Cystophorous Cercariae Research Articles

The ecsoma in Hemiuridae (Digenea: Hemiuroidea): tegumental structure and function in the mesocercaria and the metacercaria of Lecithochirium furcolabiatum (Jones, 1933) Dawes, 1947

AbstractUltrastructural, histochemical and autoradiographical techniques have been used to investigate the development and function of the tegument of both somal and ecsomal body regions in the hemiurid Lecithochirum furcolabiatum. The terms mesocercaria and metacercaria are here adopted for those stages in the copepod second and fish third intermediate hosts respectively on the basis of morphology and on analogy with the Strigeidae. Mesocercariae were obtained by experimental infection of the harpacticoid copepod Tigriopus brevicornis with the cystophorous cercariae (syn. Cercaria vaullegeardi), whilst metacercariae were removed from the body cavities of naturally-infected rockpool teleosts including Gobius paganellus and Blennius pholis. Observations on the mesocercaria show the origin of the ecsoma from the distal half of the excretory vesicle, which at 21 days post-infection is capable of eversion through the terminal pore. The nucleated microrugous surface layer of the ecsoma at this stage is modified or replaced in the metacercaria by anucleate syncytial tegument similar to that of the adult organ. The metacercarial stage is also associated with the more advanced development of the somal tegument. The two stages differ in metabolic activity, the somal tegument of only the metacercaria resembling that of the adult in acid phosphatase distribution. In the mesocercaria the ecsomal tegument showed the strongest uptake of 3H-tyrosine; absorption of the latter was not detected in the metacercaria. 3H-glucose uptake was restricted to the intestinal caeca of both stages.

Cercaria calliostomae Dollfus, 1923 (Digenea: Hemiuridae); development, morphology and emergence

Cercaria calliostomae, developing in rediae within the haemocoel of the gonad of the prosobranchCalliostoma ziziphinum, is described for the first time from British waters. The direct emergence of the immotile cystophorous cercaria is discussed, and its development and ultrastructure are compared to that ofCercaria vaullegeardi previously described by Matthews (1981 a). The cystophorous tail consists basically of a laminated fibrous caudal cyst, a delivery tube, and an elongated sticky caudal ribbon. At ‘encystment’ the cercarial body retracts into the caudal cyst, the sphincter muscle contracting to seal the aperture. Pressure causes delivery tube eversion and the simultaneous through-passage of the elongated body to the exterior.

Cercaria vaullegeardi Pelseneer, 1906 (Digenea: Hemiuridae); the infection mechanism

SUMMARYThe inoculative mechanism whereby cystophorous cercariae infect the copepod 2nd intermediate host is described for the first time in Cercaria vaullegeardi. Experimental infections of the harpacticoid copepod Tigriopus brevicornis are recorded and the infection process is related to the ultrastructure of the cercaria and to the feeding mechanics of harpacticoids. The cystophorous tail of C. vaullegeardi is shown to be a device whose shape and construction ensure that the cercarial body is neither damaged by copepod mouthparts nor swallowed, but reaches the host haemocoel during the initial stages of feeding. The cystophorous tail consists essentially of a caudal cyst, into which the cercarial body retracts at encystment, and various appendages including a delivery tube. The infection mechanism is triggered when the copepod mandibles bite the narrow posterior caudal cyst beak, when the delivery tube everts into the mouth and penetrates the dorsal mid-gut wall. The cercarial body, lubricated by tegumental secretions, passes simultaneously through the delivery tube and is inoculated into the host haemocoel.

Cercaria vaullegeardi Pelseneer, 1906 (Digenea: Hemiuridae); the daughter sporocyst and emergence of the cercaria

SUMMARYThe daughter sporocyst of Cercaria vaullegeardi has hitherto been regarded as occurring within the haemocoel of the digestive gland of Gibbula umbilicalis. A re-examination has shown that an important part of the sporocyst, previously overlooked, extends from the digestive gland, through the afferent renal vein, the right kidney haemocoel and the transverse pallial vessel into the blood channel within a gill filament, thus providing a means of exit from the host directly into the mantle cavity. The sporocyst is described at light and electron microscope levels, and the emergence of the cystophorous cercariae is discussed.

