Abstract
The marine benthic dinoflagellate genus Gambierdiscus currently contains ~ 16 species that can be highly morphologically similar to one another, and therefore molecular genetic characterization is necessary to complement the morphological species determination. Gambierdiscus species can produce ciguatoxins, which can accumulate through the food chain and cause ciguatera fish poisoning. Recent studies have suggested that Gambierdiscus excentricus may be one of the main species responsible for ciguatoxin production in the temperate and tropical regions of the eastern Atlantic. The present study definitively identifies the species, G. excentricus, from Madeira Island, Northeast-Atlantic Ocean (32° 38′ N 16° 56′ W) by examining the morphology of a strain using light and scanning electron microscopy and sequencing regions of the ribosomal DNA (D8-D10 LSU, SSU rDNA). Variability in the shape of the apical pore and the microarchitecture of the apical pore plate were documented for the first time, as well as variability in the width of the second antapical plate. The first SSU rDNA sequence for the species is reported. Because G. excentricus is known to produce high levels of CTX-like compounds, its presence and toxicity should be regularly monitored to establish whether it is the primary cause of the ciguatera poisoning events on Madeira Island.
Highlights
The marine benthic dinoflagellate genus Gambierdiscus was discovered in the late 1970s (Yasumoto et al, 1977) and described with G. toxicus R.Adachi & Y.Fukuyo as the type species (Adachi & Fukuyo, 1979)
Macroalgae (Halopteris and Padina) was sampled on March 21 2014 by SCUBA-diving collecting several individual thalli carefully within a plastic bag with surrounding seawater at a depth of about 6–7 m in Cais do Carvão Bay, Funchal, south coast of Madeira (32° 38.170′N 16° 56.110′W, Fig. 1). This small bay is characterized by a gentle slope with rocky substrate, i.e. basaltic rocks covered with sessile biota of mainly brown and some red macroalgae species, sponges, sea anemones, sea urchins and sea cucumbers
The south coast of Madeira Island is protected from the prevailing NE-Trade winds, so the wave action is rather low with prevailing westerly waves of less than 2 m significant height and mean sea surface temperatures ranging from 18 °C (February/March) to 23–24 °C (August/ September)
Summary
The marine benthic dinoflagellate genus Gambierdiscus was discovered in the late 1970s (Yasumoto et al, 1977) and described with G. toxicus R.Adachi & Y.Fukuyo as the type species (Adachi & Fukuyo, 1979). ~ 16 species of Gambierdiscus have been described, based on their distinct morphological and genetic characteristics (Adachi & Fukuyo, 1979; Chinain et al, 1999; Faust, 1995; Fraga et al, 2011; Litaker et al, 2009; Litaker et al, 2010; Nishimura et al, 2014; Fraga & Rodriguez, 2014; Fraga et al, 2016; Smith et al, 2016; Kretzschmar et al, 2017; Rhodes et al, 2017). Gambierdiscus excentricus S.Fraga was described as a new species in 2011 from Tenerife, Canary Islands (Spain) and was recorded from La Gomera and La. Hoppenrath et al Marine Biodiversity Records (2019) 12:16. The profile of CTX toxins of G. excentricus has not been confirmed with LC-MS/MS
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