Baltic larval cod Gaaus mornua are infested with a protistan endoparasite in the yolk sac

Bh, Pedersen; Buchmann, K.; Køie, Marianne

doi:10.3354/dao016029

Cited by 11 publications

(13 citation statements)

References 1 publication

(1 reference statement)

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“…Table 1 shows the areas from which the parent fish originated. As in a previous study (Pedersen et al 1993), infected embryos and larval offspring were found from Baltic cod. In addition, embryos from cod from the Dresund, Kattegat and North Sea were infected.…”

Section: Resultssupporting

confidence: 77%

“…1C (also cf. Pedersen et al 1993). The other is the ejection of numerous parasite-like bodies from thin-walled structures (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…First, the higher the magnification, the more parasites are found; and second, the parasites are difficult to observe, as they are frequently covered by the tail of the embryo or, in case of turbot, by the oil droplet in the yolk. Further, the prevalence declines with time due either to the breaking up of larger specimens into numerous very small parasites (Pedersen et al 1993) or to the dying off of infected animals. Finally, at the time of recording the prevalences, we were unaware that the thick-walled refractile spheres were of protistan origin (tubular rnitochondrial cristae).…”

Section: Discussionmentioning

confidence: 99%

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A protistan endoparasite in embryos and yolk-sac larvae of cod Gadus morhua and turbot Scophthalmus maximus

Pedersen¹,

Køie²

1994

Dis. Aquat. Org.

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A protistan endoparasite has recently been discovered in the yolk of embryos and yolksac larvae of cod Gadus morhua and turbot Scophthalmusmaximus. Eight batches of cod embryos were studied, and all batches were infected with minimum prevalences ranging from 14 to 88 %. The endoparasite seemed to be transmitted to the cod embryos via the fish gametes, and the infection occurred in cod from all the major seas surrounding Denmark. Infected cod embryos and yolk-sac larvae have a higher mortality rate than uninfected ones. Several stages of the parasite were identified. The smaller stages of the cod endoparasite invaded the larval tissues and bloodstream. The large, multinucleated stages of the parasite can multiply by budding off small parasites. Other features are associated with endoparasitic infection, i.e. thin-walled and thick-walled spherical structures were observed in the yolk. The thin-walled structures ejected multiple parasite-like bodies of varying sizes into the yolk. The thick-walled, highly refractile hollow spheres in the yolk were of protistan origin. Light microscopy of the turbot endoparasite has previously indicated a strong resemblance with the cod endoparasite. Present transmission electron microscopy reveals that the turbot and cod endoparasites are identical or very closely related.

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Section: Resultssupporting

confidence: 77%

“…1C (also cf. Pedersen et al 1993). The other is the ejection of numerous parasite-like bodies from thin-walled structures (Fig.…”

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A protistan endoparasite in embryos and yolk-sac larvae of cod Gadus morhua and turbot Scophthalmus maximus

Pedersen¹,

Køie²

1994

Dis. Aquat. Org.

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“…The infection occurred at 6-11∞C (Pedersen et al, 1993). In the experiment using sterilized seawater for fertilization of cod eggs and subsequent incubation of fertilized eggs, the embryos were infected, suggesting that the parasite transmitted vertically through the fish gametes (Pedersen and Køie, 1994).…”

Section: Discussionmentioning

confidence: 99%

Endoparasitic Dinoflagellate of the Genus Ichthyodinium Infecting Fertilized Eggs and Hatched Larvae Observed in the Seed Production of Leopard Coral Grouper Plectropomus leopardus

et al. 2007

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-Since 1990, mass mortality of fertilized eggs and hatched larvae of the leopard coral grouper Plectropomus leopardus has occurred repeatedly during its seed production in Okinawa Prefecture. A hitherto unknown protozoan parasite multiplied in the yolk sac in great numbers. The yolk sac of fertilized eggs and hatched larvae eventually burst and parasites were released to sea water. The development of the parasite was briefly described, which is very similar to that of the dinoflagellate Ichthyodinium chabelardi, known to infect yolk of several marine fish larvae in Europe. Based on the similarities of, and minor differences in, the mode of infection, development and SSU rDNA sequence, the parasite is tentatively designated as Ichthyodinium sp. PL (= PL for the abbreviated form of the scientific name for the host). Although the life cycle of the parasite is unknown, the disease outbreak was controlled by rearing the broodstock and incubating fertilized eggs in oxidant-treated seawater. The PCR diagnosis using specific primers designed from part of SSU rDNA sequence of the parasite revealed that disease outbreaks in different years were caused by a single species of parasite. This is the first report of Ichthyodinium infection in tropical fish from the Asia-Pacific region.

