poisonous fishAmong herpetologists, those scientists who study reptiles, “hot” means venomous. By that definition, Shedd has a lot of hot spots where you can find venomous, as well as poisonous, animals. (A refresher from earlier in this series: Venom is injected, poison is ingested.)

The hotbeds of toxicity at Shedd are Wild Reef and Amazon Rising. Both represent two of the world’s most biologically diverse ecosystems, where a lot of species wage constant turf (or surf) wars for food, habitat and mates. Diversity and competition go hand in hand. But venomous animals often have the upper hand.

The very foundation of Wild Reef is a war zone as corals—soft, anchored and vulnerable—snag prey and fend off predators with stinging cells. The ocellated dragonet is all bright colors and bull’s-eye patterns on a 2½-inch body coated in poisonous slime. The striking black, white and yellow foxface rabbitfish is arrayed with stout, needle-sharp venomous dorsal and pectoral spines. Sabertooth blennies, as you might anticipate from their name, are equipped with fearsome dentition for delivering venomous bites. Of course, you’ll also find stately lionfish, their fanned fins tipped with toxic spikes; stingrays, each with a barbed venomous spine locked and loaded in its tail; and sea urchins bristling with prickly spines that carry a mild toxin. Wild Reef is also home to the crown-of-thorns sea star, one of the most beautiful “starfishes” that can have scarlet and purple skin punctuated by thick yellow or pink spines. The crown-of-thorns is also the only venomous one among 1,800 sea star species. Those hot colors broadcast “toxic.”

Many of Amazon Rising’s hot residents are more subtle—the color of mud, leaf litter, or sedimented river water. An assortment of invertebrates, including Shedd’s trio of tarantula species, are renowned for their painful, but usually nonlethal, venomous bites.

Freshwater rays are more feared in the Amazon than any other fishes—including piranhas—because it is so easy to accidentally step on one buried in shoreline mud, triggering reflexive lashing of the ray’s tail. The knifelike barbed tail spine, which is covered in mucus and neurotoxic venom, can lodge in the offender’s flesh, causing intense pain, tissue breakdown around the wound, paralysis, fluctuations in blood pressure and heart rate, and even death without medical attention.

venomous catfishAnother group of fishes in the Amazon’s animal arsenal might surprise you: venomous catfish.

Yes, catfish.

Scientists (and probably a lot of fishermen) already knew some catfishes produce toxic skin secretions. But recent research also found that a number of catfish species have venom gland tissue adjacent to the sharp, bony spines on the edges of the pectoral and dorsal fins. The spines can be locked into place when the fish is threatened. As a spine spears a would-be predator, the skin around the venom gland cells tears and releases a protein-based toxin into the puncture. The venom wreaks havoc with the nervous system and breaks down red blood cells. Potency—and chemical composition—varies somewhat by catfish family, and even by species. Reactions in people unlucky enough to be scratched or stabbed include intense pain and redness and swelling around the wound. One marine species, however, the striped eel catfish (on view in Wild Reef), is extremely venomous to humans.

Toxicity seems to be a family affair, so when you’re in Amazon Rising, be sure to check the catfish listed on the electronic identification panels for these families: Callichthyidae (armored catfishes, including the cory cats), Doradidae (the thorny or talking catfishes), Pimelodidae (antennae catfishes) and Auchenipteridae (driftwood catfishes).

While most catfish envenomations in people are fishing related, driftwood catfishes pose a unique threat to the residents of small villages along the rivers of the Amazon floodplain. Many riverside dwellers bucket bathe, dropping a plastic bucket on a rope into the river, hauling the bucket back in and dumping the water over themselves—a safer practice than getting into the river with caimans and assorted predatory fishes. At the time of the customary evening bath, schools of tiny nocturnal driftwood catfish are at the surface of the water feeding on insects. Frequently, the catfish are scooped up undetected and thrown over the bather’s body with the water. The disturbed fish lock their venomous spines and, as they fall, injure the bather, most commonly around the hands, head and neck. In addition to the initial pain, the puncture wounds can become infected—a risk with all catfish stabs.

Venomous catfish aren’t exotic exceptions to the Amazon. Scientists figure that between 1,250 and 1,600 species in the global catfish clan (order Siluriformes, with upwards of 3,000 known species) might be venomous. That includes more than 50 species in family Ictaluridae—our own North American bullhead catfishes.

madtomThe Local Waters gallery’s catfish hotspot is the Streams habitat where the madtoms reside. Great name. But don’t expect wild-eyed frenzied fishes whipping up the water. The 4½-inch tadpole madtom sticks to quiet shallows, hiding amid underwater vegetation or fallen branches during the day and searching for insect larvae and small crustaceans at night. The foot-long stonecat, largest of the madtoms, lives in faster water but hides under flat rocks. These species’ normally secretive demeanor, however, does belie their erratic swimming and “mad” attempts to stab with their pectoral fin spines when they’re disturbed or caught. A scratch or stab from a madtom reportedly feels a lot like a bee sting.

At Jazzin' at the Shedd, take a closer look at Shedd’s toxic stingers, stabbers, slimers and biters. Hot, encountered in the right spot, is pretty cool.

Posted by Karen Furnweger, web editor