haven't measured any parameters but doubt they appreciate it so try and avoid it. After feeding I will do a small slow change daily to lessen the chances of an NH3 build up.

One supplier mentions using reverse osmosis water and adding their brand of water conditioners, this sounds a good idea. If using r/o I'm sure just adding 10% of tap would do (or a small amount of sodium bicarbonate?) I use normal London tap-water, as mentioned from another tank or having been left to stand overnight.

Feeding; This is obviously the biggest draw and drawback of keeping them, a few sites mention offering bloodworms, earthworms and bits of liver to them. None of these will be accepted by Hirudo but may be eaten by some smaller pond species (although if the liver was fresh from a still warm body they may latch on, and possibly wash it down with a nice Chianti?)
Another site mentions putting them onto your pet cat, I'm not going to bother discussing that one.

And of course there's the option of feeding them on yourself. 
That sounded cool when I was younger, now it sounds like a pain in the arse (soo to speak). A wound that takes ages to stop bleeding, the possibility of a reaction from the saliva and the possibility of an infection all make me think nope. Going to A+E because of any silly shenanigans is always something I like to avoid as they are busy enough without having to deal with my escapades.
If you plan on doing it I would suggest keeping the tank super clean and add a u/v filter to the set up if possible. I'd suggest don't share leeches and just to be extra careful don't use leeches from the tank someone else's leech has been put into. Possibly overkill? I don't know but why take the risk for a pet.
Some sites don't say about feeding them, just keep in a jar looking cool until they die then replace. Although they are “just a worm” I cant think this is a good way to look at something in your care. Hirudotherapy practitioners don't normally keep their leeches any length of time, they order in as close to the appointment as possibly, let them feed then dispatch them humanly.

Feeding that will work;
Getting fresh blood from a butchers is very hard as the animals they sell have been bled out at the abattoir, anything you see in the trays of meat is myoglobin and is possibly no use (see below). I contacted a few abattoir (all halal as the only ones I could see near London) about blood and one said yes but seemed hesitant when I asked about if its clear of anthelmintic (anti worm treatments for parasites in cattle etc). I'm sure all livestock has to have a period of time between slaughter and last treatment but couldn't find it. In future I think I will just buy and keep my fingers crossed...

Frozen blood; Again not easy to source, I found a company in Germany that sells it (Nov 2019) and brought the minimum amount to ship and keep frozen, that's 5kg, a lot of blood to store.
This has worked really well soo far however I'm not sure of the legislation of importing now we have left the E.U and the company hasn't replied to my request, (possibly as they don't know either) but this amount should last me most of the year. They say you can defrost it a bit then refreeze the rest, I don't think this is good so I have cut up the plastic bottles into chunks so I can defrost a portion as needed.

Do not do this when the neighbours are about!

I use dried sausage skins (again ebay) which you need to soak for a while to remove the salt preservative. I then pour the blood in, tie the top then leave to soak in warm water before offering it to them. You can use forceps to move the leeches to the food or put the sausage near the leeches and any hungry animals should latch on. Make up two or three sausages to use if there are more than one leech so you can attract them separately if needed.

One paper I read says the best temperature is around 24oC for feeding but cooler temperatures are preferred after a meal.
I normally defrost the blood slowly in the fridge, pour into the sausage skin then soak in warmer water till around 24oC, if they latch on but let go without feeding it seems the blood may cool too much and they dont then go for it. This seems surprising as it doesn't cool that quickly so it may be because of something else. One option is to put the tray into a heated tank but that adds another layer of hassle to what is basically keeping a worm.
I have seen them fed using petri dishes, either just placed into them when filled with blood or with a membrane stretched over (sorry I can't remember what that was, possibly sausage skin?) I have just ordered some 100% dried blood off ebay (sold to make blood pudding) so will try out all of the above soon and update!
After feeding, any animals that haven't fed may latch onto others and bite them. This can kill the specimen straight away or often gives the wounds on the body which see to cause constrictions making it hard for the to shed their skin in the future. Although it doesn't always happen it's worth separating feeders and non feeders for at least a few days. Here's a clip of a time I didn't do it. First you can see one biting another, then where I've separating them and the indentations on the bitten ones body. Lastly a vw of the tank the next morning as the animal has either vomited or bled out some of its meal.

