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The occurrence of paralytic shellfish toxins in two species of xanthid crab from Suva barrier reef, Fiji Islands
Toadraon, Vol . 21, No. 4, pp . 547-351, 1983 . Printed in Great Britain .
0041-0101/83 f3 .00+ .00 ® 1983 Perpmon P. lAd .
THE OCCURRENCE OF PARALYTIC SHELLFISH TOXINS IN TWO SPECIES OF XANTHID CRAB FROM SUVA BARRIER REEF, FIJI ISLANDS* UDAY RAJ, 1 HAzRA HAQ, 1 YASUKATSU OSHIMA2 and TAKESHI YASUMOT02t 'Institute of Marine Resources, University of the South Pacific, Suva, Fiji and 'Faculty of Agriculture, Tohoku University, Tsutsumi-dori, Sendai 980, Japan (Accepted for publication 28 December 1982) U. RAJ, H. HAQ, Y. OsmmA and T. YAsumoTo . The occurrence of paralytic shellfish toms in two species of xanthid crab from Suva barrier reef, Fiji Islands. Toxicon 21, 547-551, 1983 . Five species of crabs commonly occurring on Suva barrier reef, Fiji Islands, were tested for the presence of paralytic shellfish toxins . All 35 specimens of Atergatisloridus and all 18 specimens of Zosimusaeneus tested were lethal to mice, whilst none of 12 specimens of Carpilius maculates, 8 of C. convexes and 10 of Diphia sebana tested were lethal . A. ,Jloridus contained saxitoxin (55-6054), neosaxitoxin (35-4054), gonysutoxin-II (less than 5%) and a new toxin previously found in a toxic dinoflagellate, Pyrodinium bahamense vac. compressa, and tentatively coded PBT (I %) . Z. aeneus contained the same components, with additional trace amounts of gonyautoxin-I and III, but neosaxitoxin was the major component in this species. Comparison with the results of testing Okinawan specimens of Z. aeneus, A. floridus and Platipodia granulosa suggests that the toxin profile is specific to species. INTRODUCTION
SEVERAL species of crab have been reputed to cause severe poisoning when consumed by humans (HALSTEAD, 1965 ; HOLTHUIS, 1968; HASHIMOTO, 1979). HOLTHUIS (1968) expressed doubts concerning the existence of toxins in crabs but SOMMER (1932) and SOMMER and MEYER (1937) experimentally confirmed the presence of paralytic shellfish
poison in the common sand crab, Emerita analoga, during a Protogonyaulax (= Gonyaulax) red tide . HASHIMOTO et al. (1967) demonstrated the occurrence of very high levels of toxicity in Zosimus aeneus and Platipodia granulosa from Ryukyu and Amami Islands of Japan. Later, Atergatis floridus was also found to be highly toxic (INOUE et al., 1968). TEH and GARDINER (1970, 1974) showed that Lophozozymus pictor from Singapore is poisonous, but the toxin is different from that in the aforementioned species. Following the isolation of saxitoxin from Z. aeneus (NOGUCHI et al., 1969), YASumOTO et al. (1981) conducted a detailed analysis of the toxins of Z. aeneus, A. loridus and P. granulosa from Ishigaki Island, Okinawa, and showed that several different toxins were present. Moreover, the primary source of the toxins was identified as a calcareous red alga, Jania sp. (KOTAKi et al., 1983), and ten species of crab covering four families were also shown to be toxic on a reef where this alga was abundant (YASumOTO et al., 1983). *Studies on paralytic shellfish poisoning in tropical waters - VII. t To whom correspondence should be addressed . 547
548
U. RAJ et al. 1i8*E
Serua Is . 0
20
40 km
FIG . l . MAPS OF SAMPLING SITE .
Left map shows distance between Suva on Viti Levu Island and Serua Island, where crab poisoning occurred in 1968 . An enlarged map of the area around Suva is shown to the right to pinpoint the sampling sites.
