PARASITES AND DISEASES OF THE COMMON COCKLE - Cerastoderma edule CATALOGUE OF
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CATALOGUE OF
PARASITES AND DISEASES
OF THE COMMON COCKLE
Cerastoderma edule
COCKLES PROJECT
MARCH 2021
CATALOGUE OF
PARASITES AND DISEASES
OF THE COMMON COCKLE
Cerastoderma edule
“Real knowledge is to know the
extent of one’s ignorance”
Confucius
COCKLES PROJECT
MARCH 2021
CONTENTS
5 Introduction 62 Himasthla continua
7 Guidelines for readers 64 Himasthla elongata
8 Which taxa? 66 Himasthla interrupta
9 Where are the parasites? 68 Himasthla quissetensis
9 Where is the expertise? 70 Monorchis parvus
72 Parvatrema fossarum
11 Bacteria
74 Parvatrema minutum
12 Endozoicomonas-like organisms
76 Psilostomum brevicolle
14 Vibrio aestuarianus cardii
78 Renicola roscovitus
16 Vibrio tapetis tapetis
80 Unknown metacercaria
19 Fungi 82 Cestoda
20 Hyperspora aquatica 84 Paravortex cardii
22 Steinhausia-like parasite
87 Nematoda
24 Unikaryon legeri
91 Nemertea
27 Protozoa
92 Malacobdella grossa
TITLE: Catalogue of parasites and diseases of the common cockle Cerastoderma edule 28 Eucoccidiorida
30 Nematopsis sp. 95 Arthropoda
AUTHORS: Xavier de Montaudouin, Isabelle Arzul, Assunción Cao, Maria Jesus Carballal, Bruno Chollet, Simão Correia,
32 Perkinsus chesapeaki 96 Herrmannella rostrata
Jose Cuesta, Sarah Culloty, Guillemine Daffe, Susana Darriba, Seila Díaz, Marc Engelsma, Rosa Freitas, Celine Garcia,
Anouk Goedknegt, Patrice Gonzalez, Ana Grade, Emily Groves, David Iglesias, Kurt T. Jensen, Sandra Joaquim, Sharon 34 Trichodina spp., Rynchodida-like ciliates 98 Mytilicola orientalis
Lynch, Luísa Magalhães, Kate Mahony, Francisco Maia, Shelagh Malham, Domitília Matias, Antoine Nowaczyk, Francisco 36 Haplosporidium edule 100 Afropinnotheres monodi
Ruano, David Thieltges & Antonio Villalba. 38 Minchinia mercenariae 102 Pinnotheres pisum
SCIENTIFIC ILLUSTRATIONS: Fernando Correia & Cláudia Barrocas 40 Minchinia tapetis
105 Other diseases
DESIGN: Anabela Marques
42 Urosporidium sp.
106 Disseminated neoplasia
44 Marteilia cochillia
PRINTED BY: ARTIPOL – Artes Gráficas, Lda 108 Granulomatosis
47 Platyhelminthes 110 Picornaviral-like infection
PRINT RUN: 140 copies
50 Asymphylodora demeli
PUBLISHER: UA Editora – Universidade de Aveiro 112 Conclusion
52 Bucephalus minimus
113 Cockle Anatomy
1ST EDITION: March 2021 54 Curtuteria arguinae
114 Glossary
56 Diphterostomum brusinae
ISBN: 978-972-789-671-4 118 References
58 Gymnophallus choledochus
DOI: 10.34624/9a9c-9j21
60 Gymnophallus somateriae
LEGAL DEPOSIT: 480176/21
LEAD PARTNER FOR OUTPUT
University of Bordeaux
Acknowledgement
The work described in this project has been funded by European Commission under the Horizon 2020 Framework Programme
(http://www.cockles-project.eu/).
All rights reserved
This document may not be copied, reproduced or modified in whole or in part for any purpose without the written permission
from the COCKLES Consortium. In addition to such written permission to copy, reproduce or modify this document in whole or
part, an acknowledgement of the authors of the document and all applicable portions of the copyright must be clearly referenced.
This catalogue is associated to website http://cockles-project.eu/gis-viewer or https://utmar.cetmar.org/cockles-viewer
INTRODUCTION
Lazy or timeless readers who wouldn’t read the whole in- no problem at all and Bon Appétit!
troduction should however courageously reach the end of A second interesting point is the ecological aspect. For-
this sentence: 1) none of the parasites/diseases of cockles ty percent of Eucaryotic organisms in the world are
(Cerastoderma edule) is harmful for human consumers; parasites, and then parasites in our edible cockle signif-
2) parasites are part of the biodiversity; and 3) some icantly participate to this hidden diversity. Who would
(few) parasites/diseases are dramatically deleterious at imagine than when picking a cockle you have more
their host population scale. than a dozen of species in your hand, without evoking
When COCKLES Project colleagues met the first time bacteria and viruses. It is true that the cockle is some
in Madrid, in 2017, they certainly didn’t envisage that kind of a champion to shelter more or less deleteri-
the last year(s) of their project would be in a human ous inhabitants (the majority being rather innocuous).
pandemic framework and that their discussions would Here, we described 38 taxons (+ 3 diseases). We also
be by remote means or through ugly but safe masks. decided to add two species that are parasites of cockle
Conversely, they already had many ambitions for this parasites (“hyperparasites”) and thus, finally, which could
project, one of them being to gather all knowledge con- be rather considered as friendly for cockles, helping them
cerning symbionts sensu lato, i.e. parasites and com- to get rid of some of their enemies. Besides, some of
mensals of cockles Cerastoderma edule, which should these parasites are also indicators of larger scale diver-
be useful for cockle resource management. Considering sity and environmental good health! This is the case of
this important challenge, decision was rapidly taken to trematodes which presence in cockles reveals rather good
discard C. glaucum and to focus on Atlantic waters. Our water quality and the presence of many different species
objective was mainly to bring knowledge to stakeholders, participating to their life cycle, including birds and finfish.
policy makers, fishermen, reserve managers and maybe Thus, this census reminds us that some parasites are very
educational staff and, why not, science-greedy public, pathogenic to cockles and must highlight that cockles
through an ordered, synthesised, easily understandable transfer among geographic areas shouldn’t be performed
way. During the Steering Committee in Olhão, Portugal, or with considerable precaution, which anyway will keep
however, we raised the question that such a census could risk at high level. A strong motivation to participate to this
stimulate more panic than interest: “All these nasty para- project, and in particular to the work package devoted
sites…”. We even envisaged not to use the term “parasite”. to diseases, was related to the important crisis in Galicia
But many of them are parasites, and we are scientists who associated with the cockle parasite Marteilia cochillia.
