Download FROM THE MAR DEL PLATA COAST (ARGENTINA)

REV INVEsT. DES. PEsQ N' 10: 101-107
101
(1996)
COMPARATIVE
STUDIES ON PARALYTIC SHELLFISH TOXIN PROFILES
OF MARINE SNAILS, MUSSELS AND AN Alexandrium tamarense ISOLATE
FROM THE MAR DEL PLATA COAST (ARGENTINA)
*
por
JOSE I. CARRETO" CARLOS ELBuST02, HORACIO SANCH02 , MARIO CARIGNAN" TAKESHI
y
ASUMOTO' and Y ASUKATSU OSHIMA'
1 Instituto Nacional de Investigación y Desarrollo Pesquero (lNIDEP), P.O. Box 175,
7600 Mar del Plata, Argentina.
2
Servicio Nacional de Sanidad Animal, P.O. Box 42 sucoF, 7600 Mar del Plata, Argentina.
'Faculty
of Agriculture, Tohoku University, 1-1 Tsutsurnidori Amarniyarnachi, Sendai 981, Japan.
RESUMEN
Composición
en toxinas de caracoles marinos,
mejilIones y de una cepa de Akxandrium
tamarense
aislada
de la región costera mal'platense
(Argentina).
Estudios
comparativos.
La composición
en toxinas de tres
especies de caracoles marinos (Zidona angulata, Adelomedon
brasiliana y Pachycymbiola
brasiliana), del mejillón Mytilus edulis, y de una cepa [AMI] del dinoflagelado
Alexandrium
tamarense aislada de la región costera
bonaerense,
fue determinada
utilizando una técnica altamente sensible y especifica de HPLC (Oshima et al.,
1989). Los cultivos de A. tamarense, contienen como toxinas principales a los derivados N-sulfocarbamoilados
(Cl y C2). En orden decreciente de abundancia se encuentran GTXl, neoSTX y GTX4. Entre los componentes
menores ha sido detectada la presencia inusual de toxinas decarbamoiladas.
De las 10 toxinas detectadas, STX es
la que se presenta en menor concentración.
La comparación
de los perfiles de toxinas revela diferencias
significativas entre la composición
tóxica del dinoflagelado
y la aeumulada en los tejidos de sus consumidores
primarios y secundarios. En el mejillón M. edulis, las gonyautoxinas.comprenden
más del 95 % de las toxinas totales.
STX presenta la menor concentración
entre las 8 toxinas detectables. La escasez de gonyautoxinas
en comparación con la abundancia de STX, es la característica
distintiva de los caracoles. En relación con las vísceras, el pie
y la secreción mucosa de Z. angulata exhiben un menor número de toxinas, con un incremento en la proporción
(86,3,95,2
de STX. Mientras M. edulis se detoxifica rápidamente hasta alcanzar niveY 99,3 % respectivamente)
les regulatorios,
Z. angulata mantiene niveles tóxicos por largos períodos. Estos resultados sugieren interconversiones específicas y/o retención de toxinas durante la transferencia
desde los productores hasta los consumidores
primarios y secundarios.
SUMMARY
Toxin composition
of three species of marine gastropods
(Zidona angulata,
Adelomedon
brasiliana
and
Pachycymbiola
brasiliana), the mussel Mytilus edulis, and an Alexandrium
tamarense iso late (AMI) from the Mar
del Plata coast, were determined by means of a sensitive and specific HPLC technique (Oshima et al., 1989).
Cultures of A. tamarense contain N-sulfocarbamoyl
derivatives (Cl and C2) as major toxins. The nex! most abundant components
were GTXl, neoSTX and GTX4.
As minor components,
unusual decarbamoyl
toxins were
detected. Saxitoxin was the lowest ofthe 10 detectable toxins. Comparison oftoxins profiles revealed significant
differences
between the toxic composition
of the dinoflagellate
and that accumulated
in the tissues of their pri-
. Contribución
INIDEP
N° 713
102
REv lNVEST. DES. PEsQ N' lO: 101-107
mary and secondary
consumers.
