A comprehensive study of the Hong Kong puffer fishes and their toxins

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A comprehensive study of the Hong Kong puffer fishes and their toxins

 

Author: Yu, Chun-fai
Title: A comprehensive study of the Hong Kong puffer fishes and their toxins
Degree: Ph.D.
Year: 2003
Subject: Hong Kong Polytechnic University -- Dissertations
Poisonous fishes -- Toxicology -- China -- Hong Kong
Department: Dept. of Applied Biology and Chemical Technology
Pages: xxiv, 248 p. : ill. (some col.) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1719340
URI: http://theses.lib.polyu.edu.hk/handle/200/3779
Abstract: Puffer fishes are commonly found in Hong Kong waters. Puffer fish poisoning (PEP or tetrodotoxication) results from the ingestion of the flesh or viscera of certain species of fish belonging to the order Tetraodontiformes. The principal toxin involved, which was first named as tetrodotoxin (TTX) by Tahara in 1909, was originally discovered and isolated from puffer fish. In this study, a total of ten species of puffer fishes, belonging to 2 families and 5 genera, were collected and identified along the Hong Kong coastal waters. Among the ten local species, four species were confirmed to be toxic [10-1120 mouse units (MU)/g] and one species is non-toxic by the standard mouse bioassay. The annual toxicological profiles of two local common puffer fishes, Takifugu niphobles (Jordan and Snyder) and Takifugu alboplumbeus (Richardson), were investigated continuously for 14 months. Their annual spawning seasons were found to be from October to February and December to February respectively. The toxicities of their different tissues were determined, in which the ovaries and livers were moderately toxic (100-1000 MU/g) in their non-spawning seasons. The intestines and skin were weakly toxic (between 10-100 MU/g), their flesh, however, was basically non-toxic (less than 10 MU/g) throughout the whole year. The testes, which developed only in their spawning seasons, were also non-toxic. Contrary to the most common belief, both species were discovered to be relatively less toxic during their spawning seasons. TTX has long been believed to be exclusively originated from the puffer fish since ancient times. However, the subsequent findings of the highly variable of toxicities among puffer fishes as well as the wide distribution of TTX in a variety of invertebrates and vertebrates support the proposition that the origin of TTX comes from a universal organism such as a microbe. Later on, researchers discovered that some bacteria, named as TTX-producing bacteria, isolated from the intestines of puffer fish and some TTX-bearing organisms were capable of producing TTX. However, the amount of TTX production by the bacteria is very minimal and the optimal culture conditions for maximum toxin yield still remain unknown. With the progressively worsening problems of water pollution and over-fishing, Hong Kong's seafood resources have dropped drastically over the decades. Although the global fishing industry is now shrinking, the puffer fish are in fact precious resource both in China and Japan. However, puffer fishes are banned from marketing in Hong Kong due to their toxicities. This study shows that, using the right food processing and storage methods, local consumers can actually enjoy the local puffer fish as safely as in Japan. In order to fully utilize the local marine resources in Hong Kong, the puffer fish should be a good candidate for mariculture in the near future. Apart from processing their flesh for human consumption, the viscera of puffer fish can be explored to produce the valuable TTX (a neurotoxin mainly found in puffer fishes), which is a potential anaesthetic, a promising neuropathic pain drug, a proposed formulation to treat heroin addiction and a known cancer cell suppressor.

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