In this study a screening test for toxicity was carried out on five species of commonly occurring crabs from the Suva barrier reef on Fiji Island, to evaluate their potential hazard when consumed by humans. Two species (Z. aeneus and A. jloridus) found to be toxic were further analyzed for toxins . The toxin compositions of Fijian specimens were compared with those of the same species from Okinawa to see whether toxin composition is species specific . MATERIALS AND METHODS Specimens Crabs were collected at night from two localities (Site A and Site B) in a 500 m stretch of Suva barrier reef, in the intertidal reef crest zone (Fig . 1) . They included 18 individuals of Z. aeneus, 35 of A. foridus, 12 of Carpilius maculates, 8 of Carpillus convexes and 10 of Eriphia sebana . Live specimens were transported 4 km to the laboratory where they were frozen immediately and kept at -20°C, pending analyses . Z. aeneus, A. Jloridus and P. granulosa collected at Ishigaki Island, Japan, in August 1980, were reinvestigated for a comparison of toxin composition . Lethality test Individual whole crabs were pulverized in a mortar . Part of the homogenate thus obtained was tested according to the standard mouse assay method for paralytic shellfish poison (HORWITZ, 1980). Lethal potency of the crabs was expressed as mouse unit per g of crab (MU/g), where 1 MU was defined as the amount of toxic material required to kill a mouse of 20 g body weight within 15 min. Purjfrcation and analyses of toxins Minced crabs were extracted with 754 ethanol acidified to pH 2.0 with hydrochloric acid . After evaporation of the solvent under reduced pressure, toxins were purified by successive treatment on charcoal, Bio-Gel P-2 and Bio-Rex 70 columns. The conditions for each procedure were the same as used in the previous study on Okinawan crabs (YAsumoTo et al., 1981). Identification of toxins was carried out by thin layer chromatography (Merck precoated Silica gel 60 plates activated at 120°C) with a solvent system consisting of
Toxic Crabs on Suva Barrier Reef, Fiji
54 9
pyridine-ethyl acetate-acetic acid-water (75:35:15:30) as well as by electrophoresis on cellulose acetate strips in 0.083 M Tris-HCl buffer, pH 8.7, at 0.56 mA/cm for 18 min. Saxitoxin (STX), neosaxitoxin (neoSTX), gonysutoxin I - IV (GTX,~) and Pyrodinium bahamense toxin (PBT) isolated from the cells of Protogonyaulax tamarensis and Pyrodinium bahamense var. compressa were used as standards. Toxins were detected as fluorescent spots after spraying with a 1 % hydrogen peroxide solution and heating the plate or cellulose acetate strips at 120°C for 3 min. Relative ratios of each toxin were determined by preparative thin layer chromatography and by a continuous fluorometric toxin analyzer constructed by the authors (Oshima, Machida, Sasaki and Yasumoto, unpublished), which employs a liquid chromatographic system for separation of toxic components and measures fluorophores obtained by oxidation of toxins with t-butyl hydroperoxide in a sodium hydroxide solution .
RESULTS
Toxicity levels The results of lethality tests using A . floridus and Z. aeneus are summarized in Table 1 . All specimens of A. floridus were lethal, with a mean value of 63 .2 MU/g, however, the individual lethalities ranged widely from 3 .4 to 717 MU/g . Compared to those of A . floridus, the toxin concentrations in Z. aeneus specimens were significantly lower, with a mean value of 9.1 MU/g and a highest of only 33 .8 MU/g . In both species there appears to be no correlation of lethal potency with either sex or body weight . No lethal component was found in C. maculatus, C. convexus or E. sebana specimens .
TABLE 1 . LETHAL POTENCIES OF Atergatis floridUS AND ZOSiMUS aeneus
Date of capture
Atergatis floridus
July 1981
Sex
Weight (8)
F F F F F F M M M M M M M M M M M M M Nov. 1981 F F F F M M Feb. 1982 F Mar. 1982 F MU, the amount of toxin
12 13 17 18 18 23 15 19 20 21 21 21 21 23 23 23 25 25 31 7 10 14 19 12 12 26 10 required
Lethal potency (MU/g)
Date of capture
Sex
Weight (g)
Lethal potency (MU/g)
F F F F M M M M
10 15 15 15 15 15 21 25
22 .6 6.0 9.0 6.2 20.8 6.8 20.8 11 .0
Atergatis floridus
3.4 Apr. 1982 4.6 170 16.0 17 .0 31 .0 12.0 5 .5 41 .0 Zosimus aeneus 4 .8 July 1981 24 .0 31 .0 6.0 5 .2 717 Nov. 1981 13 .0 Feb. 1982 46 .0 228 110 33 .0 108 76 .5 338 Mar. 1982 Apr. 1982 3.5 8.1 15 .2 41 .0 to kill a mouse of 20 g body
F 109 32 .0 F 113 3 .2 F 121 6.9 M 113 3 .1 M 162 2.2 F 97 2.6 F 47 3 .6 M 78 8.8 M 88 3 .2 M 114 33 .8 M 117 2.8 M 144 3.4 M 225 4.0 M 24 2.2 F 68 7.4 F 71 9.2 M 114 5.0 M 130 29 .6 weight within 15 min.
