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Light micrographs of dissected epithecal plates of Fukuyoa paulensis gen. et sp. nov. (A-F) Epithecal plates. (G-L) Precingular and apical plates. (M) Apical pore plate. (N-V) Apical plates. (W) Precingular plates 1'' and 7''. Scale bar 10 μm. doi:10.1371/journal.pone.0119676.g003
Contexts in source publication
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... species belonging to Fukuyoa: Fukuyoa yasumotoi (M.J. Holmes) F. Gómez, D. Qiu, R.M. Lopes & S. Lin, comb. nov. Basionym: Gambierdiscus yasumotoi M.J. Holmes 1998 (J. Phycol. 34, 662, Fig. 1
(Phycologia 48, 373, Fig. ...
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... 1'' is four-sided and the smallest of the precingular series, followed by plate 7'' ( Fig. 2A, 3H,J-K). Both plates are lying adjacent to the sulcus and in the posterior end of the wedge- plate 1' ( Fig. 2A-B, 3A-D,H). Plates 3'' and 6'' are the biggest of the epitheca (Fig. 2O-Q, 3B,E, F). Plate 6'' is pentagonal and the suture 1'/6'' is about twice as long as the suture 3'/6'' ( Fig. 2N, P, 3G-H). The suture 2'/3' is straight (Fig. 3S) or slightly curved (Fig. 3I). Plates 4'' and 5'' are four-sided, trapezium-shaped, and intermediate in size (about one half the area of plates 3'' or 6'') ( Fig. 3D,E). Plate 2'' is slightly bigger than plates 4'' or 5'' (Fig. ...
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... 1'' is four-sided and the smallest of the precingular series, followed by plate 7'' ( Fig. 2A, 3H,J-K). Both plates are lying adjacent to the sulcus and in the posterior end of the wedge- plate 1' ( Fig. 2A-B, 3A-D,H). Plates 3'' and 6'' are the biggest of the epitheca (Fig. 2O-Q, 3B,E, F). Plate 6'' is pentagonal and the suture 1'/6'' is about twice as long as the suture 3'/6'' ( Fig. 2N, P, 3G-H). The suture 2'/3' is straight (Fig. 3S) or slightly curved (Fig. 3I). Plates 4'' and 5'' are four-sided, trapezium-shaped, and intermediate in size (about one half the area of plates 3'' or 6'') ( Fig. 3D,E). Plate 2'' is slightly bigger than plates 4'' or 5'' (Fig. ...
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... 1'' is four-sided and the smallest of the precingular series, followed by plate 7'' ( Fig. 2A, 3H,J-K). Both plates are lying adjacent to the sulcus and in the posterior end of the wedge- plate 1' ( Fig. 2A-B, 3A-D,H). Plates 3'' and 6'' are the biggest of the epitheca (Fig. 2O-Q, 3B,E, F). Plate 6'' is pentagonal and the suture 1'/6'' is about twice as long as the suture 3'/6'' ( Fig. 2N, P, 3G-H). The suture 2'/3' is straight (Fig. 3S) or slightly curved (Fig. 3I). Plates 4'' and 5'' are four-sided, trapezium-shaped, and intermediate in size (about one half the area of plates 3'' or 6'') ( Fig. 3D,E). Plate 2'' is slightly bigger than plates 4'' or 5'' (Fig. ...
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... 1'' is four-sided and the smallest of the precingular series, followed by plate 7'' ( Fig. 2A, 3H,J-K). Both plates are lying adjacent to the sulcus and in the posterior end of the wedge- plate 1' ( Fig. 2A-B, 3A-D,H). Plates 3'' and 6'' are the biggest of the epitheca (Fig. 2O-Q, 3B,E, F). Plate 6'' is pentagonal and the suture 1'/6'' is about twice as long as the suture 3'/6'' ( Fig. 2N, P, 3G-H). The suture 2'/3' is straight (Fig. 3S) or slightly curved (Fig. 3I). Plates 4'' and 5'' are four-sided, trapezium-shaped, and intermediate in size (about one half the area of plates 3'' or 6'') ( Fig. 3D,E). Plate 2'' is slightly bigger than plates 4'' or 5'' (Fig. ...
