Contents lists available at ScienceDirect Toxicon journal homepage: www.elsevier.com/locate/toxicon Toxicity of crude organic extracts from the zoanthid Palythoa caribaeorum:A biogeography approach Reia Guppy * , Christopher Ackbarali, Damien Ibrahim Centre for Maritime and Ocean Studies, Marine Sciences, The University of Trinidad and Tobago, Chaguaramas, Trinidad and Tobago ARTICLE INFO Keywords: Palythoa caribaeorum Zoanthid Toxicity test Organic extracts Palytoxin ABSTRACT Marine isolates such as palytoxin (PTX) are of concern within the Caribbean region due to their toxicity. PTX for example has been described as a one of the most known potent marine toxins, known to prevent predation from larger species (e.g. vertebrates) as well as the prevention of being overgrown from other coral species. PTX is a polyhydroxylated polyether toxin with a very large and complex chemical structure that possesses both hy- drophilic and lipophilic properties. Previous acute toxicity tests using brine shrimp (Artemia salina) and PTX extract had shown it to be moderately toxic. In humans, PTX has been credited to be responsible for extreme symptoms such anaphylactic shock, rapid cardiac failure and eventual death occurring within minutes. Extrapolation for human dose ranges has therefore been suggested to be between 2.3 and 31.5 μg. This study isolates a potentially PTX-enriched extract from Palythoa caribaeorum and examines its organic extract toxicity from a biogeography perspective from a within-colony to a variety of reef sites around Trinidad and Tobago that are popular for marine visitors. This research represents an acute study with a high level of crude organic extract toxicity on A. salina whilst postulating potential factors which may contribute to its extreme toxicity and the risk posed to users of these environments. 1. Introduction Marine toxins are of interest to the field of biotechnology and marine natural products (Fusetani, 2010), their role in harmful algal blooms (HABs) (e.g. Olsen et al., 1984), and intra- and inter-specific interactions. Palytoxin or PTX has been described as a one of the most known if not the most potent marine toxin (Aratake et al., 2016). It is a large, complex molecule with over 60 chirality centers with more than 10 21 stereoisomers (Patocka et al., 2015), and is generally described as a polyhydroxylated polyether possessing both hydrophilic and lipo- philic properties with a molecular weight of 2680 Da (Del Favero et al., 2013). As such, PTX is considered as a super carbon chain compound, and is resistant to heat (Patocka et al., 2015), making it a stable com- pound. More information on its chemical structure and congeners are found in Patocka et al. (2018) and Klijnstra and Gerssen (2018). PTX was originally isolated from the zoanthid genus Palythoa more than 50 years ago (Wu, 2009), and since then PTX and its analogues have been found in algae, dinoflagellates, a wide variety of marine invertebrates and even fish (Aligizaki et al., 2011; Birè et al., 2013; Gleibs and Mebs, 1999; Wu, 2009). It remains uncertain if PTX is naturally occurring in such a wide taxonomic range or if this is the result of bioaccumulation up the food web (Aratake et al., 2016). However, its potency continues to be a concern in the consumption of seafood and human health (Patocka et al., 2015; Riobó and Franco, 2011). Based on acute toxicity tests with brine shrimp (Artemia salina), PTX had a lethal concentration (LC 50 ) between 80 and 250 μg/ml (Melo et al., 2012). According to Dolabela (1997), this would be characterized as moderately toxic. Studies have suggested that human lethal doses using extrapolations may have an LD 50 of 2.3–31.5 μg(Uemura, 1991), with toxicity routes in humans known to occur via administration orally, inhalation and skin contact (Munday, 2011). In fact, 30 mg/kg has been recommended as an upper limit of consumption in shellfish by the European Food Safety Authority (EFSA, 2009). Interestingly, wide PTX concentration ranges (12–945 ng/g) have been recorded within Palythoa tuberculosa (Aratake et al., 2016). Al- though the factors contributing to such wide variation remain un- known, its pharmacological effect is very clear. PTX affects the Na + /K + pump mechanism, specifically the Na + /K + -ATPase, across animal cell membranes (Artigas and Gadsby, 2004; Frelin and Van Renterghem, 1995; Rossini and Bigiani, 2011). This creates a PTX-induced cation channel (Brovedani et al., 2016; Harmel and Apell, 2006; Rodrigues https://doi.org/10.1016/j.toxicon.2019.06.020 Received 22 January 2019; Received in revised form 6 June 2019; Accepted 14 June 2019 * Corresponding author. Centre for Maritime and Ocean Studies, Marine Sciences, The University of Trinidad and Tobago, 2nd Avenue N., Western Main Road, Chaguaramas, Trinidad and Tobago. E-mail address: Reia.Guppy@utt.edu.tt (R. Guppy). Toxicon 167 (2019) 117–122 Available online 15 June 2019 0041-0101/ © 2019 Elsevier Ltd. All rights reserved. T