Surface ultrastructure of Metagonimus miyatai metacercariae and adults

Surface Ultrastructure of the Adult and Juvenile Stages of the Trematode Astiotrema Impletum (Looss, 1899) Looss 1900 (incertae Sedis) from the Nile puffer, Tetraodon Lineatus Linnaeus, 1758

A scanning electron microscope study was performed on the surface of the trematode Astiotrema impletum (Looss, 1899) Looss 1900 from the Nile puffer, Tetraodon lineatus Linnaeus, 1758 (Syn. Tetraodon fahaka) for the first time. Adult A. impletum have a markedly large, sub-terminal oral sucker and a small ventral sucker. As with most trematodes, tegumental spines are concentrated anteriorly and are absent just anterior the ventral sucker. Spines have serrated tips on a short, tongue–shaped body. At the level of the ventral sucker the base of each spine exhibits a three bulbous-like structure that can be partially or completely withdrawn into the tegument. Sensory papillae are concentrated around the oral and ventral suckers and genital pores. Papillae are conical or knob-like, either ciliated or non-ciliated; some are protruded and others are embedded inside the tegument. In the juvenile stage, spines are smaller, less well-developed and tightly packed. The cytoplasmic processes of the posterior quarter of body show brain-like velvety appearance on the adult and small cobblestone-like on the juvenile.

Metagonimus yokogawai Ancient DNA Recovered from 16th- to 17th-Century Korean Mummy Feces of the Joseon Dynasty

Metagonimiasis is foodborne intestinal parasitism occurring by the definitive hosts' ingestion of raw or undercooked fish, mostly commonly sweetfish. Most Metagonimus infection is caused by Metagonimus yokogawai but also rarely by Metagonimus takahashii as well as Metagonimus miyatai. Despite recent molecular work on Metagonimus spp., there are still insufficient data to reveal the genetic characteristics of ancient M. yokogawai in a wide geo-historical scope. In this study, we were successful in the analysis of M. yokogawai ancient DNA (aDNA) using coprolite samples retrieved from 16th- to 17th-century Korean mummies. In BLAST and phylogenetic analyses, M. yokogawai 28S rDNA of Korean mummies were clustered along with the 28S rDNA taxa of M. takahashii and M. miyatai in GenBank. Conversely, the cytochrome c oxidase subunit I (COI) of M. yokogawai aDNA from Korean mummies was distinctly clustered apart from M. takahashii and M. miyatai sequences. This study is the first report of its kind to identify M. yokogawai aDNA retrieved from the archaeological specimens and confirms the usefulness of COI in molecular diagnosis of M. yokogawai. Considering the rarity of reports on the genetics of genus Metagonimus spp., our study will be fundamental for the future study of M. yokogawai paleogenetics.

Digenean Holostephanus (Trematoda: Digenea: Cyathocotylidae) metacercariae in common carp (Cyprinus carpio Linnaeus, 1758) muscle: zoonotic potential and sensitivity to physico-chemical treatments

Metacercariae of various species within the genus Holostephanus Szidat, 1936 (Trematoda: Digenea: Cyathocotylidae) occur in muscles of both farmed and wild fish, including common carp (Cyprinus carpio Linnaeus, 1758). The life cycle includes a snail as first intermediate host, fish as second intermediate host and birds or mammals as final hosts. We studied the zoonotic potential and the viability of Holostephanus metacercariae from common carp following exposure to various physical and chemical treatments. Muscle tissue samples of common carp specimens from a fish farm in the north-eastern part of Hungary were examined and metacercariae recovered. The zoonotic potential was evaluated experimentally by using small mammals as models (albino mice, n = 2; and Syrian hamsters, n = 4) infected per os with Holostephanus cysts. Parallelly, Metagonimus metacercariae were used as positive controls. We could not confirm the zoonotic potential of Holostephanus metacercariae as they did not survive in the mammalian intestine whereas Metagonimus metacercariae developed to the adult stage. We assessed the viability of metacercariae isolated from common carp specimens during exposure to different physical treatments (temperatures of -18°C, +20°C, +40°C and +60°C) and chemical agents (5% and 10% acetic acid and 10% sodium chloride (NaCl)). Metacercariae lost viability by freezing at -18°C (2 h), heating at 60°C (20 min), incubation in 5% and 10% acetic acid (5 min) and 10% NaCl (2 h). These methods served as models to investigate the effectiveness of food preparation techniques (such as cold and hot smoking, freezing, salting and pickling) on the survival of metacercariae.

