Morphological and histochemical studies on the ovarian development and oogenesis in Paramphistomum cervi (Digenea: Paramphistomatidae)

The ovary in 4-week-old worms contains undifferentiated germ cells. The oogonial differentiation, together with the appearance of some PAS-positive material in the ooplasm occurs in the ovary of 8-week-old worms. The ovary of 16-week-old worms contains only oogonia and oocytes and no germ cells. In adult worms, the oocytes reach the pachytene stage and further development is arrested at this stage. Nucleolar fragmentation and subsequent transport of nuclei to the ooplasm have been observed. The ooplasm contains nutritive material rich in proteins, carbohydrates and lipids. Its amount varies with different stages of oogenesis. The localization of various phosphatases and dehydrogenases was studied during oogenesis and their functional significance was discussed.     

Morphological, developmental and ecological evidence for a progenetic life cycle in Neochasmus (Digenea)

Seven species of fishes, Catostomus commersonii (Lacépède), Etheostoma nigrum Rafinesque, Micropterus dolomieu Lacépède, Notemigonus crysoleucas (Mitchill), Notropis hudsonius (Clinton), Perca flavescens (Mitchill), and Percina caprodes (Rafinesque) from the St. Lawrence River, Quebec, Canada, were found infected with progenetic specimens of Neochasmus spp. in the orbits and/or the body musculature. Worms displayed varying degrees of maturation. Eggs occupied the entirety of the worm in late stages of development and persisted as distinct clusters in situ after worm death. Populations of parasites were studied monthly in E. nigrum from one site between May and October in order to follow parasite recruitment, development and maturation. Recruitment of parasites was observed in young-of-the-year fish primarily in July and continued through October. Worms matured rapidly, displaying egg production within a month. Later developmental stages, in which eggs occupied most of the worm, and clusters of eggs became abundant by September. Infections in overwintered fish collected in May consisted mainly of worms in early stages of egg production and of clusters of eggs. When hatched artificially, eggs from the clusters released viable miracidia, indicating that they survive beyond the lifespan of the adult worm. It is suggested that progenesis is a fixed characteristic of the life cycle of these species, that egg dispersal requires the death of the host and that it is facilitated by predation. All prior records of Neochasmus spp. are examined, leading us to conclude that the role of the putative definitive host (primarily basses) has been reduced to that of a dispersal agent. Current hypotheses concerning the evolution and maintenance of progenesis are considered, but it is concluded that they do not apply to this host-parasite system.     

Lasiotocus lizae sp. n. (Digenea: Monorchiidae), a new trematode from marine fish in the Taiwan Straits,China

Lasiotocus lizae sp. n. (Digenea: Monorchiidae) was collected from the intestine of Liza carinata (Valenciennes) (Mugilidae, Perciformes) in the Taiwan Straits, China. L. lizae is most similar to Lasiotocus glebulentus Overstreet, 1971 from the intestine of Mugil cephalus from the Northern Gulf of Mexico in having tightly compacted vitellaria, a genital pore sinistral to the midline, the ovary usually dextral to the acetabulum, the similar sucker ratio, and in the presence of both a canalicular and uterine seminal receptacle. It differs from L glebulentus in its cirrus sac ending anterior to rather than posterior to acetabulum, in the ending position of caeca, in smaller eggs, and in having a single rather than several conspicuous concretions in excretory vesicle.     

Morphological and molecular study of Microphallus primas (Digenea: Microphallidae) metacercaria, infecting the shore crab Carcinus maenas from northern Portugal

The present study describes the anatomy and surface topography of the metacercaria of Microphallusprimas (J?gerski?ld, 1909) infecting the shore crab Carcinus maenas (L.) in Aveiro estuary, northern Portugal. The metacercaria species identification resulted from the combined use of morphological and molecular data, particularly the 28S rDNA gene. The metacercariae encysted preferentially in the host's hepatopancreas and also in the gonads. Isolated cysts were present in two distinct forms, spherical and oval, and were shown to be the identical species by the internal transcribed spacer 1 (ITS1) sequence. Chemically excysted metacercariae were studied by light (LM) and scanning electron microscopy (SEM). Their specific characteristics observed include the particular aspect of the vesiculo-prostatic pouch surrounded by a very thin membrane, the presence of a prominent muscular papilla, and an obvious metraterm. The dorsal and ventral tegumental surfaces of the metacercaria were densely packed with similar squamous spines, which decreased in number and size towards the hindbody. The edges of the posterior and ventral face of the body were coated with numerous microvilli, whose function remains unknown. In order to identify the species of metacercariae, we compared a 28S partial rDNA sequence of the two forms of cysts with the same 28S partial region of M. primas available in GenBank. With this comparison, we determined that the sequences had a 100% similarity and therefore belonged to the same species, i.e., M. primas.     

