AN ANNOTATED CHECKLIST OF DINOFLAGELLATES (DINOPHYCEAE) FROM THE MEXICAN PACIFIC

An annotated checklist of about 605 principally free-living dinoflagellate species and infraspecific taxa from 91 genera reported from the Mexican Pacific is presented on the basis of published literature, some theses, unpublished reports, and original data. Literature references from 1878 to 2005 (in total, 311) are included in the bibliography, and taxonomic notes in regard to some taxa are given, where appropriate. The presence of illustrations divided into three categories (line drawings, light micrographs and scanning electronic micrographs) in the cited works is indicated as well as the known distribution of the taxa in the Mexican Pacific. The nomenclature is brought up to date, and 193 species and infraspecific taxa are accompanied with original comments. Four new combinations are proposed: Histioneis pieltainii (B. F. Osorio) Okolodkov comb. nov., Latifascia subantarctica (Balech) Okolodkov comb. nov., Peridiniella globosa (P. A. Dang.) Okolodkov comb. nov. and Protoperidinium curtipes (Jörg.) Balech f. asymmetricum (Matzen.) Okolodkov comb. nov. Twentynine nomina nuda were revealed. The leading genera are Protoperidinium (111 species), Ceratium (63) Dinophysis (41), Gonyaulax (25), Oxytoxum (22), Gymnodinium (22), Prorocentrum (21), Alexandrium (17) Ornithocercus (12) and Amphidinium (12). To discover the true dinoflagellate species diversity in the Mexican Pacific, more studies on the athecate Gymnodiniales species, benthic and epiphytic dinoflagellates, the ‘‘Diplopsalis group’’, the genus Protoperidinium and recently described genera of the family Podolampadaceae, are needed.


INTRODUCTION
The coastline of the Mexican Pacific extends approximately 8,475 km between 14°30' N and 32°30' N and 92° W and 117° W. This region is influenced by the California Current in its northwestern part, and by the Pacific North Equatorial Current, the Pacific Equatorial Countercurrent and the Coastal Costa Rica Current in the southeastern part, and lies within the limits of the tropical zone in a broad sense. The surface tropical waters have temperatures greater than 25° C and salinity usually less than 34 (Pacheco-Sandoval, 1991). These waters are carried by the Pacific Equatorial Countercurrent, and the northern limit of their distribution approximately corresponds to 15° N. Surface subtropical waters, characterized by a salinity of 35 to 36 and a temperature from 15 to 30° C, can be found only in the Gulf of California (Roden & Groves, 1959). Surface waters of the California Current with a temperature of approximately 20° C and a salinity of 34.6 enter the Mexican Pacific from the north and form a part of the Pacific North Equatorial Current, which is also formed by surface waters of the tropical East Pacific. In June-July, the Coastal Costa Rica Current can reach as far as Cabo Corrientes, Jalisco. In August-December and April-May, it reaches the Gulf of Tehuantepec and then goes offshore. In January-March, the current does not reach the Gulf of Tehuantepec, but goes west directly from Costa Rica, between 9° N and 12° N (Pacheco-Sandoval, 1991).
The first publication referring to the dinoflagellate species reported from the Mexican Pacific is that of Streets (1878). The next one, about dinoflagellates from the states of Oaxaca and Chiapas, with the description of new species, appeared in 1942 . Another article by Osorio-Tafall (1943) contains some dinoflagellates species names from the Sea of Cortes.  analyzed the phytoplankton samples collected during two surveys in the Gulf of California in 1939 and 1940 and identified 24 dinoflagellate species. Graham (1943) described Gymnodinium catenatum from the Gulf of California. Only three works date back to the 1950-1960s Round, 1967). A dozen works, which include dinoflagellate species names, were published in the 1970s. Beginning in the 1980s, regular studies on dinoflagellates have been carried out in the Gulf of California. The history of phytoplankton studies in Mexico in general is described by . Some theses include data that have never been published. On the other hand, many articles contain secondarily published data. In the last few years many abstracts with some new records have been published. In our opinion, there is no discriminative difference between the data published in peer reviewed journals, theses and abstracts; therefore, we considered them all. In total, 311 publications that contain species names of the dinoflagellates found in the Mexican Pacific were analyzed.
The aim of the present study was to unite all the available dinoflagellate data reported from the Mexican Pacific. This type of study, but only for the Gulf of California and the Magdalena-Almejas Lagoon System in Baja California Sur, and without any critical comments, was done by  and Gárate-Lizárraga & Verdugo-Díaz (2001). Especially in view of the growing problem of red tides and the problem of aquatic non-indigenous species in the study area, updated information, based on all the records of dinoflagellates from the Mexican Pacific, is urgently needed.