In the mussel M edulis, gonyautoxins
comprise
(1996)
more than 95% of total toxins
and STX was the lower of the 8 detectable toxins. The scarcity of gonyautoxins
in comparison with high STX
abundance,
is characteristic
of snails. In relation with viscem, the foot and the mucous secretion of Z. angulata
exhibited a decreased number of toxins, with increased proportion (86.3, 95.2 and 99.3% respectively)
of STX.
While M edulis detoxifies rapidly to the regulatory levels, Z. angulata sustain toxic levels for extending periods
of time. These results suggest specific toxin interconversions
aml/or selective retention of toxins, during transference from producers to primary and secondary consumers.
Palabras claves: Composición en toxinas, Alexandrium tamarense, mejillones, caracoles marinos, HPLC, Mar
Argentino.
Key words: Toxin composition, Alexandrium tamarense, mussels, marine snails, HPLC, Argentine Sea.
gcllate toxins. Alexandrium isolates are known to differ in
their toxicity and characteristic toxin profiles. In the several strains analyzed, at least 15 saxitoxins analogues, varying
widely in potency, have been identified (Figure 1) (Oshima
et al., 1990; Cembella et al., 1987). In addition the toxin
composition of dinoflagellate cclls may undergo changes in
the tissues oftheir primary and secondary consumers due to
metabolic transformation and/or sclective retention oftoxins
(Shimizu and Yoshioka, 1981; Sullivan et al., 1983; Oshima
et al., 1990). In order to investigate the movemcnt of PSP
toxins through the food web, toxin composition of three
species of marine snails, the mussel M edu/is and an A.
tamarense isolate from Mar del Plata coast, were analyzed
by means of a sensitive and specific HPLC technique
(Oshima et al., 1989).
INTRODUCTION
Blooms of Alexandrium tamarense are annual spring
events in the Mar del Plata coast since 1981, and are responsible for mussel M edu/is accumulating paralytic shellfish
toxins during filter feeding (Carreto et al., 1993). In recent
years, mouse bioassays showed that several species of
marine snails from the Mar del Plata coast contained high
amounts of paralytic
shellfish toxins in the viscera.
Occurrence of PSP in whelks and other marine gastropods
have been reported during blooms of toxic dinoflagellates
(Prakash et al., 1971; White et al., 1993) but their toxin composition have not been determined. In addition to these gastropods, several species ofmarine snails living on coral reefs
were shown to contain paralytic shellfish toxins, primarily
STX with trace ofneoSTX and GTX2 (Kotaki et al.,1981).
However, nothing is known regarding the nature and toxin
composition of marine snails from the Mar del Plata coast.
Another point ofinterest is the source oftoxins in these nonfilter feeder organisms. From their feeding habit as benthic
hunter is probably that the direct so urce of toxins is a benthic filter-feeder organismo which can accumulatc dinotla-
13
H~
:>=ÑH2
,
R2
--OH
OH
'\
R3
MATERIALS
AND METHODS
Specimens:
A. tamarense, isolate AMI from the Mar del Plata coast,
\\as grown in hatch culturc in f/2 medillm withollt silicon
Rl
R2
R3
H
H
H
OH
H
OH
H
H
080-3
R4:CONH2
R4: CONllSOj"
R4: H
STX
GTX5(Bl)
dcSTX
neoSTX
GTX6(B2)
dcneoSTX
GTXl
C3
dcGTXl
~H H
GTX2
Cl(epíGTX8)
dcGTX2
H
GTX3
C2(GTX8)
dcGTX3
GTX4
C4
dcGTX4
080-3
080-3 H
OH OSO3
FIGURA1. Estructura de las toxinas del complejo VI'M.
FIGURE 1. Structures ofparalytic shellfish toxins.
H
CARRETO ET AL.: COMPARATIVE
STUDIES ON TOXIN PROFlLES
103
addition on a 14: 10 LD cycle, with an irradiance of c.a. 200
/lE m-' s\ at 18°C. The mussel M edu/is and the marine
snails Z. angulata, A. brasi/iana and P brasiliana, were collected at the Mar del Plata coast. Historical data in monthly
toxicity values fram the mussel M.edu/is and the marine
snail Z. angulata were obtained fram the PSP monitoring
pragram established in the coastal region of Mar del Plata.