Backstory;

When I started at the BUGS exhibit at ZSL the Hirudo medicinalis exhibit was at first a source of wonder but soon seemed rather dull.
The problem (as I saw it) is the exhibit is kept cold to lessen the need to feed the animals thereby making less work for staff while maintaining animal welfare and I do think the cool conditions made a duller exhibit as seeing live, especially large leeches either swimming or doing their swaying in the current as they search for food is pretty cool, leeches kept cold (or well fed) don't do this very much. If the tank is disturbed they will become active but in a zoo setting the frequent tapping on the glass tends to stop them responding unless its by a keeper doing maintenance.

I can only really remember a few feeding events from when I was there as I wasn't their primary keeper; blood would turn up and they would get fed, at one point we were having issues getting fresh blood and one of the vets gave a sample of his own to feed them. This was such a palaver due to the potential safety risks it wasn't repeated. After this we were supplied with blood from culled animals from Whipsnade, there mara and wallaby run wild and sometimes their numbers need to be kept in check.

At home in Grant Towers I thought about trying this species so trawled the internet for info, there are a few sellers offering only to hirudotherapy practitioners and a few that sold to anyone. I went with one that sold to anyone but could find little in the way of realistic husbandy info.
The leeches were sent from the EU and arrived in a zip lock bag in a padded envelope, so basically the soft body of the animal had minimal protection on its journey. Although they did seem fine I won't buy from them again.
I then looked at the sources of blood I had found. I asked at a butchers (trendy organic place in a good part of town) if they sold blood, the answer was no but they could collect some off a joint for me. This they did and I offered it in a sausage skin that I'd scraped the meat out of and also in a condom. They ignored the skin but the condom was too tough to bite through.

Using a condom to feed them but they couldn't bite through it.

Second attempt using sausage skins, this was successfully but all were dead the next day.

I then tried a few days later with sausage skin I brought dried and some fresh “blood”and they all fed straight away. However all the leeches were dead by the next day, at first I thought because of a anthelmintic (wormer) but it's possby because the blood wasn't “blood” but myoglobin , a protein found in muscles and is possibly not digestible to them. I sort of want to try this again to see the result, but am not going to because it means going and getting the myoglobin then all the set up to feed and it just may mean a dead leech. So it may confirm my theory, but as I'm not reliant on that source I will leave it for now. 

I then ordered more leeches from a website offering them for sale as fishing bait (they also sell to hirudopractitioners and vets) and I was informed that the animals are all of the same quality and kept the same and the only difference is the fishing specimens haven't been starved for 6 months as ones for medical purposes would be. I brought 6 and all fed straight away on the defrosted blood (lost 1 from being bitten and another just died). All have now fed a few times so I believe the use of the frozen blood and sausage skins is working, 

Leech information online;

I have found surprisingly little of use to someone that wants to keep them well and doesn't want to feed them on themself. There are a number of places you can buy them from but all the ones I've seen seem to expect you to either use for hirudotherapy and then dispatch them straight after or appear to be people who just want to make a YouTube video showing them with their cool pet but with little info I could use. 

Here are a couple of sites I recommend.

The person I am most in debt to is Nicolas from Cafarnarium who gave me lots of information, even though I havent brought anything! This I really hope to change as his list of species is amazing!

Biopharm in Wales are the main supplier I think of most the Hirudo for sale. Although they can't sell for pets (so don't ask) the specimens available as fishing bait (yuk) are the same quality they just haven't been starved yet so cant be used for hirudology. 

Pets-rawfood.co.uk is the company I brought the frozen blood from, they are not based in the UK so you need to buy a LOT to keep it frozen in transit. 

Weaver ants, Oecophylla smaragdina

I've tried keeping Weaver ants, Oecophylla smaragdina 4 times and haven't had great success, the first colony seemed to be doing well, then the queen started walking around outside the nest and I found her dead

https://www.youtube.com/watch?v=jbnIE75P9LU

The second time I bought a queen with eggs from a UK seller, this had been labeled as queen with brood and after I'd paid they changed the wording to eggs. I wouldn't have gone for this if I'd known before as even just brood I knew would be difficult. She seemed fine and was tending the eggs but then I found her dead.

Third colony was doing well until I moved them (the whole set up as changing their tank), soon after I noticed less activity then they died out (I know it could be a coincidence on the move but...)

The colony I have now I've had for a few months from Ants from Asia and appears to be thriving.

For housing I had been using weeping figs (Ficus benjamina), small plants that have done well but lose a lot of leaves which is obviously not ideal when a nest is in the middle. I then added a peace lily (Spathiphyllum) that seemed to do well with a nest quickly made in a leaf I'd bent over to stop it touching the side glass.

