Surface ultrastructure of the developmental stages of Heterophyopsis continua (Trematoda: Heterophyidae).

Ultrastructural observations were made on the tegument of juvenile and adult stages of Heterophyopsis continua using scanning electron microscopy. On the surface posterior to the ventral sucker, the tegumental processes were bandlike in the metacercariae, cobblestonelike in the flukes 2 days postinfection (PI), and velvety at 3 days PI. The anterior surface between the oral and ventral suckers of the metacercariae was packed densely with tegumental spines having a 10- to 14-pointed tip. In flukes 6 days PI, the number of points increased to 15-17. The tegumental spines immediately behind the ventral sucker on the metacercariae surface possessed 5-7 points; posteriorly the points were reduced in size and in number. Ciliate sensory papillae (type I), as single or clumped forms of 2 or 3, were abundant around the oral and ventral suckers of metacercaria and adult worms. The clumped papillae appeared bilaterally symmetrical on the dorsal and ventral surfaces. The ciliate papillae may function in tango-, rheo-, and/or chemoreception. On the lip of the ventral sucker, 6-7 aciliate domed papillae (type II) were arranged in an equidistant manner. At 2 days PI each type II papilla became a clumped form having 2 or 3 papillae. Type II papillae may function as tango- and/or pressure-receptors. The structure and distribution of papillae suggest that the ventral sucker likely functions as a holdfast organ and the oral sucker as a probing organ involved in feeding.     

Cercaria caribbea LVIII Cable, 1963 (Digenea: Cyathocotylidae) in the Republic of Korea and its surface ultrastructure

Cercaria caribbea LVIII Cable, 1963 (Digenea: Cyathocotylidae) was detected from a brackish water gastropod species (Cerithideopsilla cingulata) in a coatal area of Shinan-gun, Jeollanam-do (Province), the Republic of Korea, and its surface ultrastructure was studied using a scanning electron microscope. The cercariae were found freely swimming or enveloped within daughter sporocysts when the snail host was mechanically broken. They were morphologically characterized by a linguiform and ventrally concave body, a long and bifurcated tail, and the presence of a holdfast (=tribocytic) organ posterior to the ventral sucker. On the whole ventral and dorsal surfaces, peg-like tegumental spines were densely distributed. Around the oral sucker, several sensory papillae, each with a short cilium, were distributed, and on the tail, sensory papillae, each with an extensively long cilium, were observed. This is the first record describing a cyathocotylid cercaria from a brackish water gastropod in the Republic of Korea.     

Auriculostoma astyanace n. gen., n. sp. (Digenea: Allocreadiidae), from the banded astyanax, Astyanax fasciatus (Characiformes: Characidae), from Nicaragua, with a reevaluation of neotropical Crepidostomum spp

Auriculostoma n. gen. (Trematoda: Allocreadiidae) is proposed for Auriculostoma astyanace n. sp. from the intestine of the characid fish Astyanax fasciatus in the Atlantic coastal drainages of Nicaragua. The new genus differs from all papillose allocreadiid genera, except Bunoderella, in possessing 2 pairs of muscular oral papillae (instead of 1 or 3), of which the ventrolateral pair is moderately developed and the dorsolateral papillae are long and auricular. Auriculostoma differs from Bunoderella Schell, 1964, in having lateral vitelline follicles, completely separated or confluent only in the posttesticular region, a uterus limited to the pretesticular region or with a few eggs at the level of the testes, and a long cirrus sac that overlaps the acetabulum or usually reaches posteriorly to the ovarian level. Three other allocreadiid species, all from South American freshwater fishes and each of which had previously been placed in Crepidostomum, are transferred to Auriculostoma based on the presence of the diagnostic muscular oral papillae. These include Crepidostomum platense Szidat, 1954, C. macrorchis Szidat, 1954, and C. stenopteri Ma?é-Garzón and Gascón, 1973. Diagnostic features for Auriculostoma also include mainly pretesticular uterus, lateral vitellaria with variation in posttesticular confluence, and tandem testes. The genus appears to be typically associated with neotropical siluriforms (catfishes) and characiforms (tetras).     

Surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae).

The surface ultrastructure of Heterophyes nocens (Trematoda: Heterophyidae) was studied by scanning electron microscopy(SEM). The adult worms were recovered from experimentally infected cats and from a naturally infected patient. They were leaf-like, ventrally concave, and ovoid or pyriform in shape. Ciliated knob-like sensory papillae (type I) were observed in single or grouped forms on and around the oral sucker, whereas non-ciliated round swellings (type II papillae) were seen on the lip of the ventral sucker. The tegumental spines around the oral sucker were 5-9 pointed, whereas those between the two suckers were 12-17 pointed. Ventrolaterally, three groups of 5-6 type I papillae were located between the oral and ventral suckers, with single ones alternating between them. The genital sucker was protruded or depressed, depending on the contraction state of the flukes, and the gonotyl spine number ranged 50-60. The number of tip points of tegumental spines was decreased posteriorly; finally they became 1-3 pointed. On the dorsal surface, 4 groups of 4-5 type I papillae were symmetrically located on both lateral sides, and the shape and distribution of tegumental spines were similar to those of the ventral surface. Although the tegumental ultrastructure of H. nocens was generally similar to those of other heterophyids, the genital sucker morphology including the number of gonotyl spines and/or the distribution pattern of tegumental spines and sensory papillae were suggested to be the characteristic features of H. nocens.     

Helminths of stocked rainbow trout (Salmo gairdneri) with special reference to Clinostomum complanatum

Rainbow trout (Salmo gairdneri) stocked into a small prairie dug-out were examined for helminths at harvest time. Five species of helminths were found (Diplostomum sp., Diplostomulum scheuringi, Clinostomum complanatum, Crepidostomum farionis and Pomphorhynchus bulbocolli); C. farionis and P. bulbocolli mature in fish while the remaining species utilize fish-eating birds as definitive hosts. Examination of stomach contents indicated that all invertebrate hosts required for the life-cycles of these helminths were present in the dug-out. The most conspicuous and prevalent helminth was C. complanatum as fish were "wormy" and unmarketable due to the presence of high numbers of metacercariae. Metacercariae of C. complanatum were recovered from most organs of rainbow trout. The low survival of stocked fish suggests that C. complanatum may cause some host mortality, but the condition of infected and uninfected fish was similar. It appears that a community of ichthyoparasites can become established in a population of stocked fish in a single growing season in north temperate regions.     

A new species of Allocreadium (Trematoda: Allocreadiidae) from freshwater fishes in the Danjiangkou Reservoir in China

A new species of Allocreadium, Allocreadium danjiangensis n. sp., is described from the intestine of several species of freshwater fish, including Abbottina rivularis (Basilewsky, 1855), Sarcocheilichthys nigripinnis nigripinns (Güther, 1873), Gnathopogon argentatus (Sauvage et Dabry 1874), Opsariichthys uncirostris bidens (Gunther, 1873), and Erythroculter mongolicus mongolicus (Basilewsky, 1855) (Cyprinidae) from the Danjiangkou Reservoir in central China. The main morphological characters of the new species are as follows: vitelline follicles numerous, extending from the level of acetabulum to posterior extremity, distributed over both sides around the ceca; cirrus sac relatively large, developed, lying obliquely anterior to the acetabulum, extending from the level of the intestinal bifurcation to the central level of acetabulum, and overlapping left or right cecal; and ovary much smaller than testes, generally close to or even overlapping the anterior border of anterior testis. Observation by scanning electron microscopy shows only 2 kinds of tegumental formations, i.e., papillae and tubercles, instead of 3 types of tegumental formations, i.e., papillae, bosses, and minute sensor receptors observed on other species of the Allocreadiidae. The tegumental striations of the present species vary on the different parts of the body. In addition, a new structure, identified as the "groove" with a tonguelike tubercle, was observed on the inner wall of acetabulum.     