A new trematode species Neoplagioporus kajika sp. n. (Digenea: Opecoelidae), parasitic in the Japanese fluvial sculpin, Cottus pollux (Osteichthyes: Scorpaeniformes: Cottidae), from Japan

The adult morphology is described and illustrated of Neoplagioporus kajika sp. n. (Digenea: Opecoelidae) found in the Japanese fluvial sculpin Cottus pollux Günther (Osteichthyes: Scorpaeniformes: Cottidae) collected in the Naka River at Terase Bridge, Narutake, Nakagawa Town, Fukuoka Prefecture, Kyushu, Japan. This new species is characterized by that the body shape is oval, that the intestinal caeca end posteriorly at the middle level of the testicular region, that the ovary is trilobed, and that the vitelline follicles are distributed between the pharyngeal level and usually the posterior end of body and fill up the lateral fields of body. The new species is different from three hitherto known Neoplagioporus species, N. zacconis (Yamaguti, 1934) Shimazu, 1990 (type species), N. ayu (Takahashi, 1928) Shimazu, 1990, and N. elongatus (Goto et Ozaki, 1930) Shimazu, 1990, in a combination of these characteristics. The new species is considered mainly infective to C. pollux in the river.     

Taxonomic status of Ascocotyle (Phagicola) rara Arruda, Muniz-Pereira et Pinto, 2002 (Digenea: Heterophyidae)

Holotype and paratype of Ascocotyle (Phagicola) rara Arruda, Muniz-Pereira et Pinto, 2002, a heterophyid trematode recently described on the basis of two worms collected by Lauro Travassos in 1921 in the intestine of Ixobrychus exilis (Gmelin) from Brazil, were studied. The morphology of the worms revealed their conspecificity with Ascocotyle (Phagicola) angeloi Travassos, 1928 found in the same host. Both the taxa have a similar length (between 600 and 900 microm) and shape of the body (long pyriform), the long intestinal caeca reaching to the ovarian level, a long posterior muscular prolongation of the oral sucker and the prepharynx, transverse uterine loops situated between the ventral sucker and testes, and the gonotyl with more than 20 digitiform pockets. Consequently, A. (P.) rara is proposed as a junior synonym of Ascocotyle (Phagicola) angeloi.     

The life cycle of Paracardicoloides yamagutii Martin, 1974 (Digenea: Sanguinicolidae)

The sanguinicolids Paracardicoloides yamagutii Martin, 1974 and Plethorchis acanthus Martin, 1975 were obtained from their definitive hosts, Anguilla reinhardtii Steindachner and Mugil cephalus Linnaeus (respectively) in the tributaries of the Brisbane River, Queensland, Australia. Two putative sanguinicolid cercariae were collected from a hydrobiid gastropod, Posticobia brazieri Smith, in the same waters. The two cercariae differ markedly in size and the form of their sporocysts. Both putative cercariae develop in the digestive gland of Po. brazieri. The ITS2 rDNA region from these sanguinicolids and a Clinostomum species (utilised as an outgroup due to the close morphological similarities between the cercarial stages of the Clinostomidae and the Sanguinicolidae) were sequenced and aligned. Comparison of the ITS2 sequences showed one cercaria to be that of P. yamagutii. This is the first sanguinicolid life history determined by a molecular method. P. yamagutii is the fourth sanguinicolid known to utilise a freshwater hydrobiid gastropod as its intermediate host. ITS2 rDNA is effective in distinguishing sanguinicolids at the species level.     

Haploporus mugilis sp. n. (Digenea: Haploporidae) from Valamugil engeli (Pisces: Mugilidae) in the Taiwan Straits,China

Haploporus mugilis sp. n. (Digenea: Haploporidae) was obtained from the intestine of kandas, Valamugil engeli (Bleeker) (Mugilidae, Perciformes) in the Taiwan Straits, China. It most closely resembles Haploporus spinosus Machida, 1996 from the intestine of Crenimugil crenilabis in Japanese and adjacent waters in the intestinal bifurcation posterior to the acetabulum, in egg-size (0.039-0.044 x 0.019-0.022 in H. mugilis and 0.034-0.042 x 0.018-0.023 in H. spinosus) and in the hermaphroditic sac armed with spines. However, it differs from the latter in its hermaphroditic sac with two long and numerous small spines rather than with four long and six small spines and in the excretory vesicle with a single prominent refractory concretion instead of being empty.     

Morphological and histochemical demonstration of hooks in the rostellar region of Cysticercus bovis.

Hooklets and early developmental stages of hooks were discovered in the tegument among the microtriches in the rostellar region of 83- and 108-day-old Cysticercus bovis. The cortical layer of hooks consists of proteins with tyrosine and SS groups. The rostellar sac and bulb are distinctly developed in the parenchyma of the rostellar region.     

Biochemical studies on sheep body louse Bovicola ovis (Schrank) (Phthiraptera: Trichodectidae): comparison of pyrethroid and organophosphate resistant and susceptible strains

Strains of sheep louse Bovicola ovis (Schrank) with various levels of resistance to pyrethroid and one strain with high degree of resistance to organophosphate (OP) insecticides were used to investigate the biochemical mechanisms of insecticide resistance, i.e., enhanced levels of general esterases, specific acetylcholinesterases (AChE), glutathione S-transferase (GST), and mixed function oxidases. Native gel electrophoresis combined with quantitative enzyme assays showed analogous expression profiles of several esterase isozymes in all the strains tested. The determination of the sensitivity of each esterase isozyme to five inhibitors (acetylthiocholine iodide, butyrylthiocholine iodide, paraoxon eserine sulfate, and pCMB) led to the identification of nine esterases in the B. ovis strain. Gel electrophoresis results are supported by enzyme assay studies where, except for the OP resistant strain, no differences in esterase activities were detected in all the pyrethroid resistant and susceptible strains assayed. Statistical analyses demonstrated that some strains have elevated GST activities compared to the susceptible reference strain.     

