Helminth communities of endemic cyprinoids of the Apennine Peninsula, with remarks on ectoparasitic monogeneans, and a description of four new Dactylogyrus Diesing, 1850 species.

The fauna of the Apennine Peninsula is, in comparison to other southern European peninsulas, relatively species-poor regarding the number of endemic cyprinoid species. Nonetheless, the recent introduction of non-native species has significantly increased the total number of freshwater species in this region. Such invasive species may represent a threat to the native fauna, associated among other things with the introduction of non-native parasites with their original hosts.In the present study, we investigated endemic cyprinoid species for the presence of helminth parasites. A total of 36 ectoparasitic monogenean species and five endoparasitic helminth species were collected from ten cyprinoid species in five localities in northern Italy. Out of 20 Dactylogyrus species (gill monogeneans specific to cyprinoids), four were identified as new to science and herein described: Dactylogyrus opertus n. sp. and Dactylogyrus sagittarius n. sp. from Telestes muticellus, Dactylogyrus conchatus n. sp. from T. muticellus and Protochondrostoma genei, and Dactylogyrus globulatus n. sp. from Chondrostoma soetta. All new Dactylogyrus species appear to be endemic to the Apennine Peninsula; however, they share a common evolutionary history with the endemic Dactylogyrus parasitizing cyprinoids of the Balkans. This common origin of cyprinoid-specific parasites supports a historical connection between these two (currently separated) geographical regions.

Occurrence and effect of trematode metacercariae in two endangered killifishes from Greece.

We report digeneans (Diplostomidae, Crassiphialinae) in the endangered freshwater fishes Valencia letourneuxi and Valencia robertae, endemics of Western Greece. Digenean metacercariae occurred in two forms in the abdominal cavity, excysted and encysted, the latter attached to the gonads, liver and alimentary tract. Parasites were, using morphological and molecular techniques, identified as two representatives of Crassiphialinae, specifically part of the Posthodiplostomum-Ornithodiplostomum clade. The spatial, seasonal, and age class variation in parasite prevalence was examined. Autumn parasite prevalence varied between the six populations sampled (18.2 to 100%). Seasonal prevalence at the two sites sampled quadannually peaked in autumn and reached its lowest value in spring; prevalence increased with size to 100% in young adult fish. We did not find a correlation between prevalence and host sex. Overall parasites' weight averaged 0.64% of the host's, while parasite weight increased with host weight. A comparison of relative condition and hepatosomatic and gonadosomatic indices of infected and metacercariae-free specimens showed that infection did not have a significant effect on host body condition and reproduction. Regarding the parasite's life cycle, planorbid gastropods are proposed as potential first intermediate hosts in view of the host's diet and occurrence data of molluscs in the ecosystem. This is the first record of a diplostomid digenean in valenciid fishes and of representatives of the Posthodiplostomum-Ornithodiplostomum clade in a native Greek freshwater fish. Our findings are discussed in conjunction to fish conservation interventions, since parasites may contribute to the decline of endangered species.

The relationship between handling time and cortisol release rates changes as a function of brain parasite densities in California killifish Fundulus parvipinnis.

This study validated a technique for non-invasive hormone measurements in California killifish Fundulus parvipinnis, and looked for associations between cortisol (a stress hormone) and 11-ketotestosterone (KT, an androgen) release rates and the density or intensity of the trematode parasites Euhaplorchis californiensis (EUHA) and Renicola buchanani (RENB) in wild-caught, naturally infected F. parvipinnis. In experiment 1, F. parvipinnis were exposed to an acute stressor by lowering water levels to dorsal-fin height and repeatedly handling the fish over the course of an hour. Neither parasite was found to influence cortisol release rates in response to this acute stressor. In experiment 2, different F. parvipinnis were exposed on four consecutive days to the procedure for collecting water-borne hormone levels and release rates of 11-KT and cortisol were quantified. This design examined whether F. parvipinnis perceived the water-borne collection procedure to be a stressor, while also exploring how parasites influenced hormone release rates under conditions less stressful than those in experiment 1. No association was found between RENB and hormone release rates, or between EUHA and 11-KT release rates. The interaction between EUHA density and handling time, however, was an important predictor of cortisol release rates. The relationship between handling time and cortisol release rates was negative for F. parvipinnis harbouring low or intermediate density infections, and became positive for fish harbouring high densities of EUHA.

