Most sanguivorous species are called as temporary parasites, rest are
permanent. that is they are not permanently attached to prey and have to
leave host as they are engorged with blood (like mites) so they are near to
predators side. Also many are faculative parasites.
http://faculty.fmcc.suny.edu/mcdarby/Animals&PlantsBook/Animals/06-Segmented
%20Worms.htm

as i understand in case they are predaceous, prey item must be so small that
they can swallow at once. marine ones are not said to bite us. they also do
not bite whales (see below), but they prey snails.

i had some mistakes caused by confusion of my live HD. see below.

this is the mistake in my mail..."largest" and "on whale" part. I AM SORRY
http://www.ianr.unl.edu/ianr/plntpath/nematode/bignema.htm
The largest nematode ever observed is Placentonema gigantisma, discovered in
the placenta of a sperm whale. This 8 meter long nematode is said to have 32
ovaries. Appearently whales do not have leeches (maybe some 50 million years
is not enough to provide a "relation") but lampreys (esp. baleen whales)
instead.

secondly the largest leech is terrestrial and may exceed 46 cm! It is Giant
Amazon Leech-Haementeria ghilianii (de Filippi, 1849, and it is also a
sucker! it lives on mammals and reptiles and you can find a lot of info on
the net [it is horribly also a medicinal species!].
See photo at http://www.junglephotos.com/animals/insects/leech.html
Also see http://www.earthlife.net/inverts/hirundinae.html


however marine species like 18-cm long Stibarobdella loricata parasitize
large fishes eg. sharks.

SEE ALSO BELOW (About snail hunters etc)




http://www.geocities.com/thesciencefiles/leeches/leeches.html

Leech Facts:
  1.. About one fifth of leech species live in the sea, where they feed on
fish.
  2.. The leech has 32 brains - 31 more than a human.
  3.. The Hirudo leech lays its babies within a cocoon; whereas the Amazon
leech carries its babies on its stomach - sometimes as many as 300.
  4.. The Amazon leech uses a different method of sucking blood. It inserts
a long proboscis into the victim, as opposed to biting.
  5.. The bite of a leech is painless, due to its own anaesthetic. The
Hirudo leech injects an anti-coagulant serum into the victim to prevent the
blood clotting.
  6.. The leech will gorge itself up to five times its body weight.
  7.. The first leech was used in medicine about 1000 B.C., probably in
ancient India.
  8.. In the past, people would stand in the lakes and pools dotted around
the country and when the leeches attached to their legs they would put them
in baskets and sell them. Today the Hirudo leech is an endangered species.
  9.. The nervous system of the leech is very similar to the human nervous
system and is of enormous benefit to researchers in their quest for the
answers to human problems.
  10.. Leeches can bite through a hippo's hide!
http://www.biokids.umich.edu/critters/information/Hirudinea.html

The species that feed on blood have special chemicals in their saliva that
prevents blood-clotting. Many blood-feeding leeches attack only fish, a few
attack any vertebrate (including people), and a few are specialists on
another group of animals, like turtles or waterbirds. There are also lots of
leech species that don't suck blood. They are predators, eating worms,
snails, aquatic insects, and other invertebrates.

http://www.invertebrate.ws/leech/intro.htm
here information is given on predaceous species on snails, insect larvae,
earthworms and amphipods. In the pdf file it is written they sense prey
using sound waves! also site reports they are also suck blood from all
aquatic or marine vertebrates (turtles, sharks, frogs, fishes, aquatic birds
etc), also other leeches.. those on small snails are usually in
Rhyncobdellida (jawless leeches)

http://reference.allrefer.com/encyclopedia/L/leech.html
Certain small leeches of the E Mediterranean region may enter the bodies of
humans and animals through drinking water and lodge as parasites in the
mouth or the respiratory passages.

http://www.fish.washington.edu/naturemapping/water/4leech1.html
In fact only 2 of the 25 genera of leeches in the U.S. are blood-suckers!

http://www.earthlife.net/inverts/hirundinae.html
Technically speaking most leeches are not parasites because they only take
one meal, or bite from a host and then leave, rather they are highly evolved
predators. Only a few leeches really are parasitic in behaviour, these
include Calliobdella lophii which lives permanently attached to Angler Fish,
Hemibdella soleae which parasitises Soles, several species of Ostreobdella
which can be found in Oysters and various species of Theromyzon which live
in the nasal cavities of some water birds.
Not all leeches are blood suckers either, many species are straight forward
predators on smaller invertebrates including insects, crustaceans and other
annelids. These prey animals are sucked in and swallowed whole. The Horse
Leech, Haemopis sanguisuga (whose scientific name means blood sucker) does
not suck blood at all. Instead it feeds mostly on smaller worms. Also the so
called Dog Leech Erpobdella octoculata is another example of a misperceived
predatory leech. It has a long and strong oesophagus which it use to suck
water snails out of their shells and it has no more interest in the blood of
dogs than the Horse Leech has in the blood of horses.

http://www.ias.ac.in/currsci/dec102002/1317.pdf

Article on Potential of the leech Glossiphonia weberi (Blanchard) in
controlling the sewage snail Physa acuta Draparnaud

some record-breakers site

http://oceanlink.island.net/records.html

http://www.nrm.se/ev/dok/djurtal.html.en

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