care about the meaning of words. Thus, the decision was Our investigation allowed to highlight that other threats
rather to explain first that parasites, diseases and other were present, in particular Disseminated Neoplasia. At the
symbionts of cockles, listed in this file, are innocuous for end of this document, we tried to hierarchise parasites/
human beings (“are not zoonotic”). Note that this census diseases according to their pathogenicity and the risk
doesn’t consider either harmful toxic algae or human-path- they represent, but we must keep in mind that this risk
ogenic microorganisms for which cockles, as any other is also related to prevalence (=% of infected individuals),
food, may act as vectors in the absence of safety condi- which is itself fluctuating and strongly related to complex
tions. Our list of parasites comprises trematode which environmental factors interactions.
is a group of parasites that could stimulate some fears Finally, like all scientists, we must point out that this
because there are some terrestrial, freshwater or tropical study revealed huge gaps in our knowledge and that
species which can induce more or less severe human dis- next generation will certainly have to write the second
eases. It is absolutely not the case with our edible cockle. tome! At this stage, we faced many unknown species,
A 200-% precaution would be to avoid consuming them raw. molecular biology is also contributing to multiply what
Then our first message is that, as far as cockles are sold we considered as a single species and global trading and
within the regulation devoted to shellfish consumption, global change will certainly bring new… surprises!
7
Guidelines for readers
1
5
2
3 6
7 8
4 9
Each parasite (or disease) is described within a double facing page
1 The accepted scientific latin name and the most com- 5 Distribution map, distinguishing data of the COCKLES
mon synonyms are mentioned. Common names are project from data based on the state of the art. The
unusual, except for some diseases or macroparasites table on the right indicates data from the project,
(e.g. “pea crabs”). Some elements of the classification with different cohorts and seasons being pooled.
were extracted from the up-to-date World Register of Prevalence is the percentage of infected cockles and
Marine Species and the direct link is provided. mean abundance is the mean number of parasite
individuals per cockle (“–”: not evaluated; ndbp: not
2 Pictures of the parasites, pathogens or infected tissues. determined, but present).
3 A general description insisting on typical morpho- 6 Methods of diagnosis are indicated and a selection
logical traits, possible complex life-cycle of the para- of gene accession numbers is proposed. A non-ex-
site, on host and environmental factors favoring the haustive list of laboratories/contacts, expert for this
development of the pathogen/lesion. type of parasite is proposed (the [number] refers to
a list in page 9).
4 A scale of pathogenicity is proposed when data are
available. This can be considered as an “expert opinion”. 7 The principal identified risks are mentioned, fo-
cusing on those in relation with climate change and
Effect Individual cross-sites trading.
SERIOUS Kills cockles
MODERATE Affects growth/condition
8 Some advices are provided to avoid spreading the
NONE None
pathogens/diseases. However, no action is generally
? UNKNOWN
Populational recommended in natural conservation areas.
Mortality reported
No obvious related mortality 9 Non-exhaustive scientific references.
None
8 9
Which taxa? Where are the parasites?
State of the art
COCKLES project
OTHER DISEASES
ARC Arcachon Bay
• Disseminated neoplasia (p. 106)
• Granulomatosis (p. 108) DUN ARO Ria of Arousa
• Picornaviral-like disease (p. 110) DEE WAS
AVE Ria of Aveiro
ARTHROPODA BUR
BSO Bay of Somme
COPEPODA
BSO
• Herrmannella rostrata (p. 96) BUR Burry Inlet
• Mytilicola orientalis (p. 98) BACTERIA
• Endozoicomonas-like (p. 12) DEE The Dee
DECAPODA
• Vibrio aestuarianus (p. 14) ARC
• Afropinnotheres monodi (p. 100) NOI & ARO DUN Dundalk Bay
• Vibrio tapetis (p. 16)
• Pinnotheres pisum (p. 102)
AVE FOR Ria Formosa
NOI Ria of Noia
FOR
WAS Texel (Wadden Sea)
PLATYHELMINTHES FUNGI
TREMATODA MICROSPORIDIA
• Asymphilodora demeli (p. 50) • Hyperspora aquatica (p. 20)
• Bucephalus minimus (p. 52) • Steinhausia-like (p. 22)
• Curtuteria arguinae (p. 54) • Unikaryon legeri (p. 24)
• Diphterostomum brusinae (p. 56)
• Gymnophallus choledochus (p. 58)
Where is the expertise?
• Gymnophallus somateriae (p. 60)
• Himasthla continua (p. 62) CHROMISTA
• Himasthla elongata (p. 64) ALVEOLATA
• Himasthla interrupta (p. 66) • Eucoccidiorida (p. 28) Expert laboratories within [2] CIMA-XUGA (Contact: antonio.villalba.garcia@xunta.gal)
• Himasthla quissetensis (p. 68) • Nematopsis sp. (p. 30) COCKLES project and [4] University of Bordeaux (Contact: xavier.de-montaudouin@u-bordeaux.fr)
• Monorchis parvus (p. 70) • Perkinsus spp. (p. 32) COCKLES collaborators.
[5] University College Cork (Contact: s.culloty@ucc.ie)
• Parvatrema fossarum (p.72) • Rynchodida-like (p. 34)
• Trichodina spp. (p. 34) Numbers correspond to the [6] Bangor University (Contact: s.malham@bangor.ac.uk)
• Parvatrema minutum (p. 74)
• Psilostomum brevicolle (p. 76) RHIZARIA partner registration numbers [10] IPMA (Contact: fruano@ipma.pt)
• Renicola roscovitus (p. 78) • Haplosporidium edule (p. 36) in the COCKLES Consortium [11] University of Aveiro (Contact: rosafreitas@ua.pt)
• Unknown metacercaria (p. 80) • Minchinia mercenariae (p. 38) and serve as identifiers in the [15] Ifremer La Tremblade (Contact: isabelle.arzul@ifremer.fr)
CESTODA • Minchinia tapetis (p. 40) expertise section of each
• Urosporidium sp. (p. 42) [17] CNRS Arcachon (Contact: patrice.gonzalez@u-bordeaux.fr)
TRYPANORHYNCHA (p. 82) parasite page.