Recently I added a large dumb cane (Dieffenbachia) which again they moved into a large leaf I'd bent over and since moving into this they are hardly on the peace lily even though it touches the dumb cane and they walk on the floor around its pot. Because of this I have taken it out.

Enclosure basics;

All glass fish tank, 48 x 60 x 60cm, water level to the top and heated to around 26oC (housing a Serrasalmus geryi since you asked). In the middle of this there is a strut holding up a tray that the plant sits on. Lighting is 2 x T5 tropical lamps on for around 11 hours. I will probably add more lights and I'd like to try adjustable ones so instead of moving the plant around I move them.

Over the tank (sitting on the glass bracing) is a glass open fronted “box”. 48 x 60 and 75 cm high. I would have gone higher but a shelf above stopped that. The front has sliding panels, like a vivarium.

As the plant was quite leafy and would have easily touched the sides I used a section of green gardeners netting to wind around it holding the leaves in. I expect this is good for the ants as its easier to join leaves but its unlikely to be nice for the plant as limits air movement and light access. 

Description

Dienffenbachia showing green mesh and first nest built in bent over leaf.

The nest was made in the leaf I'd bent in half but now a couple of others seem attached but don't look to be occupied. This is all right at the top of the plant, not sure if it's built there as I bent the leaf or because of heat from the lights. I am going to add another plant next to it soon to offer them a bigger choice or in case this plant dies.

I try and keep the different plants only lightly touching if at all, I had found with the Ficus that they would make nests using leaves from separate plants, this makes it difficult to move the plant around if you wish to change lighting or remove a dying plant. 

When I get a new plant I place it in the sink and spray the leaves with a hose to (hopefully) wash off any contaminants, I then soak the pot very well for a few hours to (hopefully) release any chemicals it may hold. I then don't use the plant for a few weeks just in case.

Temperature;

Day around 26oC

Night around 20 – 22oC

On the Ants from Asia website it mentions a winter drop to around 10 to 15 oC, this will be hard to do in my animal room (or as others call it my only room) as I keep the ambient temperature around 20oC. 

I imagine the humidity is high but there is no condensation on sides due to the ventilation. I rarely mist the plant as I'm worried about water running into the nest, if I do it's done lightly and early morning.

Feeding.

I offer a tray with dissolved sugar in, (it tends to be a strong solution so I don't have to do too often as I'm lazy) and either pre-killed larger insects (crickets, mealworms, wax moth caterpillars) or live fruit flies. I don't give larger live food as I really don't like seeing things torn apart or killed slowly if I can help it.

However I really don't know how many I should be offering so just feed as I feel each day. I also often put in old fruit flies tubs so they can catch the last ones. They seem to become less interested in them after a while, in soo much as they may not actively hunt them after a few days but still eagerly take other prey. As I often put the new food items near or on the nest this may be a defensive act that then becomes food orientated?

I have offered a few other items such as bits of fish, meat, peanut butter and fruit but have seen no great interest.

Thoughts,

I wont use Ficus any more as the small leaves and leaf drop means it may be harder for them to control humidity and temperature within the nest. One Dieffenbachia leaf is large enough as a base, although for a small colony at least I would bend the leaf over or push it against others.

I really wish I had enough space for the plants to not be confined by the mesh, even though I think it may help with nest building I doubt the plant will do well. I also wish I had space for another colony or two as back up as I'm sure I am one mistake away from losing them.

Buying colonies.

I wouldn't now buy a queen on her own or with only eggs/brood. Although there are papers online about raising small colonies these are in the country of origin, probably with a short travel time (unlike the days in transit to the UK) and commercial farmers often supplement with brood or young workers from other colonies and often raise a few queens together.

You may see sellers offer multiple queen colonies at a good price. Many of these species don't have multiple queens in the wild when mature but may when young (including Oecophylla), as they grow the queens will either disperse or fight to the death. I personally wouldn't buy like this unless very a very good price and I intended to separate the queens and some workers soon after arrival.

I would only buy this and most other difficult species as a settled colony from someone I trust.

Here is an interesting paper on raising Oecophylla 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4429428/

Here is a YouTube video from Ants Canada on a weaver set up. Its a really good video, with an open top. They are kept inside by a vasoline layer, not something I'll be trying.

