Saxitoxin Poisoning in Green Turtles (Chelonia mydas) Linked to Scavenging on Mass Mortality of Caribbean Sharpnose Puffer Fish (Canthigaster rostrata-Tetraodontidae)

Abstract

Fish within the family Tetraodontidae are potential sources of both endogenous tetrodotoxins (TTXs) and dietary derived saxitoxins (STXs). Ingestion of fish tissues containing these toxins by other vertebrates can lead to severe illness and death. The Caribbean sharpnose puffer (Canthigaster rostrata) is a widespread tetraodontid species within the western Atlantic. Mass settlement of juveniles into foraging habitats have been associated with large-scale puffer fish mortality events. In 2013, 2014, and 2017, puffer mortality events on the southern Caribbean coast of Costa Rica were also associated with strandings of green turtles (Chelonia mydas) found to have fed on C. rostrata. Stranded sea turtles were found dead without apparent cause or alive with severe neurological signs that resolved during short periods of captivity. Puffer fish and turtle organ samples were analyzed for both TTXs and STXs. Concentrations of TTXs were extremely low in the fish (0.5-0.7 µg/g) and undetectable in turtle stomach contents. However, concentrations of STXs in whole fish (16.6-47.5 µg STX-eq/g) exceeded the 0.8 µg STX-eq/g human seafood safety threshold for STXs by orders of magnitude. Saxitoxins were also detected in samples of stomach contents (ingested fish), brain, lung, kidney, and serum from three affected turtles. Study results indicate that saxitoxicosis resulting from opportunistic foraging on C. rostrata during fish mortality events may be a significant factor in episodic stranding of green sea turtles in this region.

Co-Occurrence of Tetrodotoxin and Saxitoxins and Their Intra-Body Distribution in the Pufferfish Canthigaster valentini

“…The STXs harbored by C. valentini comprise neoSTX as the main component, and dcSTX and STX as the minor components. STXs harbored by pufferfish usually comprise STX as a main component, and neoSTX as a minor component [ 10 , 11 , 13 , 16 , 17 , 18 , 19 , 20 , 24 ]. Because STX is the main STX in the intestine, which absorbs the toxin into the body, and in the liver, which is the initial transfer site of the absorbed toxin [ 7 , 46 , 47 ], it may be that the conversion of STX to neoSTX or selective uptake of neoSTX into the skin and ovary takes place inside the body of C. valentini .…”

“…Nakatani et al [ 23 ] investigated the toxin profile of a pufferfish of the same genus, Canthigaster rivulata , using two individuals of an unknown sex, and detected a trace amount of STXs in addition to the major toxin TTX in the skin. On the other hand, Barrientos et al [ 24 ] detected STXs, mainly comprising STX, with a tiny amount of TTX in Canthicaster rostrata , but the distribution of the toxins inside the body is unknown. In the present study, to clarify the distribution profile of TTX and STXs in pufferfish of the family Tetraodontidae, we investigated the composition and intra-body distribution of toxins in C. valentini .…”

Rediscovering Kemp’s Ridley Sea Turtle (Lepidochelys kempii): Molecular Analysis and Threats

“…Sea turtles are affected by marine biotoxins present in the water column, in aerosols generated by waves, or through the consumption of contaminated prey [25]. In recent years, the impacts of these phenomena have caused or contributed to sea turtle mass mortality events in C. mydas, C. caretta, L. olivacea and L. kempii [26].…”

Integrating In Vitro Data and Physiologically Based Kinetic Modeling to Predict and Compare Acute Neurotoxic Doses of Saxitoxin in Rats, Mice, and Humans

“…Saxitoxin (STX) is a naturally occurring tetrahydropurine phycotoxin (Figure ) produced mainly by marine dinoflagellates and some freshwater cyanobacteria, acting as a selective blocker to voltage-gated sodium channels on excitable membranes. , Nearly 60 structural analogues of STX have been found so far, which together are referred to as STX-group toxins . Bivalve mollusks ingest STX-producing organisms via filter-feeding, which results in STX bioaccumulation and transfer through the food web, potentially causing neurotoxicity in marine wildlife and humans . Documented human poisonings have notably increased since 1941 .…”