New data on the distribution of Torodinium robustum and T. teredo (Dinophyceae: Gymnodiniales) in the Gulf of California

The gymnodinioid marine dinoflagellates Torodinium robustum and T. teredo are reported for the Gulf of California. This is the first record of Torodinium teredo on the Pacific coast of Mexico. Both species were found mainly during the winter-spring in seawater at 19–27.5 °C. Torodinium robustum was the most frequent species. Morphological features of T. robustum and T. teredo varied widely and specimens observed in live samples and fixed in Lugol’s solution were easily recognizable. Short description and microphotographs were provided for each species.

New data on the distribution of Torodinium robustum and T. teredo (Dinophyceae: Gymnodiniales) in the Gulf of California sampling stations ( Figure 5). Geographic coordinates for each sampling station are shown in Table 1. From January 2009 to April 2012, 42 collections of phytoplankton were taken at the first sampling station ( Figure 5). Surface and vertical (15 m depth) phytoplankton tows were collected with a 50 cm diameter 20 µm mesh net. Each net tow was immediately preserved with acid Lugol's solution (5% final concentration). Subsamples were taken for observations of live phytoplankton. From February through December 2010, 19 vertical net hauls were monthly taken from 60 m depth at the second sampling station in the northern part of Bahía de La Paz. In July 2010 at Los Cabos, 4 vertical net hauls were conducted from 15 m depth to (4) Torodinium teredo. Abbreviations: epi., epicone; (gir., girdle or cingulum; hyp., hypocone; long fl., longitudinal flagellum; n., nucleus; pus., pusule; rod., rodlets or rhabdosomes; sulc., sulcus; tr. fl., transverse flagellum. the surface at Stations 3, 4, 5 and 6 ( Figure 5). Cell counts were made in 5 mL settling chambers under a Carl Zeiss inverted microscope (Hasle 1978). Both live and fixed net phytoplankton samples were analyzed by phase contrast microscopy. Sea surface temperature (SST) was recorded with a bucket thermometer. Images were recorded (SONY Cyber-shot camera, 8.1 MP) under a Carl Zeiss inverted microscope. Two Torodinium species were identified in the samples collected monthly from Bahía de La Paz from January 2009 to April 2012 and in samples of July 2010 collected at Los Cabos. Specimens of both species fit well with the diagnosis and descriptions of Kofoid and Swezy (1921). All samples containing Torodinium species were listed in Table 1. A total of 167 specimens of T. robustum were observed only in net phytoplankton hauls at the three sampling sites in this study (Table 1). Therefore, no quantitative data are presented, however, densities from 1000 to 45000 cells L -1 were reported during a multi-species red tide event (Gárate-Lizárraga et al. 2009). This species occurred in seawater with temperature of 19.0-27.5 °C. T. robustum cells have an elongated body with a very small hypocone, reduced to a conical structure ( Figure 2). Cell length is less than 3.5 greatest transdiameters, the sulcus has a reversed terminal apical loop, and the girdle forms a lefthanded spiral (Figures 6-11). Cells are about 60-75 µm (69.63±2.95 μm) long and 20-37.5 µm (28±3.81 μm) wide (n = 30). In Figure 9 the T. robustum is 60 µm long and 37.5 µm wide. The nucleus is an elongated rod with rounded end located centrally. A very long and small pusule extended to nearly the same point as the nucleus. Many greenish to brown chloroplasts, arranged into longitudinal rows, are present ( Figures 6-11).
Torodinium robustum is a planktonic species which has been found at Burnham (Essex) and Plymouth in the United Kingdom. It has been reported in the North Sea, Mediterranean Sea, and the Pacific (Kofoid and Swezy 1921;Lebour 1925;Trégouboff and Rose 1957). Some specimens from NW Africa are related with upwellings (Elbrächter 1979). More recently, T. robustum has been reported at La Jolla, California (Kimor and Reid 1989), in Japan (Yoshimatsu 1990), in the Helgoland and Sylt islands in the North Sea (Hoppenrath et al. 2009), andin Kuwait (Al-Kandari et al. 2009).
A total of 93 specimens of T. teredo were indentified only in net phytoplankton hauls at sampling station 1 (Table 1). This species occurred in seawater with temperature of 19.0-24.5°C. T. teredo cells have a very elongated body (Figures 12-14). Cell length is more than 4 transdiameters; there is no loop in the terminal part of the sulcus. The epicone is very long and the hypocone is reduced to a conical structure. The sulcus arises near the apex of the cell with a loop nearly completely around the cell and then curves to meet the girdle. The nucleus is elongated and located along the centre of the cell. Cells are about 100-115 µm (108.67±4.40 μm) long and 20-27.5 µm (24.43±2.04 μm) wide (n = 30). Gómez (2009) found that T. teredo specimens had an elongated protuberance, a peduncle that protrudes from the sulcal-cingular region. This peduncle was not observed in live or fixed cells in our samples.
Torodinium teredo is a planktonic species, apparently widely distributed in temperate and tropical waters; it has been reported from several locations in the North Sea, English Channel, Mediterranean Sea, Pacific Ocean, and Gulf of Mexico (Kofoid and Swezy 1921;Lebour 1925, Trégouboff andRose 1957;Steidinger et al. 1967). In northwestern Africa T. teredo is related with water upwelling (Elbrächter 1979) and recently it was reported in several regions of the open Pacific Ocean: Oyashio and Kuroshio currents of East Asia, The Philippines, Celebes, Sulu, South China Sea, western and central equatorial Pacific, subtropical Pacific in the vicinity of the Marquesas Archipelago, in the South Pacific Gyre, and in the Perú-Chile Current (Gómez 2009) and the European Arctic (Okolodkov 2011). Torodinium teredo is now reported for the first time in the Gulf of California in Pacific waters of Mexico.
Torodinium teredo and T. robustum occur together in the North Sea, Mediterranean Sea and Gulf of California (Lebour 1925;Trégouboff and Rose 1957;this study). The species were easily recognized in live samples as well as samples fixed in Lugol's solution. T. teredo is easily distinguished from T. robustum because its length is more than four transdiameters, no loop is observed in the terminal part of the sulcus, the larger size, and the green pigmentation (Pouchet 1885;Kofoid and Swezy 1921;Steidinger and Tangen 1997;this study). Despite the morphological characteristics to distinguish both species, their ultrastructural morphology and DNA sequences should be examined more carefully once they could possibly increase the distinction between the species.  (6) T. robustum (21) T. teredo (2) 23.5 1 17/02/11 T. teredo (5) T. robustum (7) T. robustum (8) T. teredo (14)