MORPHOLOGY AND TAXONOMY OF PROROCENTRUM MEXICANUM AND REINSTATEMENT OF PROROCENTRUM RHATHYMUM (DINOPHYCEAE)¹

Abstract

Dinoflagellates collected during red tide events in Bahia Mazatlan, Mexico during the early spring of 1999 and 2000 appeared under LM to belong to Prorocentrum mexicanum Osorio‐Tafall. Observations with SEM of those populations showed marked differences in shape and microornamentation from the related species, Prorocentrum rhathymum Loeblich III, Sherley and Schmidt. In P. mexicanum, the presence and dimensions of poroids, the uneven distribution of trichocyst pores not located in depressions, and the general architecture of the periflagellar region are more closely related to Prorocentrum caribbaeum Faust. Also, P. mexicanum has a three‐horned (sometimes two‐horned) spine and is deeper in the anterior than the posterior region, whereas P. rhathymum has a simple small spine and its sagittal view is oval. Furthermore, the number and distribution of trichocyst pores in the periflagellar area is different between the two species, being located on both valves in P. mexicanum and only on the right valve in P. rhathymum. To date, true P. mexicanum has been described only from plankton sampling, whereas P. rhathymum was frequently mentioned associated with floating detritus (macroalgae) but also forming red tides. Altogether, the evidence presented demonstrates that P. mexicanum (planktonic) and P. rhathymum (epibenthic) are distinct species and are not synonyms, as is often accepted.

Recent insights about relationships between nutrient availability, forms, and stoichiometry, and the distribution, ecophysiology, and food web effects of pelagic and benthic Prorocentrum species

“…borbonicum (Nakajima et al, 1981;Pearce et al, 2005;Ten-Hage et al, 2002), P. cassubicum (Tindall et al, 1989), P. concavum (Dickey et al, 1990;Zhou and Fritz, 1993;Morton et al, 2002;and see Holmes and Lewis, 2002); P. donghaiense , and references therein), P. emarginatum (Morton et al, 2000), P. faustiae (Morton, 1998), P. hoffmannianum (Aikman et al, 1993;, P. lima (Murakami et al, 1982;Tindall et al, 1984;Torigoe et al, 1988;Bomber and Aikman, 1989;Rhodes and Syhre, 1995;Vale et al, 2009), P. maculosum (Dickey et al, 1990;Zhou andFritz, 1993, 1994a;Hu et al, 1996; note -this species has been repeatedly misidentified as P. concavum), P. mexicanum (Nakajima et al, 1981), P. micans , and references therein), P. minimum (Wikfors and Smolowitz, 1993;Grzebyk et al, 1997;Denardou-Queneherve et al, 1999;Burkholder et al, 2008, and references therein), P. rhathymum (Nakajima et al, 1981;Carlson and Tindall, 1985;Corté s-Altamirano and Sierra-Beltrá n, 2003;Pearce et al, 2005;Caillaud et al, 2010; note: toxicity attributed to P. mexicanum is instead from P. rhathymum, according to Moestrup, 2010), P. sigmoides (Hodgkiss and Ho, 1997;Ueda et al, 1998); P. triestinum , and references therein). b Marine Species Identification Portal, and references therein.…”

Histopathology in Pacific oyster (Crassostrea gigas) spat caused by the dinoflagellate Prorocentrum rhathymum

“…Water samples examined during the following periods of high spat mortality (March 2000 andMarch 2001), revealed that P. rhathymum was blooming on both occasions. This species was initially reported as Prorocentrum mexicanum, but was redefined as P. rhathymum following the redefinition of the two species by Cortés-Altamirano and Sierra-Beltrán (2003). Blooms of P. rhathymum have not previously been reported as causing damage to shellfish.…”

Identification of okadaic acid production in the marine dinoflagellate Prorocentrum rhathymum from Florida Bay

“…After its initial description in 1979 by Loeblich, the P. rhathymum taxonomy was dissolved and reclassified as P. mexicanum (Faust, 1990; Steidinger, 1983). Later the species was reinstated as a unique organism (Cortes-Altamirano, 2003). Our sequence data agrees with the concept that P. mexicanum and P. rhathymum are separate species.…”