SSO
U. RAJ et al. Area Fiji
Species Zosimus aeneus
GTXs
neoSTX
STX
PBT
Atergatis floridus Okinawa Zosimus aeneus Atergatis floridus Plati
ia granulosa
FIG . 2 . COMPARISON OF TOXIN COMPOSITION OF XANTHID CRABS FROM FUI AND OKINAWA .
The diagram shows relative amounts of gonyautoxins (GTXs), neosaxitoxin (neoSTX), saxitoxin (STX) and Pyrodinium bahamense toxin (PBT) in each species of crab in per cent .
Toxin analyses
The toxin compositions of Fijian crabs are shown in Fig. 2 and compared with those of three species of Okinawan crabs. It is clear that within the same species, both Fijian and Okinawan specimens show almost the same composition. In Z. aeneus, neoSTX is the dominant toxin, followed by STX. GTX, and traces of GTX,,' are recognizable, but they represent only 10% of the total lethal potency. In A. floridus, the relative ratio of STX and neoSTX is reversed, the former being the major toxin comprising 60%B of the lethal potency. GTX, is the only gonyautoxin to be identified and its contribution to the lethality is less than 5% . In contrast, P. granulosa is characterized by the almost exclusive presence of STX. The existence of PBT is confirmed, though in a trace amount, in all three species. DISCUSSION
The presence of paralytic shellfish toxins in A. floridus and Z. aeneus from Suva barrier reef has been experimentally shown. In some specimens of A. floridus the lethal potency was similar to that obtained in Okinawan specimens of the same species (YASUMOTO et al., 1981). Since intake of toxin levels above 3000 MU is assumed to be lethal to the adult human (HASHIMOTO, 1979), consumption of some of the specimens of A. floridus could prove fatal. Z. aeneus had a significantly lower level of lethal potency in comparison to individual specimens from Japan (HASHIMOTO et al., 1967 ; YASUMOTO et al., 1981). Nevertheless, the low concentration of toxins in Z. aeneus in this study must be viewed with caution, since wide individual and regional variation exists . The recent discovery of Jania sp. as the primary source of toxins seems to explain the differing lethalities of A . floridus and Z. aeneus. On Suva barrier reef, Jania sp. are abundant in the habitat of the former species (Site A in Fig. 1), whereas the alga was scarce in the spots where specimens of Z. aeneus were collected (Site B) . Thus, Z. aeneus and other crabs, even those found nontoxic in this study, may become highly toxic if this alga is abundant in their habitat (YASUMOTO et al., 1983). Indeed, the death of two young sisters occurred from eating Z. aeneus in 1968 in Serua Island, 60 km from Suva (Fig. 1). It is strongly advised that consumption of crabs living on coral reefs be avoided. Multiplicity of toxins was revealed by chemical analyses . Comparison between Fijian and Okinawan specimens suggests that the toxin profile is specific to species, but not to the region . Worthy of special mention is the presence of PBT in all three species.
