shaped enlargement of the muscle fiber, and after 4 to 6 weeks 

 becomes encapsulated. If not ingested by a host suitable for 

 their future development, the larvae ultimately die and there 

 is fatty degeneration and finally calcification of the cysts. 

 Trichinae are said to remain alive and infective for as long as 

 11 years in the muscles of swine, and to have lived for 12 to 24 

 years in man, according to Baylis. Prenatal infection with 

 trichinae has been demonstrated in guinea pigs by Roth 

 (1936); Mauss got negative results in rats, rabbits and 

 hamsters. In spite of the fact that the larva undergoes so 

 much growth and differentiation Staubli was unable to detect 

 any evidences of molts, and the writer has seen no reports of 

 any being seen by later observers. By analogy with other 

 nematodes, however, it seems probable that the infective larvae 

 have undergone at least two molts. Infection has not been ob- 

 tained with larvae less than 19 days old and only after 21 days 

 can one obtain a high percentage of infections. This seems to 

 indicate that the larvae undergo a change, such as a molt, 

 prior to that time. 



When the larva has undergone its full development, whether 

 encapsulated or not, it is infective when eaten by another ani- 

 mal. Development in the intestine is extremely rapid, sexual 

 maturity being reached and copulation occurring on the third 

 dav, and embryo production beginning on the fifth day. Ac- 

 cording to Kreis (1937) there are four molts in this brief 

 period, at about 4, 12, 48 and 70 hours after ingestion. How- 

 ever, his evidence is not very convincing. According to recent 

 investigations one molt was obtained after ingestion and the 

 cuticle of the resultant nema passed uninterrupted over the 

 vulva, indicating that at least one more molt would be neces- 

 sary before maturity. 



It is evident from this account that Tiichinella spiralis is not 

 only unique among nematodes in utilizing the parental host as 

 a sole resting place while awaiting an opportunity to gain ac- 

 cess to another host by cannibalism (insofar as it passes from 

 individual to individual of one species) but it is also unique 

 among the Triehuroidea in having different "organotropisms" 

 for the larval development and for the adult development, the 

 former being the striated voluntary muscles, particularly the 

 most active ones (pectoral and tongue), the latter the mucous 

 membrane of the small intestine. 



Cystoopsis acipensem 



This is an aberrant worm with respect to both its morphology 

 and its life cycle. The females with their large spherical 

 bodies and the small cylindrical males live in pairs in cyst-like 

 cavities just under the skin of young sturgeons. According to 

 Janicki and Rasin (1930), a well-developed vulva and muscular 

 vagina are present, but they seem to be used only for the en- 

 trance of sperms and not for the exit of eggs. The spherical 

 body is filled with numerous coils of the uterus filled with 

 embryonated eggs. These, according to the authors quoted, 

 escape only by a bursting of the thin wall of the cyst and 

 rupture of the parasite. 



Experimentally the embryonated eggs are eaten by certain 

 species of amphipods, and the larvae, liberated in the stomach, 

 penetrate into the body cavity. The young larvae possess a 

 mouth spear like other Triehuroidea, and are in a very early 

 stage of development. At the end of about 2 weeks they have 

 reached their full size, and then migrate into the appendages 

 or into muscle layers. Here they coil up after the manner of 

 Trichinella larvae and soon become encapsulated. The capsule 

 thickens with time, and by the end of 3 months cannot be 

 broken under a coverglass. No experiments have been per- 

 formed to prove the infectiousness of the larvae encysted in 

 Gammarus, but there seems to be no reasonable doubt but that 

 • young sturgeons are infected by eating amphipods, and that the 

 young worms migrate through the tissues of the host to their 

 location in the skin as do some species of Trichuridae. 



DIOCTOPHYMATINA 



The life cycles of members of this group are very imper- 

 fectly known. The available information concerning the genus 

 Enstrongylides has been summarized by Cram (1927). Larvae 

 described by Rudolphi as Filaria cystica from under the peri- 

 toneum and in the abdominal muscles of certain Brazilian fish 

 were regarded by Jagerskibld as belonging to this genus. 

 Ciurea (1924) found similar larvae in other fish from the 

 Danube, and he also regarded them as belonging to Eustrongi/- 

 tides. Larvae found in Brazilian fishes by Schneider and by 

 Leuckart are stated by Jiigerskiold to resemble E. ignotus of 

 water birds. 



Chapin (1926) found the preadult stage of this species in 

 Fiindulus diaphanus at Washington, D. C. From one to three 

 specimens were found in each fish, and adult characters could 



be seen beneath the last cuticle, corresponding exactly to those 

 of adult worms found by him in Ardea herodias from the same 

 locality. 