TURBELLARIA • Marteilia cochillia (p. 44) [20] INTECMAR (Contact: sdarriba@intecmar.gal)
• Paravortex cardii (p. 84)
NEMATODA (p. 87) Extra-project collaborators:
NEMERTEA [A] NIOZ-Texel (Contact: david.thieltges@nioz.nl)
• Malacobdella grossa (p. 92) [B] ICMAN-CSIC (Contact: jose.cuesta@icman.csic.es)
[C] Wageningen Bioveterinary Research (Contact: marc.engelsma@wur.nl)
[D] USC (Contact: seiladiazcostas@gmail.com)
[E] Arrhus University (Contact: kthomas@bios.au.dk)
10 11
BACTERIA 12 13
Parasite Prevalence (%)
BAC T E RI A
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Bacterial microcolonies SITE % Ab
L AT I N NAME Endozoicomonas-like organisms
SY N ONYMS None ARC 22 –
State of the art
COM M ON N AME Bacterial microcolonies
COCKLES project ARO 23 –
C L A S S I F I C AT ION Bacteria – Hahellaceae
DUN AVE 12 –
BSO 16 –
BUR + DEE
BUR 19 –
BSO
DEE 22 –
DUN 2 –
ARC
NOI + ARO
FOR 19 –
AVE
NOI 32 –
FOR WAS 0 –
General Description Diagnosis Techniques
Bacterial microcolonies have been reported in nu- tle and labial palps. The colonies are usually intracellu- • Histology: Basophilic bacterial microcolonies with variable shape and
merous marine mollusc species. They were usually lar although, in the gills, mantle and labial palps, they size are observed within epithelial cells of digestive diverticula or in
referred as Rickettsia-like organisms (RLO) but molec- can evolve to large extracellular cysts surrounded by gills. Large extracellular colonies surrounded by a fibrous cover can be
ular phylogenetic analyses demonstrate they belong a fibrous cover that, eventually, can break, thus shed- observed in the gills and, rarely, in the connective tissue of mantle and
to widely diverse bacterial groups. In Cerastoderma ding bacteria. Recent molecular phylogenetic analysis labial palps.
edule, basophilic bacterial microcolonies occur mostly showed that the bacterial microcolonies of cockles • Expertise laboratories/Contacts in the COCKLES AA consortium:
in the epithelia of the digestive diverticula and the gills correspond to endozoicomonas-like organisms. [2], [5], [10], [15], [20], [D].
and, occasionally, in the connective tissue of the man-
Risks in the Atlantic Area (AA) Advices
Individual Pathogenicity Populational Pathogenicity
• Actual situation: Unknown. Cockles from areas
• Related to trading: Unknown but no risk for human consumption. known to be infected
Detrimental effects due to • Global change: Unknown. should not be transferred
bacterial microcolonies have to areas with no record
not been reported in cockles There are no reports of cockle of bacterial microlononies.
but heavy infections with mortality events or population
No action in nature
bacterial microcolonies have decline associated with
been associated with poor bacterial microcolonies. conservation areas.
condition and even being lethal
? in other bivalve species. ?
Relevant References
Azevedo 1993; Carballal et al. 2001; Elliot et al. 2012; Longshaw & Malham 2013;
Cano et al. 2020.
14 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule BACTERIA 15
Parasite Prevalence (%)
BAC T E RI A
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data) *
Vibrio aestuarianus cardii SITE % Ab
L AT I N NAME Vibrio aestuarianus Tison & Seidler, 1983
subsp cardii Garcia et al. 2021 ARC 0 –
SY N ONYMS None State of the art
COM M ON N AME None COCKLES project ARO – –
C L A S S I F I C AT ION Bacteria – Vibrionaceae
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=570741) DUN AVE – –
BSO 0 –
BUR – –
DEE – –
DUN 3 –
FOR – –
NOI – –
WAS – –
*Only analyzed in ARC, BSO and DUN.
General Description Diagnosis Techniques
Vibrio aestuarianus cardii was associated with cockle specific macroscopic signs. Moribund animals were • Bacteriology: Isolation of bacteria on marine agar medium after 48h at 20°C.
mortality in different wild beds in France. The mor- animals lying at the surface of the sediment and Bacterial colonies appear small (1-2 mm), translucent, regular, white to cream-colored on marine agar.
tality occurred during summer and mortality events characterized by a very slow closing of their valves • Histology: Bacteria can be observed in the digestive tract in association with epithelium necrosis.
lasted from 1 to 2 months. Individuals showed no and a limited quantity of intrapallial fluid. • Molecular identification: Real time PCR specific to V. aestuarianus species.
This real time PCR does not permit to distinguish the different subspecies of V. aestuarianus.
• Sequencing: 16S gene (type strain reference: MK307684), ldh gene (type strain reference: MK315026),
gyrB gene (type strain reference: MK315009).
• Expertise laboratories/Contacts in the COCKLES AA consortium: [10], [15].
Individual Pathogenicity Populational Pathogenicity Risks in the Atlantic Area (AA) Advices
• Actual situation: High prevalence outbreak is possible and has Cockles from areas known
already been observed. to be infected should
Bacteria invade the digestive • Related to trading: No risk for human consumption. Cockles from not be transferred to
tract and induce a destruction Prevalence is unknown areas known to be infected should not be transferred to areas with areas with no record of
of digestive epithelia. but episodic high infection
no record of Vibrio aestuarianus cardii. Vibrio aestuarianus cardii.
Mortality of cockles outbreaks has been reported
experimentally challenged with high mortality. • Global change: Temperature, salinity, host dispersion. In owwysters, Eradicate moribund
with bacteria. V. aestuarianus infection dynamics are modulated by temperature i.e. cockles at the surface of
? ? the warmer the water the faster the development of infection. the sediment in production
area. No action in nature
Relevant References conservation areas.
Saulnier et al. 2009, 2017; Garcia et al. 2021.
16 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule BACTERIA 17
Parasite Prevalence (%)
BAC T E RI A
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data) *
Vibrio tapetis SITE % Ab
L AT I N NAME Vibrio tapetis Borrego et al., 1996 subsp tapetis
SY N ONYMS Vibrio P1 group ARC 0 –
State of the art
COM M ON N AME Brown ring disease
COCKLES project ARO – –
C L A S S I F I C AT ION Bacteria – Vibrionaceae
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=570804)
AVE – –
BSO 0 –
BUR – –
BSO
DEE – –
DUN – –
ARC
FOR – –
NOI – –
Vibrio tapetis (b) in the Manila clam Ruditapes philippinarum (SEM) and macroscopc view
of BRD with brown deposits in the inner side of the valve (courtesy C. Paillard & P. Maes).
WAS – –
*Only analyzed in ARC and BSO.
General Description Diagnosis Techniques
Vibrio tapetis was isolated from cockle in different inner side of the valves. Cockle could act as a carrying • Gross observation: Conchyolin deposits and malformations on the inner shell surfaces.
locations in France without mortality association. species of this bacterium. Experimentally, strong mor- • Bacteriology: Isolation of bacteria on differential media including marine agar medium after 48 h at 20°C.
In some cases, cockles could exhibit signs of Brown tality of cockles challenged with V. tapetis has been Bacteria colonies appear circular, regular in shape, translucent, and unpigmented.
Ring Disease (BRD), typical brown deposits on the observed between 7 and 14 days after inoculation. • Molecular identification: 1) Conventional PCR, and 2) real time PCR but only detect virulent strains
of V. tapetis.