Topography and ultrastructure of the tegument of Deropristis inflata Molin, 1859 (Digenea: Deropristidae), a parasite of the European eel Anguilla anguilla (Osteichthyes: Anguillidae)

The tegumental ultrastructure of the intestine fluke Deropristis inflata was studied using scanning and transmission electron microscopy. The surface of the tegument was covered by transverse cytoplasmic ridges from which protrude numerous thorn-like spines showing crenelated tips on the posterior part. Spines were arranged in staggered rows. Cobblestone-like units of the tegument were observed on a semicircle-shaped formation over the oral sucker. A tegumental excrescence was observed in the dorsal anterior side of the fluke. Ultrastructural study revealed that the tegument of D. inflata had a typical syncytial organization with a distal cytoplasm lying over a basal matrix and cytons. Cytoplasmic bridges allowed transit of secretory vesicles and granules packed in gland cells. Two types of sensory structures were examined. Type 1 sensory receptor was a button-like uniciliated papilla mounted on a folded tegumental base and surrounded by cytoplasmic ridges. This receptor consisted of a nerve bulb and a cilium that extended from a centriole. Type 2 sensory receptor was a smooth bulb-like non-ciliated papilla. It was only recovered on the ventral sucker. This receptor consisted of a nerve bulb enclosing an ovoid electron-dense structure. For both receptors, the nerve bulbs contained numerous mitochondria, nerve fibers, and electron-lucent material. Particular distributions of the sensory receptors were observed with a concentration on the anterior third of the body around the oral and ventral suckers. Diagrams were made to help in understanding the nature of these structures.

Topography and ultrastructure of the tegument of Lecithochirium musculus (Digenea: Hemiuridae), a parasite of the European eel Anguilla anguilla (Osteichthyes: Anguillidae)

The tegumental ultrastructure of the stomach fluke Lecithochirium musculus was studied using scanning and transmission electron microscopy. The surface of the tegument was smooth and covered by transverse cytoplasmic ridges. Cobblestone-like units of the tegument were observed on the ventral surface. Invagination and evagination of the ecsoma induced variations in the tegumental surface. The ultrastructural study revealed that the tegument of L. musculus had a typical syncytial organization with a distal cytoplasm lying over a basal matrix and cytons. Two types of intra-tegumental sensory structures were observed. Type 1 sensory receptor was a domed-like fusiform structure consisting of a smooth elevation of the tegument. Four receptors of this type were observed on the anterior dorsal surface of the fluke. Three nerve bulbs filled with electron-lucent material and mitochondria composed this receptor. Hemispherical electron-dense collars were observed at the top of the nerve bulbs. Striated rootlets laid just beneath the hemispherical electron-dense collars. Type 2 sensory receptor presented two morphological variations, i.e., a bulb-like monolobed structure, and a bulb-like bilobed structure observed at two different degrees of evagination. For both variations, the nerve bulb enclosed mitochondria, electron-lucent material, and a conical electron-dense collar from which extended a striated rootlet. Numerous sensory receptors of this type were observed around the ventral sucker.

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.

TAXONOMIC STATUS, REDESCRIPTION, AND SURFACE ULTRASTRUCTURE OF ASCOCOTYLE (PHAGICOLA) PINDORAMENSIS N. COMB. (DIGENEA: HETEROPHYIDAE)

Pygidiopsis pindoramensis Travassos, 1928, is redescribed from the holotype and specimens obtained from experimental infections of hamsters with metacercariae of the naturally infected poeciliids Poecilia vivipara and Phalloptychus januarius from Rio de Janeiro, Brazil. Ascocotyle (Phagicola) pindoramensis (Travassos, 1928) n. comb. is proposed, based on the presence of a solid, tapering muscular posterior prolongation of the oral sucker and Ascocotyle (Phagicola) mollienisicola (Sogandares-Bernal and Bridgman, 1960) is synonymized with A. (P.) pindoramensis because of the identical morphology and measurements of adults and metacercariae, similar spectrum of fish intermediate hosts (poeciliids), and the same site of infection of the metacercariae. Trematodes designated as Pygidiopsis pindoramensis, previously reported from Argentina and Mexico, represent another species of Pygidiopsis Looss, 1907, because they possess circumoral spines and their oral sucker is devoid of the posterior muscular prolongation. Data on the surface morphology of metacercariae and adults of A. (P.) pindoramensis are inferred from scanning electron microscopy observations.