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... globular cells, with average depth (dorso-ventral axis) 50±3 (45-56) μm, width 45±2 (41-48) μm, and length 56±3 (51-62) μm, with an average depth-to-width ratio of *1.2 (Fig. 1A-F). The cells possess small ellipsoidal plastids, 3-4 μm in diameter, with a brownish pigmentation (Fig. 1A-F, H-J). The nucleus (15-20 μm in diameter) is globular and situated in the hypotheca (Fig. 1C,G,J). The height of the hypotheca is slightly higher than the epitheca (Fig. 1A-D). In apical or antapical view the cell is oval and indented in the ventral side (Fig. 1E-F). The whole theca is covered with round pores of about 0.35 μm in diameter and at densities of 40-50 per 100 μm −2 (Fig. 2G,N-Q). The pores are evenly distributed. Plate formula is Po, 3', 7'', 6c, 7s, 5''', 1p and 2''''. Apical pore plate is an elongate ellipsoid, of 10-12 μm long and 6-7 μm wide, and centrally located in the epitheca ( Fig. 2A-C, 3A-E). Po plate has a long- shank fishhook-shaped slit, about 8 μm long, surrounded by a row of marginal pores, and a few dispersed internal pores (located inside the curved extreme of the foramen) (Fig. 2D-F, 3M). Apical pore plate contacts three plates: 1', 2' and 3' (Fig. 1L, 2A-F). Apical plate 1' is the biggest of the apical series, 20-28 μm long and 17-18 μm wide, with a pentagonal shape (Fig. 3A,B,D, K). Plate 1' is posteriorly wedge-shaped in the junction with the 1'' and 7'' plates ( Fig. 2A-C, 3G-L). In the dorsal side of the epitheca, the sum of plates 2' and 3' is 20-23 μm wide, while in the ventral side plate 1' is 17-18 μm wide. Plate 2' is elongate rectangular (30-33 μm long), and narrower (10-12 μm) than the other apical plates. It has a short suture with plates 1', and 2'' ( Fig. 3A-F). The suture 2'/3'' is long, straight (Fig. 3B,N,Q-S) or curved (Fig. 3I,V). The suture between the plates 2'/3'' is sometimes dentate (Fig. 3R-S). The shape of plate 2' resembles an an- gel's wing (Fig. 3S). Plate 3' is the smaller apical series (about 10-13 μm wide), with an irregular five-sided contour, and with the apical pore plate occupying one of the vertices. The suture 2'/ 3' is about 20 μm long, while the suture 3'/4' is short ( Fig. 2A-C, ...
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... globular cells, with average depth (dorso-ventral axis) 50±3 (45-56) μm, width 45±2 (41-48) μm, and length 56±3 (51-62) μm, with an average depth-to-width ratio of *1.2 (Fig. 1A-F). The cells possess small ellipsoidal plastids, 3-4 μm in diameter, with a brownish pigmentation (Fig. 1A-F, H-J). The nucleus (15-20 μm in diameter) is globular and situated in the hypotheca (Fig. 1C,G,J). The height of the hypotheca is slightly higher than the epitheca (Fig. 1A-D). In apical or antapical view the cell is oval and indented in the ventral side (Fig. 1E-F). The whole theca is covered with round pores of about 0.35 μm in diameter and at densities of 40-50 per 100 μm −2 (Fig. 2G,N-Q). The pores are evenly distributed. Plate formula is Po, 3', 7'', 6c, 7s, 5''', 1p and 2''''. Apical pore plate is an elongate ellipsoid, of 10-12 μm long and 6-7 μm wide, and centrally located in the epitheca ( Fig. 2A-C, 3A-E). Po plate has a long- shank fishhook-shaped slit, about 8 μm long, surrounded by a row of marginal pores, and a few dispersed internal pores (located inside the curved extreme of the foramen) (Fig. 2D-F, 3M). Apical pore plate contacts three plates: 1', 2' and 3' (Fig. 1L, 2A-F). Apical plate 1' is the biggest of the apical series, 20-28 μm long and 17-18 μm wide, with a pentagonal shape (Fig. 3A,B,D, K). Plate 1' is posteriorly wedge-shaped in the junction with the 1'' and 7'' plates ( Fig. 2A-C, 3G-L). In the dorsal side of the epitheca, the sum of plates 2' and 3' is 20-23 μm wide, while in the ventral side plate 1' is 17-18 μm wide. Plate 2' is elongate rectangular (30-33 μm long), and narrower (10-12 μm) than the other apical plates. It has a short suture with plates 1', and 2'' ( Fig. 3A-F). The suture 2'/3'' is long, straight (Fig. 3B,N,Q-S) or curved (Fig. 3I,V). The suture between the plates 2'/3'' is sometimes dentate (Fig. 3R-S). The shape of plate 2' resembles an an- gel's wing (Fig. 3S). Plate 3' is the smaller apical series (about 10-13 μm wide), with an irregular five-sided contour, and with the apical pore plate occupying one of the vertices. The suture 2'/ 3' is about 20 μm long, while the suture 3'/4' is short ( Fig. 2A-C, ...