Mouse bioassays according to AOAC methods (Horwitz,
1984) are used in toxicity determination.
15 cm, Nomura chemical) and following three mobile phases (flow rate 0.8 ml/min) were used for separation ofthe different toxin graups: (a) 1 mM tetrabutylammonium
phosphate solution adjusted to pH 6.0 with acetic acid for C1-C4
toxins,(b) 2 mM 1-heptanesulfonic acid in 10 mM ammonium phosphate buffer (pH:7.1) for the gonyautoxin group, an
c) 2 mM 1-heptanesulfonic acid in 30 mM ammoni um phosphate buffer (pH:7.1) : acetonitrile (100:5) for the saxitoxin
group. The eluate fram the column was continuously mixed
with 7 mM periodic acid in 50 mM sodium phosphate buffer
(pH: 9.0) at 0.4 ml/min, heated at 65°C by passing thraugh a
Teflon tubing (0.5 mm i.d., 10 m long), and them mixed with
0.5 N acetic acid at 0.4 ml/minjust before entering the monitor. The fluoromonitor was set at 330 and 400 nm respectively for excitation and emission wavelength. A Hitachi L6000 HPLC equipped with F-1050 fluoromonitor was used.
HPLC analysis oftoxins:
Cells of A. tamarense collected by centrifugation, were
suspended in 0.1 N acetic acid and disintegrated by hand in
a Potter-Elvejem homogenizer. Supernatant obtained by
centrifugation were analyzed directly by HPLC at the
Faculty of Agriculture of Tohoku University. Mussels and
marine snails extracts were prepared according to the standard method for mouse bioassay (Horwitz, 1984) and
applied for analysis after being passed through a sep-Pack
C18 cartridge column (Waters) which had been washed
beforehand with 10 mi each of methanol and water. The eluate between 1.5 - 2.0 mi was filtered thraugh a ultrafiltration
membrane (Ultrafree C3GC, Millipore) and subjected to
analysis.
Fluorescent HPLC using ion pair chromatography with
post column derivatization was carried out as reported previously (Oshima et al., 1989) with slight modifications. A
silica base reversed phase column (Develosil C-8-5, 0.46 x
RESULTS AND DISCUSSION
The analysis ofthe toxin composition (Figure 2) of our
isolate (AMI) of A. tamarense revealed that N-sulfocarbamoyl toxins (C1 and C2) comprise more than 50% oftotal
toxins. The next most abundant components were N-1hydraxyderivatives (GTX1, neoSTX and GTX4). Saxitoxin
was the lowest ofthe 10 detectable toxins (Table 1).
Tabla l. Composición en toxinas del dinoflagelado A. tamarense, del mejillón M edu/is y de los caracoles marinos Z. angulata,
P brasi/iana y A. brasiliana.
Table l. Toxin composition ofthe dinoflagellate A. tamarense, the mussel M edu/is and the marine snai/s Z. angulata, P brasi/iana andA. brasiliana.