Toxic Crabs on Suva Barrier Reef, Fiji
55 1
Occurrence of this component has only been reported from Pyrodinium bahamense var. compressa and bivalves infested by this dinoflagellate (HARADA et al., 1982) . Acknowledgements - The authors are grateful to Mr. M. TAJIRI for his technical assistance . The present study was supported by a grant-in-aid from the Toyota Foundation . REFERENCES HALSTEAD, B. W. (1965) Poisonous and Venomous Marine Animals of the World, Vol. 1, p. 905. Washington DC : U.S . Government Printing Office. HARADA, T., OSHIMA, Y., KAMIYA, H . and YASUMOTO, T. (1982) Confirmation of paralytic shellfish toxins in the dinoflagellate Pyrodinium bahamense vac. comprema and bivalves in Palau. Bull. Japan. Sac. scient. Fish. 48, 821 . HASHIMOTO, Y. (1979) Marine Toxins and Other Bioactive Marine Metabolites, p. 59. Tokyo: Japan Scientific Society Press. HASHIMOTO, Y., KoNosu, S., YAsumom, T., INOUE, A. and NocuCHI, T. (1967) Occurrence of toxic crabs in Ryukyu and Amami Islands. Toxicon 5, 85 . HOLTHUIs, L. B. (1968) Are there poisonous crabs? Crustaceana 15, 215 . HORWITZ, W. (Ed.) (1980) Paralytic shellfish poison . In: Official Methods of Analysis of the Association of Official Analytical Chemists, p. 298. Washington DC : Association of Official Analytical Chemists . INOUE, A., Nocucm, T., KONOSU, S. and HASHIMOTO, Y. (1968) A new toxic crab, Atergatisfloridus. Toxicon 6, 119. KOTAKI, Y., TAnRA, M., OSHIMA, Y. and YAsumom, T. (1983) Identification of a calcareous red alga as the primary source of paralytic shellfish toxins in coral reef crabs and gastropods . Bull. Japan. Soc. scient . Fish. 49, 283. NoGUCHi, T. KONOSU, S. and HASHIMOTO, Y. (1969) Identity of the crab toxin with saxitoxin. Toxicon 7, 325. SOMMER, H. (1932) The occurrence of the paralytic shell-fish poison in the common sand crab . Science, N. Y. 76, 574. SOMMER, H. and MEYER, K. F. (1937) Paralytic shell-fish poisoning. Archs Path . 24, 560. TEH, Y. F. and GARDINER, J. E. (1970) Toxin from the coral reef crab, Lophozozymus pictor. Pharmac. Res. Communs 2, 251 . TEH, Y. F. and GARDINER, J. E. (1974) Partial purification of Lophozozymus pictor toxin. Toxicon 12, 603. YAsumoTO, T., OSHIMA, Y. and KOTAA, T. (1981) Analysis of paralytic shellfish toxins of xanthid crabs in Okinawa. Bull. Japan. Soc. scient. Fish . 47, 957. YAsumoTo, T., OSHIMA, Y., TAJiRI, M. and KOTAKI, Y. (1983) Paralytic shellfish toxins in previously unrecorded species of coral reef crabs. Bull. Japan. Soc. scient. Fish. (in press) .
0041-0101/83 f3 .00+ .00 ® 1983 Perpmon P. lAd .
THE OCCURRENCE OF PARALYTIC SHELLFISH TOXINS IN TWO SPECIES OF XANTHID CRAB FROM SUVA BARRIER REEF, FIJI ISLANDS* UDAY RAJ, 1 HAzRA HAQ, 1 YASUKATSU OSHIMA2 and TAKESHI YASUMOT02t 'Institute of Marine Resources, University of the South Pacific, Suva, Fiji and 'Faculty of Agriculture, Tohoku University, Tsutsumi-dori, Sendai 980, Japan (Accepted for publication 28 December 1982) U. RAJ, H. HAQ, Y. OsmmA and T. YAsumoTo . The occurrence of paralytic shellfish toms in two species of xanthid crab from Suva barrier reef, Fiji Islands. Toxicon 21, 547-551, 1983 . Five species of crabs commonly occurring on Suva barrier reef, Fiji Islands, were tested for the presence of paralytic shellfish toxins . All 35 specimens of Atergatisloridus and all 18 specimens of Zosimusaeneus tested were lethal to mice, whilst none of 12 specimens of Carpilius maculates, 8 of C. convexes and 10 of Diphia sebana tested were lethal . A. ,Jloridus contained saxitoxin (55-6054), neosaxitoxin (35-4054), gonysutoxin-II (less than 5%) and a new toxin previously found in a toxic dinoflagellate, Pyrodinium bahamense vac. compressa, and tentatively coded PBT (I %) . Z. aeneus contained the same components, with additional trace amounts of gonyautoxin-I and III, but neosaxitoxin was the major component in this species. Comparison with the results of testing Okinawan specimens of Z. aeneus, A. floridus and Platipodia granulosa suggests that the toxin profile is specific to species. INTRODUCTION
SEVERAL species of crab have been reputed to cause severe poisoning when consumed by humans (HALSTEAD, 1965 ; HOLTHUIS, 1968; HASHIMOTO, 1979). HOLTHUIS (1968) expressed doubts concerning the existence of toxins in crabs but SOMMER (1932) and SOMMER and MEYER (1937) experimentally confirmed the presence of paralytic shellfish
