Parasitism by a Protozoan in the Hemolymph of the Giant Clam,Tridacna crocea

doi:10.1006/jipa.1997.4747

Journal of Invertebrate Pathology

Volume 71, Issue 3, May 1998, Pages 193-198

https://doi.org/10.1006/jipa.1997.4747 Get rights and content

Abstract

A parasitism by a protozoan was found in the giant clam,Tridacna crocea.The parasites were spindle-shaped, 8.6 ± 0.5 μm in length and 2.5 ± 0.3 μm in width. Structural features of the apical complex of the parasite and a molecular phylogenetic analysis of its 18S rRNA gene sequence indicate that the protozoan belongs to the Apicomplexa. No flagellum was observed in the parasitic protozoan. It infected the eosinophilic granular hemocyte, one of the three types of hemocytes in the clam hemolymph, but it is not known whether it influenced the growth of the clam.

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Cited by (8)

The presence of Apicomplexan parasites in king scallops (Pecten maximus) in Scottish waters
2021, Journal of Invertebrate Pathology
Citation Excerpt :
Some parasites of this phylum are known to cause severe diseases in different animals, such as babesiosis in domestic animals (e.g. dogs and cattle) (Carter and Rolls, 2015; Solano-Gallego and Baneth, 2011); toxoplasmosis in warm-blooded animals, including humans (Djurković-Djaković et al., 2019; Votýpka et al., 2017) and malaria in humans (Phillips et al., 2017). Previous studies have documented the presence of species from phylum Apicomplexa in marine molluscs (Azmi et al, 2018; Desser and Bower, 1997; Kristmundsson et al., 2011a; Léger and Duboscq, 1917; Lohrmann et al., 2000; Morado et al., 1984; Nakayama et al., 1998; Tedesco et al., 2017), but little is known about the effects of these Apicomplexa parasites in scallop species. Kristmundsson et al. (2011b, 2015) described mass mortalities in Icelandic scallop (Chlamys islandica) in association with an Apicomplexan-like parasite which led to the collapse of the stock in 2002.
The king scallop (Pecten maximus) is a commercially important species found around the United Kingdom coast. The association of an Apicomplexan-like parasite with mass mortality of Icelandic scallop (Chlamys islandica) in Iceland and the presence of identical parasites in king scallop (Pecten maximus) and queen scallop (Aequipecten opercularis) in Scotland raised serious concerns regarding the health of Scottish king scallops. Marine Scotland Science (MSS) conducted a survey in 2016 to assess the prevalence and the intensity of parasite infection in king scallops. King scallops were collected and sampled during the annual scallop dredge surveys in the Shetland Isles and the east and west coast of Scotland. The king scallop adductor muscle was macroscopically examined and tissue imprints taken to grade the intensity of infection. The parasite was present in the majority of the king scallops sampled in all surveyed areas: Shetland Isles 87.1%, east coast 76.0% and west coast of Scotland 64.1%. However, the parasitic infestations were light in intensity with the majority of the king scallops graded as 1 (≤20 zoites per microscopic field). No macroscopic changes in the adductor muscle were observed and histopathology examination revealed minor localized fiber degeneration of adjacent fibers to parasite clusters. The results suggested the parasite to be widespread around the Scottish coast and it appears to be able to live within the king scallop at low intensity of infection without causing significant downgrade of the adductor muscle (in terms of colour or texture) or mortality. The partial genome sequence of the parasite in king scallops from Scottish waters was identical to the one reported by Kristmundsson and Freeman (2018) in the Icelandic scallop in Icelandic waters.
Previously unknown apicomplexan species infecting Iceland scallop, Chlamys islandica (Müller, 1776), queen scallop, Aequipecten opercularis L., and king scallop, Pecten maximus L.
2011, Journal of Invertebrate Pathology
Citation Excerpt :
Merocystis) tellinovum from Tellina tenuis (Buchanan, 1979; Levine, 1988) and Margolisiella kabatai from the littleneck clam Protothaca staminae (Desser and Bower, 1997). In addition, Morado et al. (1984) and Nakayama et al. (1998) reported unidentified apicomplexans from the littleneck clam P. staminae and the giant clam Tridacna crocea, respectively. Some apicomplexan species infecting bivalves have direct life cycles, i.e. both asexual and sexual stages are present in the same host (e.g. Desser and Bower, 1997), while in others, only sexual stages have been found, which could suggest the need for an additional host (Desser et al., 1998).
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
2011, Journal of Invertebrate Pathology
Citation Excerpt :
A P. pectinis-like coccidian was reported from the scallop Argopecten irridians by Karlsson (1991), and Pseudoklossia sp. from A. irridians by Cawthorn et al. (1992) and from the cockle Cerastoderma edule by Carballal et al. (2001). Unidentified apicomplexans have also been reported from other bivalves (Leibovitz et al., 1984; Morado et al., 1984; Whyte et al., 1994; Nakayama et al., 1998; Hine, 2002). To date, no parasite species have been described from the Iceland scallop and very limited DNA data exists for apicomplexan parasites of bivalves.
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 heart’s 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.
Cellular identity of a novel small subunit rDNA sequence clade of Apicomplexans: Description of the marine parasite Rhytidocystis polygordiae n. sp. (Host: Polygordius sp., Polychaeta)
2006, Journal of Eukaryotic Microbiology
Invertebrate immune systems - Not homogeneous, not simple, not well understood
2004, Immunological Reviews
Molecular phylogeny and surface morphology of marine aseptate gregarines (apicomplexa): Selenidium spp. and Lecudina spp.
2003, Journal of Parasitology

