Synanceia is genus of fish of the family Synanceiidae, the Stonefishes, whose members are dangerous or fatal to humans. They are found in the coastal regions of Indo-Pacific oceans. They are primarily marine, though some species are known to live in rivers. Its species have potent neurotoxins secreted from glands at the base of their needle-like dorsal fin spines. The vernacular name of the species, the stonefish, derives from their behaviour of camouflaging as rocks. The type species of the genus is Synanceia verrucosa, and it includes the species Synanceia horrida that Linnaeus described as Scorpaena. The authors of Synanceia are Marcus Elieser Bloch and Johann Gottlob Schneider in the latters republication of Systema Ichthyologiae iconibus cx illustratum (Illustrated catalog of Fishes), in 1801. The desciption was accompanied by an illustration by J. F. Hennig. The misspelling Synanceja is regarded as a synonym for this genus.
Around 400 species of mantis shrimp have currently been described worldwide; all living species are in the suborder Unipeltata . They are commonly separated into two distinct groups determined by the manner of claws they possess:
Squilla mantis, showing the spearing appendagesSpearers are armed with spiny appendages topped with barbed tips, used to stab and snag prey. Smashers, on the other hand, possess a much more developed club and a more rudimentary spear (which is nevertheless quite sharp and still used in fights between their own kind); the club is used to bludgeon and smash their meals apart. The "punch" delivered has roughly the acceleration of a .22 caliber bullet. The inner aspect of the dactyl (the terminal portion of the appendage) can also possess a sharp edge, with which the animal can cut prey while it swims. Both types strike by rapidly unfolding and swinging their raptorial claws at the prey, and are capable of inflicting serious damage on victims significantly greater in size than themselves. In smashers, these two weapons are employed with blinding quickness, with an acceleration of 10,400 g and speeds of 23 m/s from a standing start , about the acceleration of a .22 caliber bullet. Because they strike so rapidly, they generate cavitation bubbles between the appendage and the striking surface . The collapse of these cavitation bubbles produces measurable forces on their prey in addition to the instantaneous forces of 1,500 N that are caused by the impact of the appendage against the striking surface, which means that the prey is hit twice by a single strike; first by the claw and then by the collapsing cavitation bubbles that immediately follow . Even if the initial strike misses the prey, the resulting shock wave can be enough to kill or stun the prey.
The snap can also produce sonoluminescence from the collapsing bubble. This will produce a very small amount of light and high temperatures in the range of several thousand kelvin within the collapsing bubble, although both the light and high temperatures are too weak and short-lived to be detected without advanced scientific equipment. The light emission and temperature increase probably have no biological significance but are rather side-effects of the rapid snapping motion. Pistol shrimp produce this effect in a very similar manner.
Smashers use this ability to attack snails, crabs, molluscs and rock oysters; their blunt clubs enabling them to crack the shells of their prey into pieces. Spearers, on the other hand, prefer the meat of softer animals, like fish, which their barbed claws can more easily slice and snag.
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