• Sequencing of different genes as: 16S gene (IS9 strain: HE795138), atpA gene (IS9 strain: HE795168),
ropA gene (IS9 strain: HE795349), gapA gene (IS9 strain: HE795378), fstZ gene (IS9 strain: HE795312),
recA gene (IS9 strain: HE795228), rpoD gene (IS9 strain: HE795288).
• Expertise laboratories/Contacts in the COCKLES AA consortium: [10], [15].
Individual Pathogenicity Populational Pathogenicity
Risks in the Atlantic Area (AA) Advices
• Actual situation: Unknown. Cockles from areas known
• Related to trading: Unknown but no risk for human consumption. to be infected should not
In the field, no reported effect. • Global change: Unknown but in Manila clams Ruditapes philippinarum, be transferred to areas
Experimentally, observation of No reported effect. temperatures that are > 21 °C have been observed to inhibit BRD with no record of Vibrio
mortality. whereas low salinity (2) favors it. tapetis. No action in nature
conservation areas.
? ?
Relevant References
Maes and Paillard 1992; Borrego et al. 1996; Paillard et al 2006; Park et al 2006;
Lassalle et al. 2007; Paul-Pont et al. 2010; Bidault et al. 2015; Rodrigues et al. 2015.
18 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule BACTERIA 19FUNGI 20 21
Parasite Prevalence (%)
FUNGI
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Hyperspora aquatica SITE % Ab
L AT I N NAME Hyperspora aquatica Stentiford et al., 2017
SY N ONYMS None ARC 0 –
State of the art
COM M ON N AME None
COCKLES project ARO 46 –
C L A S S I F I C AT ION Fungi – Microsporidia
AVE – –
BSO 0 –
BUR 0 –
DEE 0 –
DUN 0 –
ARO
FOR – –
NOI 0 –
WAS 0 –
General Description Diagnosis Techniques
Hyperspora aquatica is a hyperparasite of the para- cycle progresses from uninucleate meronts to mul- •H
istology: Hyperparasite stages are observed in the cytoplasm of the
myxid Marteilia cochillia; the latter infects the cockle ti-nucleate meronts prior to initiation of sporogony. primary cells of Marteilia cochillia infecting the cockle digestive gland.
digestive gland. Spores are spherical to ellipsoid, Sporogony involves thickening of the cell wall, budding •G
enes Accession number: KX364284.1 (SSU rDNA).
ca. 1.2 x 1.0 µm, with 4 polar filament coils in a single of sporonts and eventual development of the spore •E
xpertise laboratories/Contacts in the COCKLES AA consortium:
rank. Merogonic and sporogonic stages occur in the extrusion precursors in uninucleate sporoblasts, [2], [10], [15], [20], [D].
cytoplasm of primary cells of M. cochillia. Known life which mature to spores.
Risks in the Atlantic Area (AA) Advices
• Actual situation: None. None
• Related to trading: None.
Individual Pathogenicity Populational Pathogenicity
• Global change: Unknown.
Hyperspora aquatica causes
damage to its host Marteilia
cochillia; the latter is a highly
pathogenic cockle parasite, None.
thus H. aquatica could benefit
cockle although it has not been
? appropriately evaluated. ?
Relevant References
Villalba et al. 2014; Stentiford et al. 2017.
22 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule FUNGI 23Parasite Prevalence (%)
FUNGI
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Steinhausia-like parasite SITE % Ab
L AT I N NAME Steinhausia-like parasite Sprague et al., 1972
SY N ONYMS None ARC 0 –
State of the art
COM M ON N AME Cockle egg disease, Microsporidiosis
COCKLES project ARO 0 –
C L A S S I F I C AT ION Fungi – Microsporidia
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=559168)
AVE 0 –
BSO 0 –
BUR 0 –
DEE 0 –
DUN 0 –
FOR 0 –
20 µm 20 µm NOI 0 –
WAS 0 –
General Description Diagnosis Techniques
All infections occur in the ovocytes of cockles. The ole enclosing parasites occur per ovocyte. The inten- • Squash preparations: Microscopically evident within the ovocytes in wet mount preparations of gonadal
parasite mature spores or the precursor stages sity of infection is low with no haemocyte infiltration tissue pressed between a glass slide and coverslip.
(sporonts or sporoblasts) occur within a single large and no pathological damage to the host. However, • Histology: Observation of parasite stages (most frequently spores) inside ovocytes. Vacuoles containing
vacuole in the cytoplasm (rarely in the nucleus) of the viability of infected ova may be affected, thus the spores are usually elliptical to circular in shape, with a mean size of 20 µm, containing up to 30 spherical
cockle ovocytes. Occasionally, more than one vacu- influencing fecundity. spores 2.5-3 µm in diameter. Typically there is a single vacuole with parasites per ovocyte, however, two
vacuoles have been observed in an ovocyte.
• Expertise laboratories/Contacts in the COCKLES AA consortium: [2], [10], [15], [20], [D].
Risks in the Atlantic Area (AA) Advices
Individual Pathogenicity Populational Pathogenicity
•A
ctual situation: Unknown. Cockles from areas known
•R
elated to trading: Unknown but no risk for human consumption. to be infected should
•G
lobal change: Unknown. not be transferred to
Infected ovocytes could be When reported, the areas with no record of
unviable but, if so, the low prevalence was always Steinhausia-like parasites.
infection intensity would low, thus detrimental No action in nature
involve negligible effects population effects would conservation areas.
in female fecundity. not be expected.
? ?
Relevant References
Carballal et al. 2001; Comtet et al. 2003.
24 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule FUNGI 25Parasite Prevalence (%)
FUNGI
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Unikaryon legeri SITE %* Ab
L AT I N NAME Unikaryon legeri (Dollfus, 1912)
SY N ONYMS Nosema legeri ARC 0 –
State of the art
COM M ON N AME None
COCKLES project ARO 68 –
C L A S S I F I C AT ION Fungi – Microsporidia
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=565110)
AVE 0 –
DUN
BSO 10 –
Hyperparasitized metacercariae BUR 0 –
BSO
DEE 0 –
DUN 33 –
ARO
FOR 0 –
“Healthy” metacercariae NOI 0 –
WAS 0 –
*Estimated by dissection, under stereomicroscope.
General Description Diagnosis Techniques
Unikaryon legeri is a hyperparasite of the metacercar- parenchyma. Merogonic stages include uninucle- •H istology: Hyperparasite stages are observed in the parenchyma of metacercariae of Parvatrema
iae of Parvatrema minutum, which infect the cockle ate and binucleated dividing meronts. Uninucleate minutum infecting the cockle mantle.
mantle. Spores are ellipsoid, ca. 3.0 x 1.8 µm with sporonts become binucleate and divide giving rise to • Dissection: Squeeze between two thick glass slides, under stereomicroscope. Stages of the hyperparasite
6-6.5 polar filament coils in a single rank. Merogonic two uninucleate sporoblasts, which mature to spores. are observed within metacercariae of P. minutum infecting the cockle mantle.
and sporogonic stages occur in the metacercarial • Genes accession number: KX364285.1 (SSU rDNA).
