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Objectives: To investigate the effects of temperature and hot water immersion time on neutralising venom lethality of the Australian estuarine stonefish (Synanceia horrida)., Design: Depths of the spines were measured while venom was extracted from S. horrida individuals. The venom was then exposed to temperatures of 4°C, 37.0°C, 40.1°C, 42.3°C, 45.0°C, 47.7°C, 55.2°C, and 60.0°C for either five or 20 minutes incubation periods. Venom samples were added to cultured human cardiomyocytes and cell viability curves were produced using the ACEA's xCELLigence real-time cell monitoring system., Main Outcome Measures: Determination of venom lethality on cardiomyocytes at a range of temperatures., Results: The average depth of the spine required to go into a victims' flesh before the venom gland compressed and expelled venom was 18 mm. Cardiomyocytes exposed to heat-treated venom for five minutes required higher temperatures to neutralise 99% of the venom, namely 44.6°C in comparison to 42.1°C with an incubation time of 20 minutes., Conclusion: This study supports the use of hot water immersion therapy in the treatment of S. horrida stings. It is suggested that due to the depth of the puncture wound longer incubation times should be sought to allow heat to penetrate the deeper portions of the dermis and effectively begin venom deactivation.

Ultrastructures of late-stage spermatids and spermatozoa, and of spermatozoa after exposure to various osmolalities, were studied in the puffer, Takifugu niphobles. The mature spermatozoa consisted of a head, a midpiece of many mitochondria and a flagellum with sharp sidefins, had many ring-structures just inside of the plasma membrane of cytoplasmic sleeve and triangular-structures projecting into cytoplasmic canal at the base of flagellum. In late spermatids, the rings and projections were present, but the side-fins had round ends and the cytoplasm of flagellum was amorphous. When spermatozoa were exposed to seawater, the plasma membrane became swollen in the head-midpiece region but shrank in the tail region. In 1/2 seawater, swelling in the tail occurred in some spermatozoa. In 1/3 seawater approximately isotonic to the seminal plasma, there was little change. In 1/10 seawater, the plasma membrane swelled slightly in the head region, but swelled much more in the tail region. In buffer solution, the membrane swelled in all regions, surrounding the nucleus and many sections of axoneme. Thus, function of the plasma membrane in the head-region may be different from that in the tail-region. Spermatozoa of marine fish may fertilize the eggs when the osmolality surrounding the sperm, which changes due to the mixing of seminal plasma and seawater, reaches the correct level for the spermatozoa to obtain correct structure.

Little is known about the spinal sympathetic organization in teleosts. We examined the location of the sympathetic preganglionic neurons with horseradish peroxidase (HRP) labeling. After HRP application to the sympathetic trunk or celiac ganglion, labeled neurons were found just dorsal - dorsolateral to the central canal. They form a cell column (central autonomic nucleus) at the level of the posterior rootlet of the first spinal nerve to the third spinal nerve. HRP application to the sympathetic trunk produced labeling in almost the entire central autonomic nucleus, but HRP application to the celiac ganglion produced labeling in only the rostral half of the central autonomic nucleus. These results suggest that there is some topographical arrangement in the rostrocaudal part of the central autonomic nucleus. On the other hand, the fact that the sympathetic preganglionic neurons are within a single cell column and have no mediolateral segregation means that the target-related or function-associated mediolateral arrangement found in tetrapods is lacking in this species. We also found some labeling in the central autonomic nucleus after HRP application to the cranial nerves. This may indicate that the preganglionic neurons project to the cranial nerves.

The supramedullary cells (SMCs) of teleosts have been studied for nearly 100 years, but their peripheral connections have remained obscure. We examined the supramedullary cells of the puffer fish, Takifugu niphobles, using horseradish peroxidase transport. Horseradish peroxidase labeling was found bilaterally after application to the trigeminal, the posterior branch of the vagal, and the spinal nerves. No labeled neurons were found after application to the anterior or visceral branches of the vagal nerve. Thus, labeled SMCs were found only after application to the nerves containing cutaneous branches. Some rostrocaudal topographical labeling was found after selective application to each of the four branches of the trigeminal nerve. Labeled neurons were more common in the rostral than in the central or caudal part of the SMC region. Some topographical labeling was also found after application to the first, second, and third spinal nerves, but the topography was not very clear, and there was considerable overlap in the distribution of labeled cells. The sum total of labeled SMCs after unilateral horseradish peroxidase application to each peripheral nerve was more than three times the total number of ipsilateral SMCs, indicating that a single SMC projects several peripheral processes into different nerves. From these results, and taking previous studies into consideration, we propose that supramedullary neurons have a phylogenetic relationship with the spinal dorsal cells of the lamprey and with the extramedullary cells of the amphibian embryo.

The structure of the venom gland of stonefish Synanceja horrida was studied using light microscopy, and transmission and scanning electron microscopy. The glands were covered with a fibrous capsule which divided the glandular tissue into many septa which carried numerous nerves and blood vessels. Transmission electron microscopy showed Type I cells with electron-dense material and tubular cisterns, Type II cells with dilated cisterns, sarcoplasmic reticulum and dense secretory granules. The secretory granules were globular and seen in monomer or polymer form. The secretory cells appear to be unique in comparison with the venom gland cells of snakes, scorpions or spiders.

As man takes increasing advantage of the waters of the world for recreational, commercial and scientific purposes, the hazards of human contact with inhabitants must be appreciated. Many invertebrate and vertebrate animal species have developed natural defense mechanisms, some of which involve envenomation, with a few species posing the threat of serious injury or death. This paper discusses the more common and more serious marine envenomations encountered worldwide, including toxicology of the associated venoms and a discussion of current treatment recommendations.

Unique exocrine glands or gland-like structures were found in the skin of several species of puffer fishes of the genus Takifugu. The glands of T. pardalis and T. vermiculare porphyreum consisted only of secretory cells with a large vacuole. These cells were completely enclosed by epithelial cells with developed microfilaments, except at their opening to the lumen. The contents of the large vacuole in the peculiar secretory cell were forced out when the puffer was stimulated. Exocrine glands or gland-like structures with peculiar secretory cells were also found in the skin of T. poecilonotus, T. niphobles and T. vermiculare radiatum. A high concentration of TTX was detected in the gland contents collected directly from live specimens of T. pardalis. We therefore conclude that these glands are TTX secreting glands.

A review is presented of work on envenomation by stonefish (Synanceja spp.), which represent not only a danger for the inhabitants of tropical coasts but also for tourists. Stonefish are common in shallow water of reef areas by the shores of the Indian and Indopacific Ocean. The bizarrely shaped fish is often taken for a weed-covered stone and accidents occur when swimmers, divers or fishermen step on the stings of the dorsal fin. These stings are provided with poison glands. The venom has neurotoxic, myotoxic and hemorrhagic effects. The case of a 39-year-old diver is cited who suffered a stonefish stab which lasted for several weeks. Generally envenomations by Synanceja cause severe local pain and enormous swelling of the limb; systemic symptoms as usually found with neurotoxins are common; death may occur by shock, by paralysis of the diaphragm or cardiac arrest. For first aid bathing of the limb in hot water is recommended. Clinical measures are local analgesia, local neutralization of the venom, if possible antiserum therapy and intensive care with symptomatic treatment of systemic complications. The most effective prevention is adequate foot protection when wading in the sea.