On the morphology and life-history ofDerogenes varicus (M�ller, 1784) Looss, 1901 (Trematoda, Hemiuridae)

The cystophorous cercaria ofDerogenes varicus (Muller, 1784) Looss, 1901 (=Cercaria appendiculata Pelseneer, 1906) develops in rediae inNatica spp. The cercaria is able to swim by undulating its furcate appendage. The free-swimming cercaria is eaten by calanoid or harpactacoid copepods. Mechanical pressure of the mouth limbs of the copepod causes the evagination of the long delivery tube, which in free-swimming cercariae is coiled up in the caudal vesicle. The cercarial body is pressed through the delivery tube and injected into the body cavity of the copepod.

Démonstration expérimentale d’un cycle biologique à quatre hôtes obligatoires chez les Trématodes Hémiurides

Research on the transmission of Hemiurid Trematode Halipegus ovocaudatus in experimental and natural conditions demonstrates the following: --the miracidium grows into a sporocyst producing rediae in the Mollusc Planorbis planorbis; -- the cystophorous cercariae become mesocercariae in the hemocoele of Copepodes or finally Ostracodes when swallowed; -- the mesocercariae become matacercariae in the mesenteron of larval Odonates (Zygoptera and Anisoptera) when these larvae swallow the Crustacea; -- the metacercariae become become adults in the Amphibial Rana ridibundal perezi which feeds on dragonflies. The four hosts (Mollusc -- Crustacean -- Odonat -- Amphibian) are obligatory in the life cycle for it is impossible to infect the Insects directly with the cecariae or the frog (tadpoles as well as adults) with the mesocercariae. The different stages of the life cycle of H. oveocaudatus aredescribed and the mode of the transmission is compared with the other species of Halipegus and with the Trematodes in general. The adaptative value of the lengthening of the cycle is discussed from the point of view of the conquest of terrestrial hosts by the Hemiurid Trematodes.

Cercaria anadarae sp. n. Parasitizing a Bivalve Mollusc, Anadara brasiliana (Lamarck), from the Northwest Gulf of Mexico

Cercaria anadarae sp. n., a cytophorous cercaria of a digenetic trematode of the superfamily Hemiuroidea, was found developing in the nephridia of 39 to 356 specimens of Anadara brasiliana (Lamarck), the incongruous ark clam, collected from the beachfront in the vicinity of Galveston, Texas. The germinal sacs containing cercariae were found to leave the host clam before liberation of cercariae when infected clams were isolated in bowls of seawater. This is the first record of a hemiuroid larva from a bivalve host, all previous hemiuroids having been reported from gastropod molluscs. The Hemiuroidea (Trematoda: Digenea) are the only flukes known to produce cystophorous cercariae, and in all of the approximately 40 known species, the cercariae develop in rediae in gastropod and scaphopod molluscs (Dollfus, 1950). In most known hemiurid life cycles the cercariae are planktonic and are ingested by copepods, and the adults are found in the digestive tract of carnivorous fishes (Schell, 1970). During a survey of the helminth parasites of marine molluscs of the Galveston Bay area, Texas (Wardle, 1974), a cystophorous cercaria was found in Anadara brasiliana (Lamarck) which inhabits the sandy substrates in and beyond the shallow surf zone along the Gulf of Mexico side of Galveston Island, Texas. During the winter months, combinations of strong winds and low tides agitate the substrate and the clams are washed from their shallow sand burrows and deposited on the strand line of the beach where they were hand-collected. Two species of larval flukes were found in this clam, one a bucephalid from the gonadal area and the other a member of the Hemiuroidea which was unusual in that the host mollusc is a bivalve rather than a scaphopod or gastropod which is the usual host. The cercaria is named after the generic name of the host clam. Since many more adult hemiuroid flukes than larvae have been reported from the northwest Gulf of Mexico, and since the host and its infection are quite common, it is likely that the adult will prove to be a previously described species from one of the common coastal fishes. Measurements are in micrometers unless otherwise noted. Cercaria anadarae sp. n. (Figs. 1, 2) Diagnosis: Cystophorous cercaria (Fig. 1), body 72 to 110, elongate, pyriform, tail cyst spherical, 54 to 65 in diameter, bearing 2 latitudinal rows of 8 to 9 long curved setae each. Center of cysts bearing sac housing 9-segmented protrusile delivery tube 50 long when extended by coverslip pressure. Normally, the tube is withdrawn into the cyst. Mouth and oral sucker indistinct. Pharynx and intestine apparently lacking, body densely packed with parenchyma and with a network of larger nucleated cells connected by fibrils forming a meshwork pattern. Excretory bladder inverted pyriform, size variable in live specimens 12 to 20 long by 15 wide, not visible in preserved specimens. Excretory pore posterior and terminal. Common collecting tubules entering bladder on anterior margin. Four flame cells observed on each side of body. Further details of excretory system not observed. Body cuticula thick and aspinose. Cercariae developing in germinal sacs (Fig. 2) located in nephridia of host clam. Germinal sacs pale orange in color, very mobile, elongate, 1.3 to 4.8 mm in length by 0.30 mm wide with conical anterior end bearing birthpore, and containing hundreds of cercariae. Germinal sac appearing externally segmented due to anterior muscular annulations approximately 100 apart. Host: Anadara brasiliana (Lamarck), incongruous ark clam. Locality: Galveston Beach, Texas. Prevalence: Thirty-nine of 358 clams (10.8%).