Ants Canada weaver ants video

Compared to other species;

Having kept a few species of ants including big Atta cephalotes colonies I would say Oecophylla are up there with the best. They are diurnal, which is great and aware of movement around them so easier to get your friends impressed. Leaf ants are more amazing I think (if you can see the nest in a glass case) but take up space (same as weavers) but are also incredibly messy. The moat must be cleaned out daily which on a big colony is a lot of work.

I've worked with two of the bigger species Paraponera clavata (VERY short term!)and Dinoponera quadriceps, these are fantastic to watch as they are soo big they seem like a toy walking around. Again, these are not easy (all the ones I worked with died out in time, not my fault I add) but I would definitely try them again.

Sellers;

The colonies I have got that have done well have all been from Peter at Ants from Asia, I have been buying from him for over 8 years and totally trust him.

http://www.antsfromasia.com/home/4594459828

I will use UK sellers to get other easier species and if possible I would like to know how long they have had them and if the colony had grown at all in that time. If not it may not be an issue, but I'd like to know. People also talk about checking for diseases and parasites, to do this properly you would need total separation for each colony/species for at least a month (quarantine originally meant 40 days). Plus the means to check for diseases, none of which we are likely to be able to identify even if the ant is crawling around dying. If the seller says they've had them a while and they are doing well it's good enough for me. Personally I would then try and keep them separate from any other terrestrial invert species I have and try to service their enclosure last or to make sure I wash my hands thoroughly before touching another tank.

I got the aquarium custom built buy the Aquatic Design Centre in London where I get all my custom tanks and viv's made.

https://www.aquaticdesign.co.uk/

2016, a busy happy year.

Heres a few videos off my YouTube channel "SebastiansAnimals" from 2016
https://www.youtube.com/user/SebastiansAnimals
In no particular order I've added these clips of animals or events that I've recorded this year.

Gulper cat fish, Asterophysus batrachus First feeding on a large roach, then a few minutes later showing the large extended stomach.

Aba aba enrichment, Gymnarchus niloticus
Feeding this active inquisitive species using a feeding ball to encourage activity and extend feeding time.

Sexyfish, the resturant.
As part of the Aquatic Design team i help maintain these two large tanks in a Mayfair restaurant.

Target feeding the pinecone fish, Monocentris japonica
Using a tube to ensure the food gets down to this slow feeding species, I've been told by a few people that they are hard to keep, but websites say different so I think it may just be they don't get enough food and like seahorses they don't deposit fat due to thier hard body and need to feed often? Just my thoughts

London April 2015

Sebastian Grant on work and home life in London.

So!

How green is my best friend?*

Although keeping animals is not the "greenest" thing you can do for your planet, a lot of studies have shown that people around animals tend to have better health, or feel they have a better quality of life.

In which case;

I expect to live for a very long time.

I work around some of the most amazing animals on the planet, and at home I keep a few other amazing animals.

What we call, a win, win.

A few montages of life at Grant Towers so far this year.

April

March

Obviously works great, loads going on as always, including the recent arrival of Professor Wu, the Chinese giant salamander. 

Andrias davidianus

Here's me offering him food soon after he arrived.

With thanks to Cat1 for photography.

Rinca and Raja

 Komodo dragons

Varanus komodoensis

The two dragons were put together, and they didn't get on too well.

Rinca

Varanus komodoensis

A Komodo dragon walking around Central London
(Don't panic, it's in his outdoor paddock!)

One of the many things in my day to make me stop and feel grateful.

king cobra

Ophiophagus hannah

Here the king cobra is moved into a temporary enclosure while his old one is re-themed.

Amazing.

*There has been a lot of talk has been about a recent article in NewScientist

http://www.newscientist.com/article/mg20427311.600-how-green-is-your-pet.html

Although keeping animals at home is certainly not the greenest thing you can do, I do feel this paper doesn't cover the whole issue.

To see a slightly less biased view on this issue please read this.

http://www.ethicalconsumer.org/buyersguides/food/dogfood.aspx

Another update, October 2014

Due to increased social and work demands I'm afraid I have been rather slack on the news from

 Grant Towers lately. 

I realize it may be better to get some of my videos onto the world wide web, rather than risk them being lost for prosperity if my home computer crashes from looking at dodgy sites!

A few clips of Grant Towers and ZSL animals.

Possibly chytrid infection on mossy frogs.

This clip shows my Theloderma corticale with what I believe to have been a chytrid infection (Batrachochytrium dendrobatidis also known as Bd). The frogs had been more active during the day, including one seen sitting in the water when they are normally sleeping higher up.