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... globular cells, with average depth (dorso-ventral axis) 50±3 (45-56) μm, width 45±2 (41-48) μm, and length 56±3 (51-62) μm, with an average depth-to-width ratio of *1.2 (Fig. 1A-F). The cells possess small ellipsoidal plastids, 3-4 μm in diameter, with a brownish pigmentation (Fig. 1A-F, H-J). The nucleus (15-20 μm in diameter) is globular and situated in the hypotheca (Fig. 1C,G,J). The height of the hypotheca is slightly higher than the epitheca (Fig. 1A-D). In apical or antapical view the cell is oval and indented in the ventral side (Fig. 1E-F). The whole theca is covered with round pores of about 0.35 μm in diameter and at densities of 40-50 per 100 μm −2 (Fig. 2G,N-Q). The pores are evenly distributed. Plate formula is Po, 3', 7'', 6c, 7s, 5''', 1p and 2''''. Apical pore plate is an elongate ellipsoid, of 10-12 μm long and 6-7 μm wide, and centrally located in the epitheca ( Fig. 2A-C, 3A-E). Po plate has a long- shank fishhook-shaped slit, about 8 μm long, surrounded by a row of marginal pores, and a few dispersed internal pores (located inside the curved extreme of the foramen) (Fig. 2D-F, 3M). Apical pore plate contacts three plates: 1', 2' and 3' (Fig. 1L, 2A-F). Apical plate 1' is the biggest of the apical series, 20-28 μm long and 17-18 μm wide, with a pentagonal shape (Fig. 3A,B,D, K). Plate 1' is posteriorly wedge-shaped in the junction with the 1'' and 7'' plates ( Fig. 2A-C, 3G-L). In the dorsal side of the epitheca, the sum of plates 2' and 3' is 20-23 μm wide, while in the ventral side plate 1' is 17-18 μm wide. Plate 2' is elongate rectangular (30-33 μm long), and narrower (10-12 μm) than the other apical plates. It has a short suture with plates 1', and 2'' ( Fig. 3A-F). The suture 2'/3'' is long, straight (Fig. 3B,N,Q-S) or curved (Fig. 3I,V). The suture between the plates 2'/3'' is sometimes dentate (Fig. 3R-S). The shape of plate 2' resembles an an- gel's wing (Fig. 3S). Plate 3' is the smaller apical series (about 10-13 μm wide), with an irregular five-sided contour, and with the apical pore plate occupying one of the vertices. The suture 2'/ 3' is about 20 μm long, while the suture 3'/4' is short ( Fig. 2A-C, ...