Can parasites use predators to spread between primary hosts?

Parasites typically have low reproductive fitness on paratenic hosts. Such hosts offer other significant inclusive fitness benefits to parasites, however, such as increased mobility and migration potential. The parasite fauna of the guppy (Poecilia reticulata) is dominated by the directly transmitted ectoparasites Gyrodactylus bullatarudis and Gyrodactylus turnbulli. In the wild, close predatory and competitive interactions occur between the guppy and the killifish Rivulus hartii. Previous observations suggest that these fish can share gyrodactylids, so we tested experimentally whether these parasites can use R. hartii as an alternative host. In aquaria, G. bullatarudis was the only species able to transmit from prey to predator. Both parasite species transferred equally well to prey when the predator was experimentally infected. However, in semi-natural conditions, G. bullatarudis transmitted more successfully to the prey fish. Importantly, G. bullatarudis also survived significantly longer on R. hartii out of water. As R. hartii can migrate overland between isolated guppy populations, G. bullatarudis may have an enhanced ability to disperse and colonize new host populations, consistent with its wider distribution in the wild. To our knowledge, this is the first empirical study demonstrating a predator acting as a paratenic host for the parasites of its prey.

Monogenoidea (Dactylogyridae, Gyrodactylidae) from Red River Pupfish, Cyprinodon rubrofluviatilis (Cyprinodontiformes: Cyprinodontidae), from Kansas and Texas, USA.

BACKGROUND: The gills of Red River Pupfish (Cyprinodon rubrofluviatilis) collected from Kansas and Texas, U.S.A., were found to be infected with three monogenoideans, Fundulotrema prolongis, Gyrodactylus rubrofluviatilae n. sp., and a species of Salsuginus. RESULTS: Gyrodactylus rubrofluviatilae n. sp. appears to be a member of a group of six closely related species possessing hamuli with mesially folded roots and a linguiform ventral bar shield, and parasitizing closely related species of Cyprinodon of the North American Gulf Coast and inland waters of the Southwestern United States and northern México. Gyrodactylus rubrofluviatilae n. sp. differs from its close congeners in the morphology of the hamuli, ventral bar, ventral bar shield, and marginal hooks. Because the morphology of the male copulatory complex was not determined of what we believe will eventually be a new species of Salsuginus, a species description is deferred. This is the first report of any parasite from this host. CONCLUSIONS: Many North American species currently recognized within the Cyprinodontiformes have not yet been surveyed for species of Fundulotrema, Gyrodactylus, or Salsuginus. This, coupled with the high host specificity generally recognized for these monogeneans, portends there are likely additional new species yet to be discovered. When possible, to help augment morphological data, further studies should employ comprehensive intra- and interspecies molecular analyses to help resolve host-parasite phylogenies.

Piscinoodinium, a fish-ectoparasitic dinoflagellate, is a member of the class dinophyceae, subclass gymnodiniphycidae: convergent evolution with Amyloodinium.

All dinoflagellates that infest the skin and gills of fish have traditionally been placed within the class Blastodiniphyceae. Their relatedness was primarily based upon a similar mode of attachment to the host, i.e., attachment disc with holdfasts. Results of recent molecular genetic analyses have transferred these parasites, including Amyloodinium, to the class Dinophyceae, subclass Peridiniphycidae. In our study, a small subunit rDNA gene from a parasitic dinoflagellate that has features diagnostic for species in the genus Piscinoodinium, i.e., typical trophont with attachment disc having rhizocysts, infesting the skin of freshwater tropical fish, places this organism within the dinophycean subclass Gymnodiniphycidae. This suggests a close relationship of Piscinoodinium spp. to dinoflagellates that include symbionts, e.g., species of Symbiodinium, and free-living algae, e.g., Gymnodinium spp. These molecular and morphological data suggest that evolution of this mode of fish ectoparasitism occurred independently in 2 distantly related groups of dinoflagellates, and they further suggest that the taxonomic status of parasites grouped as members of Piscinoodinium requires major revision.