They also seemed to have more problems walking on the glass, as though their feet wouldn't stick as well. 

Some of the frogs in the clip seems to have a thickening of the skin and a wet appearance, which I have taken to mean the possible infection.

I treated with the athletes foot treatment "Lamisil" and within 3 days noted a marked improvement., after 5 days all "symptoms"  were gone. I continued the treatment for a further 5 days.

However, as I didn't swab the frogs I can't be sure the infection was Bd.

I would like to thank Christopher Micheals for his very quick and helpful advice.

Pipa pipa, the Suriname toad.

Australian swamp eel
Ophisternon gutturale

A new addition to a tank I've started for Anableps anableps, amazing tunnelers, they act a bit like a brackish garden eel! 

Not aggressive and feeding on Tetra discus, live Tubifex and frozen bloodworm.

Mainly uploaded because there's not much on them here. They seem easy to keep, slightly brackish, hence the Anableps. 

The main interest is about 40 seconds in and near the end, about 2 minutes in.

This doesn't show their amazing burrowing ability, they dig in and seem to be able to go forwards or reverse with equal ease!

Kew Gardens

The Princess of Wales Conservatory

Zone 8

Carnivorous plants.

Mainly Nepenthes and a few ferns and amazing Selaginella, this is a lovely addition to the Kew glass houses.

Lithobates catesbeianus
Albino American bullfrog

Not to everybodies taste, but I really like these frogs.

Very nervous and skittish when young, bold during the day but flighty when the lights are off. 

They will eat pretty much anything they can overpower but seem to do OK with feeder insects (not the live mammalian prey other people post them feeding on, small penis syndrome perhaps?)

I use an Arcadia T5 12%  with a reading of around 1- 1.5 UVI above half  the tank, hopefully this will stop any developmental issues but is low enough to not cause eye problems.

Top frog.....
And isnt it funny how everybody loves red eyed tree frogs, but not red eyed bullfrogs....

Work, Rest and Film...

More clips taken at ZSL London Zoo.

Its been a busy few months here at Grant Tower's, with working super hard, checking things at home (staff can be soo difficult) and living La Vida Loca (dancing like your dad) that this account of my antics has been quiet.
Fear not, here is a clip from the ZSL website showing my colleague and I, Luke Harding with our
second male Komodo dragon, Rinca.
Our first male Raja has been at the zoo for around 10 years and is amazing, beautiful, calm and could kill you.
Rinca is stunning, alert and probably would kill you....
Here we go into the exhibit with Rinca to show how careful training and professional skills (Luke's obviously) can help the staff management of the animal while spicing up Rinca's life.

Not too much of me, probably a good thing as I look quite chubby.

These are of the caiman lizard, Dracaena guianensis a specialised snail eater from South America.

Here's the official zoo video of the caiman lizard, rather better put together than mine, the only down side?
Mr Grant in view...

Easily one of my favorite animals at the zoo (although i do seem to say that a lot..) 

Watching this animal feed, the way it takes the snails and delicately rolls them around in its mouth always makes me stop and remember how amazing the world is,

unless your that snail.

Here you can see him hunt underwater, using his tongue to search out the prey which is then taken on to land to eat.

(Please excuse the music, it was either dodgy YouTube tunes or loud kids screaming in that mix of delight and disgust they do soo well.)

Its thought in the wild this species eats crayfish as well as various mollusk species, and very possibly a wide range of other things too. However, from what we know snails appear to be the primary food and this should be mimicked in captivity where possible, and if not possible, they probably shouldn't be kept until we know more about their nutritional needs and how to substitute them
As snails are difficult or expensive to obtain, many keepers offer a range of other foodstuffs, from other invertebrates, turkey meat, eggs and even cat food!
If this is harmful or not is difficult to assess, but the specimen I saw that was fed on cat food was obese and was a dull grey color, not the vibrant red and green of our specimen.
Snails brought for a supplier who caters the the human food trade normally starve the snails before selling so they are ready to eat. This means that before use you should offer them a range of good quality vegetables before feeding to the lizard.
Frozen snails are available but again will have been starved before freezing so less useful nutritionally, while snails collected from the wild may harbor parasites so it may be worth keeping for a while to help shed any possible problems.

Here is the same animal finding crayfish underwater.

The year so far... January 2014

Not a happy time overall at The Towers, a major shock has been the loss of the two Australian lungfish Neoceratodus forsteri last year to an apparent bacterial infection.