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... globular cells, with average depth (dorso-ventral axis) 50±3 (45-56) μm, width 45±2 (41-48) μm, and length 56±3 (51-62) μm, with an average depth-to-width ratio of *1.2 (Fig. 1A-F). The cells possess small ellipsoidal plastids, 3-4 μm in diameter, with a brownish pigmentation (Fig. 1A-F, H-J). The nucleus (15-20 μm in diameter) is globular and situated in the hypotheca (Fig. 1C,G,J). The height of the hypotheca is slightly higher than the epitheca (Fig. 1A-D). In apical or antapical view the cell is oval and indented in the ventral side (Fig. 1E-F). The whole theca is covered with round pores of about 0.35 μm in diameter and at densities of 40-50 per 100 μm −2 (Fig. 2G,N-Q). The pores are evenly distributed. Plate formula is Po, 3', 7'', 6c, 7s, 5''', 1p and 2''''. Apical pore plate is an elongate ellipsoid, of 10-12 μm long and 6-7 μm wide, and centrally located in the epitheca ( Fig. 2A-C, 3A-E). Po plate has a long- shank fishhook-shaped slit, about 8 μm long, surrounded by a row of marginal pores, and a few dispersed internal pores (located inside the curved extreme of the foramen) (Fig. 2D-F, 3M). Apical pore plate contacts three plates: 1', 2' and 3' (Fig. 1L, 2A-F). Apical plate 1' is the biggest of the apical series, 20-28 μm long and 17-18 μm wide, with a pentagonal shape (Fig. 3A,B,D, K). Plate 1' is posteriorly wedge-shaped in the junction with the 1'' and 7'' plates ( Fig. 2A-C, 3G-L). In the dorsal side of the epitheca, the sum of plates 2' and 3' is 20-23 μm wide, while in the ventral side plate 1' is 17-18 μm wide. Plate 2' is elongate rectangular (30-33 μm long), and narrower (10-12 μm) than the other apical plates. It has a short suture with plates 1', and 2'' ( Fig. 3A-F). The suture 2'/3'' is long, straight (Fig. 3B,N,Q-S) or curved (Fig. 3I,V). The suture between the plates 2'/3'' is sometimes dentate (Fig. 3R-S). The shape of plate 2' resembles an an- gel's wing (Fig. 3S). Plate 3' is the smaller apical series (about 10-13 μm wide), with an irregular five-sided contour, and with the apical pore plate occupying one of the vertices. The suture 2'/ 3' is about 20 μm long, while the suture 3'/4' is short ( Fig. 2A-C, ...
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... globular cells, with average depth (dorso-ventral axis) 50±3 (45-56) μm, width 45±2 (41-48) μm, and length 56±3 (51-62) μm, with an average depth-to-width ratio of *1.2 (Fig. 1A-F). The cells possess small ellipsoidal plastids, 3-4 μm in diameter, with a brownish pigmentation (Fig. 1A-F, H-J). The nucleus (15-20 μm in diameter) is globular and situated in the hypotheca (Fig. 1C,G,J). The height of the hypotheca is slightly higher than the epitheca (Fig. 1A-D). In apical or antapical view the cell is oval and indented in the ventral side (Fig. 1E-F). The whole theca is covered with round pores of about 0.35 μm in diameter and at densities of 40-50 per 100 μm −2 (Fig. 2G,N-Q). The pores are evenly distributed. Plate formula is Po, 3', 7'', 6c, 7s, 5''', 1p and 2''''. Apical pore plate is an elongate ellipsoid, of 10-12 μm long and 6-7 μm wide, and centrally located in the epitheca ( Fig. 2A-C, 3A-E). Po plate has a long- shank fishhook-shaped slit, about 8 μm long, surrounded by a row of marginal pores, and a few dispersed internal pores (located inside the curved extreme of the foramen) (Fig. 2D-F, 3M). Apical pore plate contacts three plates: 1', 2' and 3' (Fig. 1L, 2A-F). Apical plate 1' is the biggest of the apical series, 20-28 μm long and 17-18 μm wide, with a pentagonal shape (Fig. 3A,B,D, K). Plate 1' is posteriorly wedge-shaped in the junction with the 1'' and 7'' plates ( Fig. 2A-C, 3G-L). In the dorsal side of the epitheca, the sum of plates 2' and 3' is 20-23 μm wide, while in the ventral side plate 1' is 17-18 μm wide. Plate 2' is elongate rectangular (30-33 μm long), and narrower (10-12 μm) than the other apical plates. It has a short suture with plates 1', and 2'' ( Fig. 3A-F). The suture 2'/3'' is long, straight (Fig. 3B,N,Q-S) or curved (Fig. 3I,V). The suture between the plates 2'/3'' is sometimes dentate (Fig. 3R-S). The shape of plate 2' resembles an an- gel's wing (Fig. 3S). Plate 3' is the smaller apical series (about 10-13 μm wide), with an irregular five-sided contour, and with the apical pore plate occupying one of the vertices. The suture 2'/ 3' is about 20 μm long, while the suture 3'/4' is short ( Fig. 2A-C, ...