Parasites of juvenile brook trout (Salvelinus fontinalis) from Hunt Creek, Michigan

Four parasite species (Crepidostomum cooperi, Cystidicoloides ephemeridarum, Acanthocephalus dirus, Salmincola edwardsii) infected 215 juvenile brook trout (105 young-of-year; 110, 1-yr-old) from Hunt Creek, Michigan, in 2003, 2004, and 2005. Prevalences of these species in 2004 (main study year) varied from 29 to 37%. Crepidostomnum cooperi had the highest mean intensity and mean abundance, followed by C. ephemeridarum. The number of fish infected with each parasite species was significantly higher in 1-yr-old fish than in young-of-year fish. Also, the mean intensities and mean abundances of C. cooperi and C. ephemeridarum and the mean abundance of A. dirus were significantly higher in older fish. The mean intensity of C. cooperi and prevalence of A. dirus were significantly higher in fish between creek sections. Fish length had a significant positive effect on the abundances of C. cooperi and C. ephemeridarum; parasite species richness, on the abundances of A. dirus and S. edwardsii; and parasite species richness in the 2003 and 2004 trout cohorts, respectively. Crepidostomum cooperi, C. ephemeridarum, A. dirus, and S. edwardsii commonly infect Michigan brook trout. The small number of parasite species infecting Hunt Creek brook trout is similar to the number of parasite species of brook trout from other Michigan creeks.     

Tegumental ultrastructures of Echinoparyphium recurvatum according to developmental stages

The present study was performed to observe tegumental ultrastructure of Echinoparyphium recurvatum according to developmental stages. Worms (1, 3, 5 and 15-day old) were recovered from chicks experimentally infected with metacercariae from Radix auricularia coreana. One-day old worms were elongated and ventrally concave, and covered with peg-like tegumental spines except the adjacent areas of the head crown and excretory pore. Type I sensory papillae were distributed on the lip of the oral sucker, and grouped ciliated papillae were around the oral sucker. Peg-like tegumental spines were densely distributed on the anterior surface of the ventral sucker level. The ventral sucker had an aspinous tegument and no sensory papillae. Tegumental spines on the posterior surface of the ventral sucker level were sparsely distributed and disappeared posteriorly. In 3 and 5-day old worms, the tegument around the oral sucker was aspinose and wrinkled concentrically. The ventral sucker had a wrinkled tegument and many bulbous papillae. Type I sensory papillae were distributed between the bulbous papillae. Tegumental spines were spade-shaped with a terminal tip. A total of 45 collar spines including 4 end group ones on both ventral corners was alternately arranged in 2 rows. The 15-day old worms were very stout and their tegumental spines were tongue-shaped without a terminal tip. From the above results, it is confirmed that the surface ultrastructure of E. recurvatum was generally similar to that of other echinostomatid flukes. However, some features, i.e., morphological change of tegumental spines and appearance of sensory papillae on the ventral sucker according to development, and number, shape and arrangement of collar spines, were characteristic, which may be of taxonomic and bioecological significance.     

Surface ultrastructure of juvenile and adult Acanthoparyphium tyosenense (Digenea: Echinostomatidae)

The tegumental ultrastructure of juvenile and adult Acanthoparyphium tyosenense (Digenea: Echinostomatidae) was observed by scanning electron microscopy. One- to 3-day-old juveniles and 10-day-old adults were harvested from chicks experimentally fed metacercariae from a bivalve, Mactra veneriformis. The juvenile worms were minute, curved ventrally, and had 23 collar spines characteristically arranged in a single row. The lips of the oral sucker had 7 single aciliated sensory papillae and 4 grouped uniciliated sensory papillae. The ventral sucker had 25 aciliated round swellings on its lip. The anterolateral surface between the 2 suckers was densely packed with tongue-shaped tegumental spines, and the ventral surface just posterior to the ventral sucker was covered with peg-like spines. Retractile, peg-like spines were seen on the anterolateral surface, whereas scale-like spines with round tips and broad bases were sparsely distributed posterior to the ventral sucker. The cirrus was characteristically protruding and armed with minute spines. The surface ultrastructure of A. tyosenense was unique, especially in the number and arrangement of collar spines, shape, and distribution of tegumental spines and in distribution of sensory papillae.     

The ultrastructural characterization of the tegument of Clonorchis sinensis (Cobbold, 1875) cercaria.

