Venom and venom delivery systems have evolved in animal groups ranging from jellyfishes to scorpions, spiders, lizards, snakes and even primates. Surprisingly, snakes are neither the most diverse or most abundant group of venomous vertebrates, for there are more than 1,400 species of venomous fishes, which account for more than 70% of all venomous animals with backbones. It is perhaps equally surprising that only now are scientists undertaking the first detailed studies to examine the evolution of venom as a defensive specialization in fishes. Among the ten groups of venomous fishes, scorpionfishes are the focus of the present study. This is because this group is the most diverse group of venomous marine fishes. It also includes some of the world's most familiar venomous fishes (lionfishes and turkeyfishes, which are very popular with aquarists) as well as the most deadly (stonefishes, which can kill an adult human unfortunate enough to step on one). Evolutionary relationships within scorpionfishes have been contentious, yet a rigorous family tree is the critical first step to broader study of their venom and venom delivery systems. To build such a tree, this study will undertake a comparative study of more than 100 species of scorpionfishes and related groups using evidence from larval and adult anatomy and mitochondrial and nuclear DNA sequences. The resulting tree will be used not only to test competing hypotheses about the evolution of venom, but will also examine anatomical diversification and the evolution of live birth in scorpionfishes.
This study has three specific broader impacts: 1) training of a doctoral student in anatomy and molecular biology; 2) detailed information on species-level relationships of the many commercially harvested species of scorpionfishes such as California rockfishes; this is an important goal given that scorpionfishes represent more than 9% of harvested fish in the Unites States and are becoming increasingly endangered or threatened worldwide; 3) provision of a framework for making informed choices of species when screening venoms for potential pharmaceutical applications; venoms of other animals have proven to be of outstanding pharmaceutical importance, yet such investigations of fishes are in their infancy and a tree of scorpionfishes could jump-start promising bioprospecting of their venoms.