Salsuginus yutanensis n. sp. (Monogenea: Ancyrocephalidae) from Fundulus sciadicus in Clear Creek of eastern Nebraska.

Salsuginus yutanensis n. sp. (Monogenea: Ancyrocephalidae) is described from the gills of the plains topminnow, Fundulus sciadicus Cope, from Clear Creek in eastern Nebraska. Salsuginus yutanensis is distinguished from previously described species by having a shorter accessory piece and different hamulus proportions, especially in the relative lengths of deep and superficial roots. In addition, the angles between deep and superficial roots distinguish S. yutanensis from several congeners.

Patterns of morphological variation of Salsuginus yutanensis (Monogenea: Ancyrocephalidae) over space and time.

Salsuginus yutanensis occurs on the gills of the plains topminnow Fundulus sciadicus Cope. The fish of this species have been found to vary morphologically and biochemically among disjunct populations. Morphological characteristics of the sclerotized parts of S. yutanensis were examined from 3 localities in Nebraska, over a 2-yr collecting period. Analysis of variance was used to assess morphological variation with respect to site and date. Worms from 2 localities, Keith and Saunders counties, differed significantly for most characters considered. A third site, also in Keith County, contained worms for which measurement means tended to be intermediate between those in the other 2 sites. This site-related difference was maintained over a pattern of broad seasonal variation and suggests that the site-related differences are of evolutionary origin. If this interpretation is true, then the parasite populations likely are isolated in a manner analogous to those of the host. However, differences due to effects of temperature on worm development were not ruled out as possible explanations for the observations although consistent temperature differences between the sites are unlikely, given the nature of the habitats studied.

The niche of Salsuginus thalkeni, a gill parasite of Fundulus zebrinus.

Distribution of a monogenean parasitic helminth Salsuginus thalkeni on the gills of the fish Fundulus zebrinus is described by calculation of mean positions and niche breadths on the linear spatial resource gradients gill filament length, gill arch length and arch number. All distributions are given for parasites in the presence and absence of various combinations of potential competitors, namely the 6 other parasite species that occupy the same host species. Filament niche breadth was narrowest in the absence of potential competitors; breadth on arch was widest in the presence of potential competitors. Breadth on both resources was correlated positively with mean number of parasites per individual. Arch breadth exhibited cyclic seasonal changes, being lowest in early to mid-summer. Mean position exhibited no repeated pattern of variation on either resource. The results are considered consistent with predictions about the niche structures of species in unsaturated noninteractive specialist communities.

Life cycle of Calyptospora funduli (Apicomplexa: Calyptosporidae).

The taxonomic status of the extraintestinal piscine coccidium Calyptospora funduli is based in part on its requirement of an intermediate host (the daggerblade grass shrimp Palaemonetes pugio). In the present study, grass shrimp fed livers of Gulf killifish (Fundulus grandis) infected with sporulated oocysts of C. funduli exhibited numerous sporozoites suspended in the intestinal contents when fresh squash preparations were examined by light microscopy. Using this method, sporozoites were not seen in intestinal epithelial cells of the grass shrimp or in any other cell types. Ultrastructural examination, however, revealed sporozoites in the cytoplasm of the gut basal cells. Cross-sections of 1-13 sporozoites were seen within a single cell, and those sporozoites each appeared to be situated in individual membrane-bound vesicles, rather than in a single parasitophorous vacuole. These ultrastructural observations indicate that in the grass shrimp intermediate host, sporozoites that develop into an infective stage probably undergo that development in gut mucosal basal cells. Prior studies revealed that these sporozoites modified their structure over 4-5 days and that before that time, they were not infective to the fish host. Following ingestion of an infected shrimp by a killifish, the infective sporozoites apparently reach the liver of their killifish definitive hosts through the bloodstream. Sporozoites were seen in blood smears from the longnose killifish, Fundulus similis, 4 hr after fish were fed experimentally infected grass shrimp. Additionally, coccidian trophozoites and early meronts were seen in hepatocytes from several longnose killifish at 48, 72, and 96 hr postinfection. This study, in conjunction with previous findings, clearly confirms that a true intermediate host is required in the life cycle of C. funduli, that a developmental period of about 5 days in grass shrimp is necessary for sporozoites to become infective to killifishes, and that sporozoites do occur intracellularly in gut basal cells of the grass shrimp.

