Genetic diversity of Gambierdiscus spp. (Gonyaulacales, Dinophyceae) in Japanese coastal areas

Abstract

The genetic diversity of the ciguatera fish poisoningrelated dinoflagellate distributed in Japanese coastal areas was investigated. The entire sequence of the 5.8S rRNA gene and two internal transcribed (ITS) regions were determined, which included putative pseudogenes, from 19 strains of dinoflagellates assigned to the genus Gambierdiscus Adachi et Fukuyo collected from Japanese subtropical and temperate coastal areas. The sequences obtained from the 19 strains were divided into two types based on sequence similarity. Here we designate the two types as type 1 and type 2. For the relationship between the genotypes and origins of the strains used, the strains collected from subtropical areas possessed the type 1 sequence; whereas those from temperate areas possessed the type 2. This observation led us to question former reputations that Gambierdiscus cells observed in Japanese temperate areas are immigrants from Japanese subtropical areas. Subsequently, we sequenced a part of the 18S rRNA gene from two strains from subtropical areas and two from temperate areas. Unfortunately, phylogenetic analysis including the sequences obtained from various gonyaulacales dinoflagellates failed to determine the species phylogenetically closely related to and possible origin(s) of the Gambierdiscus sp. from the Japanese coastal areas.

Genetic Diversity and Distribution of the Ciguatera-Causing Dinoflagellate Gambierdiscus spp. (Dinophyceae) in Coastal Areas of Japan

“…Type 2, in the SSU rDNA tree (Fig. 1), was solely comprised of Japanese strains including 14 strains established in the present study (blue letters) and two strains (black letters) by Kuno et al [22].…”

“…type 1 from the subtropical and Gambierdiscus sp. type 2 from the temperate areas [22]. Recently in 2011, Fraga et al [15] described G. excentricus by morphological and phylogenic analyses of the LSU rDNA D1–D3 and the LSU rDNA D8–D10.…”

“…Japanese coasts have also been investigated over the past few decades and revealed that Gambierdiscus spp. distribute widely from subtropical to temperate areas [11], [22], [34], [35], [36], [37], [38]. Additionally, in previous studies in Japan, ‘ G. toxicus ’ has been found from the temperate to subtropical areas in Japanese coasts based on morphologically observations [11], [34], [35], [36], [37].…”

Gambierdiscus and Ostreopsis: Reassessment of the state of knowledge of their taxonomy, geography, ecophysiology, and toxicology

“…Two genetically distinct Gambierdiscus populations, possibly with different origins, have been isolated indicating that multiple species might be present (Kuno et al, 2010). Gambierdiscus has also been reported in the Philippines (Gillespie, 1987), Hong Kong (Lu and Hodgkiss, 2004), and Vietnam , although the species diversity at these locales remains unknown at this time.…”

“…Litaker et al (2009) did present distinguishing morphological features, however, thereby providing concordance between morphologic and genetic differences. Kuno et al (2010) isolated 19 new strains of Gambierdiscus from the coastal waters of Japan and found that the strains fell into two geographic groups (Type 1-subtropical; Type 2-temperate) based on 5.8S rRNA sequences and ITS2 base pair length. Litaker et al (2010) conducted a global survey of Gambierdiscus using a phylogenetic analysis based on the results of Litaker et al (2009), also demonstrating a wide geographic range for some species, but not for others (discussed in more detail in the Geography section of this review).…”