The funeral worker on the mudflat
At Qigu Lagoon, the water in the tidal creak gradually flows to the bund after ebb tide. Plains begin to appear at the high terrain. A few water remains on some low shoals. The cutaneous respiration is activated in the mudskippers on the mudflat. Fiddler crabs stick out from the mud holes. Shore crabs climb out from the gap between the rocks and clamshells. The largescale mullet is attracted by the waste crab trap covered by the algae. It keeps eating the algae and enters the net unconsciously. Other largescale mullet swim away with the tide. The water level in the trap becomes lower and it becomes nervous and struggles. It secretes more mucus instinctively and more sand sticks to its body. Its mouth opens and tries to breathe with gills but this action extends the pain. A swimming crab rambles on the mudflat and finds the tasty largescale mullet on the side of the cage. Its claws tear the mullet, drags it out from the trap, which is on the verge of death and it is ready to dig in. Meanwhile, another swimming crab lurking in the sand finds the mullet, too. They fight for the mullet and their claws pinching hard on each other. An egret grips them and breaks them up.
The blood and tissue fluid of the ripped largescale mullet are diffused in the water flow. The smell raises an uproar in the intertidal zone. A nassa mud snail hiding in the mudflat surface smells the death and wakes up. It sticks out its siphons, formed by the mantle and extends them out. The siphons suck the seawater into the gills in the mantle and the oscillator checks the smell in the water to find out if the smell comes from a prey, the opposite sex, an enemy or an injured nassa mud snail. Nassa mud snails are the funeral workers on the mudflat. After the nassa mud snail confirms that it is the smell of the prey, the rest of the nassa mud snails in the intertidal zone become restless. They climb out from the mud and start to crawl. They sway their siphons eagerly to detect the source of the smell. They quickly locate the largescale mullet and crawl fast towards it from different directions. The largescale mullet is a rare delicacy falling from the sky. The largescale mullet is crawling with nassa mud snails in a moment. Nassa mud snails stretch out a proboscis between the antennae and stick it into the eyes, gill covers and mouth of the fish, which are soft and without scales. Their radula on the front end of the proboscis scrapes the bones and flesh and chow down until only the skin and bones remain. The scavenger party is over.
The oscillator of the nassa mud snail is an osphradium, evolved to successfully identify the situations in nature. It helps the nassa mud snail decide whether it should flee to the right or left. The siphons sway left and right to detect objects in a larger area more effectively. They can detect the smell in water and locate the prey. When the nassa mud snail finds food, a long, pink proboscis stretches out between the two antennae and the radula on the interior of the front end of the proboscis scrapes dead fish and crabs. If it can’t detect any food, it digs into the sand and sticks out a siphon and quietly waits for the water level to decrease during ebb tide. When any food (dead body) is brought by the tide and subsided on the sand, the nassa mud snail crawls out as scavengers. The working efficiency of the nassa mud snail affects the energy cycle of the intertidal zone. Because of this skill, they’ve been unbeatable in the intertidal zone for long. They are the master of sniffing dead body and they rely on olfactory cues to feed themselves.
Since humans have invented the petrochemical plastics, their skills don’t work well anymore. Science discovered that the olfactory nerves of the nassa mud snail do not work anymore due to the plastic trash accumulated on the beach. Throughout their evolution in tens of millions of years, they don't recognize the plastics or chemicals invented in the last hundred years. These new things interfere with olfactory cues. They lurk in the sand longer and spend more time searching for food. They often make mistakes locating food and crawl slower. They spend lots of time but can’t find any food. They decrease in numbers at places with lots of plastic trash.
The tide comes in and goes out. Nutrients and energy circulate precisely in a healthy ecosystem, generating abundant productivity for the wetlands. The interaction effect between species is dense and compact. Nature utilizes all resources perfectly without waste. The nassa mud snail, the funeral worker on the mudflat and wetlands, should be a great scavenger that treats all the dead equally. However, humans have silently altered this role.
Marine gastropods gather and scrape the dead largescale mullet
Common nassa mud snail in Taijiang: Marine gastropod (Reticunassa festiva)
Common nassa mud snail in Taijiang: Olive dog whelk (Plicarcularia pullus)