Allocreadium pichi n. sp. (Trematoda: Allocreadiidae) in Galaxias maculatus (Osteichthyes: Galaxiidae) from Lake Moreno in Patagonia (Argentina)

Allocreadium pichi n. sp. (Trematoda: Allocreadiidae) is described from the intestine of Galaxias maculatus (Osteichthyes: Galaxiidae) from Moreno Lake in Patagonia, `Argentina. This species is distinguished from A. patagonicum Shimazu, Urawa &; Coria, 2000, the other species recorded in the area, by its smaller body size, the diagonal position of the testes and different ratios of the suckers, testes and cirrus-sac in relation to body size. In addition, the synonymy of A. patagonicum withPolylekithum percai Ostrowski de Núñez, Brugni &; Viozzi, 2000 is proposed herein.     

A new species of Crepidostomum (Allocreadiidae: Digenea) from northeastern Finland,with comments on its possible origin

Crepidostomum wikgreni n. sp. is described from the gall-bladder and intestine of the whitefish Coregonus acronius in Lake Yli-Kitka in NE Finland. It is morphologically similar to Crepidostomum farionis, with which it occurs sympatrically and sometimes concurrently; but it differs in that the eggs are much larger, i.e. 96±6.5 m mean-length, as opposed to 71±4.7 m mean-length for C. farionis in the same host and locality.It is suggested that the new species has arisen from C. farionis after deglaciation and since c. 8,400 BP, at which time the waters of the Lake Kitka System were isolated from those in the rest of Finland and flowed eastwards into the White Sea Basin. The isolation of the White Sea Basin appears to have been maintained by watersheds running north-south close to the Fenno-Soviet border and east-west through central Karelia. It is further suggested that C. farionis currently occurring in Lake Yli-Kitka is a recent re-introduction brought about by the translocation of fish-stocks.     

Clinostomum complanatum (Trematoda: Clinostomatidae) in five new fish hosts in Japan.

Metacercariae of Clinostomum complanatum were found in six species of natural freshwater fishes collected at Koyama Pond in Tottori City of Tottori Prefecture, Japan. Five of these fish species are reported here as new records for second intermediate hosts of C. complanatum in Japan: the silver crucian carp (Carassius gibelio langsdorfi), the deepbodied crucian carp (Carassius cuvieri), the carp (Cyprinus carpio), the topmouth gudgeon (Pseudorasbora parva) and the rose bitterling (Rhodeus ocelatus).     

Helminths from the fish Dormitator maculatus (Osteichthyes: Eleotridae) from Alvarado, Veracruz, Mexico

Dormirator maculatus (n=184) was collected in the Alvarado Lagoon, Mexico during a year period (Oct. 1993-1994). In the helminthologic review, the presence of Clinostomum complanatum (82.3%), Neoechinorhynchus golvani (76.1%), Spiroxys sp. (21.3 %), and Camallanus sp. (6.2%) was registered. Reduction of the hematocrit caused by such infection is significant (t, a= 0.05).     

Ultrastructure and chaetotaxy of sensory receptors in the cercariae of a species of Crepidostomum Braun, 1900 and Bunodera Railliet, 1896 (Digenea: Allocreadiidae)

Previous investigations of cercarial sensory systems have focused on chaetotaxy and ultrastructure of sensory receptors and have revealed chaetotaxic patterns within families, genera, and species as well as different types of sensory receptors. However, chaetotaxic and ultrastructural observations have rarely been combined. We investigated the ultrastructure of cercarial sensory receptors in conjunction with the chaetotaxy and neuromorphology in 2 allocreadiid species belonging to the genera Crepidostomum and Bunodera. Cercariae were treated with acetylthiocholine iodide and silver nitrate, and for scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Similar cholinergic nerve networks were revealed. Chaetotaxy was consistent with that of other allocreadiids. Seven and 6 types of receptors were distinguished with SEM in Crepidostomum sp. and Bunodera sp., respectively. Types differed in number of cilia (1 or 2), cilium length (short, moderately long, or long), presence or absence of a tegumentary collar and a domelike base, and tegumentary collar length (low, moderately low, or high), TEM of some types revealed unsheathed cilia, basal body, and thickened nerve collars. Some receptor types were site specific. Thus, long uniciliated receptors were concentrated on the dorsal surface. Other types, such as short uniciliated receptors, were widespread throughout most regions. Ultrastructure and site-specificity observations suggest that most receptors are mechanoreceptors.     

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.     

