Árni Kristmundsson

Negative effects of Kudoa islandica n. sp. (Myxosporea: Kudoidae) on aquaculture and wild fisheries in Iceland.

In the early 2000s, experimental rearing of spotted wolffish, Anarhichas minor, was started in Iceland. Health surveillance, carried out at regular intervals during the rearing period, revealed persistent and highly prevalent Kudoa infections of fish muscles which caused great financial losses due to post mortem myoliquefaction. In addition, during the traditional process of drying and smoking wild Atlantic lumpfish, Cyclopterus lumpus, the muscles from some fish almost completely disappear and the fish have to be discarded. To describe the etiological agent responsible for these conditions, spotted wolffish, Atlantic wolffish Anarhichas lupus, northern wolffish Anarhichas denticulatus and Atlantic lumpfish were caught off the Icelandic coast and examined for the presence of Kudoa. We describe a novel myxosporean, Kudoa islandica n. sp., using morphological and molecular data, and show with histopathology that it causes extensive myoliquefaction in three different wild fish hosts, which all are commercially valuable species in Iceland. Although some spore dimensions varied significantly between fish species, the molecular analyses showed that the same parasite was responsible for infection in all fish. The northern wolffish was not found to be infected. Although robustly placed in the Kudoa clade in phylogenetic analyses, K. islandica was phylogenetically distinct from other kudoids. A single myxosporean, K. islandica, is responsible for the infections in the somatic muscles of lumpfish and wolffish, causing extensive post mortem myoliquefaction. This myxosporean is likely to infect other fish species and it is important to study its life cycle in order to evaluate any threat to salmonid culture via the use of lumpfish as a biocontrol for sea lice.

Sphaeromyxids form part of a diverse group of myxosporeans infecting the hepatic biliary systems of a wide range of host organisms

BackgroundApproximately 40 species of Sphaeromyxa have been described, all of which are coelozoic parasites from gall bladders of marine fish. They are unique amongst the myxosporeans as they have polar filaments that are flat and folded instead of being tubular and spirally wound. This unusual feature was used as a subordinal character to erect the suborder Sphaeromyxina, which contains one family, the Sphaeromyxidae, and a single genus Sphaeromyxa.MethodsIn the present study, we examine eelpout from the genus Lycodes from Iceland for the presence of myxosporean parasites in the gall bladder and perform morphological and DNA studies.ResultsA novel myxosporean, Sphaeromyxa lycodi n. sp., was identified in the gall bladders of five of the six species of Lycodes examined, with a prevalence ranging from 29 - 100%. The coelozoic plasmodia are large, polysporous and contain disporic pansporoblasts and mature spores which are arcuate. The pyriform polar capsules encase long and irregularly folded ribbon-like polar filaments. Each spore valve has two distinct ends and an almost 180° twist along the relatively indistinct suture line. The single sporoplasm is granular with two nuclei. Sphaeromyxa lycodi is phylogenetically related to other arcuate sphaeromyxids and is reproducibly placed with all known sphaeromyxids and forms part of a robustly supported clade of numerous myxosporean genera which infect the hepatic biliary systems of a wide range of hosts.ConclusionsSphaeromyxa lycodi is a common gall bladder myxosporean in eelpout of the genus Lycodes from Northern Iceland. It has characteristics typical of the genus and develops arcuate spores. Molecular phylogenetic analyses confirm that sphaeromyxids form a monophyletic group, subdivided into straight and arcuate spore forms, within the hepatic biliary clade that infect a wide range of freshwater associated animals. The ancestral spore form for the hepatic biliary clade was probably a Chloromyxum morphotype; however, sphaeromyxids have more recently evolved from an ancestor with a spindle-shaped Myxidium spore form. We recommend that the suborder Sphaeromyxina is suppressed; however, we retain the family Sphaeromyxidae and place it in the suborder Variisporina.

Previously unknown apicomplexan species infecting Iceland scallop, Chlamys islandica (Müller, 1776), queen scallop, Aequipecten opercularis L., and king scallop, Pecten maximus L.

Examination of three scallop species from three separate locations: Iceland scallop from Icelandic waters, king scallop from Scottish waters and queen scallop from Faroese and Scottish waters, revealed infections of a previously unknown apicomplexan parasite in all three scallop species. Developmental forms observed in the shells appeared to include both sexual and asexual stages of the parasite, i.e. merogony, gametogony and sporogony, which suggests a monoxenous life cycle. Meronts, gamonts, zygotes and mature oocysts were solely found in the muscular tissue. Zoites, which could be sporozoites and/or merozoites, were observed in great numbers, most frequently in muscles, both intracellular and free in the extracellular space. Zoites were also common inside haemocytes. Examination of the ultrastructure showed that the zoites contained all the major structures characterizing apicomplexans. This apicomplexan parasite is morphologically different from other apicomplexan species previously described from bivalves. Presently, its systematic position within the phylum Apicomplexa cannot be ascertained.