More recently Mueller (1934) reported similar larvae from 

 Fttnduhis, in cysts attached to the mesenteries. They were 100 

 mm long by 0.685 mm in diameter, blood red in color, and the 

 head was provided with 12 papillae, in 2 circles of 6 each, char- 

 acteristic of the genus. Von Brand (1938) found a high per- 

 centage of Finulidus from Chesapeake Bay parasitized with 

 this same larval form; individual fish harbored from 1 to 8 

 worms. Von Brand states that the encapsulated nematodes did 

 not harm the host, but that after the host died they left their 

 capsules and endeavored to escape from the dead host by bur- 

 rowing through the tissues, eventually emerging through the 

 gill region or body wall. He Avas able to keep the worms alive 

 on sterile nutrient media for as long as 2 months, but there 

 was no growth or development. 



The larvae found by Ciurea are large, 28 to 70 mm long by 

 264 to 539 /^ wide, and are rose-red or brown-red in color. On 

 each side of the body near the anterior end is a row of small 

 lateral papillae. The mouth aperture has the form of a cleft 

 and has three small pointed papillae on each side of it, and 

 three larger papillae just outside of these. The larvae have tails 

 of two types, one enlarged near the end and regarded as that of 

 the male, and the other rounded off without enlargement and 

 regarded as that of the female. Whether the fish are first or 

 second intermediate hosts is unknown. The thick-shelled eggs 

 are undeveloped when they leave the body of the host. 



Even less is known about the life cycle of Dioclophiiwn 

 reiiale. The adults are usually found in the pelvis of the kid- 

 neys, partieularlv the right one, where they eventually destroy 

 the entire pareiichvma. Worms, often immature, are frequently 

 found in other locations, particularly in the peritoneal cavity. 

 The eggs, in an unsegmented condition, normally escape from 

 the body' with the urine. They develop slowly in water, re- 

 quiring from 1 to 7 months for embryonation, according to 

 the temperature, and then remain viable for at least 2 years, 

 although they do not hatch. Beyond this point nothing is 

 definitely known about the life cycle, but the frequency of in 

 fection in fish-eating animals makes its highly probable that 

 fish serve as vectors for this worm as well as for Eustrongyhdes. 

 Ciurea (1921) found a specimen 63 cm long in the peritoneal 

 cavity of a dog fed, between 3 and 4 months previously, on 14 

 specimens of a cvprinid fish ildiis idiis) from the Danube, Init 

 it is doubtful whether the worm was actually acquired from 

 this feeding. Ciurea also found an active larva in the muscles 

 of Idus which he thought might be that of Dioclophyma. but 

 his figure and discription are more suggestive of an ascarid 

 larva. Swales (1933) reported D. reiialc as a very common and 

 important parasite of mink in Canada, and stated that on mink 

 farms the infection was definitely associated with the feeding 

 of fish to these animals. 



It has generallv been assumed that Dioctophi/ma. after enter- 

 ing the alimentaiv canal of a definitive host, is carried via the 

 blood stream to the kidneys as a young larva, there to undergo 

 its growth to maturity. Its occurrence in the peritoneal cavity 

 was thought to be accidental and rare, and due to rupture of 

 the cvst-like remnant of the kidneys after the complete atrophy 

 of its parenchvina. As a matter of fact, however, the worms 

 are very frequently found in the abdominal cavity of dogs, in 

 the majority of cases without evidence of damage to the kid- 

 neys. Wislocki (1919) found them in that location in every one 

 of" 12 dogs which he examined, and in only two cases could a 

 portal of entry through a partially destroyed kidney be sur- 

 mised. Brown, Sheldon and Taylor (1940) found 13 of 20 

 ■ infected dogs in North Carolina with worms in the body cavity 

 onlv 6 had worms in the right kidney as well, and 1 had them 

 only' in the right kidney. Lukasiak (1930) called attention to 

 the" fact that in spite of numerous searches, especially in the 

 kidneys, larvae have never been found, and relatively young 

 forms" have been found not in the kidneys but in the alidominal 

 cavity, by preference between the lobes of the liver. Stefanski 

 and Stra'nkowski (1936) found a case in which a worm in the 

 abdominal cavity was clearly in process of entering the right 

 kidney; its anterior end was lodged in the tissue of the right 

 kidiie"y, the substance of which had not been destroyed. From 

 this and similar cases which they quote from the literature, 

 and from the other evidence cited above, these authors conclude 

 that the larvae of the worm, travelling via the blood stream, 

 stop in the liver, grow, and finally continue their development 

 in the abdominal cavitv, probably penetrating the kidney only 

 after the final molt, and hollowing out a canal in the substance 

 of this organ. Since the larvae are probably too large to enter 

 capillaries, it seems to us more probable that the worms reach 

 the body cavity by directly burrowing into it, as do Gnath- 

 ostoma "larvae;" we know of no evidence that the liver is in- 

 volved at all. 



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