This saltwater bivalve (Ctenoides ales) goes by quite a few names including “electro-flame scallop,” “electric clam,” and “disco clam” and it’s easy to see why. These animals are vibrantly colored and are among only a couple bivalves that can display a light show. Disco clams light up—flashing “lights” along their red mantle to confuse and deter predators. This light is not a form of bioluminescence, in which organisms are able to produce and emit light, but instead is created by highly reflective silica-rich cells on the edge of their mantle tissue. The clam can flex these tissues, exposing and hiding them in quick succession, creating a flashing or strobing effect due to reflection of sunlight through the water. The tissue around these display cells is a vibrant, reddish-orange hue, while the shell itself is a mottled tan color.
Researcher Lindsey Dougherty, who was a postdoctoral fellow working with the CU Museum’s invertebrate collections, and her team found that this bright red portion of the mantle is chemically different from the rest of the non-colorful tissue. The bright color is due to, in part, peptide-like compounds that may be slightly noxious and unpalatable to predators. The combination of red color and flashing display could be warning predators that the clam is distasteful. This is a valuable defense mechanism, especially since the mantis shrimp is one of the disco clam’s predators. These shrimp are known for their ability to break the shell of a clam but, fortunately for Ctenoides ales, they have sensitive eyesight that would not miss these dramatic disco displays. If the light show wasn’t enough of a deterrent, Doughtery found these clams spewed acidic mucus at the shrimp, disabling them for up to 15 minutes under laboratory conditions2.
Disco clams are distributed in tropical waters of the Indo-Pacific, where many creatures are brightly colored, thus their display is but one of many flashy shows. Like many coral-dwelling organisms, the disco clam is a rare sight in its habitat. These molluscs spawn to reproduce, meaning a male and female will release their gametes into the water for fertilization. Their ability to reproduce is reflective of plankton abundance, as plankton is their primary food source2. Few baby disco clams survive without abundant plankton. With rising ocean temperatures, many species sustained by coral reef habitats are experiencing population declines, including the disco clam. While many of us may be far from an ocean, we should remember that our actions have an impact there. Let’s keep this party called life on earth going!
1. Dougherty, L. F., Niebergall, A. K., Broeckling, C. D., Schauer, K. L., & Li, J. (2019). Brightly coloured tissues in limid bivalves chemically deter predators. Royal Society open science, 6(10), 191298.
2. https://escholarship.org/content/qt34v2q4dr/qt34v2q4dr_noSplash_4a6eb73624dd6376289becc4dc3a53ef.pdf?t=odi07b
Video credit: Lindsey Dougherty and Roy Caldwell