• Expertise laboratories/Contacts in the COCKLES AA consortium: [2], [4], [5], [10], [15], [20], [D].
Risks in the Atlantic Area (AA) Advices
•A
ctual situation: None. Not needed.
Individual Pathogenicity Populational Pathogenicity
•R
elated to trading: None.
•G
lobal change: Unknown.
Unikaryon legeri may cause
damage to or even kill its host
Parvatrema minutum; the latter
is a cockle parasite causing
None.
moderate harm to cockle,
thus U. legeri could benefit
cockle although it has not been
? appropriately evaluated. ?
Relevant References
Canning and Nicholas 1974; Lauckner 1983; Russell-Pinto 1990; Fermer et al. 2011;
Stentiford et al. 2017.
26 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule FUNGI 27PROTOZOA 28 29
Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Undetermined Coccidum SITE % Ab
L AT I N NAME None
SY N ONYMS None ARC 7 –
State of the art
COM M ON N AME None
COCKLES project ARO 7 –
C L A S S I F I C AT ION Alveolata – Eucoccidiorida
AVE 0 –
DUN
BSO 4 –
Nephridium Nephridium Nephridium Intestine DEE
BUR 0 –
BSO
DEE 2 –
DUN 2 –
ARC
NOI & ARO
FOR 0 –
NOI 14 –
WAS 0 –
General Description Diagnosis Techniques
An undetermined coccidian parasite, sometimes re- tinal epithelia or in the subjacent connective tissue, • Histology: Gamonts and developing and mature oocysts, the latter
ported as Pseudoklossia sp., is occasionally observed with very light intensity; whether this apicomplexan enclosing multiple sporocysts, can be observed in the cockle nephridia.
in the nephridium of the cockles. Gamonts (G) and parasite of the intestine is the same as or a different Coccidian gamonts are occasionally observed in the intestinal epithelia
developing (Do) and mature oocysts (O), the latter species from the nephridial coccidium is not known. or in the subjacent connective tissue.
enclosing multiple sporocysts (S), occur associated Light to moderate haemocytic infiltration is seldom • Expertise laboratories/Contacts in the COCKLES AA consortium:
with nephridial epithelium or in the lumen. Apicompl- observed in the nephridial infections. [2], [5], [10], [15], [20], [D].
exan gamonts are occasionally observed in the intes-
Risks in the Atlantic Area (AA) Advices
• Actual situation: No Risk. No action.
Individual Pathogenicity Populational Pathogenicity
• Related to trading: No risk because these parasites are widespread
through AA.
• Global change: Unknown.
No obvious damage.
Inflammatory reaction is rare Coccidian infections do not
but a combination of high threat cockle populations
intensity and haemocytic although high prevalence (up
reaction could involve some to 33%) has been reported.
nephridial dysfunction.
? ?
Relevant References
Carballal et al. 2001; Elliot et al. 2012; Longshaw & Malham 2013.
30 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 31Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Nematopsis sp. SITE % Ab
L AT I N NAME Nematopsis sp. Schneider, 1892
SY N ONYMS None ARC 75 –
State of the art
COM M ON N AME None
COCKLES project ARO 100 –
C L A S S I F I C AT ION Alveolata – Eugregarinorida
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=390581)
DUN AVE 22 –
DEE WAS
BSO 92 –
BUR
BUR 67 –
BSO
DEE 56 –
DUN 71 –
ARC
NOI & ARO
FOR 4 –
AVE
NOI 100 –
FOR WAS 88 –
General Description Diagnosis Techniques
Parasites of the genus Nematopsis have a complex every organ. The prevalence usually is very high, •H
istology: Oocysts with a thick cover enclosing a basophilic sporozoite can
life cycle involving a marine mollusc and a mol- frequently 100%. Oocysts are ellipsoid, 8-13 µm in be observed within cockle haemocytes in the connective tissue of multiple
lusc-predator crab. The parasite stage living in bi- length, consisting of a thick wall enclosing a single organs.
valves (including cockles) is the oocyst, which occurs uninucleate basophilic sporozoite. Usually, the oo- •E
xpertise laboratories/Contacts in the COCKLES AA consortium:
within host haemocytes, while the other parasitic cysts do not cause host damage and inflammatory [2], [5], [10], [15], [20], [D].
stages occur in the crabs. In cockles, haemocytes en- reaction is rare. When intensity is high, more fre-
closing one to four (usually two) Nematopsis oocysts quently in the gills, some dysfunction could occur.
may be observed in the connective tissue of almost Risks in the Atlantic Area (AA) Advices
• Actual situation: These parasites involve no risk. No action.
• Related to Trading: No risk because these parasites are widespread
Individual Pathogenicity Populational Pathogenicity
through AA.
• Global change: Unknown.
No obvious damage.
Parasites of this genus do not
Inflammatory reaction is rare
threat cockle populations even
but a combination of high
though prevalence usually is
intensity and haemocytic
very high, because the individual
reaction could involve some
pathogenicity is mostly negligible.
cockle dysfunction.
? ?
Relevant References
Azevedo & Cachola 1992; Carballal et al. 2001; Elliot et al. 2012; Longshaw &
Malham 2013.
32 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 33Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Perkinsus spp. SITE % Ab
L AT I N NAME Perkinsus chesapeaki McLaughlin et al., 2000; Perkinsus olseni
Lester and David, 1981; Perkinsus sp.
ARC 0 –
SY N ONYMS Perkinsus atlanticus (for P. olseni) State of the art
COM M ON N AME None COCKLES project ARO 0 –
C L A S S I F I C AT ION Alveolata – Perkinsea
(WoRMS links: http://www.marinespecies.org/aphia.php?p=taxdetails&id=883642 AVE 0 –
http://www.marinespecies.org/aphia.php?p=taxdetails&id=625984)
BSO 0 –
WoRMS has recently proposed Perkinsus olsenii as the valid species name instead of P. olseni
BUR 0 –
DEE 0 –
DUN 0 –
FOR 0 –
NOI 0 –
WAS 0 –
General Description Diagnosis Techniques
Parasites of the genus Perkinsus, including P. ches- rounding the trophozoite is visible (micrograph on • Histology: Different parasite stages including mature trophozoites (10-20 μm) are observed mainly in
apeaki and P. olseni, have a wide host range among the right). Prevalence estimated by the Ray’s Fluid the connective tissue of the gills, mantle and visceral mass.
molluscs. In histological sections of Cerastoderma Thioglycollate Medium procedure may be high but the • Histology does not allow to conclude about the parasite species.
edule, trophozoites (10-20 μm) of P. olseni (micro- infection intensity is so low that many cases are not • Culture: Examination of tissues placed in Fluid Thioglycollate Medium (FTM) for 3 to 14 days at 25 °C
graphs) are observed mainly in the connective tissue detected with histology. Infection with P. chesapeaki allows observing and eventually quantifying Perkinsus parasites.
of the labial palps and less frequently in gills, mantle has been reported in cockles C. edule from Catalonia • In situ hybridization, PCR and sequencing (ITS region) are needed to conclude about the parasite species.
and visceral mass; frequently an obvious wall sur- (NE Spain, Mediterranean Sea). • In C. edule, the only Perkinsus sequence available so far is P. chesapeaki (Genbank accession number KF314812).