The tegumental ultrastructure of the cercaria of the liver fluke, Clonorchis sinensis (Cobbold, 1875), was studied by scanning and transmission electron microscopy. The body surface is almost encircled by many rows of regularly arranged spines. The tegumental syncytium of the body contains many rod-shaped dense granules and central electron-lucent bodies, neither of which are present in the tail tegument. There are four rows of hooked teeth and modified spines on the oral cone. These teeth are differentiated morphologically and probably functionally from the other body spines. Disc-shaped papillae with long or short cilia are distributed on the body in a bilaterally symmetrical pattern dorsally and ventrally. There are 30 to 37 papillae with much longer cilia laterally. Four pairs of papillae were found on the tail. From their structure and location these papillae appear to have a mainly tango- or rheoreceptive function. Another type of sheathed papillae is situated around the oral sucker. The cuticular tegument is expanded laterally at the base of the tail, forming a characteristic sac-like structure.     

Ultrastructural features of the tegumental surface of a new metacercaria, Nematostrigea sp. (Trematoda: Strigeidae), with a search for potential taxonomically informative characters

The tegumental surface of a new strigeid metacercaria, Nematostrigea sp., which is a parasite of the freshwater fish Channa gachua (Hamilton) in central Vietnam, is described for the first time using scanning (SEM) and transmission (TEM) electron microscopy. In addition to the general tegumental surface in various parts of the body, details of the surface of the suckers, lappets and holdfast organ are presented, as are variations in the form and distribution of the body spines. As good taxonomic criteria are few in diplostomoid metacercariae at both specific and generic levels, a number of the ultrastructural features revealed may prove to represent taxonomically informative characters. These include the presence of: two rings of dome-shaped papillae localised at different levels on the rim of the oral sucker, a single ring of ciliated papillae on the inner margin of the ventral sucker and a band of dome-shaped papillae along the lateral margins of the broad body-fold in the ventral forebody; an unarmed oral sucker and anteroventral surface of the forebody, although the latter bears protuberant secretory pores; an armed ventral sucker covered by six-pointed spines, except on its rim; multi-pointed spines along the dorsal and ventral sides of the forebody, with the number of their teeth increasing posteriorly; multi-pointed spines on the forebody which gradually transform into single-pointed, more widely distributed spines on the hindbody, disappearing completely at posterior end of the body; the surface of the lappets with a particular distribution of pores leading to three types of secretory glands and three topographical modifications (areas where the surface is smooth, bears digitiform processes or bears recurved, dagger-shaped spines); and the surface of the holdfast organ which is covered with densely packed, straight or slightly curved, simple spines on its lateral surface but is smooth medially.     

Goezia bangladeshi n. sp. (Nematoda: Anisakidae) from an anadromous fish Tenualosa ilisha (Clupeidae)

A total of 1432 hilsa shad, Tenualosa ilisha (=Hilsa ilisha) from 11 fresh water, brackish water and marine localities in Bangladesh yielded 13 adult Goezia bangladeshi n. sp., all specimens being found in the intestine of a single fish host caught in the lower Ganges. A total of 2372 Goezia juveniles were recovered from 490 infected fish (prevalence 34.2%). This is the first Goezia species recorded from Bangladesh, and it differs from other valid species by the number of caudal papillae (pre 7-9, para 3, post 6); encircled by tiny spines, the position of double papillae, the arrangement of body spines, and the length ratio of the intestinal caecum and the ventricular appendix (1: 3.33-4.72). Juveniles were free in the gut, embedded in the gut wall and encapsulated in mesenteries. Tenualosa ilisha serves as the definitive host, but the predominance of juveniles may indicate that piscivorous hosts may also serve as such. A list of the nominal Goezia species with important characters is provided.     

