Despite being the largest freshwater arthropod in North America, spiny stream crayfish are not safe from the eight-legged predators lurking on the riverbanks. For the first time, a striped fishing spider has been seen devouring a young crayfish, after having tied it to the underside of a rock using silk fibers.
The spider was found tucking into its crustacean dinner by the side of Knox Creek in Virginia, by a team of scientists carrying out a study on endangered crayfish populations in July 2015. Describing their discovery in the journal Southeastern Naturalist, the researchers reveal how they stumbled upon the predation event after overturning a rock, finding the spider and its half-eaten victim upside down on the bottom.
Striped fishing spiders are known to feed on small fish and other aquatic creatures by using their legs to detect changes in water surface tension, before launching a rapid attack on any prey it senses nearby. When attacking fish, it usually grabs them by the back of the head, wrapping its legs around the body and delivering a venomous bite with its fangs as the knock-out blow.
Although the study authors did not witness the spider catching the crayfish, they suspect that it must have used a similar strategy in order to avoid the pincers of its prey. By the time they found it, the female spider had already demolished most of the crayfish’s abdomen, and had bored her own pincers into its body as she continued to feast. Despite being disturbed by the researchers, the spider did not show any inclination to flee, and continued to clasp its victim for the duration of the team’s 10-minute observation.
Summing up their find, the study authors note that this is possibly the first time that this species of spider has been seen eating a crayfish, adding that “crayfish are the largest freshwater arthropods in North America; it is only fitting that one of the largest araneomorph spiders in North America has now been confirmed to include them as prey.”