Sequence comparisons of 28S ribosomal DNA and mitochondrial cytochrome c oxidase subunit I of Metagonimus yokogawai, M. takahashii and M. miyatai

We compared the DNA sequences of the genus Metagonimus: M. yokogawai, M. takahashii, and M. miyatai. We obtained 28S D1 ribosomal DNA (rDNA) and mitochondrial cytochrome c oxidase subunit I (mtCOI) fragments from the adult worms by PCR, that were cloned and sequenced. Phylogenetic relationships inferred from the nucleotide sequences of the 28S D1 rDNA and mtCOI gene. M. takahashii and M. yokogawai are placed in the same clade supported by DNA sequence and phylogenic tree analysis in 28S D1 rDNA and mtCOI gene region. The above findings tell us that M. takahashii is closer to M. yokogawai than to M. miyatai genetically. This phylogenetic data also support the nomination of M. miyatai as a separate species.

Surface ultrastructure of the adult stage of Acanthotrema felis (Trematoda: Heterophyidae)

The surface ultrastructure of Acanthotrema felis (Trematoda: Heterophyidae) adults, recovered from a kitten experimentally infected with the metacercariae, was observed using a scanning electron microscope. The worm was leaf-like, ventrally concave and covered with scale-like multi-pointed tegumental spines. The spines on the anterior surface were short but broad, and had 10-12 pointed tips. The cytoplasmic processes protruded around the spines, like pockets for the spines. The ventrogenital opening was crescent, or kidney-shaped, and had protuberances with minute spines on its surrounding tegument. The spines on the posterior surface were long, but narrow, with 6-8 pointed tips. The cytoplasmic processes on this tegument were ridge-like, and elevated along the row of the spines. The surface ultrastructure of A. felis is generally similar to that of other heterophyid flukes, but some features are characteristic, and may be of taxonomic and bio-ecological significance.

Surface ultrastructure of Pygidiopsis summa (Digenea: Heterophyidae) adult flukes

A scanning electron microscopic study was performed on the surface ultrastructure of Pygidiopsis summa (Digenea: Heterophyidae) adults. Metacercariae were collected from gills and muscles of mullets (Mugil cephalus) caught in a known endemic area, and adult flukes were harvested from dogs after 8 weeks of experimental infection. The worm was calabash form with its posterior part broader than the anterior part. Tegumental spines were densely distributed over the body surface, except on the suckers and genital apparatus, and around the excretory pore. Well differentiated spines were observed on the anterior half of the body, with 14-16 tips ventrally, and 19-20 tips dorsally. On the oral sucker, three pairs of type I sensory papillae (uni-ciliated knob-like swellings) and one pair of type II sensory papillae (aciliated round-swellings) were observed on the anterior and posterior parts of the lip, respectively. On the lip of the ventral sucker, one pair of type II sensory papillae was distributed only on its posterior part. Sperms were seen emerging from or entering into the genital apparatus. The results showed that the surface ultrastructure of P. summa was unique among the heterophyid trematodes, especially in digitation of tegumental spines and in distribution of sensory papillae on oral and ventral suckers.

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.

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 Metagonimus takahashii metacercariae and adults

A scanning electron microscopic study was performed on the surface ultrastructure of metacercariae and adults of Metagonimus takahashii. Metacercariae were collected from the scale of crucian carp (Carassius auratus), and adult flukes were harvested 1-4 weeks after infection to rats. In excysted metacercariae, the oral sucker had type I (numerous) and type II (seven in total) sensory papillae. Tegumental spines were dense and digitated into 5-7 points on the surface anterior to the ventral sucker, but became sparse and less digitated posteriorly toward the end of the body. In adults, seven type II sensory papillae were characteristically arranged around the lip of the oral sucker, and on the inner side of the lip four small and two large type I sensory papillae were symmetrically seen on each side (12 in total). Tegumental spines on anterior two-thirds of the body, were digitated with 9-12 tips ventrally and 8-13 tips dorsally. Sperms entering into the Laurer's canal were observed. The results show that the surface ultrastructure of M. takahashii is generally similar to those of M. yokogawai and M. miyatai except for the digitation of tegumental spines.

A cytogenetic study on human intestinal trematodes of the genus Metagonimus (Digenea: Heterophyidae) in Korea

In order to analyze chromosome numbers and karyotypes of intestinal trematodes belonging to the genus, Metagonimus, the gonad tissues of M. takahashii, M. miyatai, and M. yokogawai were prepared and examined. The number of bivalents in the first meiotic division of M. takahashii was nine (n = 9). The diploid number of M. miyatai was observed to be eighteen (2n = 18) and their chromosomes consisted of one pair of metacentric, 7 pairs of submetacentric, and one pair of telocentric chromosomes. The diploid number of M. yokogawai was thirty-two (2n = 32) and the chromosome complements were composed of two pairs of metacentric, 11 pairs of submetacentric, and three pairs of subtelocentric chromosomes. These results could be a supporting evidence for the validity of the new species, M. miyatai, distinct from M. yokogawai.