Tegumental ultrastructure of the juvenile and adult Himasthla alincia (Digenea: Echinostomatidae)

The tegumental ultrastructure of juvenile and adult Himasthla alincia (Digenea: Echinostomatidae) was observed by scanning electron microscopy. One-, 5- (juveniles) and 20-day-old worms (adults) were harvested from chicks experimentally fed metacercariae from a bivalve, Mactra veneriformis. The juvenile worms were elongated and curved ventrally. The head crown bore 31 collar spines, arranged in a single row. The lip of the oral sucker had 12 paired, and 3 single type I sensory papillae, and the ventral sucker had about 25 type II sensory papillae. The anterolateral surface between the two suckers was densely packed with tegumental spines with 4-7 pointed tips. The adult worms were more elongated and filamentous, and had severe transverse folds over the whole body surface. On the head crown and two suckers, type I and II sensory papillae were more densely distributed than in the juvenile worms. Retractile brush-like spines, with 8-10 digits, were seen on the anterolateral surface, whereas claw-shaped spines, with 2-5 digits, were sparsely distributed posteriorly to the ventral sucker. The cirrus characteristically protruded out, and was armed with small spines distally. The surface ultrastructure of H. alincia was shown to be unique among echinostomes, especially in the digitation of its tegumental spines, the distribution of sensory papillae and by severe folds of the tegument.     

On the morphology of Acanthostomum spiniceps (Looss, 1896) and A. absconditum (Looss, 1901) (Digenea: Cryptogonimidae: Acanthostominae) with particular reference to the juvenile stage

The morphology of juvenile and adult stages of Acanthostomum spiniceps and A. absconditum, from bagrid fish of the river Nile in Egypt, was studied with both light and scanning electron microscopy. In early juveniles, circumoral spines are absent and the entire body surface is covered with tegumental spines. Late juveniles show gradual differentiation of the circumoral tegument into a collar of spines associated with a reduction in density of tegumental spines at the posterior extremity of the body. Genital primordia appear when juveniles are about 1.75 mm long. The distributions of tegumental spines on adult A. spiniceps and A. absconditum are similar. Spines are denser on the dorsal and ventral surfaces of the anterior and middle parts of the body and less dense towards the posterior end. The tegumental fold surrounding the ventral sucker of A. absconditum has spines while the fold of A. spiniceps lacks them. The most important morphological features differentiating both species are the number of circumoral spines, body shape, ratio of body length to width, sucker sizes, and the presence or absence of spines on the ventral sucker.     

Ultrastructural and histochemical observations on the tegument of Gastrodiscoides hominis (Paramphistoma: Digenea)

The tegument of the paramphistome, Gastrodiscoides hominis, is basically similar to that of other digeneans. It is folded into concentrically arranged furrows and ridges bearing numerous tightly packed tubercules, and extends into the oral cavity. An area of specialized tegument is present on the ventral surface, anterior to the disc region. Mitochondria are absent from the tegumental syncytium and underlying tegumental cells, suggesting that the tegument may serve principally as a protective layer rather than in active uptake phenomena. However, extensions of the lymph and parenchyma systems are closely associated with the base of the tegumental syncytium and may provide ATP for active processes. Ciliated and non-ciliated sensory papillae are present, particularly around the oral opening. Numerous lymph channels are present in the sub-tegument and may be involved in osmoregulation.     

Brachylaima cribbi (Digenea: Brachylaimidae): scanning electron microscopical observations of the life-cycle stages

Brachylaima cribbi is a recently described species of terrestrial trematode that infects mammals and birds with helicid land snails as its first and second intermediate hosts. The adult worm is 2.5-6.0 mm long by 0.5-0.8 mm wide being a long slender cylindrical worm with oral and ventral suckers in the anterior quarter and genital pore in the posterior quarter. Scanning electron microscopy shows that there is a dense covering of tegumental spines at the anterior end which diminishes towards the posterior extremities of the worm. Development of spines was observed in juvenile and mature adult worms. In young worms 1-3 weeks post infection (wpi) spines appear as buds with a serrated edge each having 1-4 spikes per spine. As the worm ages the spines broaden and by 5 wpi the number of spikes per spine increases to an average of 8.1. The serial development of oral sucker papillae in the cercaria, metacercaria and adult worm was observed with the finding of an elongated papilla with a bifurcated tip on the cercaria becoming a shorter and thicker elongated papilla with a large central stoma on the metacercaria. In the adult worm, this papilla becomes dome-shaped with a small central stoma. For some of these papillae a cilium could be seen extended from the central stoma. Other life-cycle stages illustrated were the hatched egg with an extruded egg membrane minus an operculum and a portion of the branched sporocyst dissected from the digestive gland of the land snail Theba pisana showing a terminal birth pore. Scanning electron microscopy morphological features of the adult worm observed for the first time in a Brachylaima were the unarmed cirrus extended from the genital pore with released sperm present and the Laurer's canal opening visible in tegumental folds on the dorsal surface approximately 300 microm posterior to the genital pore.     

