Epaulette Shark - Biology and Ecology

Biology and Ecology

As an adaptation for navigating its complex reef environment, the epaulette shark moves by seemingly walking, bending its body from side-to-side and pushing off of the substrate with its paddle-shaped pectoral and pelvic fins. The shark only swims to escape from a threat, and then not very far. The cartilaginous supports of the epaulette shark's paired fins are reduced and separated when compared to other sharks, allowing them to be rotated for use as limbs. This mode of locomotion even enables the shark to crawl out of the water to access isolated tidal pools. The gait of the epaulette shark is convergently similar to those of tetrapods such as salamanders, suggesting that the movements needed for walking on land may predate, and facilitated the evolution of, the first terrestrial vertebrates. Epaulette sharks are largely nocturnal and are most active in low water. They often hide inside or below coral heads, though it is enough for the head to be covered even if the rest of the body is exposed. Sometimes they perch in the open on sandy flats or atop reefs facing into the current, a form of orientation known as rheotaxis that may improve respiration or predator awareness.

Epaulette sharks are preyed upon by larger fishes such as other sharks. Its coloration provides protective camouflage, while its epaulette is speculated to be an eyespot for distracting or deterring predators. Epaulette sharks are almost all parasitized by the praniza (parasitic) larval stage of gnathiid isopods. The larvae feed on blood and mostly attach to the skin around the cloaca and the claspers, though they are also found inside the mouth and on the gills. These parasites cause little damage and are not believed to adversely affect the health of the shark. Other parasites of this species include a species of myxosporean in the genus Kudoa, which infests the skeletal muscles, the hemogregarine protozoan Haemogregarina hemiscyllii, which infects the blood, the ostracod Sheina orri, which attaches to the gills, and the nematode Proleptus australis, which infests the stomach.