Three species of Magnibursatus Naidenova, 1969 (Digenea: Derogenidae) from Atlantic and Black Sea marine teleosts

Three species of Magnibursatus Naidenova, 1969 are described from marine teleosts: M. skrjabini (Vlasenko, 1931), the type species of the genus, from the gobiid Zosterisessor ophiocephalus on the Bulgarian Black Sea coast; M. bartolii sp. n. from the sparid Boops boops off the Atlantic coast of Spain; and M. minutus sp. n. from the gobiid Neogobius eurycephalus on the Bulgarian Black Sea coast. M. bartolii differs from all other Magnibursatus species in its larger sinus-sac (length > 250 microm, width > 150 microm) and the more posterior location of testes. This species is also unusual in that it occurs in the branchial chamber and on the gills of its host. M. minutus is distinguished by the distinctly smaller dimensions of the body (length < 1000 microm, width < 200 microm), organs and eggs. These species are also distinguished from both M. caudofilamentosa (Reimer, 1971) and Tyrrhenia blennii Paggi et Orecchia, 1975. A key to the species of Magnibursatus is presented.     

Rhaphidotrema kiatkiongi, a new genus and species of blood fluke (Digenea: Aporocotylidae) from Arothron hispidus (Osteichthyes: Tetraodontidae) from the Great Barrier Reef, Australia

A new genus of fish blood flukes (Aporocotylidae Odhner, 1912) is proposed for a species found on reefs surrounding Lizard Island on the northern Great Barrier Reef. Rhaphidotrema kiatkiongi gen. et sp. n. was recovered from the heart of the stars-and-stripes pufferfish, Arothron hispidus (L.) (Tetraodontidae). Rhaphidotrema kiatkiongi is notable as the first digenean reported to possess a penis stylet. It also differs from all other aporocotylid flukes in having a combination of 18-19 testes in a group at the ends of the intestinal caeca, a broad lanceolate body shape with a dextrally-directed posterior bend at the level of the male genital pore, and separate genital pores, with the female genital pore distinctly sinistral and the male genital pore slightly dextral to midline. This is the second species of aporocotylid fluke reported from this pufferfish.     

Some aspects of histochemical studies on the parasite and tissue reaction in bovine cysticercosis

Histochemical studies on the cysticercus and surrounding tissue reaction were performed at various intervals after experimental infection. It was found that acid mucosubstances and proteins with SH- and SS-groups appeared first in the granulation tissue around the cysticercus (on about day 14 p.i.) and only later (on day 28 p.i.) in the tegument of the cysticercus where they were localized in the rim of microtriches. This envelope consisting of mucosubstances and proteins seems to be identical with the electron-dense substance found on the surface of developing cysticercus during electron-microscopical studies. It is considered to be a mimicry enabling the cysticerci to survive even in an immunologically unfavourable environment. Phospholipids were found in activated fibroblasts and in some cells of macrophage type on days 21 and 30 p.i. and in a large number in subtegumental cells of cysticercus on days 28-34 p.i. This phenomenon seems to be correlated with the increased activity of subtegumental cells of the larva in this period. In morphologically fully differentiated cysticerci, the reaction for phospholipids in subtegumental cells and distal cytoplasm was only feebly positive. Phospholipids were not detected in the rim of microtriches at any time after infection.     

Posterotestes unelen gen. et sp. n. (Digenea: Apocreadiidae) from Percichthys trucha (Osteichthyes: Percichthyidae) in Patagonia, Argentina

Posterotestes gen. n. (Digenea: Apocreadiidae, Apocrcadiinae) is proposed for specimens with the following features: spiny body, posterior position of gonads, extension of vitelline follicles up to level of intestinal bifurcation and absent at post-testicular space, long oesophagus and extension of caeca up to anterior testis. Posterotestes unelen sp. n. is described from the intestine of the native fish, Percichthys trucha (Cuvier et Valenciennes) (Osteichthyes: Percichthyidae) from Patagonian Andean lakes.     

Transmission electron microscopy of intra-tegumental sensory receptors in the forebody of Crepidostomum metoecus (Digenea: Allocreadiidae)

In the adult fish trematode Crepidostomum metoecus (Braun, 1900), four types of sensory receptors were observed inside the forebody tegument and one type beneath the tegument basal lamina. Two types of sensory receptors extend through the thickness of tegument and have a free cilium inside a pit (types I and II). Two types (III and IV) are nonciliate and entirely intra-tegumental in location. Type IV receptor with large horizontal and thin vertical rootlets was described earlier in aspidogastreans only. Below the basal lamina, nerve endings in close association with muscle fibres, comparable with those in the Aspidogastrea, were detected.