Life Cycle of Diphyllobothrium Latum (1950)

nearly 10 million people are parasitized by the tapeworm dilum latum in the cooler regions of the northern hemisphere those who Harbor the parasite May develop a blood condition resembling pernicious anemia this tapeworm requires three hosts to complete its life cycle a fish eating mammal such as man or the dog and two aquatic animals a cop pod one of the crustations and a fish usually a species of Pike the adult worm is located in the small intestine of the Mamon host in the copi Pod a small larvel stage develops while in the fish host is found the larger and final larvel stage the adult dilum latum is Ivory colored attains a length of from 3 to 30 fet in the intestine of man and may live there for a year or more this parasite is called the fish tapeworm or the broad tapeworm because of the width of its segments or proglottids in the intestine of the host the adult tapeworm May release hundreds of thousands of Eggs Daily when infected people defecate in or near bodies of fresh water or when raw sewage is discharged into these Waters the eggs become a potential health hazard the egg averages about 70 microns in length and 50 microns in width at one end of the light brown shell is located a lid the operculum and at the opposite end there is generally seen a knob likee thickening of the shell the egg is filled with a mass of yolk cells as development occurs in fresh water the early embryo stage is visible continuing growth the embryo becomes spherical almost filling the egg the embryo begins to show movement especially of the hooks which are characteristic of tapeworm embryos after a week or more of development the embryo is mature and it hatches Left Behind Yol debris and the vitalin membrane are forced out of the shell the operculum remains attached the hatched embryo is known as a coridium newly hatched corus cidia swim rapidly and have a rather elongated shape later they become spherical and their movement slows down Coria May spin or become stationary here the hooks may be seen again there are six hooks with sickle-shaped ends the movement of the coridium in water is caused by the beating of cyia present on the surface of the spherical larvae the action of the cyia may be studied to better advantage in slow motion the cyia arm much longer on one side of the larvae when the coridium is moving forward the long cilia are at its anterior pole each coridium has two small flame cells with vibrating cyia these structures are part of the Primitive extrator system Coria consists of two parts an outer ciliated envelope the embryo 4 and the inner true embryo or osphere containing the hooks and Flame cells the coridium is the only free living motal stage in the life cycle of driam latum actively moving these organisms may live for several days in Cool Water even though they lack a digestive tract the first aquatic host of dilum Lum is a copi pod several species of the genus diaptomus and a few species of other Genera are susceptible to infection Coria are ingested by the copi poot in its stomach the embryo four or outer ciliated envelope is ruptured releasing the osphere the six hooked osphere becomes active pushing against the intestinal wall with the hooks it breaks through into the blood sinuses of the copi pood here the Aquos speres round up and become almost Motionless these larve are now called prids they begin to grow and are considerably larger in about 5 days after 2 or 3 weeks the prids are almost half a millimeter long they are now motal and have a codal appendage this Cal appendage is the circle Mir in older prids the circle Mir becomes more rounded within it are the six hooks seen in the osphere the body of the procercoid is muscular contains numerous calcarius cor pusles and the anterior end is characterized by an invagination and the presence of glands a copi pod can Harbor several fully grown prids copi pods are an important constituent of the plankton life in streams and lakes they serve as food for small fishes copi pods infected with prids of the broad tapeworm may be eaten by minnows and the larv released in the intestine of the fish or minnows containing live procercoid or infected copepods recently ingested may be eaten by small game fish minnows and small game fish are in turn eaten by species of Pike in Pike the common fish hosts of the broad tape worm the final larvo stage develops this larvae the pleros ciroid lies free free among the muscle fibers when removed into saline solution some of the ploids become very active they vary in size some reaching a length of 5 cm the plos ciroid is cylindrical and glistening white in appearance the most striking morphological feature is the partially developed anterior region bearing a dorsal and ventral Groove the lips of the ventral Groove are seen live plerocercoids of dium Lum are unwittingly ingested by man when infected fish are eaten raw or when infected fish are improperly cooked when living plerocercoids are eaten they survive Passage through the stomach in the small intestine they attach by their anterior ends to the mucosa and grow rapidly in two or 3 weeks the worm is several feet long and sexually mature since dilum Lum sometimes attains a length of 30 ft the worm Loops back and forth on itself in the intestine the anterior end is attenuated and the remainder of the body ribbonlike the whole organism is known as a stroba the strob is made up of three distinct regions the Skol X or head the short neck and the long body the skx and neck comprise only the first few millimeters of the stroba the Skol X is muscular it has two grooves with membranous edges dorsally and ventrally located from these grooves called bothria is derived the generic name dilum the bothria are for attachment and anchor the adult worm to the mucosal surface of the intestine just behind the scolex is the short unsegmented neck region behind the Skol X and neck segmentation begins this is the region of the immature and undifferentiated Broad proglottids superficially these proglottids reveal no internal structures following the region of the immature proglottids the stroba is sexually mature the mature proglottids which contain both male and female reproductive organs show distinct centrally located uteri resembling rosettes these characteristic rosettes are of diagnostic importance dilum latum being the only tapeworm of man with this feature these uterine rosettes are filled with with thousands of eggs through birth pores the eggs Escape into the Lumen of the host's intestine as many as a million per day from a single worm broad tapeworm infections are diagnosed by finding eggs in the feces at the posterior end of the stroba is the region of scile or spent prds from which most of the eggs have already been discharged e