poison in the common sand crab, Emerita analoga, during a Protogonyaulax (= Gonyaulax) red tide . HASHIMOTO et al. (1967) demonstrated the occurrence of very high levels of toxicity in Zosimus aeneus and Platipodia granulosa from Ryukyu and Amami Islands of Japan. Later, Atergatis floridus was also found to be highly toxic (INOUE et al., 1968). TEH and GARDINER (1970, 1974) showed that Lophozozymus pictor from Singapore is poisonous, but the toxin is different from that in the aforementioned species. Following the isolation of saxitoxin from Z. aeneus (NOGUCHI et al., 1969), YASumOTO et al. (1981) conducted a detailed analysis of the toxins of Z. aeneus, A. loridus and P. granulosa from Ishigaki Island, Okinawa, and showed that several different toxins were present. Moreover, the primary source of the toxins was identified as a calcareous red alga, Jania sp. (KOTAKi et al., 1983), and ten species of crab covering four families were also shown to be toxic on a reef where this alga was abundant (YASumOTO et al., 1983). *Studies on paralytic shellfish poisoning in tropical waters - VII. t To whom correspondence should be addressed . 547
548
U. RAJ et al. 1i8*E
Serua Is . 0
20
40 km
FIG . l . MAPS OF SAMPLING SITE .
Left map shows distance between Suva on Viti Levu Island and Serua Island, where crab poisoning occurred in 1968 . An enlarged map of the area around Suva is shown to the right to pinpoint the sampling sites.
In this study a screening test for toxicity was carried out on five species of commonly occurring crabs from the Suva barrier reef on Fiji Island, to evaluate their potential hazard when consumed by humans. Two species (Z. aeneus and A. jloridus) found to be toxic were further analyzed for toxins . The toxin compositions of Fijian specimens were compared with those of the same species from Okinawa to see whether toxin composition is species specific . MATERIALS AND METHODS Specimens Crabs were collected at night from two localities (Site A and Site B) in a 500 m stretch of Suva barrier reef, in the intertidal reef crest zone (Fig . 1) . They included 18 individuals of Z. aeneus, 35 of A. foridus, 12 of Carpilius maculates, 8 of Carpillus convexes and 10 of Eriphia sebana . Live specimens were transported 4 km to the laboratory where they were frozen immediately and kept at -20°C, pending analyses . Z. aeneus, A. Jloridus and P. granulosa collected at Ishigaki Island, Japan, in August 1980, were reinvestigated for a comparison of toxin composition . Lethality test Individual whole crabs were pulverized in a mortar . Part of the homogenate thus obtained was tested according to the standard mouse assay method for paralytic shellfish poison (HORWITZ, 1980). Lethal potency of the crabs was expressed as mouse unit per g of crab (MU/g), where 1 MU was defined as the amount of toxic material required to kill a mouse of 20 g body weight within 15 min. Purjfrcation and analyses of toxins Minced crabs were extracted with 754 ethanol acidified to pH 2.0 with hydrochloric acid . After evaporation of the solvent under reduced pressure, toxins were purified by successive treatment on charcoal, Bio-Gel P-2 and Bio-Rex 70 columns. The conditions for each procedure were the same as used in the previous study on Okinawan crabs (YAsumoTo et al., 1981). Identification of toxins was carried out by thin layer chromatography (Merck precoated Silica gel 60 plates activated at 120°C) with a solvent system consisting of
Toxic Crabs on Suva Barrier Reef, Fiji
54 9
pyridine-ethyl acetate-acetic acid-water (75:35:15:30) as well as by electrophoresis on cellulose acetate strips in 0.083 M Tris-HCl buffer, pH 8.7, at 0.56 mA/cm for 18 min. Saxitoxin (STX), neosaxitoxin (neoSTX), gonysutoxin I - IV (GTX,~) and Pyrodinium bahamense toxin (PBT) isolated from the cells of Protogonyaulax tamarensis and Pyrodinium bahamense var. compressa were used as standards. Toxins were detected as fluorescent spots after spraying with a 1 % hydrogen peroxide solution and heating the plate or cellulose acetate strips at 120°C for 3 min. Relative ratios of each toxin were determined by preparative thin layer chromatography and by a continuous fluorometric toxin analyzer constructed by the authors (Oshima, Machida, Sasaki and Yasumoto, unpublished), which employs a liquid chromatographic system for separation of toxic components and measures fluorophores obtained by oxidation of toxins with t-butyl hydroperoxide in a sodium hydroxide solution .