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... globular cells, with average depth (dorso-ventral axis) 50±3 (45-56) μm, width 45±2 (41-48) μm, and length 56±3 (51-62) μm, with an average depth-to-width ratio of *1.2 (Fig. 1A-F). The cells possess small ellipsoidal plastids, 3-4 μm in diameter, with a brownish pigmentation (Fig. 1A-F, H-J). The nucleus (15-20 μm in diameter) is globular and situated in the hypotheca (Fig. 1C,G,J). The height of the hypotheca is slightly higher than the epitheca (Fig. 1A-D). In apical or antapical view the cell is oval and indented in the ventral side (Fig. 1E-F). The whole theca is covered with round pores of about 0.35 μm in diameter and at densities of 40-50 per 100 μm −2 (Fig. 2G,N-Q). The pores are evenly distributed. Plate formula is Po, 3', 7'', 6c, 7s, 5''', 1p and 2''''. Apical pore plate is an elongate ellipsoid, of 10-12 μm long and 6-7 μm wide, and centrally located in the epitheca ( Fig. 2A-C, 3A-E). Po plate has a long- shank fishhook-shaped slit, about 8 μm long, surrounded by a row of marginal pores, and a few dispersed internal pores (located inside the curved extreme of the foramen) (Fig. 2D-F, 3M). Apical pore plate contacts three plates: 1', 2' and 3' (Fig. 1L, 2A-F). Apical plate 1' is the biggest of the apical series, 20-28 μm long and 17-18 μm wide, with a pentagonal shape (Fig. 3A,B,D, K). Plate 1' is posteriorly wedge-shaped in the junction with the 1'' and 7'' plates ( Fig. 2A-C, 3G-L). In the dorsal side of the epitheca, the sum of plates 2' and 3' is 20-23 μm wide, while in the ventral side plate 1' is 17-18 μm wide. Plate 2' is elongate rectangular (30-33 μm long), and narrower (10-12 μm) than the other apical plates. It has a short suture with plates 1', and 2'' ( Fig. 3A-F). The suture 2'/3'' is long, straight (Fig. 3B,N,Q-S) or curved (Fig. 3I,V). The suture between the plates 2'/3'' is sometimes dentate (Fig. 3R-S). The shape of plate 2' resembles an an- gel's wing (Fig. 3S). Plate 3' is the smaller apical series (about 10-13 μm wide), with an irregular five-sided contour, and with the apical pore plate occupying one of the vertices. The suture 2'/ 3' is about 20 μm long, while the suture 3'/4' is short ( Fig. 2A-C, ...
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... sinister (= left) anterior or posterior], t (transitional cingular plate), S.m.a. and S.m.p. (sulcal media anterior or posterior) (Fig. 4E-I,K). The two posterior sulcal plates (s. d.p, s.s.p) are lying in the base of the sulcal hollow and anteriorly placed adjacent to the forked plate 2'' ( Fig. 4E-I,K). The S.m.a. and S.m.p. plates are minuscule. The S.m.a. resides between the S.d.a. and transitional cingular (t) plates, whereas the S.m.p. is located below the t plate and adjacent to the S.d.p. plate (Fig. 3G). Plate t lies parallel to the upper surface of plate S.d.p. (Fig. 2M, 4E-G,I). The hypotheca also contains five postcingular plates, one large intercalary posterior plate (1p) and two small antapical plates (Fig. 2H-L, 4K-U). Plate 1''' is trapezoidal and the smallest of the postcingular plates (Fig. 2H-L,O). Plates 2''' and the 4''' are the biggest of the postcingular series ( Fig. 2O,P,4O). Plate 2''' is five-sided ( Fig. 4O,P-U) and the suture 2'''/1p is three times longer than in the suture with plate 1'''' (Fig. 2H, 4A-B). Plate 4''' is quadrangular (Fig. 4C). Plate 3''' and 5''' are intermediate in size (Fig. 2P,Q). Plate 3''' is trapezoidal (Fig. 4A,B) and 5''' is triangular (Fig. 4D,K). Plate 1p is long, broad and pentagonal in shape (Fig. 2H,K-L, 4O-U). It usually remains attached to plate 2''' after the theca dissection (Fig. 4A-B, Q-U). The size of the 1p plate is between 33-39 μm long, and 19-23 μm wide. The suture length is small with plate 3''' (of about 10-12 μm) and large with plate 2'' (Fig. 2Q, 4L-O). The antapical plates 1'''' and 2'''' are intermediate in size. Plate 1'''' is more or less quadrangular in shape (Fig. 2M, 4A,B), and lies immediately posterior to plate 1''' and adjacent to the sulcus, 2''' and 1p. Plate 2'''' is small (about 19 μm long, 10 μm wide) and placed posteriorly to plate 5''' (Fig. 2H-L, 4C). It invades the sulcus with a forked side in contact with the right and left posterior sulcal plates (Fig. 2I-K, P,R, ...