Neoceratodus forsteri ; A fish caught in time. The first fish had a raised scale with the flesh showing white and puffy, I wasn't overly worried because if a fish with large scales loses one it looks much worse that a smaller fish with a graze and this fish continued to feed well. Two days later the area of damage had grown as more scales appeared to have been knocked off. I worried that something may have been rasping at them so decided to separate and treat. That evening the caudal fin had red streaks through it, the following morning the fish was dead. Two days later the other fish had lighter patches appear on its skin, none having fungus or obvious breaks but obviously not right. I started to treat and the infection faded within a day but in the 10 days the fish was separated it didn't feed and was obviously unhappy being in the much smaller hospital tank. It was moved to a larger but bare hospital tank in the hope of starting to feed again and after 3 days looked like it was taking interest in some earthworms. Two days later, raised scales with white puffy flesh appeared in a patch on its lower body and it appeared to have trouble with buoyancy as its tail was at an angle in the water. Back in the smaller tank for treatment but I'm afraid it too died within 24 hours.  I talked to someone who looks after more of these fish from the same import. I had originally thought that something in my tank was causing the infection, possibly mechanical damage at first then a pathogen within my animals. Now it looks like it’s a longer term problem, inherent either in the fish themselves or with the husbandry that both separate tanks have…. The cause of the death seems to be a Mycobacterium infection, and although Myco is probably found in lots (possible all tanks?) its not normally a problem with young animals. As these fish are a CITES appendix 2 species they were micro-chipped before being sent to the UK, one possible cause of infection was contamination when this was done although this is just a speculation. So I've lost both of these specimens and 6 more from the same import died the same way, luckily 2 other fish are doing well. It's a species I've wanted to be around for around 30 years and no change of getting more due to the cost. You win some, you lose some, but it tends to be the one's you loose that stick in your mind the longest....

       South American water snake, Helicops angulatus. 

The short painful story of when I got a reaction from a Helicops angulatus bite! 

As we learn more about what species may have venom, our awareness when servicing our captives will become ever more vigilant, this obviously wasn’t what I was thinking when I took out the female  Helicops angulatus to assist her slough. The large female was sloughing and had some retained skin so I thought I'd help...
Even though I’d see papers saying these snakes could cause envenomations and of course the work done to highlight the anti-coagulant venom in the Komodo dragon Varanus komodoensis spring to mind. (Although if you’ve a 60KG lizard trying to tear your arm off I'd not be thinking, “ooh! This is soo going to bleed tomorrow!” but maybe that’s just me?)

I had handled this species and this individual on many occasions and had previously had a minor bite but never a reaction, or worried about one.
And then… she had started to slough successfully but the skin on her head was still there so I decided to “help her out”. I removed her from the tank and started to try and peel back the skin but although the body slough was coming off, the head area was difficult so I restrained her by “pinning” her . This went well and I managed to remove some of the skin but then let her go so I could assess how it was going. Although you frequently see people pinning snakes on tele, its not something that should be done lightly as if carried out wrongly damage can easily occur to the snake's vertebrae (or gets you bit...)
I decided to remove some skin from her body so using the towel that I had her in I allowed her to slide through, taking the slough with her, I noticed a small patch of skin on her head and decided to take it off before putting her back. 
With a venomous species or particularly aggressive species I would have then pinned her again, but as these aren't on the DWA I just reached forward, she suddenly flipped back and managed to get hold of my thumb. So, rather than take her off and pin her, I let her hold on while I removed the shed skin.
Not very painful and much better to get the job done in one go. I thought as she chewed away…
After putting her back I carried on my usual evening routine, within an hour I noticed my thumb had started to ache, then to swell. This could obviously be a symptom of mechanical damage so I didn't take much notice.
When it spread to the knuckles I realised something (writeable) was going on. As the hand became swollen I started to wonder how bad I should let it get before seeking advice, I quickly read up the few papers I could find to confirm its not considered life threatening, but still contacted someone I was planning to meet the following day so they were aware I may be indisposed.

The swelling went down over night, but the next day while walking around it swelled across the thumb and all the knuckles, to stop this I held the hand high and this reversed the swelling.
Did I think my life was in danger? No, never, I did think work the next day was going to be difficult (I couldn't cut my dinner and did get a few stares as it looked like I'd punched a wall or similar, not that I do that, but I must look the type?)
The moral of this story? Read up, and dont get bit...