Leech Cocoons

In a series of papers, recently, Dan Shain (Rutgers University) and his colleagues have been carefully examining the structural and chemical properties of leech cocoons. As background, these cocoons are egg-cases that are secreted by the clitellum of leeches and they show some striking diversity. Brooding glossiphoniid leeches have a membraneous cocoon, erpobdellids and fish-leeches (below) cement their hardened cocoons to surfaces, and the medicinal leech cocoons (above) are pretty spongy looking. If you think about it, the material that goes into making these eggs cases must be pretty strange. First, whatever is secreted must adhere and polymerize quickly underwater and without any light or heat. Secondly, there's eveidence that leech cocoons are highly
resistant to denaturation or degredation; so much so that they seem to be showing up in Jurassic and Triassic deposits (e.g., Manum et al., 1991. Zoologica Scripta 20: 347-366; Jansson, et al. In Press, Early Jurassic leech cocoons from eastern Australia. Alcheringa). The work led by Shain has covered a variety of perspectives including the molecular composition of the proteins involved (one seems to belong to the same family as the factor Xa anticoagulants!), the structure of the cocoons and their biophysical properties.

Leeches clear a blocked carotid stent?

The Sydney Morning Herald reports that a Mehdi Jaffari (at left here) managed to clear his 80%-blocked carotid artery by self-treatment with an Australian medicinal leech, Richardsonianus australis. Mr. Jaffari had had 4 heart attacks last year, and had a stent put in his carotid, only to be told in January that he had "advanced cardiovascular damage, with his left carotid artery almost 80 per cent blocked". Five days of leech therapy and the next angiogram showed it cleared. Hmm. Regardless of the veracity of the (as yet unrepeated) claim, the article contains an untruth: "while hirudin was known to dissolve blood clots, it was not known to dissolve plaque". In fact, hirudin only prevents clots. It does not dissolve them.

Leeches - PBS Wednesday - NOVA ScienceNOW

Anoher reminder about our leech segment on NOVA this coming Wednesday (typically 9 pm). The NOVA website already has a few items up online. Including an accompany us in the field hunt for the Giant Amazonian leech, as well as an ask the expert interactive. A nice video podcast, distinct from the broadcast episode has been up on youtube:

Macrobdella the Mimic

McCallum and colleagues, in an article just published in the Southeastern Naturalist, convincingly demonstrate that the rather striking colors of Macrobdella species, the North American medicinal leeches, the dorsal polka-dots, ventral orange with black specks, represent a case of Batesian or Müllerian mimicry.

Leeches in the Osage Creation Myth

The North American native Osage Nation's creation legend concerns their ancestors' spirits ("the little ones") arriving on Earth but finding it totally covered in water. Eventually, the Great Elk manages to make the land appear by throwing himself down on the water, but not before the little ones have consulted a variety of animals, such as Macrobdella decora...

The Wi'-gi-e
The Sho'-ka hastened to the Red-breasted leech
And quickly returned with him
To the Red-breasted leech the people spake, saying: O, grandfather,
It is not possible for the little ones to dwell upon the surface of the water.
We ask that you make a search for a way out of our difficulty.
The Leech replied: You say it is not possible for the little ones to dwell upon the surface of the water.
You ask me to a search for a way out of your difficulty
I shall make search for a way.
Thereupon he pushed forth even against the current
Pulling himself repeatedly as he pushed on.
He came to a fourth bend in the current
Where he paused and spake, saying: It is not possible, O, my grandchildren.
Although it is not possible for me to give you help,
I will tell you: My walk in life is on the surface of the water.
The little ones shall make of me their bodies.
When the little ones make of me their bodies,
They shall be free from all causes of death.
When the little ones make of me their bodies,
They shall cause themselves to be difficult to overcome by death.
When the little ones make of me their bodies,
They shall enable themselves to live to see old age as they travel the path of life.
The days that are calm and beautiful
The little ones shall also enable themselves to live and see.

---

Francis La Flesche, 1922, Annual report of the Bureau of American Ethnology #36

Thanks to Peter Whiteley for informing me about this, to Kara O'Neil for sending me these particularly pretty specimens of Macrobdella decora from her pond, and to Sara Watson for the photos.

How to ratchet up the hit rate...

It seems our friends over at the Dechronization blog have discovered that the internet was made for porn.

I will not be outdone. Herewith, a pair of Chtonobdella (c.f.) bilineata in-copulo! (Credit to Ralph Davis of Sydney, Australia).

Leeches are hermaphrodites, and most of these terrestrial jungle leeches have their male and female gonopores separated by 5 or fewer annuli. The male gonopore from which the penis is pushed out, is anterior to the female gonopore and the vagina; hence the head-to-tail (69) copulation technique. In fact, internal fertilization, though also a characteristic of aquatic medicinal leeches, seems to have originated in their terrestrial ancestors as a way to avoid sperm dessication.

