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Fasciola hepatica life cycle.ppt

1. The document describes the male and female reproductive systems of the liver fluke (Fasciola hepatica). 2. It details the developmental stages from egg to miracidium larva, sporocyst larva, redia larva, cercaria larva, and finally the metacercaria larva which can infect the primary host when consumed. 3. The life cycle involves sexual reproduction in the primary host, followed by a complex asexual development within the intermediate snail host, before the infective metacercaria stage can continue the life cycle in a new primary host.

Education◦
Male and Female Reproductive System of LIVER FLUKE (Fasciola hepatica) Core Course No. ZOOA – P1T, Group-A, Topic No. 6
Male Reproductive System 1. Testes: 1 pair; highly lobed, tubular; one behind another 2. Vasa deferentia (VD): 2 in number, one from each testis, runs side by side, anteriorly upto the level of acetabulum 3. Seminal vesicle: A large pear-shaped, 2 VD unite here, act as storage of sperm. 4. Cirrus sac: a narrow ejaculatory duct (ED)  into a muscular penis or cirrusGenital atrium Gonopore 5. Prostate gland: Numerous, unicellular, surrounds and open into ED
Female Reproductive System 1. Ovary: Single, highly branched, tubular, anterior to testes 2. Oviduct and Uterus: a short, narrow oviduct, posterior to ovary. Oviduct median vitelline duct Ovo-vitelline duct/Uterus. Laurer’s canal (a short muscular copulatory tube connected to oviduct). 3. Vitellaria (Vi): composed of Vitelline glands (VG) and Mehlis’s glands (MG). Vi cells secrete yolk for nourishment of developing egg and also form egg shell VG (cluster of follicles) Ductules Lateral longitudinal ducts (2) Transverse duct Yolk reservoir Median vitelline duct Uterus • MG (shell glands): cluster of unicellular glands in the junction of oviduct, its secretion lubricate uterus for smooth passage of eggs.
Life Cycle
• F. hepatica is a digenic parasite • F. gigantica is more common in India • Worldwide distribution • Endoparasites (Adult in the bile duct of sheep) • Primary host: sheep, goat, cattle, horse etc. • Secondary or intermediate host: Fresh water snail of genus Lymnaea (Lymnaea marginalis is Indian species) , Bulinus, Planorbis
Life History Developmental stages 1.Copulation 2.Development of Zygote 3.Formation of Miracidium larva 4.Infection of Secondary Host 5.Sporocyst Larva 6.Redia Larva 7.Cercaria Larva 8.Metacercaria Larva 9.Infection of Primary Host
Copulation • Cross fertilization • Development of fertilized eggs and formation of zygote in the uterus • Covered by yolk and shell like component
Development of Fertilized egg • Shelled eggs are known as capsules • Each about 130-150 µm long and 60-90 µm wide. • Each fluke can gives 3000-35000 eggs/ year (there are about 200 flukes in the liver) • Operculum present at one end. • Unequal holoblastic cleavage gives rise to two cells. Larger cell is considered as somatic cells, smaller cell is propagatory cell (PC). PC divides further to embryonic cell and germ cell. • Eggs are comes out with host faecal matter. • In humid environment, at 22-25ºC, after 14-17 days development within eggs is complete which gives rise to Miracidium larva.
Development of Fertilized egg
Development of Miracidium Larva • 0.03 mm long, anterior part broad and posterior part tapering • 21 ciliated epidermal plate arrange in 5 rows as 6-6-3-4-2 • Apical papilla has an apical gland • A pair or cephalic or penetration gland • 2 eye spots • circular and longitudinal muscles beneath the epidermis • 2 flame cells are present in both sides. • swims for 8-30 hrs in fresh water to find suitable secondary host (snail) • proteolytic enzymes from penetration gland helps in penetration to mantle cavity or pulmonary sac
Development of Sporocyst Larva • 0.03 mm long, anterior part broad and posterior part tapering •circular, longitudinal muscles and mesenchyme beneath the epidermis • Protonephridium of each side with 2 flame cells opens in common excretory pore. • presence of germ ball • Each sporocyst gives rise to 5-8 radiae by parthenogenesis
Development of Radia Larva • 1.3-1.6 mm long, sac-like • Mouth at the middle of anterior end leads to short muscular pharynx. Pharynx has pharyngeal glands. Elongated sac-like gut. • presence of birth pore posterior to collar • a pair of projections called lappets present posteriorly. • presence of germ ball • a pair protonephridia is present. • Each Radia gives rise to 20 cercariae by parthenogenesis
Development of Cercaria Larva • 0.25-0.35 mm long, presence of tail. • they comes out from the birth pore of radia and live in the digestive gland of snail. From there to pulmonary sac and outside the body of snail. • Body covered by cuticle • presence of cystogenous gland • presence of anterior and ventral sucker • Mouth within anterior sucker leads to muscular pharynx, oesophagus and bifercated intestine. •presence of germ cells • numerous flame cells opens into two lateral longitudinal canals opens outside through nephridiopore
Development of Metacercaria Larva • Cercaria larva swims for 2-3 days and attach to the vegetation near land, remove its tail • 0.2 mm in diameter • cystogenous gland secretes cyst surrounding the body • called Juvenile fluke consumed by primary host, comes to small intestine, cyst dissolved, comes to portal vein by penetrating the gut, reach the bile duct and within 3 months the become sextually matured.
Disease and Clinical Features Fascioliasis • Inflammation of bile duct • Pharygeal Fascioliasis • Obstractive Jaundice • Adenoma
References • Kotpal R.L. (2015). Modern Text Book of Zoology Invertebrates. 11th Edition. Rastogi Publications.