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“…Dis Aquat Org 88: [161][162][163][164][165][166][167] 2010 1993, Pedersen et al 1993). It is, however, also possible that the disappearance of the parasite is a result of elevated mortality among infected larvae (Pedersen 1993).…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

Ribosomal RNA gene sequences confirm that protistan endoparasite of larval cod Gadus morhua is Ichthyodinium sp.

Skovgaard¹,

Meyer²,

Overton³

et al. 2010

Dis. Aquat. Org.

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An enigmatic protistan endoparasite found in eggs and larvae of cod Gadus morhua and turbot Psetta maxima was isolated from Baltic cod larvae, and DNA was extracted for sequencing of the parasite's small subunit ribosomal RNA (SSU rRNA) gene. The endoparasite has previously been suggested to be related to Ichthyodinium chabelardi, a dinoflagellate-like protist that parasitizes yolk sacs of embryos and larvae of a variety of fish species. Comparison of a 1535 bp long fragment of the SSU rRNA gene of the cod endoparasite showed absolute identity with I. chabelardi, demonstrating that the 2 parasites are very closely related, if not identical. This finding is discussed in relation to some morphological differences that appear to exist between I. chabelardi and the cod endoparasite. KEY WORDS: Fish egg · Yolk sac parasite · Endoparasite · Gadus morhua · Ichthyodinium Resale or republication not permitted without written consent of the publisherDis Aquat Org 88: [161][162][163][164][165][166][167] 2010 1993, Pedersen et al. 1993). It is, however, also possible that the disappearance of the parasite is a result of elevated mortality among infected larvae (Pedersen 1993). When the protistan endoparasite of cod and turbot was first discovered, a similarity to the dinoflagellate-like parasite of marine fish eggs Ichthyodinium chabelardi was noted , Pedersen & Køie 1994. It was also clear from the beginning, on the other hand, that the protistan endoparasite was not identical to I. chabelardi in all respects. In particular, the aggressiveness of the infection and the development of the parasite appeared unlike that of I. chabelardi. I. chabelardi was first described infecting eggs of sardine Sardina pilchardus in the Bay of Algiers in the Mediterranean Sea (Hollande & Cachon 1952, 1953, and it is the only other protist known to parasitize yolk sacs of marine fish embryos and larvae. Since the 1952/1953 studies many other fish species have been reported as hosts for Ichthyodinium spp. Among these are species that are important for human consumption in Europe, e.g. mackerel Scomber scombrus (Meneses et al. 2003), gilthead seabream Sparus aurata (Marinaro 1971), and in southeast Asia, e.g. yellowfin tuna Thunnus albacares (Yuasa et al. 2007) and leopard coral grouper Plectropomus leopardus . A recent study showed that European and Asian isolates of Ichthyodinium spp. represent 2 different phylotypes (Skovgaard et al. 2009). Despite the ubiquitous occurrence of I. chabelardi, its life cycle and route of infection are still not completely understood. Recent data indicate that free-swimming I. chabelardi cells infect fish eggs after spawning , Yuasa et al. 2007), but it was previously suggested that the protistan endoparasite of cod and turbot is transferred vertically through the fish gametes (Pedersen & Køie 1994).The morphology and ultrastructure of the endoparasite of cod have been relatively well studied, but the organism exhibits only few characteristic morphological traits, and none of these are sufficient f...

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Baltic larval cod Gaaus mornua are infested with a protistan endoparasite in the yolk sac

Cited by 11 publications

References 1 publication

A protistan endoparasite in embryos and yolk-sac larvae of cod Gadus morhua and turbot Scophthalmus maximus

A protistan endoparasite in embryos and yolk-sac larvae of cod Gadus morhua and turbot Scophthalmus maximus

Endoparasitic Dinoflagellate of the Genus Ichthyodinium Infecting Fertilized Eggs and Hatched Larvae Observed in the Seed Production of Leopard Coral Grouper Plectropomus leopardus

Ribosomal RNA gene sequences confirm that protistan endoparasite of larval cod Gadus morhua is Ichthyodinium sp.

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