Host specificity of Rhabdochona canadensis (Nematoda: Rhabdochonidae) in Nebraska.

Intermediate and definitive host specificity of Rhabdochona canadensis in Nebraska were investigated. Mayfly nymphs Trichorythodes sp. and Caenis sp. were found to serve as experimental intermediate hosts. Development inside the nymphs required approximately 10 days, with the worms passing through 2 molts and then becoming encapsulated in the hemocoel as infective third-stage juveniles. Survey data revealed that only the red shiner Cyprinella lutrensis serves as definitive host for R. canadensis in nature. Laboratory infections of Notropis dorsalis, N. stramineus, and Fundulus zebrinus, all of which were uninfected in nature, were attempted to determine if observed specificity was due to physiological or ecological factors. Two individuals of N. dorsalis became infected with R. canadensis, but no development was observed. Both N. stramineus and F. zebrinus were incapable of becoming infected. Thus, definitive host specificity in this system seems to be mediated by both physiological and host ecological factors.

Diversity of the parasite assemblage of Fundulus zebrinus in the Platte River of Nebraska.

Changes in the values of the Shannon H' diversity index as determined for individual hosts (infraassemblage diversity), host samples (sample assemblage diversity), and for species density are reported for an assemblage of 7 parasites in Fundulus zebrinus in the Platte River in Nebraska for a 5-yr period. The parasites were: Myxosoma funduli (gill), Trichodina sp. (gill), Gyrodactylus bulbacanthus (gill), Salsuginus sp. (gill), Gyrodactylus stableri (body surface), and Neascus sp. (= Posthodiplostomum; eyes and body cavity). In addition, relative abundance and equitability are given for each of the study years. Mean infraassemblage diversity, sample assemblage diversity, species density, and equitability were all significantly negatively correlated with river streamflow (measured in cubic feet per second) of the year prior to the sample, but were independent of the concurrent year's streamflow. Over the long term, M. funduli and Trichodina sp. were the most, and G. bulbacanthus was the least, abundant. Species pair prevalence and relative density correlations showed few long-term patterns of co-occurrence or microallopatry. The strongest association was between M. funduli and the Neascus sp. and was attributed to similarities in ecological requirements of intermediate hosts.

Biology and pathogenesis of the coccidium Eimeria funduli infecting killifishes.

Epizootics of Eimeria funduli involved estuarine killifishes (Fundulus grandis, F. pulvereus, F. similis, and F. heteroclitus) in Mississippi, Alabama, and Virginia. All of more than 500 specimens examined of F. grandis from Mississippi during 1977 though 1979 had infections, regardless of age, sex, or season collected. Oocysts occurred primarily in the liver and pancreas, replacing up to 85% of both those organs. Infrequent sites of infection were fatty tissue of the body cavity, ovary, intestine, and caudal peduncle. Living fish did not discharge oocysts. Eimeria funduli is the first known eimerian to require a second host. To complete the life cycle, an infective stage in the grass shrimp Palaemonetes pugio had to be eaten. In 6-mo-old killifish reared in the laboratory at 24 C, young schizonts were first observed in hepatic and pancreatic cells 5 days postfeeding, followed by first generation merzoites by day 10, differentiation of sexual stages during days 15 to 20, fertilization between days 19 and 26, sporoblasts from days 25 to 30, and sporozoites about day 60. Unique sporopodia developed on sporocysts by day 35 when still unsporulated. Temperatures of 7 to 10 C irreversibly halted schizogony. Both schizogony and sporogony progressed slower as age of host increased. When infective shrimp in doses ranging from 1 to 10% of a fish's body weight were eaten, the level of intensity of resulting infections did not differ significantly. Pathogenesis followed a specific sequence, with the host response apparently unable to contend with extensive infections as seen typically in nature and in our experiments. Premunition was indicated. When administered Monensin orally, infected fish exhibited a reduction in oocysts by 50 to 70% within 20 days as compared with untreated fish. Furthermore, infected killifish exclusively on a diet of TetraMin for 3 mo completely lost their infections.