Ultrastructural observations on the sensory papillae of juvenile and adult Gorgoderina vitelliloba (Trematoda: Gorgoderidae)

Hoole D. and Mitchell J.B. 1981. Ultrastructural observations on the sensory papillae of juvenile and adult Gorgoderina vitelliloba (Trematoda : Gorgoderidae). International Journal for Parasitology11: 411–417. Ultrastructural observations have been made on the juvenile and adult stages of Gorgoderina vitelliloba from Rana temporaria. Four types of sensory papillae occur; button, rosette, ciliated and domed. Button papillae, which contain a ciliary-rootlet but lack a cilium, occur on the oral sucker, dorsal preacetabular surface and the lateral margins of the fluke. Scanning electron microscopical observations reveal that the tegumental protuberances of the papilla are transformed from a spiked or conical appearance in juvenile flukes to a rounded form in adult flukes. Rosette papillae, which also contain a rootlet, occur on the lip of the ventral sucker of both juvenile and adult flukes. Ciliated papillae only occur on the oral sucker of juvenile flukes. Domed papillae, which contain a large area of electron-dense material, occur on the internal surface of the ventral sucker of both juvenile and adult flukes. The functions of papillae and their possible role in the migration of the parasite are discussed.     

Fischoederius cobboldi: A scanning electron microscopy investigation of surface morphology of adult rumen fluke

Adults Fischoederius cobboldi are conical-shaped, concave ventrally and convex dorsally, measures about 8-10mm in length and 4-6mm in width across the mid section. Scanning electron microscopy (SEM) of entire body showed that the tegumental surface exhibits highly corrugation and transverse folds alternating with grooves and without spines. At higher magnification, the surface of each fold is further increased with a meshwork of ridges separated by irregular-sized pits. The ventral surface has more complex corrugations and invaginations than those of the dorsal surface of the body. Both anterior and posterior suckers have thick edges covered with transverse folds and appear spineless. The genital pore is located at the anterior one-third of the body. There are two types of sensory papillae on the surface: type 1 is bulbous in shape and nipple-like tips, measuring 10-15 μm in diameter at the base, and also type 2 is a similar shape and has short cilia on tips. These sensory papillae occur in large clusters, each having between 7 and 25 units depending on the region of the body. Clusters of papillae on the ventral surface and around the anterior suckers tend to be more abundant and larger in size. The dorsal side of the body exhibit similar surface features, but papillae appear less numerous and are smaller. Corrugations and invaginations of the dorsal aspect are also less extensive than those on the ventral surface of the body.     

Tegumental ultrastructure of adult Gynaecotyla squatarolae (Digenea: Microphallidae)

Gynaecotyla squatarolae (Digenea: Microphallidae) adult flukes were recovered from experimental chicks at day 4-6 post-infection and their tegumental ultrastructure was observed with a scanning electron microscopy. They were pyriform in shape, and their anterior halves were concaved ventrally. The whole body surface was covered with tegumental spines, which were wide and 16-17 digitated between oral and ventral suckers. The density of spines and number of digits decreased posteriorly. The oral sucker was subterminal and the excretory pore was at the posterior end of the worm. Two ventral suckers were similar in appearance and protruded near midline of the worm. The genital atrium was dextral to the small ventral sucker. The dorsal surface was covered with tegumental spines, but the spines were sparser than on the ventral surface. On the middle portion of the dorsal surface, a small opening presumed to be the Laurer's canal was seen. From these findings, it has been confirmed that the adult G. squatarolae has unique characteristics in the surface ultrastructure.