RESULTS
Toxicity levels The results of lethality tests using A . floridus and Z. aeneus are summarized in Table 1 . All specimens of A. floridus were lethal, with a mean value of 63 .2 MU/g, however, the individual lethalities ranged widely from 3 .4 to 717 MU/g . Compared to those of A . floridus, the toxin concentrations in Z. aeneus specimens were significantly lower, with a mean value of 9.1 MU/g and a highest of only 33 .8 MU/g . In both species there appears to be no correlation of lethal potency with either sex or body weight . No lethal component was found in C. maculatus, C. convexus or E. sebana specimens .
TABLE 1 . LETHAL POTENCIES OF Atergatis floridUS AND ZOSiMUS aeneus
Date of capture
Atergatis floridus
July 1981
Sex
Weight (8)
F F F F F F M M M M M M M M M M M M M Nov. 1981 F F F F M M Feb. 1982 F Mar. 1982 F MU, the amount of toxin
12 13 17 18 18 23 15 19 20 21 21 21 21 23 23 23 25 25 31 7 10 14 19 12 12 26 10 required
Lethal potency (MU/g)
Date of capture
Sex
Weight (g)
Lethal potency (MU/g)
F F F F M M M M
10 15 15 15 15 15 21 25
22 .6 6.0 9.0 6.2 20.8 6.8 20.8 11 .0
Atergatis floridus
3.4 Apr. 1982 4.6 170 16.0 17 .0 31 .0 12.0 5 .5 41 .0 Zosimus aeneus 4 .8 July 1981 24 .0 31 .0 6.0 5 .2 717 Nov. 1981 13 .0 Feb. 1982 46 .0 228 110 33 .0 108 76 .5 338 Mar. 1982 Apr. 1982 3.5 8.1 15 .2 41 .0 to kill a mouse of 20 g body
F 109 32 .0 F 113 3 .2 F 121 6.9 M 113 3 .1 M 162 2.2 F 97 2.6 F 47 3 .6 M 78 8.8 M 88 3 .2 M 114 33 .8 M 117 2.8 M 144 3.4 M 225 4.0 M 24 2.2 F 68 7.4 F 71 9.2 M 114 5.0 M 130 29 .6 weight within 15 min.
SSO
U. RAJ et al. Area Fiji
Species Zosimus aeneus
GTXs
neoSTX
STX
PBT
Atergatis floridus Okinawa Zosimus aeneus Atergatis floridus Plati
ia granulosa
FIG . 2 . COMPARISON OF TOXIN COMPOSITION OF XANTHID CRABS FROM FUI AND OKINAWA .
The diagram shows relative amounts of gonyautoxins (GTXs), neosaxitoxin (neoSTX), saxitoxin (STX) and Pyrodinium bahamense toxin (PBT) in each species of crab in per cent .
Toxin analyses
The toxin compositions of Fijian crabs are shown in Fig. 2 and compared with those of three species of Okinawan crabs. It is clear that within the same species, both Fijian and Okinawan specimens show almost the same composition. In Z. aeneus, neoSTX is the dominant toxin, followed by STX. GTX, and traces of GTX,,' are recognizable, but they represent only 10% of the total lethal potency. In A. floridus, the relative ratio of STX and neoSTX is reversed, the former being the major toxin comprising 60%B of the lethal potency. GTX, is the only gonyautoxin to be identified and its contribution to the lethality is less than 5% . In contrast, P. granulosa is characterized by the almost exclusive presence of STX. The existence of PBT is confirmed, though in a trace amount, in all three species. DISCUSSION
The presence of paralytic shellfish toxins in A. floridus and Z. aeneus from Suva barrier reef has been experimentally shown. In some specimens of A. floridus the lethal potency was similar to that obtained in Okinawan specimens of the same species (YASUMOTO et al., 1981). Since intake of toxin levels above 3000 MU is assumed to be lethal to the adult human (HASHIMOTO, 1979), consumption of some of the specimens of A. floridus could prove fatal. Z. aeneus had a significantly lower level of lethal potency in comparison to individual specimens from Japan (HASHIMOTO et al., 1967 ; YASUMOTO et al., 1981). Nevertheless, the low concentration of toxins in Z. aeneus in this study must be viewed with caution, since wide individual and regional variation exists . The recent discovery of Jania sp. as the primary source of toxins seems to explain the differing lethalities of A . floridus and Z. aeneus. On Suva barrier reef, Jania sp. are abundant in the habitat of the former species (Site A in Fig. 1), whereas the alga was scarce in the spots where specimens of Z. aeneus were collected (Site B) . Thus, Z. aeneus and other crabs, even those found nontoxic in this study, may become highly toxic if this alga is abundant in their habitat (YASUMOTO et al., 1983). Indeed, the death of two young sisters occurred from eating Z. aeneus in 1968 in Serua Island, 60 km from Suva (Fig. 1). It is strongly advised that consumption of crabs living on coral reefs be avoided. Multiplicity of toxins was revealed by chemical analyses . Comparison between Fijian and Okinawan specimens suggests that the toxin profile is specific to species, but not to the region . Worthy of special mention is the presence of PBT in all three species.
