When jellyfish wash up on beaches or are found floating lifelessly in coastal waters, determining their state can be challenging. Understanding the changes that occur after a jellyfish dies helps in identifying them accurately and understanding natural marine processes. This article guides you on recognizing dead jellyfish and the reasons for their altered appearance.
Identifying Characteristics
A dead jellyfish loses its vibrant, translucent appearance, often becoming opaque, milky, or discolored. Colors shift to brown, gray, or faded hues, contrasting sharply with the clear and sometimes iridescent bells of living specimens. The once-defined bell often collapses, appearing flattened, deflated, or as an amorphous, blob-like mass. Its delicate tentacles and oral arms may become tangled, shriveled, or detached.
The texture of a dead jellyfish changes from a firm, gelatinous consistency to something more flaccid, slimy, or rubbery. If exposed to sun and air, it can dry out and become brittle, sometimes resembling a “crunchy carpet” on the sand. Active movement, such as rhythmic pulsations of the bell or coordinated tentacle movements, will be entirely absent. Any observed movement would be due to currents or wave action.
Why Their Appearance Changes
The transformation of a jellyfish after death is due to its composition and environmental factors. Jellyfish are composed of approximately 95% water, which contributes to their rapid decomposition outside their aquatic environment. When stranded on land, water quickly evaporates, leading to desiccation and a shriveled or deflated appearance.
Cellular breakdown begins immediately after death, causing loss of transparency and changes in color and texture. Microbial degradation, driven by bacteria, rapidly breaks down protein-rich tissues. This process can lead to the liquefaction of the jellyfish. Environmental elements like wave action, strong currents, and exposure to sand and debris can further alter the form of a dead jellyfish, causing physical damage or embedding particles within its remains.
Distinguishing Them From Other Objects
Differentiating a dead jellyfish from other objects requires observing specific biological indicators. A living jellyfish exhibits rhythmic bell pulsations and active tentacle movements. In contrast, a dead jellyfish shows no self-propelled movement, and its structure is compromised.
Plastic bags can sometimes mimic the appearance of dead jellyfish, especially when floating in water, leading to confusion for marine animals like sea turtles. However, plastic lacks any biological structure; it often has handles, folds, or seams, and it does not decompose organically. Other gelatinous marine organisms, such as salps, might also resemble jellyfish. Salps are typically barrel-shaped and often form chains, and they do not possess stinging cells or tentacles like jellyfish. Even when dead, a jellyfish, or a detached tentacle, can still sting, a notable difference from harmless debris.