The California Blackworm

I find myself preaching blackworms by accident in many of my posts, simply because I love the li'l guys so much. So, I decided to start a thread just for them. I'll be posting real information as well as my own very biased observations and anecdotes.

Here is my favorite photo of a cluster of 'em in the front right hand corner of my odyssea B9 bowfront 9gal aquarium. They are accompanied by some cheeky planaria and the photo was taken in super macro mode on a Canon Powershot S3 IS at close to 0 inches distance from the glass.

Lumbriculus variegatus
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Lumbriculus variegatus
Scientific classification
Kingdom: Animalia
Phylum: Annelida
Class: Clitellata
Subclass: Oligochaeta
Order: Lumbriculida
Family: Lumbriculidae
Genus: Lumbriculus
Species: L. variegatus
Binomial name: Lumbriculus variegatus

Lumbriculus variegatus, sometimes known as blackworm (or even California blackworm), is the name given to at least three distinct species of worms which are identical in outward appearance. Until 2009, the species were regarded as one.[1][2]

These species of worms live in shallow water marshes, ponds, and swamps, feeding on microorganisms and organic material. They live throughout North America and Europe.

On average, an adult blackworm can have from 150 segments to 250, each of which has the ability to regenerate into a whole new individual when separated from the rest of the animal; in most populations, this is the primary mode of reproduction, and sexually mature individuals are exceedingly rare - in large areas (including Asia, most of North America and the greater part of Europe) sexually mature individuals have never been found.

Characteristics

Among the characteristics of the genus are a green pigmentation of the anterior end, its two-pointed setae, and its curious reflex escape mechanisms. When touched, Lumbriculus will attempt to escape, either by swimming in a helical ("cork-screw") fashion, or by reversing its body. Which of these two escape patterns are used, depends on where the worm is touched: the anterior end elicits body reversal, and the posterior end helical swimming. Lumbriculus has a quick reflex that allows it to use its photoreceptors to escape. The photoreceptors can detect shadows and movement. The posterior end lifts out of the water and forms a right angle. It is then exposed to air and is used to exchange oxygen and carbon dioxide. Although, this exposes its posterior to its enemies. If the photoreceptors detect a shadow or movement, the posterior rapidly shortens in response to a threat.

Reproduction

Regeneration in L. variegatus follows a set pattern. If the regenerating segment originated less than eight segments from the anterior tip, this amount of segments are regenerated; if, however, the segment was originally from a more posterior position, only eight segments are regenerated. Posterior to the segment, a variable number of segments are regenerated, and the original segment undergoes transformation to become suited to the new, often more anterior position. L. variegatus is presumed to be holarctic in distribution, although in East Asia and North America (and perhaps other places as well) it is probably replaced by the other species of the genus (many of which are known from very small areas; Lumbriculus illex, for instance, is known only from three individuals found in a stream to the North of Vladivostok). Mature Lumbriculus can easily be told apart by a number of genital characters, but as few of the species in the genus ever become sexually mature, it is often difficult to know which species you are dealing with. A physical description of L. variegatus is, to a large extent, valid for the entire genus.

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References

^ Press Release, University of Gothenburg, April 22, 2009
^ Genetic variation in the popular lab worm Lumbriculus variegatus (Annelida: Clitellata: Lumbriculidae) reveals cryptic speciation, Daniel R. Gustafssona, David A. Priceb and Christer Erséus, University of Gothenburg

I have NEVER observed blackworms lifting their posteriors out of the water and into the air, and I've set them up in situations where the water was very shallow so they could if they'd wanted to and been physically capable. I doubt they really do this behavior, even if Wikipedia says they do. I'd like to be proven wrong, however.

What I do see them do is burrow down through the aerobic layer of substrate and into the anaerobic layer, but extending their posteriors up, out of the substrate altogether. Presumably this is to aid in respiration since their heads are buried in anaerobic muck where they dine on bacteria and god only knows what else.

Included are two photos of the same worms, one showing the typical tails in the air view of the worms and one better showing the buried part of the worm including the circulatory system full of rich, haemoglobin based blood. In both of them you can see that the worms venture down into a mucky region. I'm trying to get some photos showing them venturing down into black sand, which they do sometimes, always with their tails sticking out of the substrate.

Blackworms are a key part of the freshwater deep sand bed. I believe they keep the upper layers of sand well open to circulation and that they assist in the exchange of water/nutrients/oxygen between the aerobic and anaerobic layers of the substrate. In this way they help denitrification to take place. Along with malaysian trumpet snails and rooted plants they make my sand "live sand."

My experience has been that my nitrates never pass 10ppm and are often lower, though I only add water to replace what evaporates except for a 15% water change every month. I attribute this to dense vegetation and the freshwater "live sand."

As an experiment, I buried my dwarf gourami at the bottom of the sand bed by the glass when it died of that weird disease so many dwarf gouramis die of. I have included a photo of the area through the glass and circled the place where the gourami was/is in red and also circled a dreaded gas pocket in blue. The root systems of some cabomba caroliniensis can be seen infiltrating the heavily anaerobic black sand and numerous blackworms can be seen living in the sand immediately above the strongly anaerobic region. There is a remarkably sharp boundary between the black sand and the aerobic sand directly above the corpse of the fish.

The fish has been buried for almost eighteen months and still generates several daily flurries of gas bubbles. There is no evidence of poisoning in the tank. I believe that the bacteria in the aerobic layer of live sand are metabolizing the products of anaerobic decay in the upper layers of sand, neutralizing any toxins.

bradlgt21 said:

I always thought blackworms were food for fish.

and why would you bury a dead diseased fish in your tank. You ever heard of quarentine. There is a reason we do it. Not just for the fish but for the rest of the fish so they don't get sick. Thats like taking someone who died of the plague and storing him in your basement.

Click to expand...

Well thanks for that.

I don't believe that the TB is likely to grow anaerobically and emerge from the sand. Especially since it's been like a year and a half that the dead fish has been down there and no other fish in that tank have come down sick with any kind of bacterial illness the whole time.

I have heard of quarantine and I even know how to spell it. Also, it's more like taking a person who died of the plague and burying him under many feet of sand in my basement than just storing him in the cellar exposed to open air.

Yes, blackworms are excellent fish food! My fish love stalking them and trying to sneak up and snap 'em down before they can retract their tails into the substrate and escape. I'll attach a photo of my blue ram, Prettyboy, just as he's about to pounce. Look how excited and engaged he is! Live food is just so good for fish!

If you aren't interested in what I have to write or if I am somehow ticking you off with what I write, I sincerely hope you can find something more fulfilling to read and comment on.

That said, I invite any corrections, non-snide comments, disputes, etc. I'm just really into cali blackworms and wanted to share. I love learning so anyone with anything to say please do chime in.