Convergence; venomous fish (Introduction)

by David Turell , Monday, July 11, 2016, 15:18 (2849 days ago) @ David Turell

A study of the many examples of venomous fish both salt and fresh water:-https://www.sciencedaily.com/releases/2016/07/160705160206.htm-"A new article catalogs instances of venomous aquatic life, for the first time showing that venom has evolved 18 separate times in fresh and saltwater fishes. -***-"•In contrast to squamates like lizards and snakes, very few fishes have evolved venomous fangs or teeth
•The predominant function for venom in fishes is defense rather than offense
•Venom in freshwater is dominated by catfishes, as opposed to marine environments where it is widespread across many groups
•It is surprising how comparatively common venom is in deep-sea sharks (30 percent of venomous sharks) compared to deep-sea bony fishes (5 percent of venomous bony fishes)-***-"'Fish venoms are often super complicated, big molecules that have big impact," he said. "Venom can have impacts on blood pressure, cause local necrosis, breakdown of tissue and blood, and hemolytic activity -- it prevents clotting to spread venom around prey. Venom is a neurotoxin. The average response is incredible pain and swelling."-"According to Smith, because fishes have to live with their own venom, "there might be helper molecules that protect the fishes themselves and help them survive." He said these also could have therapeutic value to people. (my bold)-"Smith said that up to 95 percent of venomous fish use their toxins defensively, usually gathering venom within their dorsal spines, where it can be deployed in case the fish is crushed or another fish attempts to swallow it.-"Some, however, use venom offensively to debilitate their prey and can sometimes injure people."-Comment: How is a venom developed stepwise without harm to the organism that develops it? Note the bold statement. It must develop simultaneously with self-protective mechanisms. Saltation.