Leech Morphology

The leech body is, "dorso - ventrally flattened". Meaning they are flat from top to bottom and measuring from 6 cm to 30 cm in length and are equipped with a sucking disk at both the anterior and posterior ends. The body is made up of 34 segments and had 3 pairs of eye at the anterior. A leech has a small anterior sucker and a larger posterior one. The anterior mouth contains three toothed plates or jaws. Colorations vary considerable, with most prominent colors being mottled black and green also black and brown. The underside of a leech is typically lighter in color than the backside. Tiny, paired, segmental nephridiopores are present laterally on the ventral surface of most of the body except the extreme anterior and posterior ends.

The pores are inconspicuous but are marked by a tiny pale spot on the posterior edge of the second annulus of the segment and are spaced 5 annuli apart for most of the length of the body. Leeches are parasites rather than predators, and suck the body fluids of their victims without killing them. One of these suckers surrounds the leech's mouth, which contains three sets of jaws that bite into the host's flesh, making a Y-shaped incision (Mercedes-Benz star).









Y shape incision

Leeches can stretch out as long and slender as a toothpick one moment, and be contracted into a tight ball the next. Leeches swim in an undulating moves and are quite rhythmic in their motion.
They typically swim in a slow up but when agitated can move at a much faster pace. Leeches consume the blood of a wide variety of animal hosts, ranging from fish, reptiles, amphibians and mammals.

Leech Behavior

Leech has two type of movement which is in water and on land. Leech moves in water by undulating up and down motion. Movement on land is accomplished by means of looping. The posterior sucker is attached to a substrate and the leech stretches out and attaches to the substrate with the anterior sucker, the posterior sucker is then detached and pulled up to the anterior sucker. For the resting posture, leech lies under large objects on the shoreline, partially out of water. In aquarium, after they feed their meals, leech will stick to the wall of the aquarium and also to the water hyacinth that has been provided.

Movement of Leech, AS: Anterior sucker; HS: Posterior sucker.

Leeches-Biology introduction

Introduction

Leeches are completely soft-bodied animals and could not be expected to leave a marked fossil record. Although there are two putative fossils from Bavarian deposits dating from the Upper Jurassic period (about 145 million years ago), Epitrachys rugosus (Ehlers, 1869) and Palaeohirudo eichstaettensis (Kozur, 1970). The evolutionary relationships of leeches demonstrate that the ancestral hirudinid was a blood feeder in a freshwater environment. This finding suggests that leeches are no older than vertebrates and probably no older than amphibians (Apakupakul et al., 1999).

Leeches are related to earthworms and lugworms (Oligochaetes), and bristle worms (Polychaetes). Leech is the common name for more than 300 species of annelid worms. Leeches belong to the class Hirudinea that prey on small invertebrates in fresh water or suck blood from vertebrate animals.

Every leech has muscular sucker at the rear end of the body; many have a second sucker around the mouth. These organs are used to assist a leech in the feeding process (Milne, 1987).

Leeches are external parasites (David Nichols and John Cooke, 1971). Leeches consume the blood of a wide variety of animal hosts, ranging from fish to humans (Godfrey, 1997). As predators, parasites of animals, vectors of parasites, and as food for semi - aquatic and aquatic animals, leeches are important components of food webs and leeches are also hermaphroditic but do not self-fertilize (Peckarsky et al., 1990).

Leeches are among the most poorly studied invertebrate taxa with respect to their evolutionary histories (Apathy, 1888; Selensky, 1915; Wendrowsky, 1928; Livanow, 1931; Autrum, 1939).The study of Leech is chosen because leeches have a unique body structure. Being a parasitic organism, leech brings a problem to the farmer and will slow down the growth of aquaculture especially during the reproductive period. My data can be used for further study.

Leech Taxanomy

Autrum (1936, 1939) was the first to summarize all pertinent publications on the taxonomic and phylogenetic relationships among the clitellates (Oligochaeta and Hirudinea). In general, the Clitellata can be defined as a monophyletic group of cylindrical (or disk-shaped) segmented invertebrates without parapodia that are characterized by a clitellum (Ax, 1999; McHugh, 2000). All Clitellata are hermaphrodites. They are comprised of two separate groups, the Oligochaeta (earth-worms and other non-carnivorous detritus feeders) and the Hirudinea (leeches, i. e., carnivorous predators or parasites).

The Euhirudinea or true leeches have been classified according to their mode of feeding as follows: Pharyngobdellida (pharynx unarmed, i. e., no jaws or a proboscis present), Gnathobdellida (oral sucker with jaws within the buccal cavity), and Rhynchobdellida (jawless pharynx; these worms utilize an evertible proboscis to penetrate the skin of their hosts). This scheme of classification (Autrum, 1939) has been used in the literature without many modifications (Mann, 1962; Herter, 1968).

The order Arhynchobdellida is comprised of leeches that are characterized by the lack of a proboscis: the non-sanguivorous (unarmed) Erpobdelliformes and the jawed (armed) Hirudiniformes.

Leech Habitat

Leeches (Hirudinea, Clitellata) are among the most numerous freshwater animals occurring in both standing and running waters (Scrimgeour et al., 1998). Most of the common leech species are classified as inhabitants of eutrophic, polysaprobic, moderately and highly stressed freshwater environments (Lenat, 1993). All of them use dissolved oxygen in respiration and have on easy-to-penetrate body surface (Neubert and Nesemann, 1999).

Alkalinity is a requirement for leech survival with pH levels above 5.0 desired. The presence of dissolved oxygen is also required. Turbidity and salinity are thought to play small roles. Leeches have a high tolerance for pollution including eutrophication, oil, copper sulfate and pesticides. They have no tolerance, however, for zinc (Ginsberg, 1998). The factors which determine leech distribution in freshwater environments are, in approximate order of significance (Sawyer, 1986): availability of food organisms, nature of the substrate, depth of water, presence of water currents, size and nature of the body of water, hardness and pH, temperature of the water, dissolved oxygen, siltation and turbidity, and salinity.

The single most important factor in a leech life is the presence of food. Leeches are limited by a very low pH, but otherwise the level of alkalinity does not have an effect on leech distribution. The medicinal leech is amphibious, needing both land and water, and resides exclusively in fresh water.

A typical habitat for H. medicinalis would be a small pond with a muddy bottom edged with reeds (Sawyer, 1986). It is found in warm, protected shallow areas of ponds with little wave action. It stays concealed during the day in dark places provided by vegetation, stones, and debris, and is most active at night (Moore, 1923).