Ultrastructural study of spermiogenesis and the spermatozoon of Crepidostomum metoecus (Digenea: Allocreadiidae), a parasite of Salmo trutta (Pisces: Teleostei)

Spermiogenesis and the spermatozoon of Crepidostomum metoecus, an intestinal parasite of brown trout Salmo trutta, were studied by transmission electron microscopy. Spermiogenesis begins with the formation of a differentiation zone in front of 2 centrioles associated by an intercentriolar body. Each centriole is linked to a striated rootlet, and gives rise to a flagellum. The rotation of flagella is greater than 90 degrees; their fusion with the median cytoplasmic extension is proximodistal and asynchronous. The spermatozoon is formed after constriction of arched membranes. The spermatozoon possesses 2 axonemes of the 9 + "1" pattern, a nucleus, mitochondria, and glycogen. A major feature is the presence, in the anterior part, of external ornamentation and a lateral expansion associated with spinelike bodies. Another attribute is the presence of 2 mitochondria rather than just 1, as in most of the digenean spermatozoa. To our knowledge, this study is the first undertaken with a species of the Allocreadiidae.     

Redescription of Echinostoma trivolvis (Cort, 1914) (Trematoda: Echinostomatidae) with a discussion on its identity

The life-cycle of Echinostoma trivolvis (Cort, 1914) has been completed experimentally and the validity and identity of this species are discussed. Synonyms for cercariae and adults of E. trivolvis are as follows: Cercaria trivolvis Cort, 1914, C. trisolenata Faust, 1917, C. acanthostoma Faust, 1918, C. complexa Faust, 1919; Distoma echinatum Zeder, 1803, of Leidy (1888, 1904) and Hassall (1896); E. echinatum (Zeder, 1803) of Hassall (1896), Stiles & Hassall (1895), Barker & Laughlin (1911), Barker (1916) and Swales (1933); E. revolutum (Frölich, 1802) Dietz, 1909 of Johnson (1920), Fallis (1934), Beaver (1937) and Fried & co-workers (1968–1989); E. armigerum Barker & Irvine, 1915; E. coalitum Barker & Beaver, 1915; E. callawayensis Barker & Noll, 1915; E. paraulum Dietz, 1909 of Miller (1937); E. multispinosum Vigueras, 1944; and Echinoparyphium contiguum Barker & Bastron, 1915. The first intermediate host is the planorbid snail Helisoma trivolvis. Second intermediate hosts are various pulmonate and prosobranch snails, mussels, planarians, fishes, frogs, tadpoles and freshwater turtles. Final hosts are various birds and mammals. E. trivolvis occurs only in North America.     

Systematics of the Deropristiidae Cable & Hunninen, 1942 (Trematoda) and biogeographical associations with sturgeons (Osteichthyes: Acipenseridae)

The 11 nominal species of the Deropristiidae, belonging to the genera Deropristis (three species), Pristicola (one species), Skrjabinopsolus (five species) and Cestrahelmins (two species) were re-evaluated for a phylogenetic and biogeographical analysis of the group. Skrjabinopsolus elongatus (Madhavi, 1974) (= S. indicus Gupta & Ahmad, 1976, S. kurotchkini Parukhin, 1976), S. sanyaensis Shen, 1990, Deropristis paurosoma Wang, 1989 and Cestrahelmins Fischthal, 1957, do not belong to the Deropristiidae. The genus Opisthodiplomonorchis Madhavi, 1974 is resurrected for its type-species, O. elongatus (= S. elongatus), and D. paurosoma is also transferred to this genus. Species of Opisthodiplomonorchis occur in polynemid fishes of the Indo-Pacific. Five nominal species thus comprise the Deropristiidae, i.e. S. armatus Ivanov in Ivanov and Mrygin, 1937, S. manteri (Cable, 1952), D. hispida (Abildgaard, 1819), D. inflata (Molin, 1859) and P. sturionis (Little, 1930), which corresponds to the original composition of the family. A comparison of Skrjabinopsolus from acipenserids in North America and Europe revealed variability in morphological characters considered diagnostic in the past (body size and position of the ovary and testes). Based on the morphology and biology, the two species of Skrjabinopsolus can be considered incipient species. A phylogenetic analysis of the redefined Deropristiidae indicates that Deropristis and Pristicola may form a monophyletic group with Skrjabinopsolus as the sister taxon. The biogeography of the Deropristiidae suggests an origin and distribution associated with the formation of the North Atlantic basin. Freshwater and marine/estuarine origins for the family are equally parsimonious possibilities. A freshwater origin can be traced at least to Cretaceous Laurasia followed by a drift-vicariance separation and subsequent association with North Atlantic drainages. Support for a marine ancestry of the Deropristiidae is indicated by the biogeography of its sister taxa (outgroups in this study) and of its hosts, and is also consistent with an Atlantic origin. The deropristiids evidently originated and speciated within the Acipenseridae in the Atlantic region, with a host switch into Atlantic Anguilla spp.     

