Parasites of Moroccan desert Coptodon guineensis (Pisces, Cichlidae): transition and resilience in a simplified hypersaline ecosystem.

Sebkha Imlili (Atlantic Sahara) is a salt flat with over 160 permanent holes of hypersaline water generated in the Holocene and inhabited by euryhaline organisms that are considered to be relics of the past, including the cichlid fish Coptodon guineensis. We surveyed the fish parasites four times over one year, to i) identify the parasites, and ii) determine possible seasonality in infection patterns. Over 60% of the fish were infected by one to three helminths: an acanthocephalan in the intestine and two digenean metacercariae in the kidney, spleen, liver, muscle, and mesenteries. The acanthocephalan Acanthogyrus (Acanthosentis) cf. tilapiae was identified morphologically and molecularly; only one digenean (the heterophyid Pygidiopsis genata) could be identified molecularly. Both identified parasites were present throughout the sampling periods; the unidentified metacercariae were present only in summer and fall. Mean intensities, but not prevalence of infection by the acanthocephalan, reflected a biannual pattern of transmission. Infection accrued with fish size, possibly due to cannibalism. Because the water holes include only a few invertebrates, the intermediate hosts of these parasites can be inferred to be the gastropod Ecrobia ventrosa for the digeneans and either the copepod Cletocamtpus retrogressus or the ostracod Cyprideis torosa for the acanthocephalan. This ecosystem appears stable and provides a window into the past, as the acanthocephalan likely switched from freshwater tilapia to C. guineensis when the Sebkha formed. However, this is a vulnerable environment where the survival of these parasites depends on interactions maintained among only very few hosts.

Title: Parasites de Coptodon guineensis (Pisces, Cichlidae) du désert marocain : transition et résilience dans un écosystème hypersalin simplifié. Abstract: La Sebkha d'Imlili est une sebkha (étendue désertique sableuse et salée) dans le Sahara Atlantique caractérisée par la présence de plus de 160 poches permanentes d'eau hypersaline qui sont apparues à l'Holocène et qui sont habitées par des organismes considérés comme des reliques du passé, dont un poisson cichlidé, Coptodon guineensis. Nous avons fait l'inventaire des parasites de ce poisson au cours des quatre saisons d'une année pour 1) identifier les parasites et 2) déterminer une éventuelle transmission saisonnière. Plus de 60 % des poissons étaient infestés par un à trois helminthes : un Acanthocéphale dans l'intestin et des métacercaires de deux espèces de Digène dans le rein, la rate, les muscles et le mésentère. L'Acanthocéphale Acanthogyrus (Acanthosentis) cf. tilapiae a été identifié morphologiquement et génétiquement mais seul un des deux Digènes (l'hétérophyidé Pygidiopsis genata) a pu être identifié par séquençage. Ces deux parasites étaient présents à chaque période d'étude, mais la métacercaire non identifiée était présente seulement en été et en automne. L'intensité moyenne de l'infestation par l'Acanthocéphale, mais pas sa prévalence, reflète une transmission biannuelle. L'infestation augmente avec la taille du poisson, peut-être à cause du cannibalisme. L'identité des hôtes intermédiaires de ces parasites peut être avancée parce que cet écosystème est simplifié et inclut seulement quelques invertébrés : pour les Digènes, le Gastéropode Ecrobia ventrosa, et pour l'Acanthocéphale, le Copépode Cletocamtpus retrogressus ou l'Ostracode Cyprideis torosa. Cet écosystème apparait stable et offre une vue sur le passé étant donné que l'Acanthocéphale a sans doute été transféré d'un tilapia d'eau douce quand la sebkha s'est formée. Cependant, c'est un environnement vulnérable où la survie de ces parasites dépend d'interactions entre très peu d'espèces hôtes.

Molecular data reshape our understanding of the life cycles of three digeneans (Monorchiidae and Gymnophallidae) infecting the bivalve, Donax variabilis: it's just a facultative host!

The coquina, Donax variabilis, is a known intermediate host of monorchiid and gymnophallid digeneans. Limited morphological criteria for the host and the digeneans' larval stages have caused confusion in records. Herein, identities of coquinas from the United States (US) Atlantic coast were verified molecularly. We demonstrate that the current GenBank sequences for D. variabilis are erroneous, with the US sequence referring to D. fossor. Two cercariae and three metacercariae previously described in the Gulf of Mexico and one new cercaria were identified morphologically and molecularly, with only metacercariae occurring in both hosts. On the Southeast Atlantic coast, D. variabilis' role is limited to being a facultative second intermediate host, and D. fossor, an older species, acts as both first and second intermediate hosts. Sequencing demonstrated 100% similarities between larval stages for each of the three digeneans. Sporocysts, single tail cercariae, and metacercariae in the incurrent siphon had sequences identical to those of monorchiid Lasiotocus trachinoti, for which we provide the complete life cycle. Adults are not known for the other two digeneans, and sequences from their larval stages were not identical to any in GenBank. Large sporocysts, cercariae (Cercaria choanura), and metacercariae in the coquinas' foot were identified as Lasiotocus choanura (Hopkins, 1958) n. comb. Small sporocysts, furcocercous cercariae, and metacercariae in the mantle were identified as gymnophallid Parvatrema cf. donacis. We clarify records wherein authors recognized the three digenean species but confused their life stages, and probably the hosts, as D. variabilis is sympatric with cryptic D. texasianus in the Gulf of Mexico.