Specimen
Z. angulata
Víscera
2
C1
C2
GTX1
GTX2
GTX3
GTX4
dcGTX2
dcG TX3
neoSTX
dcSTX
STX
ND
ND
0,2
2,4
0,6
ND
0,1
TR
7,9
0,9
81,1
TOTAL
93,1
0,2
2,6
0,7
0,1
8,4
0,9
87,1
Foot
1
ND
ND
ND
TR
TR
ND
ND
ND
0,4
0,1
9,7
10,2
P brasiliana
A. brasi/iana
Foot
Foot
Mucus
2
0,4
0,2
3,6
0,6
95,2
1
ND
ND
ND
0,1
TR
ND
ND
ND
ND
ND
8,9
9,0
2
0,6
0,2
99,3
1
ND
ND
ND
TR
TR
ND
ND
ND
ND
0,1
11,9
2
0,2
0,0
0,6
97,9
12,0
l:nmole/g, 2:mole%, 3:nmole/ml of extract. ND: non detected, TR: trace «0,1)
2
ND
ND
ND
TR
TR
ND
ND
ND
ND
0,1
6,7
6,8
0,5
0,2
1,2
97,9
M. edu/is
Whole
1
2
0,1
0,2
5,8
3,8
3,7
0,6
ND
ND
0,1
ND
0,1
14,3
0,7
1,3
40,6
26,4
25,9
4,2
0,5
0,4
A. tamarense
3
2
27,3
40,7
23,2
1,3
1,1
7,4
1,3
1,4
13,8
ND
0,19
23,2
34,6
19,7
1,1
1,0
6,3
1,1
1,2
11,7
117,7
0,1
104
REy. INVEsT. DES. PESQ. N' ID: 101-107
(1996)
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CARRETO ET AL.: COMPARATIVE
STUDIES ON TOXIN PROffiES
105
An interesting feature is the presence of dcGTX2 and
dcGTX3, as these toxins have heen only detected in trace
amounts in other Alexandrium species (Oshima el al., 1990).
Although the two toxins have been reported as enzymatic
hydrolysis products by a cIam (SuIlivan et al., 1983), their
presence in the dinoflageIlate Gymnodinium calenalum
have been recentIy confirmed (Oshima el al., 1990). Toxin
profiles of the mussel Medu/is were much different from
those of toxin producer organism isolated in cultures. Prior
studies have shown that the toxin profile in bivalve tissues
may differ from that of the ceIls upon which they feed
(Shimizu and Yoshioka, 1981; SuIlivan el al., 1983; Oshima
el al., 1990). Oshima el al., (1990) reported a rapid degradation ofN-1-hydroxy toxins and conversions of 11-I3-hydroxysulfate toxins to 11-a-epimeres during accumulation
processes in scaIlops, mussels and oysters. The rapid conversion ofIess potent but more labile N-sulfocarbamoyl toxins (C 1 and C2) to their corresponding gonyautoxins (GTX2,
GTX3) was also found to occur in the hard clam Mercenaria
mercenaria (Bricelj el al., 1991). "In vitro" studies demonstrated enzymatic conversions of gonyautoxins and neoSTX
to STX through removal of the 11-hydroxysulfate and N-1
hydroxyl groups in tissue homogenates of the scaIlop
Placopeclen magellanicus (Shimizu and Yoshioka, 1981).
Enzymatic decarbamoylation of toxins was also found to
occur rapidly in tissue homogenates of the littleneck cIam
Prololhaca slaminea (SuIlivan el al., 1983). In addition,
some species of bacteria isolated from the viscera of coral
reef crabs and marine snails, transform GTX1, GTX2 and
GTX3 to STX by reductively eliminating N-1-hydroxyl and
C-11 hydroxysulphate groups (Kotaki el al., 1985). Also a
rapid differential elimination of C1 and C2 toxins was
reported in the scalIop Patinopeclen yessoensis (Oshima el
al.,1990 ) and in the cIam M mercenaria (Bricelj el al.,
1991) foIlowing exposure of toxic dinoflageIlates.
Although complicated processes might be involved in
the accumulation and elimination oftoxins, direct comparison of toxic profiles between A. lamarense and M edu/is,
might reflect conversions from GTX1 - GTX4 to GTX2 GTX3 or selective degradation of GTX1 - GTX4 and also
the rapid elimination ofC1 and C2 toxins during depuration
processes. Hence the toxin profile of M edu/is support that
the dinoflagellate isolate was the actuaIly causative toxic
organisms in the area.