• Expertise laboratories/Contacts in the COCKLES AA consortium: [2], [10], [15], [20], [D].
Individual Pathogenicity Populational Pathogenicity Risks in the Atlantic Area (AA) Advices
• Actual situation: Unknown. Cockles from areas known
• Related to trading: Unknown but no risk for human consumption. to be infected should
The infection intensity of The intensity of the infection •G lobal change: Unknown, however, in grooved carpet shell clams not be transferred to
Perkinsus spp. in Cerastoderma with Perkinsus spp. is usually Ruditapes decussatus prevalence and intensity of infection with areas with no record of
edule is usually low; serious low in Cerastoderma edule; no P. olseni increased with increasing temperatures. Perkinsus spp. No action in
effects on cockles have not populational effect has been nature conservation areas.
been reported. reported.
? ?
Relevant References
Villalba et al. 2005; Lassalle et al. 2007; Darriba et al. 2010; Longshaw & Malham
2013; Carrasco et al. 2014.
34 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 35Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Trichodina spp. & Rynchodida-like ciliates SITE % Ab
L AT I N NAME Trichodina spp., Rynchodida-like ciliates
(Hypocomella raabei=cardii; Hypocomidium fabius, …)
ARC 3 –
SY N ONYMS None State of the art
COM M ON N AME Ciliates COCKLES project ARO 44 –
C L A S S I F I C AT ION Alveolata – Cyliophora
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=11) DUN AVE 1 –
DEE WAS
BSO 21 –
BUR
A B C BUR 2 –
BSO
DEE 2 –
DUN 4 –
ARC
NOI & ARO
FOR 3 –
AVE
NOI 15 –
FOR WAS 41 –
Trichodina sp. (A&B); Hypocomella-like ciliates (C).
Diagnosis Techniques
General Description • Wet Mounts: Ciliates can be observed in scrapings of the mantle or gills (x100).
They generally occur as commensals on the gills and low and most infections are innocuous. At Irish sites, • Histology: Trichodina appears as disc-shaped protozoa (37 to 45 μm in length) characterized by a circlet
mantle surface of cockles with no obvious host-re- prevalence was observed to be highest in cockles in of eosinophilic denticles, ciliary fringes, and a horse-shoe shaped macronucleus. Rynchodida-like ciliates
sponse. Although prevalence can reach 100% in some summer and autumn. appear as pear-shaped ciliates (18 to 25 μm in length) often lacking cilia during life stage that is attached
cockle populations, intensity of infection is usually to host with large, densely basophilic nuclei. Attached to the gill and palp surfaces during parasitic stage
of the life cycle.
• Expertise laboratories/Contacts in the COCKLES AA consortium: [2], [10], [15], [20], [D].
Risks in the Atlantic Area (AA) Advices
Individual Pathogenicity Populational Pathogenicity
•A
ctual situation: No risk. No specific
•R
elated to trading: No risk. recommendation.
Occasionally, abundance of
Hypocomella-like ciliates is so high •G
lobal change: Unknown.
that the branchial water channels
are obliterated, interfering with Not documented, but
feeding and respiration. Heavy considering prevalence and
infection by Trichodina spp. in less individual pathogenicity, a
than one year old Cerastoderma populational effect is plausible.
? edule was associated with ?
emaciation and mortalities in the
German and Dutch Wadden Sea. Relevant References
Lauckner 1983; Carballal et al. 2001; Longshaw & Malham 2013.
36 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 37Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Haplosporidium edule SITE % Ab
L AT I N NAME Haplosporidium edule Azevedo et al., 2003
SY N ONYMS None ARC 0 –
State of the art
COM M ON N AME None
COCKLES project ARO 0 –
C L A S S I F I C AT ION Rhizaria – Haplosporida
(WORMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=395976)
AVE 0 –
BSO 0 –
BUR 0 –
DEE 0 –
DUN 0 –
FOR ?* –
NOI 0 –
WAS 0 –
*Undetermined haplosporidan at 1% prevalence.
General Description Diagnosis Techniques
Plasmodia, sporonts and sporocysts containing spores slender wall projections with bifurcated tip. Infections •H
istology: Parasite stages are observed in histological sections of the gills, mantle and gonad, and
occur in the connective tissue of gills, gonad mantle induce an haemocytic response, which is heavier when predominantly in the digestive gland. Molecular tools should be used for species identification.
and, predominantly, digestive gland. The sporogony the plasmodial stage is dominant. The lowest cockle •S
canning electron microscopy: Spores show slender wall projections with bifurcated tip.
is asynchronous. Spores are ca. 3.2 x 2.2 µm in size length at which infection has been recorded is 13 mm. •G
enBank accession number: DQ458793.1 (SSU rDNA).
and show characteristic ornamentation consisting of •E
xpertise laboratories/Contacts in the COCKLES AA consortium: [2], [5], [10], [15], [20], [C], [D].
Risks in the Atlantic Area (AA) Advices
• Actual situation: Recorded prevalence has been always very low with Considering its very low
no mortality outbreak. prevalence, no special
Individual Pathogenicity Populational Pathogenicity
• Related to Trading: It only has been recorded in Galicia (rias of Vigo, advice for the areas with
Arousa and O Barqueiro), the Netherlands (Oosterschelde) and Wales occurrence records.
Haplosporidium edule can (Burry Inlet), thus movements could potentially contribute to spread it.
be lethal to cockles because, This parasite is not threatening • Global change: Unknown.
at advanced infection stage, cockle populations because its
the connective tissue of most prevalence is very low. However,
organs of the host is heavily if the prevalence became higher
infiltrated by sporulation stages for any reason, H. edule would be
of the parasite and is destroyed, a real threat.
? leading to general dysfunction. ?
Relevant References
Carballal et al. 2001; Azevedo et al. 2003; Engelsma et al. 2011; Elliot et al. 2012.