Observations on Tubulovesicula pinguis (Linton, 1910) Manter, 1947 and on systematics of the hemiuroid trematodes.

Dinurus pinguis Linton, 1940 was described from a large collection of small trematodes, assembled during the previous forty years. Many of them had been assigned to other, different, species in earlier publications. There was no type-specimen but the account was based primarily on material from Menidia menidia. The specific diagnosis was indefinite, imprecise, and so general that it might include members of more than one genus. Dinurus pinguis was transferred by Manter (1947) to the genus Tubulovesicula Yamaguti, 1934. The species, as restricted, is common in Menidia menida at Woods Hole, Massachusetts and is redescribed from juvenile and adult specimens.Sinclair, Smith and Sullivan (1972) suppressed Stomachicola magnus (Manter, 1931) Manter, 1947 as a synonym of Stomachicola rubeus (Linton, 1910) Manter, 1947 and predicated that Tubulovesicula pinguis is merely a stage in the life-cycle of S. rubeus. The identity of S. rubeus and S. magnus may be accepted, but the proposal that T. pinguis may develop into S. rubeus is rejected.The collection, organization and integration of information on the genetic relations and systematics of the hemiurid trematodes discloses different interpretations and evaluations of taxonomic features. The present status is reviewed. The divergence of opinion results in large measure from lack of knowledge of life-cycles and developmental stages of marine species. Information from freshwater species, although limited, is significant and helpful. Homologous features, common to all hemiurid species, include the nature of the eggs, the peculiar bristle-bearing miracidia, the presence of rediae in the life-cycle, the characteristic cystophorous cercariae that are eaten by small crustaceans, and the unencysted metacercariae in various planktonic invertebrates. These striking features, shared by all members, portray a common genetic constitution and support the postulate of Odhner (1905), Fuhrmann (1928) and others that the Azygiidae, Hemiuridae and Didymozoidae are members of a common superfamily.

Two cystophorous cercariae, C. introverta Faust, 1942, and C. longicerca n. sp. from fresh water snail, Semisulcospira spp. in Japan, with a list of cystophorous cercariae.

Two cystophorous cercariae, C. introverta Faust, 1942, and C. longicerca n. sp. from fresh water snail, Semisulcospira spp. in Japan, with a list of cystophorous cercariae.

Cercaria sphaerula n. sp. from Helisoma trivolvis Infecting Cyclops

A larval trematode of the family Hemiuridae was observed by the writer and a student, Arthur Dean Johnson, while at the University of Michigan Biological Station the summer of 1932. As it is one of the few cystophorous cercaria in this group described from freshwater snails of North America and as notes on the life history were obtained which may shed some light on infestations in marine as well as freshwater forms this preliminary report is given.

A Cystophorous Cercaria, C. projecta n.sp., from the Snail, Helisoma antrosa, North America

A new species of larval trematode, C. projecta, infects Helisoma antrosa. The very small distome cercaria is ontogenetically young, showing no traces of reproductive anlagen even after excystment. It belongs to the cystophorous cercariae, and has a vesicular tail into which the body of the cercaria withdraws when mature. In this encysted state the cercaria is expelled from the snail and awaits ingestion by the next host. The redia is a large, elongate sac, without “feet,” possessing a small pharynx, short intestine and an excretory system consisting of a longitudinal channel and at least sixty flame cells on each side of the body. Excystment is caused by mechanical pressure which releases a force within the cyst, which projects the cercaria very rapidly through a long cuticular tube, the excretory projection, to a considerable distance away from the cyst. Various complex appendages of the tail vesicle along with parts of the excretory system play a large part in this process of excystment. As postulated, the purpose of this type of excystment is to throw the larva away from its cyst, to prevent it from being regurgitated from the body with the empty cyst.

A New Cystophorous Cercaria from California

A New Cystophorous Cercaria from California