High contents of toxins were also observed in aIl
species of marine snails analyzed. The highest value (210
MU/g) was detected in the viscera of Z. angulala; much
lower levels occurred in the foot and mucous secretion
(Table 2). Toxin composition of the different species anaIyzed were similar to each other, with STX as the main component (87 - 99%) and only trace amounts of neoSTX,
dcSTX, GTX2 and GTX3 (Table 1). In relation to the viscera, the foot and the mucous secretion of Z. angulala
exhibited a decreased number oftoxins, with increased proportions (86.3, 95.2 and 99.3%, respectively) of STX. This
result suggest toxins interconversion processes during their
transit from the digestive gland to the tissues and/or a selective retention of STX in the tissues. The direct source of
toxin in these gastropods was not confirmed yet, but the
most probably is the mussel M edu/is as this filter feeder
organism can accumulate high amounts of toxins. Although
the toxin profiles of the Z. angulala viscera were much different from those of M. edu/is, we can speculate that the
gonyautoxins (more than 95% of M edu/is toxins) had been
converted to STX and neoSTX via reductive cleavage of 11hydroxysulfate and reduction ofN-1-hydroxyl during transference through food chain. These reactions ,have been
reported to occur by enzyme and bacteria (Shimizu and
Yoshioka, 1981; Kotaki el al., 1985) and explain the relative
enrichment of STX in Z. angulala, P brasi/iana and A.
TABLA2. Valores de toxicidad (bioensayo) del dinoflagelado A. lamarense, del mejillón M edu/is y de los caracoles marinos Z.
angulala, P brasi/iana y A. brasi/iana.
TABLE 2. Toxicity (mouse bioassay) ollhe dinoflagellale A. lamarense, lhe mussel M edu/is and lhe marine snails Z. angulala,
P brasi/iana and A. brasi/iana.
SPECIMEN
ORGAN
TOXICITY
Zidona angulala
Viscera
210
Zidona angulala
Foot
25
Zidana angulala
Mucus
17
Foot
17
Pachycymbiola
Adelomedon
brasi/iana
brasi/iana
Mytilus edu/is
Alexandrium
* MU/ml
lamarense
Whole
28
Whole
143
147*
(MU/g)
106
REv INVEST. DES. PESQ. N' lO: 101-107
brasi/iana tissues.
It is interesting to note that while M. edu/is accumulate
high amounts of toxins during blooms of A. tamarense, and
detoxify to the regulatory levels (80 /lg STXeq./100g) within a few weeks, Z. angulata sustain toxic levels for extended
periods of time, ranging from several months to over the
year (Figure 3). These results suggest that in addition to
toxin interconversion, a selective retention of STX occurs
within these animals. The experimental studies of Kvitek
and Beitler (1991) strongly suggest that butter c1ams
(Saxidomus giganteus) are able to retain and to utilize this
highly lethal neurotoxin as an effective defense against a
wide range of vertebrate predators. However, the possible
existence of alternative exogenous toxin sources can not be
discarded, as recently tetrodotoxin (TTX) and PSP toxins
have been found to be produced by marine bacteria, which
are widely distributed in the environment (Sato et al.,1993).
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FIGURA 3. Valores máximos mensuales de toxicidad (19861991) en el mejillón M. edu/is (-)
y en el caracol mari) de la región costera marplatense.
no Z. angulata (
FIGURE 3. Maximum monthly toxicity (1986-1991) of the
mussel M edulis ( -)
and the marine snail Z. angulata
) from the Mar del Plata coast.
(
-
-
(1996)
A. 1993. An exploratory analysis of the Mar del Plata
shellfish toxj¡;ity area (1980-1990). In: SMAYDA T.l&
SHlMlZU y (Eds.). Toxic Phytoplankton Blooms in the
Sea. Proccedings of the Fifth International Conference
on Toxic Ma¡ine Phytoplankton, Newport, Rhode Island,
USA. Elsevier, Amsterdam, 377-382.
Ca1BELLA A.D., SULL!VANll, BOYER G.L., TAYLORF.J.K
& ANDERSONR.J. 1987. Variation in paralytic shellfish
toxin composition within the Protogonyaulax tamarensis
/ catenella species complex. Biochem. Syst. EcoL, 15:
171-186.
KOTAKI Y, OSHIMA Y & YASUMOTO T. 1981.
Analysis
of
paralytic shellfish toxins of marine snails. Bull. Japan.
Soco Sci. Fish., 47 (7): 943-1046.