Evolutionary constraints on population structure: the parasites of Fundulus zebrinus (Pisces:Cyprinodontidae) in the South Platte River of Nebraska.

Population and community descriptor values (parasites per host, prevalence per parasite species, variance/mean ratios, species density, and diversity indices) for the 7-species parasite community of 61 relatively homogeneous samples of Fundulus zebrinus (Pisces: Cyprinodontidae) in the South Platte River of Nebraska, U.S.A., taken over a 14-yr period, are reported. South Platte River streamflow fluctuates over 2 orders of magnitude on several time scales-monthly, annually, and over multiple year wet-dry cycles. Relatively homogeneous sampling of a single host species with several parasite species provided a system that allowed assessment of the contribution of evolved parasite life cycles to population structure in an everchanging environment. No significant negative species-to-species associations were observed. Species abundance, order of abundance, and diversity were affected most strongly by streamflow, with high water reducing prevalence and abundance of larval trematode parasites. Each parasite species had its characteristic long- and short-term patterns of variation in population descriptor values, with mostly long-term stability superimposed on sometimes extreme short-term fluctuations of descriptor values. The differences in these characteristic patterns were considered products primarily of the evolved life cycle traits and transmission mechanisms operating in the common fluctuating environment. The parasite community as a whole showed resilience, returning to preperturbation diversity following extended periods of high water.

Host specificity of Calyptospora funduli (Apicomplexa: Calyptosporidae) in atheriniform fishes.

Calyptospora funduli has a broad host specificity, infecting at least 7 natural and 10 additional experimental definitive hosts, all atheriniform fishes within 5 families, but most in the genus Fundulus. Barriers, apparently innate ones, prevent any development of C. funduli in perciform fishes but allow incomplete or abnormal development of the parasite in a few unnatural atheriniform hosts. In the freshwater species Fundulus olivaceus and Fundulus notti, these abnormalities consisted of asynchronous development, degeneration of the parasite in early stages of development, and the formation of numerous macrophage aggregates. Rivulus marmoratus has the ability to eliminate infections with a granulomatous inflammatory response. Additional barriers that limit natural infections of C. funduli in other hosts include feeding behavior, environmental conditions, and geographic isolation.

A new species of Swingleus (Monogenea: Gyrodactylidae) from the mummichog Fundulus heteroclitus, in the Delaware Bay.

Swingleus ancistrus n. sp. (Monogenea: Gyrodactylidae) is described from the skin and fins of Fundulus heteroclitus from Canary Creek Marsh, Lewes, Delaware. Subsequent records from New Jersey, Maryland, Virginia, and North Carolina are reported. Swingleus ancistrus is differentiated from S. polyclithroides, the only other species of the genus, primarily by its size, haptoral morphology, host, and locality. Swingleus ancistrus is larger in almost every dimension and exhibits a distinct notch on the anterior border of the opisthaptor, and several features of the haptoral anatomy and peduncular bar are unique. The prevalence of infection in hosts collected from the type locality in August was 100%. The maximum number of S. ancistrus recovered from a single host was 134. The average intensity of infection was 24 S. ancistrus per host from the type locality.

Gill parasites of mummichogs, Fundulus heteroclitus (Teleostei: Cyprinodontidae): effects of season, locality, and host sex and size.