View all citing articles on Scopus

^☆: W. S. Fisher

¹: Current address: Marine Biotechnology Institute, Kamaishi Laboratories, 3-75-1 Heita, Kamaishi, Iwate 026, Japan.

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Journal of Invertebrate Pathology

Abstract

References (25)

Ribosomal RNA sequences ofSarcocystis muris, Theileria annulataCrypthecodinium cohnii

Mol. Biochem. Parasitol.

Phylogenetic position of the genusPerkinsus

Mol. Biochem. Parasitol.

Mass culture of giant clams (F. Tridacnidae) in Palau

Aquaculture

Morphological and functional characterization of hemocytes in the giant clam,Tridacna crocea

J. Invertebr. Pathol.

Calcification in the green algaHalimeda.²⁺

J. Exp. Bot.

Reproduction in the giant clamsTridacna gigasT. derasa in situ

Coral Reefs

Histochemical comparison of naphthol AS-phosphates for the demonstration of phosphatases

J. Nat. Cancer Inst.

PHYLIP Phylogeny inference package (Version 3.2)

Cladistics

Phylogeny of the Haplosporidia (Eukaryota: Alveolata) based on small subunit ribosomal RNA gene sequence

J. Parasitol.

Occurrence ofPerkinsus

Diseases in Aqua. Org.

On the utilization of photosynthetic products from zooxanthellae and of a dissolved amino acid inTridacna maxima

J. Zool. London

Dinoflagellate 17S rRNA sequence inferred from the gene sequence: Evolutionary implications

Proc. Natl. Acad. Sci. USA

Cited by (8)

The presence of Apicomplexan parasites in king scallops (Pecten maximus) in Scottish waters

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

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

Cellular identity of a novel small subunit rDNA sequence clade of Apicomplexans: Description of the marine parasite Rhytidocystis polygordiae n. sp. (Host: Polygordius sp., Polychaeta)

Invertebrate immune systems - Not homogeneous, not simple, not well understood

Molecular phylogeny and surface morphology of marine aseptate gregarines (apicomplexa): Selenidium spp. and Lecudina spp.

Regular ArticleParasitism by a Protozoan in the Hemolymph of the Giant Clam,Tridacna crocea☆

Abstract

Mol. Biochem. Parasitol.

Mol. Biochem. Parasitol.

Aquaculture

J. Invertebr. Pathol.

Calcification in the green algaHalimeda.2+

J. Exp. Bot.

Reproduction in the giant clamsTridacna gigasT. derasa in situ

Coral Reefs

Histochemical comparison of naphthol AS-phosphates for the demonstration of phosphatases

J. Nat. Cancer Inst.

PHYLIP Phylogeny inference package (Version 3.2)

Cladistics

Phylogeny of the Haplosporidia (Eukaryota: Alveolata) based on small subunit ribosomal RNA gene sequence

J. Parasitol.

Occurrence ofPerkinsus

Diseases in Aqua. Org.

On the utilization of photosynthetic products from zooxanthellae and of a dissolved amino acid inTridacna maxima

J. Zool. London

Dinoflagellate 17S rRNA sequence inferred from the gene sequence: Evolutionary implications

Proc. Natl. Acad. Sci. USA

Regular Article
Parasitism by a Protozoan in the Hemolymph of the Giant Clam,Tridacna crocea☆

Calcification in the green algaHalimeda.²⁺