RESULTS
About 311 publications, abstracts, theses and reports on the phytoplankton, dinoflagellates and toxicity were analyzed. Genera and species within them are ordered alphabetically. Latin names of the taxa are updated, and only the names of the synonyms given in the original publications on the Mexican Pacific are also presented. The nomenclatural and taxonomic synomyms are separated. The works where the species are illustrated are marked with asterisks: an asterisk (*) meaning line drawings, two asterisks (**) meaning light micrographs, and three asterisks indicating (***) scanning electron micrographs. No difference is indicated between the authors' original illustrations and those taken from the works by other authors (usually concerning line drawings). The words ''also as'' before a taxonomic name mean that the taxon was reported under more than one name in the same publication. When the name of the same author is spelled differently in various publications, the spelling is unified. Spanish double surnames are written with a dash regardless of their spelling in the original publications.
The present list does not pretend to be a checklist in a strict sense, and to check identifications of dinoflagellates made by other authors was impossible. Furthermore, the illustrations are comparatively rare. Abbreviations of authors of scientific names are used according to Brummitt & Powell (1992) unless they are not listed in the book. The original comments are given for 194 species and infraspecific taxa. Some names of the taxa were found to be a nomen nudum. Sometimes, specimens were tentatively identified to a species or generic level using the Latin abbreviations aff. or cf., and in this case the taxonomic names are given. The obvious orthographic errors in the names of the taxa are corrected unless there are several of them in one word and the interpretation may be different from ours. Critical comments are given only for several taxa, mainly to clarify their nomenclature or to give our opinion in especially difficult cases. The checklist is not only a compilation, but presents a multi-year work of both authors with the samples taken from coastal waters of all the maritime states of the Mexican Pacific but Sonora in different seasons (in total, we analyzed about 600 samples taken with a water bottle and a net of mesh size 20 to 40 μm).
The  (Fig. 1). For some relatively rare taxa, the original dimensions are given. If the records have not been previously published, they are referred to as ''this study'' after the author's name, and the name of the location within a Mexican maritime state is specified; the Gulf of Tehuantepec is abbreviated as GT in the text ( Fig. 2 and 3). Dinoflagellates recorded from the Mexican Pacific comprise about 605 species and infraspecific taxa, not taking into account the taxa identified to genus. Twenty-nine nomina nuda were revealed.    According to Sournia (1973Sournia ( , 1978Sournia ( , 1982Sournia ( , 1990, some species and infraspecific taxa originally described under the International Code of Zoological Nomenclature given in the checklist lack a Latin diagnosis. Under the current International Code of Botanical Nomenclature (Saint Louis 1999 Code), Chapter IV, Section 2, Article 45.4, ''any of its names need satisfy only the requirements of the pertinent nonbotanical Code for status equivalent to valid publication under the present Code'' (Greuter et al., 2000). Therefore, we considered it superfluous to give Latin diagnoses for these taxa.
Note:  and , mention the name of Protoperidinium orbiculare, which is obviously a mistake for Diplopsalopsis orbicularis (= Peridinium orbiculare) and should be considered a nomen nudum (also see Protoperidinium orbiculare).
Diplopsalopsis ovata (T. H. Abé) J. D. Dodge & Toriumi, 1993: 145, fig. 29, 30. Okolodkov et al., 2003Mich. (El Faro). Note: The only cell observed was 51 μm long and 51 μm wide.  Okolodkov et al., 2003;Gro. (Zihuatanejo). Note: The only examined cell was 76 μm long and 55 μm wide. The species has been previously reported from the tropical Pacific (Schiller, 1937). Note: Because the name of Erythropsis Hertwig is a later homonym of Erythropsis Lindl. (Sterculiaceae), it was replaced with Erythropsidinium P. C. Silva (Silva, 1960;Sournia, 1973). Note: One should take into account that the designation of the apical plates in the description of the type species Fragilidium heterolobum Balech (Balech, 1959a) is different from that used by Balech (1988b) in the description of F. mexicanum. The plates 2', 3', 4' and 1' in the former correspond to 1', 2', 3' and 4' in the latter, respectively. Moreover, some errors in the designation of thecal plates in the key for identification of Fragilidium Balech ex A. R. Loebl. species (Balech, 1988b: 484) did not permit us to make a more detailed comparison of these two morphologically similar species.  Okolodkov et al., 2003;Gro. (Zihuatanejo). Note: Our identification of this taxon is preliminary. The only examined cell, 59 μm long, 58 μm wide and 45 μm deep, had a higher hypotheca with more concave sides than in Gaarder (1954). Furthermore, the cingulum had a more pronounced displacement of one cingular width. While Gaarder pictured the cell having the 1' plate not contacting the cingulum and located on the left side of the epitheca, our specimen had the 1' plate of the ortho-type contacting both the cingulum and the pore plate, characteristic of such genera as Protoperidinium Bergh and Alexandrium Halim, which makes our identification preliminary even at the generic level. However, we disagree with Balech (1967Balech ( , 1985, who placed G. concavum first into the genus Gonyaulax and then into Alexandrium Halim. Although the connection of the 1' plate and the pore plate in some Alexandrium species (e.g., A. minutum and A. kutnerae (Balech) Balech) is optional, the difference in the shape and connection of the 1' plate between G. concavum and A. concavum seems to us to be too big to consider them synonymous. Another discriminative feature that we consider important is the position of the cingulum, anterior in G. concavum and equatorial in A. concavum (only in Balech, 1967: pl. 6, fig. 108). The latter is characterized by a slightly anterior position of the left part of the cingulum. Note: The only cell studied was 56.5 μm long and 58.5 μm wide.
Note: The only specimen found in Oaxaca was 69 μm long and 59 μm wide.
Protoperidinium achromaticum (Levander) Balech, 1974: 56. González-López, 1994GC. Note: Balech (1976) who described a new species, Protoperidinium finitimum, believes that it was previously referred to as Peridinium achromaticum or Protoperidinium achromaticum. The aspect of P. finitimum and Peridinium achromaticum is very much alike but their cingular and sulcal plates greatly differ. The species also differ in ecology: real P. achromaticum has been found in fresh and brackish waters whereas Protoperidinium finitimum is a marine species. If the identification of the species found in the MP was correct, most likely it is P. finitimum.
Note: The studied cells were 35-43 μm long (43-56.5 μm with spines) and 27.5-30 μm wide. Although originally Balech (1971a) described Protoperidinium cassum and P. decens as two different species, later he amalgamated them into P. cassum (Balech, 1988a). In fact, the differences between the two varieties of this species are subtle, and Balech (1971a) himself presents drawings of P. cassum var. decens that look intermediate in terms of cell shape between P. cassum var. cassum and var. decens in his later work (Balech, 1988a).