Margolisiella islandica sp. nov. (Apicomplexa: Eimeridae) infecting Iceland scallop Chlamys islandica (Müller, 1776) in Icelandic waters

Wild Iceland scallops Chlamys islandica from an Icelandic bay were examined for parasites. Queen scallops Aequipecten opercularis from the Faroe Islands and king scallops Pecten maximus and queen scallops from Scottish waters were also examined. Observations revealed heavy infections of eimeriorine parasites in 95-100% of C. islandica but not the other scallop species. All life stages in the apicomplexan reproduction phases, i.e. merogony, gametogony and sporogony, were present. Trophozoites and meronts were common within endothelial cells of the hearts auricle and two generations of free merozoites were frequently seen in great numbers in the haemolymph. Gamonts at various developmental stages were also abundant, most frequently free in the haemolymph. Macrogamonts were much more numerous than microgamonts. Oocysts were exclusively in the haemolymph; live mature oocysts contained numerous (>500) densely packed pairs of sporozoites forming sporocysts. Analysis of the 18S ribosomal DNA revealed that the parasite from C. islandica is most similar (97.7% identity) to an unidentified apicomplexan isolated from the haemolymph of the giant clam, Tridacna crocea, from Japan. Phylogenetic analyses showed that the novel sequence consistently grouped with the Tridacna sequence which formed a robust sister clade to the rhytidocystid group. We propose the name Margolisiella islandica sp. nov., referring to both type host and type locality.

Is an Apicomplexan Parasite Responsible for the Collapse of the Iceland Scallop (Chlamys islandica) Stock

Due to the total and unexpected collapse of the Iceland scallop, Chlamys islandica, stocks around Iceland during the 2000s, a commercial fishing ban has been imposed on this valuable resource since 2003. Following the initial identification of an apicomplexan parasite in the scallops, a long-term surveillance program was established to evaluate the effect of the parasite on the population. The infections were highly prevalent in all shell sizes throughout the study. However, the parasite only impacts mature scallops where they cause severe macroscopic changes, characterized by an extensively diminished and abnormally coloured adductor muscle. A highly significant relationship was observed between infection intensity and gonad and adductor muscle indices. The first four years of the study, were characterized by high infection intensity and very poor condition of the adductor muscle and gonads, whilst during subsequent years, infections gradually decreased and the condition of the scallops improved. Histopathological changes were restricted to the presence of apicomplexan zoites which were widely distributed, causing varying degrees of pathology in all organs. In heavy infections, muscular and connective tissues were totally necrotized, destroying significant parts of numerous organs, especially the adductor muscle, digestive gland and gonads. The progression of the disease was in good synchrony with the mortality rates and the subsequent decline observed in the scallop stock and recruitment indices. Our findings strongly suggest that the apicomplexan parasite played a major role in the collapse of the Iceland scallop stock in Breidafjordur. In addition to causing mortality, the infections significantly impact gonad development which contributes further to the collapse of the stock in the form of lower larval recruitment. Furthermore, compelling evidence exists that this apicomplexan pathogen is causing serious disease outbreaks in other scallop populations. Similar abnormal adductor muscles and the parasite itself have been identified or observed in association with other mass mortality events in several different scallop species and commercial stocks in the northern hemisphere.

Prosorhynchoides borealis Bartoli, Gibson & Bray, 2006 (Digenea: Bucephalidae) cercariae from Abra prismatica (Mollusca: Bivalvia) in Icelandic waters

This paper reports the adult stage of Prosorhynchoides borealis (Digenea) from Lophius piscatorius in Icelandic waters and infections with the larval stages (sporocysts and cercariae) found for the first time in the bivalve Abra prismatica (Semelidae). The previously known first intermediate host was Abra alba (Semelidae). Ribosomal DNA sequencing studies on all three life stages of the parasite (cercariae, metacercariae, adults) were performed to confirm their identites. Morphometric measurements confirmed that the adult worms belong to the newly described species P. borealis. Prosorhynchoides borealis sporocysts filled with cercariae were found in 16% of A. prismatica bivalves sampled at depths between 34 and 93 m off South Iceland. Prevalence ranged from 0 to 44% between different localities. The parasite was found only in the larger bivalves. Extensive sporocyst infection in the haemocoel of the foot caused mechanical muscle damage with subsequent degeneration and necrosis. Other tissues, including the digestive gland, nephridia, gills and intestine, were less heavily infected. Only focal necrosis was observed in the digestive gland, nephridia and gills, and local atrophy in the intestine. Cercariae were also observed in the lumen of both the stomach and intestine. This is the first report of A. prismatica as an alternative first intermediate host for P. borealis. Ribosomal DNA sequence data reveals 100% homology in the data between cercariae, metacercariae and adult digeneans, supporting the morphological data suggesting that all stages belong to the same species.

