• There are four pairs of small flask-shaped structures, called spermathecae
or receptacula seminales, one pair in each of the segments 6, 7, 8 and 9.
These receive sperms from another worm during copulation, and store them
in their diverticula.
• Fertilisation is external and takes place in cocoon or egg capsule. A cocoon
may contain many fertilised eggs but only one embryo develops, growing at
the expense of other eggs serving as nurse cells.
• Development direct. Newly hatched young worm receives no parental care
and resembles the adult except for size and absence of clitellum.
Class – Hirudinea
Hirudinaria
granulosaThe Indian
cattle leech• It occurs in freshwater ponds, lakes, tanks, swamps and slow streams.
• It has a blood sucking (sanguivorous) habit, feeding on the blood of fish and
frogs and also of cattle and man.
• Skin is moist and shiny due to abundant secretion of mucus, which helps in
cutaneous respiration.
• Body is metamerically divided into 33 segments or somites.
• Except the first two and the last seven, each segment is further superficially
subdivided into rings or annuli. A typical segment possesses five annuli.
• A temporary clitellum is formed by segments 9th, 10th and 11th, during
breeding season.
• The 5 pairs of eyes appear as a semicircle of black dots at the anterior end.
• A pair of suckers (anterior or cephalic sucker and posterior or anal sucker)
are primarily meant for adhesion and locomotion.
• Beneath the longitudinal muscles and immediately surrounding the alimentary
canal is found the characteristic botryoidal tissue. This tissue fills the entire
coelom except a few spaces termed the haemocoelomic spaces.
• Mouth leads into a muscular suctorial pharynx. Cavity of pharynx alternately
expands and contracts to serve as a suction pump so that blood oozing from
the host’s wound is sucked in.
• Secretion of salivary gland contains hirudin or anticoagulin which prevents
coagulation of blood while the leech is feeding.
• Blood vascular system is replaced by haemocoelomic system.
• Excretory system consists of 17 pairs of nephridia, one pair in each segment
from 6th to 22nd.
• Nephridia are of two types, testicular and pre-testicular.
• Nitrogenous waste is mostly ammonia and small quantities of urea.
• Leeches do not reproduce asexually. They are hermaphroditic, however,
cross fertilisation by copulation is a rule.
• Internal fertilisation takes place in the vagina of each individual and the
fertilised ova are discharged into a cocoon for further development.
• Development direct without any larval stage.
Class - ArchiannelidaPolygordius • It is a marine worm with a narrow, elongated and cylindrical body which is 3
to 10 cm long.
• External segmentation is indistinct.
• Parapodia, setae, cirri and gills are altogether absent.
• Coelom is completely divided by septa. Each segment of coelom contains a
pair of metanephridia.
• It is unisexual.
• Development includes a larval stage. Larva is called as Loven’s larva (typical
trochophore).