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... cingulum is descending and displaced twice its width (Fig. 1F). The cingulum is bor- dered by a narrow list and contains six narrow plates about 4 μm wide (Fig. 3L, 4A-B,J). The sulcus is deep and excavated, mostly surrounded by a ridged sulcal list (Fig. 2H-L,P,R). The sul- cus consists of seven plates, namely S.d.a., S.d.p. [sulcal (dexter = right) anterior or posterior], S.s.a., ...
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Citations
... Monitoring Gambierdiscus populations on specific fishing grounds is a key aspect of ciguatera assessment and management campaigns. The genus displays a remarkable morphological and genetic diversity with no fewer than 13 currently-known distinct species and three related globular species (Fukuyoa spp.), each of which is widely-distributed geographically and has a different toxicity level [19, 20, 21]. Differences in toxicity can also be observed between the strains of the same species [22]. ...
... The two described globular Gambierdiscus species, G. yasumotoi (MJ Holmes) [12] and G. ruetzleri (Faust, Litaker, Vandersea, Kibler, Holland & Tester) [6], were recently transferred to the newly described genus Fukuyoa (F. ruetzleri (F Gómez, D Qiu, RM Lopes, S Lin); F. yasumotoi (F.Gómez, D Qiu, RM Lopes & S Lin), based on cell morphology and molecular phylogenetic evidence [13]). At the same time, a new type species for the genus, F. paulensis (F Gómez, D Qiu, RM Lopes, S Lin) was described, with the species present varying depending on location [14]. ...
Background:
Ciguatera is a circumtropical disease produced by polyether sodium channel toxins (ciguatoxins) that enter the marine food chain and accumulate in otherwise edible fish. Ciguatoxins, as well as potent water-soluble polyethers known as maitotoxins, are produced by certain dinoflagellate species in the genus Gambierdiscus and Fukuyoa spp. in the Pacific but little is known of the potential of related Caribbean species to produce these toxins.
Methods:
We established a simplified procedure for extracting polyether toxins from Gambierdiscus and Fukuyoa spp. based on the ciguatoxin rapid extraction method (CREM). Fractionated extracts from identified Pacific and Caribbean isolates were analysed using a functional bioassay that recorded intracellular calcium changes (Ca2+) in response to sample addition in SH-SY5Y cells. Maitotoxin directly elevated Ca2+i, while low levels of ciguatoxin-like toxins were detected using veratridine to enhance responses.
Results:
We identified significant maitotoxin production in 11 of 12 isolates analysed, with 6 of 12 producing at least two forms of maitotoxin. In contrast, only 2 Caribbean isolates produced detectable levels of ciguatoxin-like activity despite a detection limit of >30 pM. Significant strain-dependent differences in the levels and types of ciguatoxins and maitotoxins produced by the same Gambierdiscus spp. were also identified.
Conclusions:
The ability to rapidly identify polyether toxins produced by Gambierdiscus spp. in culture has the potential to distinguish ciguatoxin-producing species prior to large-scale culture and in naturally occurring blooms of Gambierdiscus and Fukuyoa spp. Our results have implications for the evaluation of ciguatera risk associated with Gambierdiscus and related species.
... Recently, two of the previous species (G. yasumotoi and G. ruetzleri) have been re-described to new genus Fukuyoa Gó mez, Qiu, Lopes and Lin, with a description of new species Fukuyoa paulensis (Gó mez et al., 2015). A phylogeographical study of Gambierdiscus spp. ...