Toxic Crabs on Suva Barrier Reef, Fiji
55 1
Occurrence of this component has only been reported from Pyrodinium bahamense var. compressa and bivalves infested by this dinoflagellate (HARADA et al., 1982) . Acknowledgements - The authors are grateful to Mr. M. TAJIRI for his technical assistance . The present study was supported by a grant-in-aid from the Toyota Foundation . REFERENCES HALSTEAD, B. W. (1965) Poisonous and Venomous Marine Animals of the World, Vol. 1, p. 905. Washington DC : U.S . Government Printing Office. HARADA, T., OSHIMA, Y., KAMIYA, H . and YASUMOTO, T. (1982) Confirmation of paralytic shellfish toxins in the dinoflagellate Pyrodinium bahamense vac. comprema and bivalves in Palau. Bull. Japan. Sac. scient. Fish. 48, 821 . HASHIMOTO, Y. (1979) Marine Toxins and Other Bioactive Marine Metabolites, p. 59. Tokyo: Japan Scientific Society Press. HASHIMOTO, Y., KoNosu, S., YAsumom, T., INOUE, A. and NocuCHI, T. (1967) Occurrence of toxic crabs in Ryukyu and Amami Islands. Toxicon 5, 85 . HOLTHUIs, L. B. (1968) Are there poisonous crabs? Crustaceana 15, 215 . HORWITZ, W. (Ed.) (1980) Paralytic shellfish poison . In: Official Methods of Analysis of the Association of Official Analytical Chemists, p. 298. Washington DC : Association of Official Analytical Chemists . INOUE, A., Nocucm, T., KONOSU, S. and HASHIMOTO, Y. (1968) A new toxic crab, Atergatisfloridus. Toxicon 6, 119. KOTAKI, Y., TAnRA, M., OSHIMA, Y. and YAsumom, T. (1983) Identification of a calcareous red alga as the primary source of paralytic shellfish toxins in coral reef crabs and gastropods . Bull. Japan. Soc. scient . Fish. 49, 283. NoGUCHi, T. KONOSU, S. and HASHIMOTO, Y. (1969) Identity of the crab toxin with saxitoxin. Toxicon 7, 325. SOMMER, H. (1932) The occurrence of the paralytic shell-fish poison in the common sand crab . Science, N. Y. 76, 574. SOMMER, H. and MEYER, K. F. (1937) Paralytic shell-fish poisoning. Archs Path . 24, 560. TEH, Y. F. and GARDINER, J. E. (1970) Toxin from the coral reef crab, Lophozozymus pictor. Pharmac. Res. Communs 2, 251 . TEH, Y. F. and GARDINER, J. E. (1974) Partial purification of Lophozozymus pictor toxin. Toxicon 12, 603. YAsumoTO, T., OSHIMA, Y. and KOTAA, T. (1981) Analysis of paralytic shellfish toxins of xanthid crabs in Okinawa. Bull. Japan. Soc. scient. Fish . 47, 957. YAsumoTo, T., OSHIMA, Y., TAJiRI, M. and KOTAKI, Y. (1983) Paralytic shellfish toxins in previously unrecorded species of coral reef crabs. Bull. Japan. Soc. scient. Fish. (in press) .