Sucker Free Sunday €? Issue 37

Updated: 24 September 1999The text below simply represents a crude lecture outline of one of the topics covered in class. Itis not meant to substitute for attending lectures or ignoring the textbook. Additional material,including line drawings, kodachromes, and more extensive information on life-cycles and basicbiology, will be supplied in the lectures. TOPIC #4. Basic characteristics of the Class: Digena2 suckers usually oral (usually anterior) sucker. Surrounds mouth. acetabulum (ventral sucker).2-more hosts in life cycleAll but a few monecious (self or cross fertilize)Types of adult flukes distome [most common; oral sucker & ventral acetabulum] amphistome [oral sucker; posterior sucker, usually posterior to testes] monostome [oral sucker only] gasterostome [mouth in center of oral, ventral sucker] holostome [forebody & hindbody; tribocytic organ posterior toacetabulum] echinostome [collar of spines around anterior sucker]Tegument Two Zones outer cytoplasmic syncytium with microvilli [mitochondria, ER, vacuoles, lipids, etc.][pinocytosis; spines]inner area of nucleated cell bodies - cytonszones separated by basal lamina (C.T.)also, circular & longitudinal muscle under basal laminanumerous chemicals in tegumentmucopolysaccharides to inhibit host digestive enzymesacid & alkaline phosphatases, esterases, and aminopeptidases for digestionAlimentary tract incomplete gut pharynx, when present, masticates food esophagus leads to 2 blind caecae entire gut secretion by cells along gut; proteases, lipases, etc. in cecae, absorption too different species feed on different things: blood mucus epitheliumMale reproductive system usually 2 testes; taxonomic importancevas efferens - vas deferens - cirrus pouchcirrus pouch encloses seminal vesicle, prostate glands, and cirrus; some with externalseminal vesicle outside of pouchsperm stored in seminal vesicleprostate secretes fluid to keep sperm aliveFemale reproductive system usually single ovary2ndry oocytes releasedthrough short oviduct, into ootype3 organs enter into ootype:Mehlis glandcluster of unicellular glands, enhance egg tanning by maintaining correct pH. Differentcell types in glandsecretions cause release of shell globules from vitelline glandssecretes first membrane around egglubricates uterusactivates sperm, which are passed down ootypeCommon vitelline duct [passage of vitelline gland secretions for eggshell formation]Duct from seminal receptacle [absent in some species]Occasionally a fourth duct, vitelline reservoir, as diverticulum of vitelline duct Excretory system protonephridia (flame cells)excretory bladder in posterior, with excretory poreEgg usually operculatelid pops off during hatching (in schistosomes, no lid; shell splits)miricidium produces lytic enzymes in response to proper stimulus (i.e. light). Membrane between operculum and cushion dissolves; water enters. Cushion expands, andcement of operculum dissolvedMiricidiumhatches from egg - penetrates mollusc (rarely annelids)asexual stages from miricidium morphologic characteristics:apical stylet [in some species]apical papilla [where ducts from glands open; also nerve endings for chemoreception]apical gland [histolytic enzymes]cephalic glands [lytic enzymes]photoreceptors [eyespots]germinal mass [initiate asexual stages]cilia [locomotion]excretory poreactively swimchemoreception to snail mucus [1980, Acta Tropica 37: 303-318]attaches to snail with apical papillae; lytic enzymes dissolve tissues. About 30 min forpenetration.Sporocyst asexual stage, various shapesno mouth or digestive systemabsorbs nutrients through tegumentmay produce rediae, daughter sporocysts, or cercariaeRedia develop directly from miricidium, or from embryos generated from sporocystselongate; crawl activelymuscular pharynx, mouth, blind-ended sac caecum1-more ambulatory buds for movement oftenbecause ingestion, many species cause extensive damage to hostwill form daughter rediae or cercariaeCercariae from redia or sporocystfree-swimming, leaves snail and seeks hostminiature immature fluke with tailsenarios penetrate skin of definitive hostencyst on vegetation as metacercariaeencyst as metacercariae in intermediate hosteaten by intermediate or definitive hostmesocercariae (unencysted juvenile) in tissuesTypes, some systematics based on sucker placement of cercariaemonostome1 sucker only, anterior2 eyespotslong, simple tailsdevelop from rediagive rise to monostome adultsamphistomeposterior sucker, often anterior tooeyespotsdevelop from rediagive rise to amphistome adultsall in superfamily: Paramphistomoideagasterostomemouth ventraldevelop into gasterostome adultsall in family: Bucephalidaedistome2 suckers, one oral and one ventralmost common typeanother classification, based on cercarial tail shape and other structurespleurolophocercousdorsoventral fold on tailall in superfamily: Opisthorchioideadevelop from rediafurcocercousforked tailsome with eyespotswith pharynx, holostomes and strigeidswithout pharynx, schistosomesechinostomecollar of spines anteriorlyechinostome adultsxiphidiocercariaewith anterior styletdevelop from sporocystsophthalmocercariae [with eyespots]Take me home Home Search What'sNew Help Comments Kansas State University Biology Division

Sucker Free Sunday – Issue 37

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