Redescription of the African fish leechBatracobdelloides tricarinata (Blanchard, 1897) (Hirudinea: Glossiphoniidae)

A study of well over one thousand specimens provided proof to put the conspecifity of the two supposed species originally described asHelobdella tricarinata andClepsine nilotica beyond all doubt. Evidence is presented which indicates that the striking changes in body-shape and drastic alteration in the appearance of the tuberculation at different stages of reproduction and nutrition combined with individual variation in tuberculation, annulation, and in the arrangement and pigmentation of the eyes were responsible for earlier confusion as to the identity of this species. Since the early accounts were incomplete and contained some important errorsBatracobdelloides tricarinata is redescribed and, for the first time, comprehensively figured.     

The phylogenetic position of Allocreadiidae (Trematoda: Digenea) from partial sequences of the 18S and 28S ribosomal RNA genes

Species of Allocreadiidae are an important component of the parasite fauna of freshwater vertebrates, particularly fishes, and yet their systematic relationships with other trematodes have not been clarified. Partial sequences of the 18S and 28S ribosomal RNA genes from 3 representative species of Allocreadiidae, i.e., Crepidostomum cooperi, Bunodera mediovitellata, and Polylekithum ictaluri, and from 79 other taxa representing 78 families of trematodes obtained from GenBank, were used in a phylogenetic analysis to address the relationships of Allocreadiidae with other plagiorchiiforms/plagiorchiidans. Maximum parsimony and Bayesian analyses of combined 18S and 28S rRNA gene sequence data place 2 of the allocreadiids, Crepidostomum cooperi and Bunodera mediovitellata, in a clade with species of Callodistomidae and Gorgoderidae, which, in turn is sister to a clade containing Polylekithum ictaluri and representatives of Encyclometridae, Dicrocoelidae, and Orchipedidae, a grouping supported by high bootstrap values. These results suggest that Polylekithum ictaluri is not an allocreadiid, a conclusion that is supported by reported differences between its cercaria and that of other allocreadiids. Although details of the life cycle of callodistomids, the sister taxon to Allocreadiidae, remain unknown, the relationship of Allocreadiidae and Gorgoderidae is consistent with their larval development in bivalve, rather than gastropod, molluscs, and with their host relationships (predominantly freshwater vertebrates). The results also indicate that, whereas Allocreadiidae is not a basal taxon, it is not included within the suborder Plagiorchiata. No support was found for a direct relationship between allocreadiids and opecoelids either.     

Role of the daily food ration of perch fry (Perca fluvialis) in infestation with Bunodera luciopercae (Trematoda, Allocreadiidae)

The list of intermediate hosts of Bunodera luciopercae is given. In Lake Syamozero they are represented by crustaceans Heterocope, Ophryoxus. Data on their role in the ration of juvenile perch are given. Diurnal dynamics of the ratio between infected and noninfected plankton in feeding and the process of the formation of fish infection have been studied.     

Parasitism (Trematoda,Digenea) in medusae from the southwestern Atlantic Ocean: medusa hosts,parasite prevalences,and ecological implications

Digenean are important endoparasites of fish with complex life cycles; some genera include medusae as secondary hosts. Their transmission to fish occurs when fish prey on these jelly hosts. Fish predation on jellyfish is a widespread phenomenon, even though predation by fish on jellyfish has not been determined through parasitism yet. We hypothesized that medusae with high prevalences of digeneans could be important for their transmission to fish. A total of 48,900 specimens of 50 medusa species were analyzed; 2,181 harbored digeneans. Opechona sp. and Monascus filiformis were the most frequent and abundant parasites with the widest range of hosts. Hemiuridae gen. sp. and Bacciger sp. were found in few specimens of some medusa species. Prevalences were unevenly distributed in the region. Three groups with high prevalence values were identified mainly related to frontal areas: Río de la Plata, Bahía Blanca, and North Patagonian tidal front. Eucheilota ventricularis, Clytia hemisphaerica, Proboscidactyla mutabilis, Liriope tetraphylla, and Aequoerea spp. were the medusae that contributed the most as secondary hosts to M. filiformis and Opechona sp. The high prevalences found in these medusae suggest that may be a fundamental part of the life cycles of both parasites in these areas.     

Trematoda of the genus aporocotyle (Sangyinicolata: Aporocotylidae) from fish far eastern seas

According to our research there are two species of trematoda of genus Aporocotyle: A. simplex and A. theragrae in the far eastern seas.