38 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 39Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Minchinia mercenariae SITE % Ab
L AT I N NAME Minchinia mercenariae Ford et al., 2009
SY N ONYMS None ARC 0 –
State of the art
COM M ON N AME None
COCKLES project ARO 0 –
C L A S S I F I C AT ION Rhizaria – Haplosporida
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=563582)
AVE 0 –
BSO 0 –
BUR 0 –
DEE 0 –
DUN 0 –
FOR ?* –
NOI 0 –
WAS 0 –
*Undetermined haplosporidan at 1% prevalence.
General Description Diagnosis Techniques
Uninucleate, binucleate cells and multinucleate plas- places in Ireland but they were never observed in • Histology: The above described parasite stages are observed in histological sections of digestive gland,
modia occur throughout the connective tissue of Galicia (NW Spain). Species identification should gills and gonad, but their morphology alone is not appropriate for species identification, for which
digestive gland, gills and gonad; the parasite has not be confirmed with molecular tools. In Ireland, the sequencing molecular tools are required.
been reported in epithelia. The multinucleate plas- highest prevalence was observed in cockles in spring. • GenBank accession number: KY522821.1 (SSU rDNA).
modial stage is dominant and enclose 3 to 14 nuclei. The lowest cockle length at which infection has been • Expertise laboratories/Contacts in the COCKLES AA consortium: [2], [5], [10], [15], [20], [C], [D].
Spores have been reported in cockles from various recorded is 10 mm.
Risks in the Atlantic Area (AA) Advices
• Actual situation: Prevalence may be high but infection intensity is Considering its very low
usually light and no mortality outbreaks have been reported associated prevalence, no special
Individual Pathogenicity Populational Pathogenicity
with this parasite. advice for the areas with
• Related to Trading: Risk of transmission if cockles from affected areas occurrence records.
Infection intensity is moderate The recorded prevalence are immersed into non-affected zones.
or heavy in most records. Cockles has always been low. This
with abundant plasmodia show • Global change: Unknown.
parasite has never been
heavy inflammatory reaction, associated with abnormal
mainly in digestive area. cockle mortality. Nevertheless,
The lesions caused by heavy the characterisation of this
infections and the inflammatory parasite in cockles is recent, thus
? reaction may lead to dysfunction ? experience is reduced.
and host weakness. Relevant References
Ford et al. 2009; Elliot et al. 2012; Ramilo et al. 2018; Albuixech-Martí et al. 2020;
Lynch et al. 2020.
40 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 41Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Minchinia tapetis SITE % Ab
L AT I N NAME Minchinia tapetis (Vilela, 1953)
SY N ONYMS Haplosporidium tapetis ARC 1 –
State of the art
COM M ON N AME None
COCKLES project ARO 0 –
C L A S S I F I C AT ION Rhizaria – Haplosporida
AVE 0 –
BSO 0 –
BUR 0 –
DEE 0 –
DUN 0 –
ARC
NOI
FOR ?* –
NOI 26 –
WAS 0 –
*Undetermined haplosporidan at 1% prevalence.
General Description Diagnosis Techniques
Uninucleate and binucleate cells and multinucleate around parasite foci. Sporogonic stages have not been • Histology: The above described parasite stages are observed in histological sections of digestive gland, but
plasmodia (3-6 nuclei) occur in the connective tissue reported although spores are known to occur in the their morphology alone is not appropriate for species identification, for which molecular tools are required.
of the digestive gland and rarely in digestive epithelia. clam Ruditapes decussatus. Prevalence can reach up • GenBank accession number: AY449710.1 (SSU rDNA).
The parasite stages appear in foci, mostly close to to 100%; it shows seasonal pattern of variation, higher • Expertise laboratories/Contacts in the COCKLES AA consortium: [2], [5], [10], [15], [20], [C], [D].
stomach branches or digestive primary ducts. Fre- in summer and lower in winter. The lowest cockle
quently, the parasites appear surrounded by fibrous length at which infection has been recorded is 7 mm.
material. Cockles show heavy haemocytic infiltration Risks in the Atlantic Area (AA) Advices
• Actual situation: Prevalence was high but infection intensity was light No action in affected
and no mortality outbreaks have been reported associated with this areas.
parasite.
Individual Pathogenicity Populational Pathogenicity
• Related to trading: Risk of transmission if cockles from affected areas
are immersed into not affected zones.
Prevalence has reached up to
100% but heavy infection intensity • Global change: A significant positive correlation was found between
Reported infection intensity M. tapetis prevalence and seawater temperature. Increase of
has never been recorded.
was mostly light, less frequently temperature due to climate change could cause increase of prevalence
This parasite has never been
moderate and never heavy.
associated with abnormal cockle of this parasite in cockles.
The inflammatory reaction can
mortality. Nevertheless, the
cause some damage and host
detection of this parasite in
weakness.
? ? cockles is recent, thus experience
is reduced. Relevant References
Engelsma et al. 2011; Elliot et al. 2012; Albuixech-Marti et al. 2020; Carballal et
al. 2020.
42 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 43Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Urosporidium sp. SITE % Ab
L AT I N NAME Urosporidium sp.
SY N ONYMS None ARC – –
State of the art
COM M ON N AME None
COCKLES project ARO 4 –
C L A S S I F I C AT ION Rhizaria – Haplosporida
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=562865)
AVE – –
BSO – –
BUR – –
DEE – –
DUN – –
NOI & ARO
FOR – –
NOI 1 –
WAS – –
General Description Diagnosis Techniques
Urosporidium sp. is a hyperparasite of the turbellarian tissue of the turbellarian host. The sporocysts are • Histology: Parasite stages are observed in histological sections of
Paravortex cardii; the latter inhabits the cockle diges- rounded with hundreds of spores present. Mature flatworms inhabiting cockle digestive lumen
tive lumen. Sporocysts with spores or uninucleate spores are uninucleate, refringent, round to oval and • Expertise laboratories/Contacts in the COCKLES AA consortium:
sporoblasts and plasmodia occupy the connective measure 4-5 µm in length. Prevalence is low. [2], [5], [15], [20], [C].
Risks in the Atlantic Area (AA) Advices
• Actual situation: None. No action in affected
• Related to Trading: None. areas.
• Global change: Unknown.
Individual Pathogenicity Populational Pathogenicity
Urosporidium sp. causes damage
to the turbellarian Paravortex
cardii but without significant
effects on cockles because None.
the flatworm host could be
considered a commensal rather
? than a cockle parasite. ?
Relevant References
Carballal et al. 2005.
44 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 45Parasite Prevalence (%)
P ROTOZOA
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Marteilia cochillia SITE % Ab
L AT I N NAME Marteilia cochillia Carrasco et al., 2013
SY N ONYMS None ARC 0 –
State of the art
COM M ON N AME Cockle marteiliosis
COCKLES project ARO 73 –
C L A S S I F I C AT ION Rhizaria – Paramyxida
AVE * 1 –
BSO 0 –
BUR 0 –
DEE 0 –
DUN 0 –
ARO
FOR * 11 –
AVE
NOI 0 –
FOR WAS 0 –
*Occurrence of M. cochillia has not been confirmed with molecular tools (AVE and FOR).
