The genus Pseudo-nitzschia (Bacillariophyceae) in Malaysia, including new records and a key to species inferred from morphology-based phylogeny

Abstract

Species of the diatom Pseudo-nitzschia are known to produce domoic acid that is responsible for amnesic shellfish poisoning (ASP). To investigate the potential risk of ASP and species occurrence of toxic or potentially toxic Pseudo-nitzschia in Malaysian waters, plankton samples were collected from 17 locations. Samples were examined through transmission electron microscopy. Species of Pseudo-nitzschia were identified on the basis of the frustule morphology and morphometric measurements. Twentytwo well-described species were recorded, of which 14 are new records for Malaysia. A new morphotype, closely resembling species in the pseudodelicatissima complex, was also discovered. The morphotype differs from other species in the complex by its lower densities of fibulae and striae. Nine of the species have previously been associated with ASP events worldwide. Our study recorded for the first time high species richness of Pseudo-nitzschia in the confined coasts of Malaysia. In addition, we performed a morphology-based phylogeny and proposed a key to Pseudo-nitzschia species, with a special emphasis on the poroid structure of the striae, to aid in species identification.

Pseudo-nitzschia species (Bacillariophyceae) identification and delineation using mitochondrial cox1 gene sequences as compared to LSU rDNA

“…Screening of ASP-toxin production among the cultured strains of P. pungens (Grunow ex Cleve) Hasle showed undetectable levels of DA [4], even though the species is commonly found in Malaysian waters [5,6]. High species diversity of Pseudo-nitzschia species in Malaysian coastal waters was reported by Teng et al [5], with more than 23 species documented.…”

Pseudo-nitzschia fukuyoi (Bacillariophyceae), a domoic acid-producing species from Nha Phu Bay, Khanh Hoa Province, Vietnam

“…Cell pellets were acid-washed using 37 % HCl [12], KMnO 4 and 10 % oxalic acid [4] to remove the organic material. Cleaned cells were mounted on a Formvar-coated copper grid and dried at 70 °C overnight.…”

“…TEM micrographs were taken with an Erlangshen ES500 W camera and morphometrics were obtained using Digital Micrograph software (Gatan, Pleasanton, CA, USA). Detailed morphological characters were compared with those in previous studies [2][3][4]13].…”

Harmful Microalgae Assemblage in the Aquaculture Area of Aman Island, Northen Strait of Malacca

“…In Malaysia, no incidence of ASP has yet been reported, however Pseudo-nitzschia spp. has been shown to be widely distributed in Malaysian waters [31,32,33], and a toxic species, P. kodamae has been reported [27].…”