In Japan, ciguatera fish poisoning (CFP) has been increasingly reported not only in subtropical areas but also in temperate areas in recent years, causing a serious threat to human health. Ciguatera fish poisoning is caused by the consumption of fish that have accumulated toxins produced by an epiphytic/benthic dinoflagellate, genus Gambierdiscus. Previous studies revealed the existence of five Gambierdiscus species/phylotypes in Japan: Gambierdiscus australes, Gambierdiscus scabrosus, Gambierdiscus sp. type 2, Gambierdiscus sp. type 3, and Gambierdiscus (Fukuyoa) cf. yasumotoi. Among these, G. australes, G. scabrosus, and Gambierdiscus sp. type 3 strains exhibited toxicities in mice, whereas Gambierdiscus sp. type 2 strains did not show any toxicity. Therefore, it is important to monitor the cell abundance and dynamics of these species/phylotypes to identify and characterize CFP outbreaks in Japan. Because it is difficult to differentiate these species/phylotypes by observation under a light microscope, development of a rapid and reliable detection and enumeration method is needed.
In this study, a quantitative PCR assay was developed using a TaqMan probe that targets unique SSU rDNA sequences of four Japanese Gambierdiscus species/phylotypes and incorporates normalization with DNA recovery efficiency. First, we constructed standard curves with high linearity (R2 = 1.00) and high amplification efficiency (≥1.98) using linearized plasmids that contained SSU rDNA of the target species/phylotypes. The detection limits for all primer and probe sets were approximately 10 gene copies. Further, the mean number of SSU rDNA copies per cell of each species/phylotype was determined from single cells in culture and from those in environmental samples using the qPCR assay. Next, the number of cells of each species/phylotype in the mixed samples, which were spiked with cultured cells of the four species/phylotypes, was calculated by division of the total number of rDNA copies of each species/phylotype in each sample by the number of rDNA copies per cell. The numbers of cells of each species/phylotype quantified by qPCR assay were similar to the number of cells of each species/phylotype that were spiked. Finally, the cell densities of the target species/phylotypes were quantified using the qPCR assay in 30 environmental samples collected from Japanese coastal areas. Total cell densities of the four Gambierdiscus species/phylotypes quantified by qPCR assay were similar to those of Gambierdiscus spp. quantified by direct counting under a light microscope. The qPCR assay developed in this study is expected to be a powerful new tool for determining detailed distribution patterns and for monitoring the cell abundance and dynamics of each Japanese Gambierdiscus species/phylotype in the coastal areas of Japan.
Tetrodotoxins (TTXs) are a group of potent neurotoxins named after the Tetraodontidae fish family (pufferfish). TTXs have been reported in several animal taxa, both terrestrial and marine. The ingestion of TTX‐contaminated flesh can cause serious neurotoxic symptomatology and can eventually lead to death. Traditionally, TTXs have been associated with Asian countries, in particular with pufferfish consumption. However, they have also been reported in bivalve mollusks farmed in the Pacific area and, recently, in European seas. In Europe, different countries have reported TTXs, especially those bordering the Mediterranean Sea. As a consequence, in 2017 the European Food Safety Authority (EFSA) released an opinion with reference to TTX present in marine gastropods and bivalves, proposing a safety limit of 44 µg/kg TTXs in shellfish meat, below which no adverse effects should be observed in humans. Nevertheless, this limit has been exceeded on many occasions in European shellfish and, while for bivalves there have been no registered human intoxications, that is not the case for marine gastropods. However, TTXs have not yet been included in the list of marine biotoxins officially monitored in live bivalve mollusks within the European Union (EU). Thus, the aims of this manuscript are to discuss the increasing occurrence of TTXs in live bivalve mollusks from European sea waters, to acknowledge the still ongoing knowledge gaps that should be covered and to stimulate constructive debate on the eventuality of adopting a shared regulatory context, at least in the EU, for monitoring and managing this potential threat to food safety.
Ciguatera fish poisoning (CFP) is an illness contracted through the ingestion of seafood containing ciguatoxins. It is prevalent in tropical regions worldwide, including in Australia. Ciguatoxins are produced by some species of Gambierdiscus. Therefore, screening of Gambierdiscus species identification through quantitative PCR (qPCR), along with the determination of species toxicity, can be useful in monitoring potential ciguatera risk in these regions. In Australia, CFP is prevalent in tropical Queensland and increasingly in sub-tropical regions of Australia, but has a report rate of approximately 10%. Yet the identity, distribution and abundance of ciguatoxin producing Gambierdiscus spp. is largely unknown. In this study, we developed a rapid qPCR assay to quantify the presence and abundance of Gambierdiscus lapillus, a likely ciguatoxic species first described from Australia. We assessed the specificity and efficiency of the qPCR assay. The assay was tested on 25 environmental samples from the Heron Island reef in the southern Great Barrier Reef, a ciguatera endemic region, to determine the presence and patchiness of this species across samples from Chnoospora sp., Padina sp. and Sargassum sp. macroalgal hosts.
