Sea Robins

September 30, 2024

David Kingsley, the Rudy J. and Daphne Donohue Munzer Professor in the department of developmental biology at Stanford University’s School of Medicine, first came across an odd looking fish in 2016 when he stopped into a small public aquarium in Woods Hole, Massachusetts.  “The fish on display completely spun my head around because they had the body of a fish, the wings of a bird, and multiple legs like a crab,” Kingsley said.  Kingsley and his colleagues decided to study the fish in the lab and found differences between the sea robin species and the genetics responsible for their unusual traits.  The findings of the study team’s new research show how evolution leads to complex adaptations in specific environments, such as the ability of sea robins to be able to “taste” prey using their highly sensitive appendages.  According to their research, some types of the bottom-dwelling ocean fish use taste bud-covered legs to sense and dig up prey along the seafloor.  Sea robins are so adept at rooting out prey on the ocean floor with their leglike appendages that other fish follow them around hoping to snag some of the freshly uncovered prey themselves.

When I looked online, I found sea robins (order, Triglidae), commonly known as gurnards, are a family of bottom-feeding scorpaeniform ray-finned fish.  Triglidae is one of the five largest orders of bony fishes and is divided into 3 subfamilies and 8 genera that include 125 species distributed in temperate and tropical seas worldwide.  Most species are around 12 to 16 inches (30 to 40 cm) in length with the females typically being larger than the males.  They have an unusually solid skull, and many species possess armored plates on their bodies.  Another distinctive feature is the presence of a “drumming muscle” that makes sounds by beating against the swim bladder.  Sea robins have three “walking rays” on each side of their body that are derived from the supportive structures in the pectoral fins (fin-rays).  During development, the fin-rays separate from the rest of the pectoral fin and develop into walking rays.  These walking rays have specialized muscle divisions and unique anatomy that differ from typical fin-rays to allow them to be used as supportive structures during underwater locomotion.  The rays are used for locomotion and prey detection on the seafloor via tasting (chemoreception) and are highly sensitive to the amino acids in marine invertebrates.

While all sea robins have leglike appendages, only some have the macroscopic sensory organs that allow them to taste the environment.  Research revealed digging sea robins depend on a regulatory gene called tbx3a not only to develop their specialized fin adaptations but also to form the papillae that cause them to dig. Tbx3 also plays a role in limb development in humans, chickens, mice, and other fish species.  The fish grew legs using the same genes that contribute to the growth of our limbs and then repurposed these legs to find prey using the same genes our tongues use to taste food.  Sea robins stand out among other walking fishes because their pectoral fins (walking fin rays) are highly jointed and their skeletal and muscular anatomy showcase unique modifications that enable the sea robins to walk. 

THOUGHTS:  Sea robins have firm white flesh that holds together in cooking, making them well-suited to soups and stews such as the French bouillabaisse.  They were often caught in British waters as a bycatch and discarded, but as other species became less sustainable and more expensive, they became more popular.  Sea robins (gurnards) are used as bait by lobster fishers but are also now appearing in fish markets in the US.  As desirable species are overfished or become scarce humans turn to the “next one up” to meet our food needs.  We need to find ways to make fishing sustainable, or even the rough (trash) fish will be in short supply.  Act for all.  Change is coming and it starts with you.