Morphology of the marine, planktonic, thecate dinoflagellate Gonyaulax areolata (Dinophyceae), a species causing red tides in the tropical Mexican Pacific

ABSTRACT

Blooms of marine planktonic dinoflagellates are usual along the Pacific coast of Mexico, sometimes producing toxic red tides. The thecate dinoflagellate Gonyaulax areolata was found to produce a red tide event in the tropical Mexican Pacific. The species was originally described in 1911 by Kofoid and Michener without an illustration. The morphology of G. areolata was studied here by LM and SEM. Photosynthetic, solitary cells were fairly small, polyhedral, with a short apical protrusion and ‘shoulders’ on the epitheca, and two short, asymmetrical antapical spines. The cingulum was approximately median, cavozone, with the ends fairly displaced but with no, or only slight, overhang. The thecae were strongly ornamented with striae, areolae and pores. The plate formula was Po, 4ʹ, Q, 6ʹʹ, 6c, 4s, 6ʹʹʹ, 1p, 1ʹʹʹʹ, as recently attributed to some species of Gonyaulax. Details of important plates are given. Gonyaulax areolata seems to be morphologically closely related to other small species with a slight cingulum displacement and overhang, such as G. minima and G. striata, and more distantly related to G. spinifera. The maximum concentration of G. areolata was 1.74 × 10⁶ cells l^–1, in association with lower numbers of other dinoflagellates and diatoms. Yessotoxins were not detected. Oceanographic conditions during the bloom indicated moderate to weak upwelling, confirmed by both relatively low surface temperature and high Chl a concentration (14 µg l^–1).

KEYWORDS:

• Algal blooms
• Gonyaulacaceae
• Light and scanning electron microscopy
• Phytoplankton
• Yessotoxins

ACKNOWLEDGEMENTS

We thank Prof. Dr. Allan Cembella (AWI, Germany) for the analysis of a fixed sample of the red tide to determine the possible presence of yessotoxins. We are deeply grateful to Helena Hernández-Tapia who prepared Fig. 28. Many thanks to Dr. Nataly Quiroz-González (Fac. Ciencias, UNAM) for the intensive attempts to get molecular sequences from fixed samples.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

Additional information

Funding

Partial support for this study was provided by PAPIIT, DGAPA, UNAM [projects IN226209-3 and IN296516]. Coordinación de la InvestigaciónCientífica (CIC), Universidad Nacional Autónoma de México (UNAM) approved and supported the use of the R/V ‘El Puma’ (oceanographic cruise ‘MareaR IV’, 10–22 April 2012). The coauthor (G. V.-J.) received a fellowship from CONACYT for a M. Sc. degree.