An expedition to North Meyer Island, Kermadec Islands, in November 2015, resulted in the isolation of two Gambierdiscus species, G. australes and a previously unknown Gambierdiscus species maintained in the Cawthron Institute Culture Collection of Micro-algae as CAWD242. Identifications were based on morphology and DNA sequence data analysis. Nine isolates of G. australes produced maitotoxin-1 (MTX-1) ranging from present (detectable but below the confidence level) to 36.6 pg per cell. One further isolate did not produce MTX-1, but all G. australes isolates produced putative MTX-3. Isolate CAWD242 was negative for MTX-1 but produced MTX-3. Ostreopsis sp. 3 isolated from samples collected during an earlier expedition in 2013 produced low concentrations of palytoxin (PLTX)-like compounds (0.013 pg per cell), but an isolate of the same species from samples collected in 2015 was non-toxic. Other dinoflagellates isolated and identified were Coolia malayensis, Amphidinium carterae and Prorocentrum hoffmannianum.
The dinoflagellate genus Coolia, which contains potentially toxic species, is an important component of epiphytic assemblages in marine ecosystems. The morphology of C. malayensis has been illustrated from strains isolated in Asia and Oceania.In this study, strains of C. malayensis isolated from the CaribbeanSea in Puerto Rico, and for the first time from the South Atlantic Ocean in Brazil, were investigated by light, epifluorescence and scanning electron microscopies. No significant morphological differences between these new strains and other geographically distant strains of C. malayensis were observed. In the LSU rDNA phylogeny, the C. malayensis sequences from Brazil and Puerto Rico branched within the clade of strains from Oceania and Asia. The recently described species C. santacroce branched as a sister group of C. monotis, and C. palmyrensis was basal to the combined group of C. monotis/C. malayensis/C. santacroce. A tentative undescribed species from Florida and New Zealand branched as a sister group of C. malayensis. Our results confirm that C. malayensis showed a cosmopolitan distribution in tropical to subtropical waters, while the type species C. monotis remains endemic for the Mediterranean Sea and the temperate North Atlantic.
Ciguatera fish poisoning is caused by toxins produced by dinoflagellates of the genus Gambierdiscus. This genus has recently been revised and new research on the physiology and ecology of the revised species is needed. While it has been demonstrated that Gambierdiscus spp. are predominately epiphytic, there is also evidence that they are conditional, not obligate, epiphytes and that not all algae hosts are preferred equally by Gambierdiscus populations. This experiment exposed five Caribbean species of Gambierdiscus to living conditions among 8 different species of macroalgal hosts, and their epiphytic behavior (attachment vs. non-attachment) and growth were monitored over 29 days. Additionally, the experiment was carried out under two separate nutrient conditions, ambient versus enriched Florida Keys seawater.
Results demonstrate variable responses in epiphytic behavior within the Gambierdiscus genus to different macroalgal hosts, and stimulation and/or inhibition of Gambierdiscus growth by different macroalgal hosts. Attachment data indicate that Gambierdiscus populations prefer attachment to hosts that have a filamentous structure, but those species did not always support high cell abundances. Certain algal host species appear to stimulate growth of some Gambierdiscus species while others seem to inhibit the growth of other species. Control treatments (no host) reveal that some Gambierdiscus reached higher cell abundances without the presence of any host algae, suggesting inhibition by the hosts. No overall attachment preference was observed among Rhodophytes, Chlorophytes, and Phaeophytes, and no phyla stimulated growth or cell abundance more than the others. There was also no difference in attachment to hosts that were nutrient-enriched versus those that were not. The variability of growth responses and attachment behavior to different hosts by the various Gambierdiscus species in this experiment add complexity to our understanding of the epiphytic nature of Gambierdiscus and the dynamics of blooms.