KOTAKIY, OSHIMAY & YASUMOTOT. 1985. Bacterial tranformation of Paralytic Shellfish Toxins. In: ANDERSON
D.M., WHITE A.W. & BADEN D.G. (Eds). Toxic
Dinoflagellates. Proceedings of the Third International
Conference
on Toxic Dinoflagellates,
SI. Andrews,
Canadá. EIsevier, New York, 287-292.
KVlTEK KG. & BEITLERM.K. 1991. Relative insensitivity
of butter clam neurons to saxitoxin: a preadaptation for
sequestering paralytic shellfish poisoning toxins as a
chemical defense. Mar. EcoL Prog. Ser., 69: 47-54.
OSHIMAY, SUGINOK. & YASUMOTOT. 1989. In: S. NATORI,
K. HASHIMOTO& Y UENO (Eds.). Mycotoxins and phycotoxins 1988. Elsevier, New York, 319-326. Cited in:
OSHlMA Y, SUGINO K., ITAKURA H., HrROTA M. &
YASUMOTOT. 1990. Comparative studies on paralytic
shellfish toxin profiles of dinoflagellates and bivalves.
In: E. GRANEL!, SUNDSTROMB., ELDER L. & ANDERSON
D.M. (Eds.). Toxic marine phytoplankton. EIsevier, New
York,391-396.
OSHIMAY, SUGINOK., ITAKURAH., HIROTAM. & YASUMOTO T. 1990. Comparative studies on paralytic shellfish
toxin profile of dinoflagellates
and bivalves. In: E.
GRANEL!,SUNDSTROMB., ELDER L. & ANDERSON D.M.
(Eds.). Toxic marine phytoplankton. Elsevier, New York,
391-396.
BIBLIOGRAPHY
HORWITZ W. (Ed.).
ed. AOAC.
1984.
Section
Official
methods
18-086-18-092.
of analysis.
Arlington,
14th
VA, USA.
BRICELJV.M., LEE J.H. & CaABELLAAD. 1991. Influence
of dinoflagellate cell toxicity on uptake and loss of paraIytic shellfish toxins in the northern quahog Mercenaria
mercenaria. Mar. EcoL Progg. Ser., 74: 33-46.
CARRETO l1.,
EL BUSTO C., SANCHO H., CARIGNAN M.O.,
CUCCHI COLLEONI AD.,
DE MARco
PRAKASHA., MEDCOF lC. & TE!\1NANTAD. 1971. Paralytic
shellfish poisoning in eastern Canada. BulL Fish. Res.
Bd. Can., 177: 87 pp.
S.G. & FERNANDEZ
SATOS., OGATAT. & KODAMAM. 1993. Wide distribution of
toxins with sodium channel blocking activity similar to
tetrodotoxin and paralytic shellfish toxins in marine animals. In: SMAYDA T.l& SHIMIZU Y (Eds.).
Toxic
Phytoplankton Blooms in the Sea. Proceedings of the
Fifth International
Conference
on Toxic Marine
Phytoplankton, Newport, Rhode Island, USA. EIsevier,
Amsterdam, 429-434.
CARRETO
liT AL.: COMPARATIVE
STUDIES ON TOXIN PROFILES
SHIMIZU y & Y OSHIOKA M. 1981.
Transformation
of para-
Iytic shellfish as demonstrated in scallop homogenates.
Science, 212: 547-549.
SULLIVAN J.J.O.,
IWAOKA W.T. & LrsToN J. 1983. Enzymatic
transformation of PSP toxins in the lirtleneck clam
(Protothaca staminea).
Biochem. Biophys. Res.
Commum., 114: 465-472
107
WHITE A.W., NASSIF J. & SHUMWAYS.E.
occurrence of paralytic shellfish toxins in
fish in the northeastem United States. In:
SFIMIZU y (Eds.). Toxic Phytoplankton
1993. Recent
offshore shellSMAYDAT.J.&
Blooms in the
Sea. Proceedings of the Fifth International Conference
on Toxic Marine Phytoplankton, Newport, Rhode Island,
USA. EIsevier, Amsterdam, 435-440.