General Description Diagnosis Techniques
As all the Marteilia parasites, M. cochillia is characterised parasite takes place. At advanced infection stage, the • Gross observation: Cockles suffering heavy infections show extremely emaciated meat with pale digestive
by the particular cells-inside-cells structure. Develop- digestive gland epithelia appear heavily occupied by par- gland, but these observations are not clinical signs because they are not specific.
mental stages of M. cochillia inside cockles consist of asite sporulation stages that, eventually, are released to • Digestive gland imprints: Rapid diagnostic method showing parasite sporulation stages but only sensitive
primary cells that enclose up to eight secondary cells; digestive lumina, even almost obliterating the intestinal enough in advanced infections.
the secondary cells cleave internally to produce six lumen, to be discharged through whitish faeces. The life • Histology: Different stages of the parasite are observed in the digestive gland epithelia; at advanced
tertiary cells, which evolve in tri-cellular spores (inner, cycle of M. cochillia is complex (direct cockle-to-cockle infection stage, parasite sporulation stages may fill the intestinal lumen.
intermediate and outer sporoplasms). Digestive gland of transmission does not seem to occur) and may include • GenBank accession number: KF278722.1 (SSU rDNA + ITS1).
C. edule is the target organ where the sporulation of the zooplanktonic copepods as intermediate hosts. • Expertise laboratories/Contacts in the COCKLES AA consortium: [2], [10], [15], [20], [C], [D].
Individual Pathogenicity Populational Pathogenicity Risks in the Atlantic Area (AA) Advices
• Actual situation: Cockle fisheries of southern Galician rias are in risk. Cockles from areas known
Sporulation process causes Recurrent mass mortalities in
cockle beds of southern Galician rias • Related to trading: High risk if cockles from affected areas are to be infected should not
the complete destruction of
digestive diverticula of cockles, occur since the first detection of M. immersed into non-affected zones. No risk for human consumption. be transferred to areas
leading to cockle death by cochillia in 2012. It is highly prevalent • Global change: Unknown. with no record of M.
starvation. M. cochillia infection (up to 100% in outbreaks) affecting cochillia.
also reduces cockle fecundity both juvenile and adult cockles,
because the host cannot fuel causing cockle fishery collapse.
? gametogenesis or even retrieve ? Recently, prevalence and host
gonad reserves to meet other mortality tended to decrease there, Relevant References
priorities. likely due to resistance increase Carrasco et al. 2013, Villalba et al. 2014, Navas et al. 2018, Carballal et al. 2019,
through natural selection. Iglesias et al. 2019, Darriba et al. 2020.
46 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PROTOZOA 47PLATYHELMINTHES 48 49
TREMATODA
Digenetic trematodes are a large group of metazoan (or redia) will develop into a more mature daughter
parasites belonging to the Platyhelminthes phylum. sporocyst (or daughter redia) that will asexually pro-
These parasites have been reported to infect almost duce cercariae. Cercariae (e), the second free-living
every known mollusc bivalve species and are consid- stage, emerge from the first intermediate host and
ered the most important macroparasites of these swim actively to infect the second intermediate host,
organisms. They display a complex and heteroxenous a vertebrate or invertebrate, usually through their
life cycle, i.e. they infect more than one host, and feeding activity. At this stage, the cercariae transform
exhibit alternations between asexual multiplication into metacercariae (f) and the transmission to the
and sexual reproduction phases. As a result of their definitive host, a vertebrate (usually shorebirds or
transition among different hosts, they also present fish), occurs when the second intermediate host is
parasitic and free-living stages in their life cycle. predated. In the final host, the metacercariae meta-
The typical life cycle of a trematode begins when an morphose into adult stages (g) that will reproduce
egg (a) hatches releasing the miracidium (b). This sexually, generating eggs that will be released into
first free-living stage penetrates the tissue of the first the environment through the faeces of the final host,
intermediate host, a mollusc, where it transforms originating a new cycle. A total of 15 species of dige-
into a sac-like sporocyst (c) or a redia (d), a devel- netic trematodes have been identified (+ at least 2
oped form with the presence of a mouth, depending unidentified) infecting the edible cockle, Cerastoder-
on the trematode species. The mother sporocyst ma edule, as first and/or second intermediate host.
50 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PLATYHELMINTHES 51Parasite Prevalence (%)
P L AT Y H E L M INTHES
Distribution Map in the Atlantic Area (signalisation) and Mean Abundance (Ab)
(COCKLES project data)
Asymphylodora demeli SITE % Ab
L AT I N NAME Asymphylodora demeli Markowski, 1935
SY N ONYMS None ARC 0 0.0
State of the art
COM M ON N AME None
COCKLES project ARO 0 0.0
C L A S S I F I C AT ION Trematoda – Lissorchiidae
(WoRMS link: http://www.marinespecies.org/aphia.php?p=taxdetails&id=109116)
AVE 0 0.0
BSO 0 0.0
BUR 0 0.0
DEE 0 0.0
DUN 0 0.0
FOR 0 0.0
NOI 0 0.0
WAS 0 0.0
*Only in Cerastoderma glaucum.
General Description Diagnosis Techniques
Asymphylodora demeli needs 3 different hosts to found in the hepatopancreas, mantle and gills. Several •H istology: Possible to detect metacercariae but difficult species identification.
accomplish its life-cycle (hydrobid snails, gastropods/ polychaete species may serve as alternative 2nd inter- •D issection: Squeeze between two thick glass slides, under stereomicroscope.
cockles, cyprinid/gobiid fishes). In the cockle (2nd in- mediate hosts and the polychaete Hediste diversicolor • Genes Accession number: No sequences available in genbank.
termediate host), the encysted metacercariae can be may be an alternative definitive host. •E xpertise laboratories/Contacts in the COCKLES AA consortium: [A].
Risks in the Atlantic Area (AA) Advices
• Actual situation: Distribution probably restricted to the Baltic Sea. No action in nature
However, Asymphylodora demeli has apparently been observed in fish conservation areas.
and gastropods in Belgium but not in cockles.
Individual Pathogenicity Populational Pathogenicity
• Related to Trading: No risk within AA, at least between 28°N
(Morocco) and 60°N (Norway).
• Global change: Change of temperature can modify host dispersion
Prevalence in cockles can and infection success.
be locally high in the Baltic
Unknown Sea (64%) but populational
pathogenicity has not been
reported.
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Relevant References
Reimer 1970; Lauckner 1971; Reimer 1973; Kesting et al. 1996.
52 CATALOGUE OF PARASITES AND DISEASES OF THE COMMON COCKLE Cerastoderma edule PLATYHELMINTHES 53You can also read