Pseudobranchial X-cell pseudotumors in young wild and farmed Atlantic cod Gadus morhua in Iceland

This study investigated the prevalence of pseudobranchial X-cell pseudotumors in 2 year classes of wild juvenile cod and to a lesser extent in older cod in NW Iceland. The disease was also monitored in farmed wild-caught juvenile cod. The youngest wild cod detected that had X-cell infections were 6.5 to 13.0 cm in length, with prevalence reaching a maximum level of 7%. The highest prevalence (23%) was recorded in 18.5 to 27.0 cm fish. The mean prevalence in older cod (25.0 to 76.0 cm in length) was 7% but decreased with increasing age. The mean prevalence of X-cell pseudotumors in farmed juvenile cod was < or =1% during winter rearing in land-based tanks. Higher prevalence (2 to 15%) was noted in dead and moribund fish. Diseased farmed fish were usually emaciated, and mortality due to the disease was noticeable.

Harmless sea snail parasite causes mass mortalities in numerous commercial scallop populations in the northern hemisphere

Apicomplexans comprise a group of unicellular, often highly pathogenic, obligate parasites exploiting either one or two hosts to complete a full reproductive cycle. For decades, various scallop populations have suffered cyclical mass mortality events, several of which shown to be caused by apicomplexan infections. We report the first dual mollusc life cycle for an apicomplexan: a species highly pathogenic in various pectinid bivalve species, but apathogenic when infecting the common whelk as Merocystis kathae. The sympatric distribution of the common whelk and scallops in the North Atlantic makes transmission extremely effective, occurring via the gastrointestinal tract, by scavenging and predation in whelks and unselective filter feeding in scallops. Infective sporozoites from whelks utilize scallops´ haemocytes to reach muscular tissue, where asexual reproduction occurs. Phylogenetically, this apicomplexan is robustly placed within the Aggregatidae and its inclusion in analyses supports a common ancestry with other basal invertebrate apicomplexans. Scallops seem able to regulate low-level infections of M. kathae as they exist in normal populations while epizootics occur during high levels of exposure from locally infected whelks. A targeted removal of whelks from valuable scallop grounds would be advantageous to minimize the occurrence of M. kathae epizootics and prevent damaging economic losses.

Demodex folliculorum, hársekkjamítill, vangreind orsök hvarmabólgu

UNLABELLED Meibomian gland dysfunction (MGD) is a common cause of dry eye disease. Demodex mites can cause MGD with symptoms like itching, dryness and general ocular discomfort. It is important to consider infestation with Demodex mites in individuals who are non responsive to traditional MGD treatment but also equally important when cylindrical dandruff is seen at the base of the eye lashes.. We report two individuals who had not responded to ocular and systemic treatment for MGD and were then diagnosed with Demodex mites. Treatment with BlephEx and Tea tree oil was successful. This is the first report on Demodex folliculorum in Iceland where a genetic analysis was done. KEY WORDS Demodex, blepharitis, debris, tea tree oil, dry eye. Correspondence: Sigurlaug Guðrún Gunnarsdóttir sigurlaug@sjonlag.is.

Gray meat in the Atlantic sea scallop, Placopecten magellanicus, and the identification of a known pathogenic scallop apicomplexan

Atlantic sea scallop (Placopecten magellanicus) meats are normally firm and creamy white. However, scallops with small, darkened and stringy adductor muscle (gray meat) episodically occur along the Eastern Seaboard, most recently in the rotational management areas of Georges Bank after extended fishing closures. These gray meat scallops are associated with reduced harvestable biomass and mass mortality events. We tested age, nutritional stress and disease as causative agents for this condition. Adult scallops of different shell heights (SH) ranging from (90-145mm) were collected from Georges Bank and analyzed for meat quality and the presence of pathogens using biochemical, histopathological and molecular methods. Gray meat occurrence was weakly correlated with shell height only explaining 8.49% of the variance in a generalized additive model (GAMS). Gray meat weights were lower than white meat (p<0.001) and there was a dramatic reduction in protein content (p<0.05) in gray meat scallops associated with extensive myodegeneration. Amino acid profiles confirmed the breakdown of muscle tissue with an increase in free hydroxyproline in gray meat scallops. Infection by an apicomplexan parasite was detected in the muscle tissue of all gray meat scallops tested. An intermediate pathology stage (brown meat) was also identified. As the parasitic infection increased, meat quality decreased. Numerous developmental stages of the parasite were present in various organs of the scallops. This apicomplexan has an identical SSU rDNA sequence to a novel parasite occurring in the Iceland scallop during a recent mass mortality event. The range of this parasite in Atlantic sea scallops and the effect of abiotic/biotic stressors on pathogenicity are currently unknown. Results from this study link an apicomplexan species, known to be highly pathogenic in scallops, to gray meat occurrence with a potentially high impact on the fishery.