So there... "porn", "penis", "vagina", "69", "sperm" and "copulation" all in one post.

Myth Busters: Leech Anaesthetic

   Perhaps the most common misconception about leech bites, and one that I keep hearing, is that leeches have an anaesthetic in their salivary secretions. The idea seems to have started with Sawyer's Leech Biology and Behaviour, and has even been repeated in normally reputable journals and academic websites frequented by the public for information on various animals.
   The theory goes that leeches, being stealthy, inject an anaesthetic so as to avoid detection. Most notable was an NPR Science Friday story from August 26, 2005 in which a homeopath (Woodson Merrell, of Beth Israel Hospital) and a neurobiologist (George Stefano, Director of the Neuroscience Research Institute, SUNY at Old Westbury) promogulating the story that leeches inject a morphine-like substance to "numb" host tissue.
   Of course, the real story is that leech 'morphine-like' substances are in the neural tissues not in salivary tissue as had been known five years earlier (Laurent et al., 2000. Morphine-like substance in leech ganglia. Evidence and immune modulation. Eur J Biochem. 267:2354-61).
   It should come as little surprise that the myth of a salivary anaesthetic would be further repeated by BioPharm, Leeches USA, Niagara Medical Leeches, and Ricarimpex, (all purveyors of medicinal leeches). After all, patients might resist leech therapy if it is going to hurt.
   In my experience, the bites do hurt. Usually just a little, sometimes rather acutely (especially if your skin is not numbed from having been in cool water for half an hour), and in at least one case, intensely enough to cause one of us to nearly kick the dashboard off a rental car.
   More importantly, there is not a single refereed article in the scientific literature that in any way points to an anaesthetic in leech salivary gland secretions. Twenty years ago, Meir Rigbi and colleagues showed rather convincingly that it does not exist ( Rigbi et al., 1987. The saliva of the medicinal leech Hirudo medicinalis - II. Inhibition of platelet aggregation and of leukocyte activity and examination of reputed anaesthetic effects. Comp. Biochem. Physiol. 83C, 95).

BUSTED

If PBS Doesn't Do It, Who Will?

Be sure to watch NOVA Science Now on your local public television station,Wednesday, July 23 at 9pm in which one of the segments is all about leeches!
A web dispatch (different from the July 23rd televised program) is available as a podcast from our time in the field doing the shoot last October.

Leech Pre-Meeting

A meeting of leech biologists is planned for November 14th, 2008 in Washington D.C. in advance of the 2008 Neurobiology meetings. The meeting is NOT restricted to neurobiology. Please contact Dr. Otto Friesen (wof) at University of Virginia (virginia.edu) to express interest.

American Society of Parasitologists Award for Leech Research

The best student paper presentation at the 87th Annual American Society of Parasitologists went to Anna J. Phillips for her present entitled "Hirudinidae³: Towards a Revision of the World's Medicinal Leeches". Here's the abstract...

Hirudindae contains the most notorious of the bloodfeeding leeches, the medicinal leeches. These worms gained in popularity with physicians practicing bloodletting, or phlebotomy, due to anticoagulants in the saliva that causes the bite to bleed freely, even after the leech has left. This treatment was performed worldwide, for centuries, with a member of the Hirudinidae native to the area. While a higher-level analysis of the Arhynchobdellidae, by Borda and Siddall (2003), found that the Hirudinidae is surprisingly comprised of two groups, this more intensely focused preliminary analysis shows that the Hirudinidae is actually split among three groups. A morphological analysis of twenty-two morphological characters, based on jaw dentition, sexual anatomy, and external morphology, failed to provide a resolution for most of the relationships in the family. DNA sequence data from nuclear 18S rDNA, nuclear 28S rDNA, mitochondrial 12S rDNA, and mitochondrial cytochrome c oxidase subunit I, were examined separately, and in combination, in a parsimony analysis. This analysis of representative species of the Hirudiniformes indicates that the world’s medicinal leeches comprise multiple independent groups. Clade membership is only partially indicated by continental origin. The African Hirudinidae are split between two clades, with the unexpected results of the North African and Eastern European taxa being sister to select genera of Central and South America, one of which is a new genus with a unique morphology among leeches. These results suggest that, what was previously considered the family Hirudinidae, is actually 3 families: the Macrobdellidae Richardson, constituted by most New World taxa; the “true” Hirudinidae, with the type species (Hirudo medicinalis); and a new family, including the subset of African species grouped with Limnatis nilotica and associated New World taxa.