I investigated the prevalences and densities of gill parasites in 4 seasonal samples of mummichog, Fundulus heteroclitus (n=242), from 2 creeks differing in salinity in central Chesapeake Bay. The parasites (and overall prevalence ranges) were: mobile (12-88%) and sessile (0-50%) peritrichs (Ciliophora); Myxobolus funduli (58-94%) (Myxozoa); Gyrodactylidae (0-94%) (includes Gyrodactylus sp. and Fundulotrema sp.) and Salsuginus sp. (74-100%) (Monogenea); metacercariae of Phagicola diminuta (75-100%) and Echinochasmus schwartzi (79-100%) (Digenea); Ergasilus manicatus (25-100%) (Copepoda); Lironeca ovalis (0-11%) (Isopoda); and cysts of unknown etiology, or CUEs (64-94%) (unknown taxon). CUEs were more abundant in fall and gyrodactylids in winter. The myxozoan, copepod, and 1 species of digenean were most abundant in spring. Except for gyrodactylids and CUEs, densities were greater in the less saline creek for all taxa. There were no significant differences between sexes except in 1 sample; digenean densities increased with host length for females but not males. There was a strong positive relationship of CUE density with host length and weaker positive associations of gyrodactylid and Salsuginus sp. densities with host length.

Infestation and pathological alterations by Ergasilus sarsi (Copepoda) on the Tanganyika Killifish from Africa.

A total of 204 Ergasilus sarsi, a copepod, were collected from Tanganyika Killifish Lamprichthys tanganicanus in Lake Tanganyika during March 2010. The prevalence was 86.40%, the mean intensity was 7.56, and the mean abundance was 6.38. Only 27 of the fish were infested, and the highest infestation on one fish was 29. Proliferation of mucus cells and lamellar fusion occurred. Haemorrhage due to blood vessel compression was noted. This is the first record of E. sarsi from Tanganyika Killifish. This study is also the first to provide a description of the pathological alterations caused by E. sarsi.

The description and host-parasite relationships of a new quadrigyrid species (Acanthocephala) from the Persian tooth-carp, Aphanius farsicus (Actinoptreygii: Cyprinodontidae) in Iran.

Acanthogyrus (Acanthosentis) barmeshoori n. sp. (Quadrigyridae) is described from the Persian tooth-carp, Aphanius farsicus Teimori, Esmaeili, and Reichenbacher, 2011 (Cyprinodontidae) in the Maharlu Lake basin, southern Iran. Aphanius farsicus is an endemic freshwater fish found in streams and springs that drain into Maharlu Lake, Shiraz, Iran. The new species is the smallest of all the 44 known species of the subgenus Acanthosentis Verma and Datta, 1929, measuring between 0.26 and 1.68 mm in length. It is further distinguished by having a short cylindrical proboscis with very long anterior hooks widely separated from very small hooks in 2 very close circles posteriorly (hook length ratio about 4:1). It is separated from 4 other species of Acanthosentis with similar proboscis armature but with less-extreme diversification of hook length. The new species is also distinguished in having anterior para-receptacle structures (PRS) and a similar posterior structure like those reported in only 1 other species of Acanthosentis from Japan. Proboscis receptacle is single walled with a large triangular cephalic ganglion. Testes are large, pre-equatorial, and Saefftigen's pouch is prominent. Fourteen to 25 circles of spines cover the anterior 50-70% of the trunk, but a few spines may be present at posterior end of trunk. This is the first species of Acanthosentis where SEM images, showing external morphological details, are provided. From a total of 357 fish specimens examined between July 2006 and June 2007, 173 specimens (48.5%) were infected with individuals of the new species. The prevalence of infection decreased with increasing fish size. The parasite was observed all year, with the highest abundance and intensity in May while the prevalence was highest in February. The prevalence of acanthocephalans decreased with increasing fish size. While most worms were recovered in fish within the length range of 18-29.9 mm, 1 of the longest parasites (1.68 mm long) was found in fish within the range of 30-33.9 mm long.