TITLE: Les données moléculaires remodèlent notre compréhension des cycles de vie de trois Digènes (Monorchiidae et Gymnophallidae) parasites du bivalve Donax variabilis : ce n'est qu'un hôte facultatif ! ABSTRACT: La telline, Donax variabilis, est un hôte intermédiaire connu de digènes Monorchiidae et Gymnophallidae. Le nombre limité de critères morphologiques pour identifier les hôtes et les stades larvaires des parasites sont à la base de confusion dans la littérature. Dans cette étude nous avons identifié par séquençage les tellines collectées sur la côte Atlantique des États-Unis. Nous démontrons que les séquences pour D. variabilis dans GenBank sont incorrectes et que celle du spécimen américain est en fait celle de D. fossor. Deux cercaires et trois métacercaires décrites au préalable dans le Golfe du Mexique ainsi qu'une nouvelle cercaire ont été identifiées morphologiquement et par séquençage. Les métacercaires seules infectent les deux hôtes. Sur la côte sud-est Atlantique, D. variabilis a un rôle limité à seulement celui de second hôte intermédiaire facultatif, et D. fossor, une espèce plus ancienne, est premier et second hôte intermédiaire. Le séquençage a montré 100 % de similarité entre les stades larvaires de chacun des trois digènes. Des sporocystes avec des cercaires à queue simple et les métacercaires dans le siphon inhalant ont des séquences identiques à celles de Lasiotocus trachinoti, pour qui nous donnons le cycle complet. Les adultes des deux autres digènes ne sont pas connus et les séquences des stades larvaires ne sont identiques à aucune dans GenBank. Des sporocystes de grande taille, les cercaires (Cercaria choanura) et les métacercaires enkystées dans le pied des tellines sont identifiées comme étant Lasiotocus choanura (Hopkins, 1958) n. comb. Des petits sporocystes avec des furcocercaires et des métacercaires dans le manteau des tellines sont identifiées comme étant le gymnophallide Parvatrema cf. donacis. Nous clarifions les rapports de la littérature dans lesquels les auteurs ont reconnu les trois espèces de digènes mais ont confondu leurs stades larvaires et probablement les hôtes étant donné que D. variabilis vit en sympatrie avec l'espèce cryptique D. texasianus dans le Golfe du Mexique.

Dynamics of infection and pathology induced by the aporocotylid, Cardicola laruei, in Spotted Seatrout, Cynoscion nebulosus (Sciaenidae).

The sciaenid Spotted Seatrout (Cynoscion nebulosus) are infected by blood flukes (Cardicola spp.). A 2 year survey in estuaries of South Carolina, USA, showed that adult flukes and granulomas occurred throughout the year but their prevalence was highest in summer (61% and 84%, respectively), indicating an unusually high level of infection for wild fish. Granulomas remained after adult flukes could no longer be found. PCR-Restriction Fragment Length Polymorphism (RFLP) of a subsample of specimens allowed identification of Cardicola laruei as the only species infecting these seatrout during the period of study. Mean intensity of infection by flukes was higher in female seatrout, suggesting endocrine and/or immune system involvement. The prevalence of granulomas declined sharply in winter, indicating possible mortality of infected seatrout as this species is known to be cold-sensitive. Granulomas were studied using histology, immunohistochemistry, and transmission electron microscopy. Eggs were encapsulated by an inner core of dark epithelioid cells, and an outer core of large epithelioid cells undergoing epithelialization. Fibrosis was observed around granulomas and some granulomas detached from the surrounding damaged myocardium. Numerous inflammatory cells appeared mobilised around granulomas and pathology could be severe, in some cases showing grossly visible blister-like extrusions scattered in the damaged epicardium. At the gross level, some granulomas possessing eggs with live miracidia were observed at the surface of the epicardium. These findings suggest that granulomas carrying both dead and live eggs can clear the fish heart by host-mediated transport through the myocardium, as is known to occur in related human Schistosoma infections.

Candidatus Cryptoplasma Associated with Green Lizards and Ixodes ricinus Ticks, Slovakia, 2004-2011.

During 2004-2011, we collected green lizards and Ixodes ricinus ticks in Slovak Karst National Park in Slovakia; 90% (36/40) of lizards and 37% of ticks removed from lizards were infected with family Anaplasmataceae bacteria. Only Candidatus Cryptoplasma sp. REP (reptile) was identified in these samples. Green lizards transmit this bacterium.

Philometrids of the southern flounder Paralichthys lethostigma: a multidimensional approach to determine their diversity.

Two species of philometrid nematode, Philometra overstreeti and Philometroides paralichthydis, infect the southern flounder, Paralichthys lethostigma. Individuals of P. overstreeti are located between the teeth and inside the bony part of the branchial arches of the fish. Individuals of P. paralichthydis are associated with the bones of the buccal cavity and among muscles that control the dorsal and anal fins. Sequencing of part of the cytochrome oxidase I gene revealed 4 distinct genetic clades, each corresponding exactly to the 4 respective locations of the parasites in the host, suggesting the need for taxonomic revision. We hypothesized that each clade represented a separate species and, because the worms are morphologically indistinguishable, compared population level parameters of the clades comprising each currently recognized species. For each currently recognized species, the presence of worms from 1 clade was negatively correlated with the presence of worms from the other. Results also indicated significant differences between the clades in prevalences relative to both biotic and abiotic factors. Results clearly indicated major differences in the ecology of the philometrids constituting each clade. Taken as a whole, molecular and ecological data support the contention that the 4 genetic clades are likely 4 distinct species.

Synchronization of occurrence of the ovarian philometrid, Philometra carolinensis, with the spawning season of its fish host, the spotted seatrout, Cynoscion nebulosus.

The philometrid Philometra carolinensis inhabits the ovaries of the spotted seatrout, Cynoscion nebulosus. A 2-year study in estuaries of South Carolina showed that each year adult female worms were present only during the spawning season of the host and that only sexually mature fish were infected. Overall prevalence was 13.1%. Young-of-the-year fish were uninfected and mature 1-year-old fish were less frequently infected than older fish. Abundance of the philometrid was significantly different in age-1 and -2 spotted seatrout. Prevalence, mean abundance, and intensity peaked during the first 2 months of the host's 4-month spawning season, which then declined abruptly. Occurrence of the philometrid in the fish host was unaffected by water temperature, salinity, and dissolved oxygen. Histological studies revealed that the worms were hematophagous. Worms induced disruption of the ovarian lamellar walls resulting in the interruption of development and the loss of host eggs into the ovarian lumen prior to their maturation. The data show that development of this parasite is linked to the host's reproductive status and suggest that paratenesis plays an important role in the maintenance of the parasite's life cycle.

Chemokinetic effect of interleukin-1 beta on cultured Biomphalaria glabrata embryonic cells.

Previous studies have indicated that a molecule with cytokine activity, possibly an interleukin-1-like (IL-1) molecule, plays a role in the killing of larval stages of the blood fluke Schistosoma mansoni in the snail host Biomphalaria glabrata. The purpose of the present experiment was to test the effects of recombinant-human IL-1beta (rhIL-1beta) on embryonic B. glabrata (Bge) cell motility to determine whether the cells respond to the cytokine. Response was measured using a variation of a chemokinetic assay in which cells in culture were separated from variable concentrations of rhIL-1beta by a semi-permeable membrane containing pores to allow migration. A double staining technique was developed to ascertain cell movement across the membrane. The number of cells moving across the membrane significantly increased in a concentration-dependent manner relative to the presence of increasing amounts of rhIL-1beta below the membrane. The number of cells that moved across the membrane increased until a threshold was reached, after which migration decreased. Further, the rhIL-1beta-mediated increase in Bge cell migration across the membrane was abrogated by the addition of IL-1 receptor antagonist protein. These data indicate that Bge cells respond specifically to rhIL-1beta. As such, these data also indicate that Bge cells may serve as a useful model for elucidation of the role of cytokines or cytokine-like molecules in the snail/schistosome relationship.

Population dynamics of the philometrid nematode Margolisianum bulbosum in the southern flounder Paralichthys lethostigma (Pisces: Paralichthyidae) in South Carolina, USA.

This is the first report of the philometrid nematode Margolisianum bulbosum Blaylock and Overstreet, 1999 from the southern flounder Paralichthys lethostigma on the east coast of the USA. Observation of adult female worms was used as an indication of the parasite's presence in the fish. Adult females were found only in P. lethostigma >50 mm total length. The overall prevalence was 74%, with a mean intensity of 5 female nematodes per parasitized fish. Infected flounders were found throughout the year with a statistically significant decrease in intensity in the winter months. Neither salinity, water temperature, fish gender nor fish age were found to influence either prevalence or intensity of infection in the flounder. While larvigerous (gravid) females were found throughout the year, the significant decrease in their occurrence during the summer through fall, in concert with an observed decrease in intensity of infection during the winter, indicated that the life cycle of this philometrid species is likely to be annual.